A positive electrode active material, a method for manufacturing the same, and a battery

Abstract

This application relates to a positive electrode active material and its preparation method, and a battery, belonging to the field of battery technology; the positive electrode active material has a core-shell structure, the core of the core-shell structure includes a lithium-rich manganese-based active material, and the shell layer of the core-shell structure includes Li2SO4, Li2SeO4, and Li2Se. x S 1‑x At least two of the following O4, wherein 0 < x < 1, are obtained by coating Li2SO4, Li2SeO4 and Li2Se with a lithium-rich manganese-based active material. x S 1‑x At least two of the shells formed in O4, utilizing Li2SO4, Li2SeO4, and Li2Se x S 1‑x O4 and other materials have high ionic conductivity, which can effectively promote the transport of lithium ions at the interface of lithium-rich manganese-based active materials, giving the positive electrode active material a high ion diffusion coefficient.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a positive electrode active material, its preparation method, and a battery. Background Technology

[0002] Among cathode active materials, lithium-rich manganese-based active materials are considered one of the main next-generation cathode active materials due to their high specific capacity (up to 250 mAh / g) and high operating voltage. However, the low ion diffusion coefficient of lithium-rich manganese-based active materials affects their application in batteries, especially in solid-state batteries. Summary of the Invention

[0003] This application provides a positive electrode active material with a high ion diffusion coefficient.

[0004] In a first aspect, embodiments of this application provide a positive electrode active material having a core-shell structure. The core of the core-shell structure comprises a lithium-rich manganese-based active material, and the shell layer comprises Li₂SO₄, Li₂SeO₄, and Li₂Se. x S 1-x At least two of O4, where 0 < x < 1.

[0005] In the technical solution of this application embodiment, Li2SO4, Li2SeO4 and Li2Se are coated with lithium-rich manganese-based active materials. x S 1-x At least two of the shells formed in O4, utilizing Li2SO4, Li2SeO4, and Li2Se x S 1-x O4 and similar substances possess high ionic conductivity, which effectively promotes lithium-ion transport at the interface of lithium-rich manganese-based active materials, resulting in a high ion diffusion coefficient for the cathode active material. Simultaneously, the shell layer prevents direct contact between the lithium-rich manganese-based active material and the electrolyte, effectively improving the interfacial stability of the cathode active material.

[0006] As an optional implementation, the lithium-rich manganese-based active material is doped with at least one of the elements Se or S.

[0007] In the above implementation process, by doping non-metallic elements such as Se and / or S into lithium-rich manganese-based active materials, the generation of oxygen vacancies in the materials can be suppressed, which is beneficial to the structural stability, electrochemical performance, and safety of the materials. It can also improve the electronic conductivity of the materials.

[0008] As an optional implementation, the molar ratio of Se to S in the positive electrode active material is 0.2 to 0.4.

[0009] In the above implementation process, by controlling the molar ratio of Se and S elements within a suitable range, Li2SO4, Li2SeO4, and Li2Se can be formed relatively well. x S 1-x O4 and other shell materials effectively promote lithium-ion transport at the interface of lithium-rich manganese-based active materials, giving the cathode active material a high ion diffusion coefficient and preventing direct contact between the lithium-rich manganese-based active material and the electrolyte, thus improving the interfacial stability of the cathode active material. Simultaneously, some elements can act as dopants, suppressing the formation of oxygen vacancies in the lithium-rich manganese-based active material, which is beneficial to the structural stability, electrochemical performance, and safety of the lithium-rich manganese-based active material, and also improves its electronic conductivity. Furthermore, it can make the pores of the cathode active material more uniform, improving the ionic conductivity of the lithium-rich manganese-based active material.

[0010] As an optional implementation, the mass percentage of Se element in the positive electrode active material is 1000ppm to 3000ppm.

[0011] In the above implementation process, when the molar ratio of Se and S elements meets the requirements, by controlling the mass percentage of Se element within a suitable range, Li2SO4, Li2SeO4, and Li2Se can be formed relatively well. x S 1-x O4 and other shell materials effectively promote lithium-ion transport at the interface of lithium-rich manganese-based active materials, giving the positive electrode active material a high ion diffusion coefficient and preventing direct contact between the lithium-rich manganese-based active material and the electrolyte, thus improving the interfacial stability of the positive electrode active material. Simultaneously, they can suppress the formation of oxygen vacancies in lithium-rich manganese-based active materials, which is beneficial to the structural stability, electrochemical performance, and safety of the materials, and also improves their electronic conductivity.

[0012] As an optional implementation, the mass percentage of sulfur in the positive electrode active material is 1000ppm to 4000ppm.

[0013] In the above implementation process, when the molar ratio of Se and S elements meets the requirements, by controlling the mass percentage of S element within a suitable range, Li2SO4, Li2SeO4, and Li2Se can be formed relatively well. x S 1-xO4 and other shell materials effectively promote lithium-ion transport at the interface of lithium-rich manganese-based active materials, giving the positive electrode active material a high ion diffusion coefficient and preventing direct contact between the lithium-rich manganese-based active material and the electrolyte, thus improving the interfacial stability of the positive electrode active material. Simultaneously, they can suppress the formation of oxygen vacancies in lithium-rich manganese-based active materials, which is beneficial to the structural stability, electrochemical performance, and safety of the materials, and also improves their electronic conductivity.

[0014] As an optional implementation, the positive electrode active material includes Li[Li a Ni x Co y Mn z M b O 2-e-f D e E f Where a+x+y+z+b=1, 0.1≤a≤0.25, 0.12≤x≤0.4, 0≤y≤0.15, 0.5≤z≤0.75, 0≤b≤0.1, 0<e≤0.1, 0≤f≤0.05, M is a metallic element, including at least one of Fe, Cr, Mo, W, Ta, Ti, Nb, Sb, Hf, Ce, Zr, Sn, V, Ca, La, Al, Mg, K or Na, and D includes SO42-. 2- and SeO4 2- E includes at least one of F, P or Cl.

[0015] As an optional implementation, the positive electrode active material is a secondary particle formed by the agglomeration of primary particles, and the Dv50 of the positive electrode active material is 1μm~7μm.

[0016] In the above implementation process, the larger the particle size of the positive electrode active material, the greater the compaction of the positive electrode sheet, which can improve the overall energy density; the smaller the particle size of the positive electrode active material, the shorter the internal ion transport path, which is beneficial to the construction of ion transport pathways in the battery, and thus improves the rate performance of the battery. By controlling the Dv50 of the positive electrode active material to be 1μm~7μm, the positive electrode active material can achieve both high energy density and short ion transport path.

[0017] As an optional implementation, the specific surface area of ​​the positive electrode active material is 0.5 m². 2 / g~3.5m 2 / g.

[0018] In the above implementation process, the smaller the specific surface area of ​​the positive electrode active material, the better its contact area with the electrolyte can be controlled, reducing the possibility of side reactions and thus maintaining the battery's cycle performance; the larger the specific surface area of ​​the positive electrode active material, the larger its contact area with the solid electrolyte, enabling the construction of good ion transport channels. By controlling the specific surface area of ​​the positive electrode active material to 0.5 μm... 2 / g~3.5m 2 / g allows the positive electrode active material to balance the possibility of low side reactions and good ion transport channels.

[0019] Secondly, embodiments of this application provide a method for preparing the aforementioned positive electrode active material, the method comprising: The lithium-rich manganese-based active material precursor and lithium source are subjected to a first calcination to obtain an intermediate. The intermediate, the first Se source, and the first S source are subjected to a second calcination to obtain the positive electrode active material.

[0020] In the technical solution of this application embodiment, a positive electrode active material is prepared by first calcining a lithium-rich manganese-based active material precursor and a lithium source, and then calcining an intermediate, a first Se source, and a first S source together in a second calcination. This process forms a core of lithium-rich manganese-based active material and a shell of Li2SO4, Li2SeO4, and Li2Se. x S 1-x At least two of the O4 components are core-shell structured positive electrode active materials, which utilize Li2SO4, Li2SeO4, and Li2Se. x S 1-x O4 and other compounds possess high ionic conductivity, which effectively promotes lithium-ion transport at the interface of lithium-rich manganese-based active materials, resulting in a high ion diffusion coefficient for the cathode active material. Simultaneously, the shell layer prevents direct contact between the lithium-rich manganese-based active material and the electrolyte, effectively improving the interfacial stability of the cathode active material. Furthermore, the formed Li2SO4 and Li2SeO4 act as fluxes, contributing to the good porosity of the lithium-rich manganese-based active material.

[0021] As an optional implementation, the lithium-rich manganese-based active material precursor includes at least one of a nickel source, a cobalt source, or a manganese source.

[0022] As an optional implementation, the lithium-rich manganese-based active material precursor includes at least one of nickel cobalt manganese hydroxide, nickel cobalt manganese carbonate, or nickel cobalt manganese oxide.

[0023] As an optional implementation, the lithium source includes at least one of lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium sulfate, lithium sulfite, lithium nitrate, lithium nitrite, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium sulfide, lithium perchlorate, lithium manganese oxide, lithium peroxide, lithium superoxide, or lithium acetate.

[0024] As an optional implementation, the first Se source includes at least one of selenium powder, selenium dioxide, lithium selenate, sodium selenate, sodium perselenate, sodium selenite, ammonium selenate, or selenourea.

[0025] As an optional implementation, the first S source includes at least one of sulfur powder, lithium sulfate, sodium sulfate, sodium persulfate, sodium sulfite, ammonium sulfate, ammonium persulfate, sodium thiosulfate, or thiourea.

[0026] As an optional implementation, the first calcination step includes: mixing the doping source, the lithium-rich manganese-based active material precursor, and the lithium source.

[0027] Optionally, the doping source includes at least one of a second Se source or a second S source.

[0028] Optionally, the second Se source includes at least one of selenium powder, selenium dioxide, lithium selenate, sodium selenate, sodium perselenate, sodium selenite, ammonium selenate, or selenourea.

[0029] Optionally, the second S source includes at least one of sulfur powder, lithium sulfate, sodium sulfate, sodium persulfate, sodium sulfite, ammonium sulfate, ammonium persulfate, sodium thiosulfate, or thiourea.

[0030] As an optional implementation, the atmosphere for the first calcination is an oxygen-containing atmosphere.

[0031] As an optional implementation, the first calcination includes a first-stage calcination and a second-stage calcination.

[0032] As an optional implementation, the holding temperature for the calcination stage is 300℃~600℃.

[0033] As an optional implementation, the holding time for the first calcination stage is 3h to 6h.

[0034] As an optional implementation, the heating rate of the calcination stage is 1℃ / min to 10℃ / min.

[0035] As an optional implementation, the holding temperature for the two-stage calcination is 800℃~900℃.

[0036] As an optional implementation, the holding time for the second-stage calcination is 10h to 24h.

[0037] As an optional implementation, the heating rate of the two-stage calcination is 1℃ / min to 10℃ / min.

[0038] As an optional implementation method, the holding temperature for the second calcination is 500℃~700℃.

[0039] As an optional implementation, the holding time for the second calcination is 8h to 15h.

[0040] Thirdly, this application provides a battery, which includes a positive electrode sheet, a positive electrode sheet including a positive electrode active material layer, a positive electrode active material layer including a positive electrode active material, and the positive electrode active material including the positive electrode active material provided in the first aspect or the positive electrode active material prepared by the preparation method of the positive electrode active material provided in the second aspect.

[0041] As an optional implementation, the battery is a solid-state battery.

[0042] In the above implementation process, the positive electrode active material has a high ion diffusion coefficient, making it particularly suitable for solid-state batteries. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart illustrating the methods provided in some embodiments of this application.

[0045] Figure 2 This is a SEM image of the positive electrode active material provided in Example 2 of this application.

[0046] Figure 3 The XRD diffraction patterns of the positive electrode active materials provided in Examples 2, 3 and Comparative Example 1 of this application are shown.

[0047] Figure 4 XPS spectrum of the positive electrode active material provided in Example 2 of this application.

[0048] Figure 5 This is a cross-sectional SEM image of the positive electrode active material provided in Example 2 of this application.

[0049] Figure 6 EDS cross-sectional image (Se element) of the positive electrode active material provided in Example 2 of this application. Detailed Implementation

[0050] The present application is hereby disclosed in detail with appropriate reference to the accompanying drawings. However, some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially the same structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter of the claims.

[0051] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0053] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0054] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if a method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined. In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0055] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0056] Currently, judging from market trends, the application of batteries is becoming increasingly widespread. Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of the application areas of power batteries, the market demand for them is also constantly increasing.

[0057] Among the positive electrode active materials for batteries, lithium-rich manganese-based active materials are considered one of the main next-generation positive electrode active materials due to their high specific capacity (up to 250 mAh / g) and high operating voltage. However, the low ion diffusion coefficient of lithium-rich manganese-based active materials affects their application in batteries, especially in solid-state batteries.

[0058] To improve the performance of lithium-rich manganese-based active materials, this application provides a positive electrode active material with a high ion diffusion coefficient.

[0059] This application provides a positive electrode active material having a core-shell structure. The core of the core-shell structure comprises a lithium-rich manganese-based active material, and the shell layer comprises Li₂SO₄, Li₂SeO₄, and Li₂Se. x S 1-x At least two of O4, where 0 < x < 1.

[0060] Among them, lithium-rich manganese-based active materials refer to modified or unmodified lithium-rich manganese-based active materials, with modifications including element doping or coating.

[0061] The shell materials include Li2SO4, Li2SeO4 and Li2Se x S 1-x At least two of the O4 components, for example, may include Li2SO4 and Li2SeO4, Li2SO4 and Li2Se. x S 1-x O4, Li2SeO4 and Li2Se x S 1-x O4, Li2SO4, Li2SeO4 and Li2Se x S 1-x O4, etc., where x can be 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, etc., or any value in the range 0 < x < 1.

[0062] The core and shell composition of the positive electrode active material can be determined by XPS testing.

[0063] This positive electrode active material is obtained by coating Li2SO4, Li2SeO4 and Li2Se with lithium-rich manganese-based active materials. x S 1-x At least two of the shells formed in O4, utilizing Li2SO4, Li2SeO4, and Li2Se x S 1-x O4 and similar substances possess high ionic conductivity, which effectively promotes lithium-ion transport at the interface of lithium-rich manganese-based active materials, resulting in a high ion diffusion coefficient for the cathode active material. Simultaneously, the shell layer prevents direct contact between the lithium-rich manganese-based active material and the electrolyte, effectively improving the interfacial stability of the cathode active material.

[0064] In some embodiments, lithium-rich manganese-based active materials are doped with Se.

[0065] In some embodiments, the lithium-rich manganese-based active material is doped with sulfur (S).

[0066] The elements doped in lithium-rich manganese-based active materials can be determined by SEM and EDS testing.

[0067] By doping lithium-rich manganese-based active materials with non-metallic elements such as Se / S, the formation of oxygen vacancies can be suppressed, which is beneficial to the structural stability, electrochemical performance, and safety of these materials. Simultaneously, it can also improve the electronic conductivity of lithium-rich manganese-based active materials.

[0068] In some embodiments, the molar ratio of Se to S in the positive electrode active material is 0.2 to 0.4.

[0069] The molar proportions of each element (Se and S) in the positive electrode active material can be determined by inductively coupled plasma atomic emission spectrometry (ICP) combined with SEM and EDS tests.

[0070] By controlling the molar ratio of Se and S within a suitable range, Li₂SO₄, Li₂SeO₄, and Li₂Se can be formed more effectively. x S 1-x O4 and other shell materials effectively promote lithium-ion transport at the interface of lithium-rich manganese-based active materials, giving the positive electrode active material a high ion diffusion coefficient and preventing direct contact between the lithium-rich manganese-based active material and the electrolyte, thus improving the interface stability of the positive electrode active material. Simultaneously, some elements can act as dopants, suppressing the formation of oxygen vacancies in lithium-rich manganese-based active materials, which is beneficial to the structural stability, electrochemical performance, and safety of lithium-rich manganese-based active materials, and also improves the electronic conductivity of lithium-rich manganese-based active materials. It can also make the pores of the positive electrode active material more uniform (see [reference]). Figure 5 As shown in the figure, the pores of the positive electrode active material are relatively uniform, which improves the ionic conductivity of lithium-rich manganese-based active materials.

[0071] For example, the molar ratio of Se to S in the positive electrode active material can be 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, etc., or any value in the range of 0.2 to 0.4.

[0072] In some embodiments, the mass percentage of Se in the positive electrode active material is 1000 ppm to 3000 ppm. When the molar ratio of Se to S meets the requirements, controlling the mass percentage of Se within a suitable range allows for the effective formation of Li₂SO₄, Li₂SeO₄, and Li₂Se. x S 1-xO4 and other shell materials effectively promote lithium-ion transport at the interface of lithium-rich manganese-based active materials, giving the positive electrode active material a high ion diffusion coefficient and preventing direct contact between the lithium-rich manganese-based active material and the electrolyte, thus improving the interfacial stability of the positive electrode active material. Simultaneously, they can suppress the formation of oxygen vacancies in lithium-rich manganese-based active materials, which is beneficial to the structural stability, electrochemical performance, and safety of the materials, and also improves their electronic conductivity.

[0073] For example, in the positive electrode active material, the mass percentage of Se element can be 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, 2000ppm, 2100ppm, 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm, 3000ppm, etc., or it can be any value in the range of 1000ppm to 3000ppm.

[0074] In some embodiments, the mass percentage of sulfur (S) in the positive electrode active material is 1000 ppm to 4000 ppm. When the molar ratio of Se and S is equal, by controlling the mass percentage of S within a suitable range, Li₂SO₄, Li₂SeO₄, and Li₂Se can be formed effectively. x S 1-x O4 and other shell materials effectively promote lithium-ion transport at the interface of lithium-rich manganese-based active materials, giving the positive electrode active material a high ion diffusion coefficient and preventing direct contact between the lithium-rich manganese-based active material and the electrolyte, thus improving the interfacial stability of the positive electrode active material. Simultaneously, they can suppress the formation of oxygen vacancies in lithium-rich manganese-based active materials, which is beneficial to the structural stability, electrochemical performance, and safety of the materials, and also improves their electronic conductivity.

[0075] For example, the mass percentage of sulfur in the positive electrode active material can be 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, 2000ppm, 2100ppm, 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm, 3000ppm, 3100ppm, 3200ppm, 3300ppm, 3400ppm, 3500ppm, 3600ppm, 3700ppm, 3800ppm, 3900ppm, 4000ppm, etc., or it can be any value within the range of 1000ppm to 4000ppm.

[0076] In some embodiments, the positive electrode active material includes Li[Li a Ni x Co y Mn z M b O 2-e-f D e E f Where a+x+y+z+b=1, 0.1≤a≤0.25, 0.12≤x≤0.4, 0≤y≤0.15, 0.5≤z≤0.75, 0≤b≤0.1, 0<e≤0.1, 0≤f≤0.05, M is a metallic element, including at least one of Fe, Cr, Mo, W, Ta, Ti, Nb, Sb, Hf, Ce, Zr, Sn, V, Ca, La, Al, Mg, K or Na, and D includes SO42-. 2- and SeO4 2- E includes at least one of F, P or Cl.

[0077] Doping positive electrode active materials with elements such as fluorine (F) can form stronger non-lithium metal-F bonds, which can suppress metal migration and oxygen vacancy formation, thus improving the structural stability, electrochemical performance, and safety of lithium-rich manganese-based active materials. It can also lower the O 2p band center, reducing electron loss from oxygen under high voltage. Furthermore, fluorine and other elements can partially replace oxygen, reducing the proportion of capacity provided by oxygen ion redox reactions, thereby improving initial efficiency.

[0078] Understandably, during the charging and discharging process of a battery, the insertion and extraction of active metal Li occurs, and the content of active metal Li in the positive electrode varies depending on the state of discharge. The content of active metal Li can be measured using molar content, but is not limited to this. Simultaneously, when positive electrode active materials are applied to the positive electrode in a battery system, the content of active metal Li in the positive electrode active material typically changes after charge-discharge cycles. In the examples of positive electrode active materials listed in this application, unless otherwise specified, the content of active metal Li refers to the initial state of the material. Regarding "the content of active metal Li refers to the initial state of the material," the initial state of the material refers to the state before it is added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode active materials; non-limiting examples include coating modification.

[0079] In some embodiments, the positive electrode active material is a secondary particle formed by the agglomeration of primary particles, and the Dv50 of the positive electrode active material is 1μm~7μm.

[0080] The Dv50 of the positive electrode active material refers to the median volumetric particle size of the positive electrode active material. Dv50 represents the particle size corresponding to 50% of the cumulative volumetric particle size distribution. The cumulative volumetric particle size distribution, also known as the differential particle size distribution, is a curve plotted with particle size on the x-axis and the differential distribution of particle size at different dimensions on the y-axis. It accurately reflects the particle size distribution characteristics of the material. A laser particle size analyzer can be used to determine the volumetric particle size distribution and plot the interval particle size distribution curve. When measuring the median particle size of the positive electrode active material layer in the positive electrode sheet, the positive electrode active material layer can be removed, immersed in the solvent NMP, and the binder in the positive electrode active material layer can be washed out to obtain the powder material of the positive electrode active material layer. After drying the powder material, a Mastersizer 3000 laser particle size analyzer is used to detect the cumulative volumetric particle size distribution, and the Dv50 of the positive electrode active material can be obtained from the peaks in the cumulative volumetric particle size distribution.

[0081] The particle size of the positive electrode active material can be obtained using a Mastersizer3000 laser particle size analyzer.

[0082] Larger particle size of the positive electrode active material results in greater compaction of the positive electrode sheet, which improves the overall energy density. Smaller particle size of the positive electrode active material results in shorter internal ion transport paths, which is beneficial for building ion transport pathways in the battery and thus improves the battery's rate performance. By controlling the Dv50 of the positive electrode active material to be between 1μm and 7μm, the positive electrode active material can achieve both high energy density and short ion transport paths.

[0083] For example, the Dv50 of the positive electrode active material can be 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm, 3μm, 3.2μm, 3.4μm, 3.6μm, 3.8μm, 4μm, 4.2μm, 4.4μm, 4.6μm, 4.8μm, 5μm, 5.2μm, 5.4μm, 5.6μm, 5.8μm, 6μm, 6.2μm, 6.4μm, 6.6μm, 6.8μm, 7μm, etc., or it can be any value in the range of 1μm to 7μm.

[0084] In some embodiments, the specific surface area of ​​the positive electrode active material is 0.5 m². 2 / g~3.5m 2 / g.

[0085] The specific surface area test procedure for positive electrode active materials can be as follows: Take 5g of the positive electrode active material powder to be tested, place it in a sample tube, heat it to degas, weigh it after degassing, and place it on the testing instrument. Under constant temperature and low temperature (-296.7℃), after measuring the amount of gas adsorbed on the solid surface at different relative pressures, the monolayer adsorption amount of the sample is obtained based on the Brownauer-Etter-Taylor (BET) multilayer adsorption theory and its formula, thereby calculating the specific surface area of ​​the positive electrode material.

[0086] A smaller specific surface area of ​​the positive electrode active material allows for better control of its contact area with the electrolyte, reducing the possibility of side reactions and thus maintaining the battery's cycle performance. Conversely, a larger specific surface area allows for a larger contact area with the solid electrolyte, enabling the construction of effective ion transport channels. By controlling the specific surface area of ​​the positive electrode active material to 0.5 μm... 2 / g~3.5m 2 / g allows the positive electrode active material to balance the possibility of low side reactions and good ion transport channels.

[0087] For example, the specific surface area of ​​the positive electrode active material can be 0.5 m². 2 / g、1 m 2 / g, 1.5 m 2 / g、2 m 2 / g, 2.5 m 2 / g、3 m 2 / g, 3.5 m 2 / g, etc., can also be 0.5m. 2 / g~3.5m 2 Any value within the range / g.

[0088] Having introduced the composition and structure of the positive electrode active material, the preparation method of the positive electrode active material will be described in detail below.

[0089] Please see Figure 1 , Figure 1 This is a flowchart illustrating the method provided in some embodiments of this application. Embodiments of this application provide a method for preparing a positive electrode active material, the method comprising: S110. The lithium-rich manganese-based active material precursor and the lithium source are subjected to a first calcination to obtain an intermediate.

[0090] S120. The intermediate, the first Se source and the first S source are subjected to a second calcination to obtain the positive electrode active material.

[0091] This method prepares the positive electrode active material by first calcining a lithium-rich manganese-based active material precursor and a lithium source, and then calcining the intermediate, a first Se source, and a first S source together in a second calcination. This results in a core composed of a lithium-rich manganese-based active material and a shell composed of Li₂SO₄, Li₂SeO₄, and Li₂Se. x S 1-x At least two of the O4 components are core-shell structured positive electrode active materials, which utilize Li2SO4, Li2SeO4, and Li2Se. x S 1-x O4 and other compounds possess high ionic conductivity, which effectively promotes lithium-ion transport at the interface of lithium-rich manganese-based active materials, resulting in a high ion diffusion coefficient for the cathode active material. Simultaneously, the shell layer prevents direct contact between the lithium-rich manganese-based active material and the electrolyte, effectively improving the interfacial stability of the cathode active material. Furthermore, the formed Li2SO4 and Li2SeO4 act as fluxes, contributing to the good porosity of the lithium-rich manganese-based active material.

[0092] In some embodiments, the precursor of the lithium-rich manganese-based active material includes a nickel source, a cobalt source, or a manganese source. The lithium source refers to a substance containing lithium, the first Se source refers to a substance containing selenium, and the first S source refers to a substance containing sulfur, wherein the valence state of S in the substance is ≥0, for example, it can be a substance with a valence state of 0 or higher, or a substance containing sulfate / persulfate / sulfite. Using a sulfur source with a valence state of 0 or higher can achieve coating more gently, reducing the possibility of damage to the surface structure of the core lithium-rich manganese-based active material. At the same time, the sulfur source with a valence state of 0 or higher reacts to generate Li2SO4 and / or Li2Se. x S 1-x O4 has a shorter reaction pathway, making it easier to react completely and reducing the possibility of phase separation, which is beneficial to Li2SO4 and / or Li2Se. x S 1-x The formation of O4. In contrast, sulfur sources in a negative oxidation state are less likely to react to form Li2SO4 and / or Li2Se.x S 1-x O4 cannot effectively achieve the formation of Li2SO4 and / or Li2Se on the surface of the cathode material. x S 1- x O4 coating.

[0093] In some embodiments, the lithium-rich manganese-based active material precursor includes at least one of a nickel source, a cobalt source, or a manganese source. A nickel source refers to a substance containing nickel, a cobalt source refers to a substance containing cobalt, and a manganese source refers to a substance containing manganese. Preferably, the nickel source, cobalt source, and manganese source are the same substance, i.e., one substance simultaneously contains nickel, cobalt, and manganese. In some embodiments, the lithium-rich manganese-based active material precursor includes at least one of nickel-cobalt-manganese hydroxide, nickel-cobalt-manganese carbonate, or nickel-cobalt-manganese oxide.

[0094] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium sulfate, lithium sulfite, lithium nitrate, lithium nitrite, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium sulfide, lithium perchlorate, lithium manganese oxide, lithium peroxide, lithium superoxide, or lithium acetate.

[0095] In some embodiments, the first Se source includes at least one of selenium powder, selenium dioxide, lithium selenate, sodium selenate, sodium perselenate, sodium selenite, ammonium selenate, or selenourea.

[0096] In some embodiments, the first S source includes at least one of sulfur powder, lithium sulfate, sodium sulfate, sodium persulfate, sodium sulfite, ammonium sulfate, ammonium persulfate, sodium thiosulfate, or thiourea.

[0097] In some embodiments, the first calcination includes mixing the dopant source, the lithium-rich manganese-based active material precursor, and the lithium source. That is, during the preparation of the intermediate, the dopant source can be added and sintered together to allow the dopant element to be incorporated into the positive electrode active material. For example, selenium doping can be performed during the first calcination. Cationic selenium doping can suppress the generation of oxygen vacancies in the lithium-rich manganese-based active material, which is beneficial to the structural stability, electrochemical performance, and safety of the lithium-rich manganese-based active material. It can also improve the electronic conductivity of the lithium-rich manganese-based active material. Additionally, the selenium portion produces selenium dioxide gas volatilization, which is beneficial for achieving uniform porosity. Optionally, the dopant source includes at least one of a second Se source or a second S source. The second Se source refers to a substance containing selenium, and the second S source refers to a substance containing sulfur, wherein the valence state of S in the substance is ≥0, for example, it can be a 0 valence state or a substance containing sulfate / persulfate / sulfite. Further, the second Se source includes at least one of selenium powder, selenium dioxide, lithium selenate, sodium selenate, sodium perselenate, sodium selenite, ammonium selenate, or selenourea. The second S source includes at least one of sulfur powder, lithium sulfate, sodium sulfate, sodium persulfate, sodium sulfite, ammonium sulfate, ammonium persulfate, sodium thiosulfate, or thiourea.

[0098] In some embodiments, the atmosphere for the first calcination is an oxygen-containing atmosphere. An oxygen-containing atmosphere refers to an atmosphere containing oxygen or an oxidizing gas.

[0099] In some embodiments, the first calcination includes a first-stage calcination and a second-stage calcination.

[0100] Optionally, the holding temperature for the first stage of calcination is 300℃~600℃. For example, the holding temperature for the first stage of calcination can be 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, etc., or any value within the range of 300℃~600℃.

[0101] Optionally, the holding time for one calcination stage is 3h to 6h. For example, the holding time for one calcination stage can be 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, 4.2h, 4.4h, 4.6h, 4.8h, 5h, 5.2h, 5.4h, 5.6h, 5.8h, 6h, etc., or any value within the range of 3h to 6h.

[0102] Optionally, the heating rate of a single calcination stage is 1℃ / min to 10℃ / min. For example, the heating rate of a single calcination stage can be 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min, 7℃ / min, 7.5℃ / min, 8℃ / min, 8.5℃ / min, 9℃ / min, 9.5℃ / min, 10℃ / min, etc., or any value within the range of 1℃ / min to 10℃ / min.

[0103] Optionally, the holding temperature for the second-stage calcination is 800℃~900℃. For example, the holding temperature for the second-stage calcination can be 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, etc., or any value within the range of 800℃~900℃.

[0104] Optionally, the holding time for the second-stage calcination is 10h to 24h. For example, the holding time for the second-stage calcination can be 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h, 16h, 16.5h, 17h, 17.5h, 18h, 18.5h, 19h, 19.5h, 20h, 20.5h, 21h, 21.5h, 22h, 22.5h, 23h, 23.5h, 24h, etc., or any value within the range of 10h to 24h.

[0105] Optionally, the heating rate of the two-stage calcination is 1℃ / min to 10℃ / min. For example, the heating rate of the two-stage calcination can be 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min, 7℃ / min, 7.5℃ / min, 8℃ / min, 8.5℃ / min, 9℃ / min, 9.5℃ / min, 10℃ / min, etc., or it can be any value within the range of 1℃ / min to 10℃ / min.

[0106] In some embodiments, the holding temperature for the second calcination is 500℃ to 700℃. For example, the holding temperature for the second calcination is 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, etc., or any value within the range of 500℃ to 700℃.

[0107] In some embodiments, the holding time for the second calcination is 8h to 15h. For example, the holding time for the second calcination can be 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, etc., or any value within the range of 8h to 15h.

[0108] This application also provides a battery, which includes a positive electrode sheet, a positive electrode active material layer, and a positive electrode active material layer, which includes a positive electrode active material. The positive electrode active material includes the positive electrode active material provided above or a positive electrode active material prepared by the method provided above.

[0109] In some embodiments, the battery is a solid-state battery. A solid-state battery refers to a battery in which the electrolyte is a solid electrolyte membrane. Examples include sulfide solid-state batteries and halide solid-state batteries. This positive electrode active material has a high ion diffusion coefficient, making it particularly suitable for solid-state batteries. The positive electrode active material layer of the solid-state battery's positive electrode includes a positive electrode active material, a solid electrolyte, a conductive agent, and a binder. The negative electrode of the solid-state battery includes lithium metal alloys, lithium metal, graphite, and Si. C composite anode and at least one of indium metal, etc.

[0110] The following examples will describe one or more embodiments in more detail. Of course, these examples do not limit the scope of the one or more embodiments.

[0111] Example 1 A positive electrode active material, the preparation process of which is as follows: A Dv50 of 3.0 μm and a specific surface area of ​​14.4 m² were selected. 2 / g of hydroxide precursor Ni 0.167 Co 0.167 Mn 0.666 (OH)2, the hydroxide precursor Ni 0.167 Co 0.167 Mn 0.666 (OH)₂ and lithium carbonate were mixed uniformly, with a molar ratio of Li / (Ni+Co+Mn) = 1.5. Then, 500 ppm of SeO₂ was added and thoroughly mixed to obtain a mixture. The mixture was placed in an atmosphere-controlled furnace for a first calcination, which included a first-stage calcination and a second-stage calcination. The first calcination process was as follows: First-stage calcination: the temperature was increased from room temperature to 500℃ at a rate of 2℃ / min and held for 4 hours. Second-stage calcination: the temperature was increased to 870℃ at the same rate and held for 12 hours to obtain an intermediate. Then, 900 ppm of SeO₂ and 8000 ppm of Li₂SO₄·H₂O were added and thoroughly mixed for a second calcination. The second calcination was held at 600℃ for 12 hours. The mixture was then naturally cooled to room temperature in the furnace to obtain the positive electrode active material. The Se / S molar ratio was 0.2.

[0112] The positive electrode active material prepared in this example is: Li[Li 0.2 Ni 0.133 Co 0.133 Mn 0.534 O 1.994 (SeO4) 0.001 (SO4) 0.005 .

[0113] Example 2 The difference from Example 1 is that 1600 ppm of SeO2 was added during the second calcination. The Se / S molar ratio was 0.3, and all other aspects were the same as in Example 1.

[0114] Example 3 The difference from Example 1 is that 2300 ppm of SeO2 was added during the second calcination. The Se / S molar ratio was 0.4, and all other aspects were the same as in Example 1.

[0115] Example 4 The difference from Example 1 is that 3700 ppm of SeO2 and 1.20% of Li2SO4·H2O were added during the second calcination. The Se / S molar ratio was 0.4, and all other aspects were the same as in Example 1.

[0116] Example 5 The difference from Example 1 is that 2600 ppm of SeO2 and 1.20% of Li2SO4·H2O were added during the second calcination. The Se / S molar ratio was 0.3, and all other aspects were the same as in Example 1.

[0117] Example 6 The difference from Example 1 is that 1600 ppm of SeO2 was added during the second calcination, and the second calcination temperature was 800°C. The Se / S molar ratio was 0.3, and all other aspects were the same as in Example 1.

[0118] Example 7 The difference from Example 1 is that 1600 ppm of SeO2 was added during the second calcination, and the second calcination temperature was 900°C. The Se / S molar ratio was 0.3, and all other aspects were the same as in Example 1.

[0119] Example 8 The difference from Example 1 is that 900 ppm of SeO2 and 16000 ppm of Li2SO4·H2O were added during the second calcination. The Se / S molar ratio was 0.1, and all other aspects were the same as in Example 1.

[0120] Example 9 Example 9 differs from Example 1 in that 4700 ppm of SeO2 and 1.20% of Li2SO4·H2O were added during the second calcination. The Se / S molar ratio was 0.5, and all other aspects were the same as in Example 1.

[0121] Example 10 Example 10 differs from Example 1 in that 1600 ppm of SeO2 was added during the second calcination. The Se / S molar ratio was 0.3, and sulfur powder with a mass fraction of 2000 ppm was used as the S source. All other aspects were the same as in Example 1.

[0122] Example 11 Example 11 differs from Example 1 in that 3700 ppm of SeO2 and 1.60% of Li2SO4·H2O were added during the second calcination. The Se / S molar ratio was 0.3, and all other aspects were the same as in Example 1.

[0123] Example 12 Example 12 differs from Example 1 in that 1600 ppm of SeO2 was added during the second calcination, and the calcination holding temperature was 1000°C. The Se / S molar ratio was 0.3, and all other aspects were the same as in Example 1.

[0124] Example 13 Example 13 differs from Example 1 in that a Dv50 of 1.0 μm and a specific surface area of ​​22.9 m² are selected. 2 / g of hydroxide precursor Ni 0.167 Co 0.167 Mn 0.666 (OH)2, and the rest of the contents are the same as in Example 1.

[0125] Example 14 Example 14 differs from Example 1 in that a Dv50 of 7.0 μm and a specific surface area of ​​10.4 m² are selected. 2 / g hydroxide precursor, all other contents are the same as in Example 1.

[0126] Example 15 The difference between Example 15 and Example 1 is that the mixture contains a W source, while the rest is the same as in Example 1.

[0127] The preparation process of the mixture is as follows: A Dv50 of 3.0 μm and a specific surface area of ​​14.4 m² were selected. 2 / g of hydroxide precursor Ni 0.167 Co 0.167 Mn 0.666 (OH)2, the hydroxide precursor Ni 0.167 Co 0.167 Mn 0.666 (OH)2 and lithium carbonate are mixed evenly, and then 500 ppm of SeO2 and 1260 ppm of tungsten oxide are added and mixed thoroughly to obtain a mixture with a molar ratio of Li / (Ni+Co+Mn+W)=1.5.

[0128] The positive electrode active material prepared in this example is: Li[Li 0.2 (Ni 0.133 Co 0.133 Mn 0.534 ) 1.9995 W 0.0005 O 1.994 (SeO4) 0.001 (SO4) 0.005 .

[0129] Example 16 The difference between Example 16 and Example 1 is that the mixture contains an F source, while the rest is the same as in Example 1.

[0130] The preparation process of the mixture is as follows: A Dv50 of 3.0 μm and a specific surface area of ​​14.4 m² were selected. 2 / g of hydroxide precursor Ni 0.167 Co 0.167 Mn 0.666 (OH)2, the hydroxide precursor Ni 0.167 Co 0.167 Mn 0.666 (OH)2 and lithium carbonate are mixed evenly, with a molar ratio of Li / (Ni+Co+Mn)=1.5. Then, 500 ppm of SeO2 and 3280 ppm of magnesium fluoride are added and mixed thoroughly to obtain a mixture.

[0131] The positive electrode active material prepared in this example is: Li[Li 0.2 Ni 0.133 Co 0.133 Mn 0.534 O 1.990 (SeO4) 0.001 (SO4) 0.005 F 0.004 .

[0132] Comparative Example 1 The difference from Example 1 is that SeO2 was not added in the first calcination, and neither SeO2 nor Li2SO4·H2O was added in the second calcination. All other contents are the same as in Example 1.

[0133] Comparative Example 2 The difference from Example 1 is that no SeO2 was added in the first and second calcinations. The Se / S molar ratio was 0, and all other aspects were the same as in Example 1.

[0134] Comparative Example 3 The difference from Example 1 is that 1600 ppm of SeO2 was added in the second calcination, and Li2SO4·H2O was not added. All other contents are the same as in Example 1.

[0135] Comparative Example 4 The difference from Example 1 is that no SeO2 was added in the first calcination and no SeO2 was added in the second calcination. Instead, 1.4% Li2SO4·H2O was added, and the molar ratio of Se / S was 0. All other contents were the same as in Example 1.

[0136] Comparative Example 5 The difference from Example 1 is that Li2SO4·H2O was not added in the second calcination, but SeO2 with a mass fraction of 4400ppm was added. All other contents are the same as in Example 1.

[0137] Comparative Example 6 A positive electrode active material, the preparation process of which is as follows: A Dv50 of 3.0 μm and a specific surface area of ​​14.4 m² were selected. 2 / g of hydroxide precursor Ni 0.167 Co 0.167 Mn 0.666 (OH)2, the hydroxide precursor Ni 0.167 Co 0.167 Mn 0.666 (OH)₂ and lithium carbonate were mixed uniformly, with a molar ratio of Li / (Ni+Co+Mn) = 1.5. Then, 2100 ppm of SeO₂ and 5437 ppm of manganese sulfide were added and thoroughly mixed to obtain a mixture. The mixture was placed in an atmosphere-controlled box furnace for a first calcination, which included a first-stage calcination and a second-stage calcination. The first calcination process was as follows: first-stage calcination: the temperature was increased from room temperature to 500℃ at a rate of 2℃ / min and held for 4 hours; then second-stage calcination: the temperature was increased to 870℃ at the same rate and held for 12 hours to obtain an intermediate. This intermediate was then subjected to a second calcination, with a holding temperature of 600℃ and a holding time of 12 hours. The furnace was then naturally cooled to room temperature to obtain the positive electrode active material. The Se / S molar ratio was 0.3.

[0138] The main parameter controls for each embodiment and comparative example are shown in the table below:

[0139] In the table, " / " indicates that the value does not exist.

[0140] The positive electrode active materials provided in each embodiment and comparative example were tested, including: Ion diffusion coefficient test: GITT test using constant current intermittent titration. A coin cell was fabricated, and GITT testing was performed on a Blue Battery testing system. The test started at 100% charge after a spark discharge. 0.1C for 300s was selected as the excitation parameter, and the relaxation time was set to at least 4 hours. Voltage-time curves were obtained. The ion diffusion coefficient was calculated using a formula.

[0141] Shell composition analysis: Valence state information of the cathode active material surface was obtained through XPS testing. After sample preparation, full-spectrum and fine elemental spectra were analyzed. Analysis of fine spectra such as S 2p and Se 3p allows for qualitative analysis of the existence forms of S and Se elements.

[0142] Element mass fraction and molar ratio test: The mass fraction of Se, S and other dopants in the cathode active material is obtained by ICP test, and the molar ratio of Se and S in the cathode active material is calculated accordingly.

[0143] Dv50 test: A Mastersizer3000 laser particle size analyzer was used to obtain a cumulative particle size distribution map. The Dv50 of the positive electrode active material can be obtained from the peaks in the cumulative particle size distribution map.

[0144] Specific surface area test: 5g of the positive electrode active material powder to be tested was placed in a sample tube and heated to degas. After degassing, it was weighed and placed on the testing instrument. At a constant temperature and low temperature (-296.7℃), the amount of gas adsorbed on the solid surface at different relative pressures was measured. Based on the Brown-Etter-Taylor (BET) multilayer adsorption theory and its formula, the monolayer adsorption amount of the sample was calculated, thereby calculating the specific surface area of ​​the positive electrode material.

[0145] The test results are shown in the table below:

[0146] As can be seen from the table above, the positive electrode active material prepared by the method provided in the embodiments of this application has a high ion diffusion coefficient.

[0147] The positive electrode active materials prepared in each embodiment and comparative example were used to prepare batteries. The preparation process is as follows: Preparation of the positive electrode sheet The positive electrode material NCM, solid electrolyte, and conductive agent (VGCF) were weighed into a mortar at a mass ratio of 85:15:1 and manually mixed for at least 30 minutes to obtain a mixture. Then, 1% (by mass) of polytetrafluoroethylene (PTFE) particles were added. The mixture was heated at 150°C for 5 minutes on a heating table and then manually ground to form a film, pre-fiberizing the PTFE. The resulting film was then heated and rolled on a calender at 150°C. The film thickness was adjusted by controlling the gap width between the two hot rollers. Repeated rolling was performed to obtain a composite positive electrode material film with a thickness of 40 mm. The composite cathode material film was rolled to a thickness of 60 μm onto the surface of a 15 μm thick Al foil current collector to obtain a cathode sheet.

[0148] Preparation of the negative electrode sheet LiIn foil is used as the negative electrode.

[0149] Preparation of electrolytes Li6PS5Cl sulfide solid electrolyte was used to prepare a solid electrolyte membrane.

[0150] [Battery Manufacturing] The positive electrode is die-cut into a circular sheet with a diameter of 8mm. Then, it is stacked with a Li6PS5Cl sulfide solid electrolyte membrane and a LiIn foil in a glove box filled with Ar atmosphere and cold-pressed to obtain an all-solid-state battery.

[0151] The batteries using the positive electrode active materials provided in each embodiment and comparative example were tested, including: First-time coulombic efficiency, first-cycle charge specific capacity, first-cycle discharge specific capacity, rate performance, and capacity retention: all-solid-state batteries at 25 At 30℃, the battery was charged at a constant current rate of 0.1C until the voltage reached 4.2V (vs. Li+ / LiIn). The specific capacity at this point was recorded as the first-cycle charging specific capacity. After resting for 5 minutes, the battery was discharged at a constant current rate of 0.1C until the voltage reached 1.4V (vs. Li+ / LiIn). The specific capacity at this discharge point was recorded as the battery's first-cycle discharge specific capacity. The battery's initial coulombic efficiency (%) = first-cycle discharge specific capacity / first-cycle charging specific capacity × 100%. Afterward, the battery was charged at a constant current rate of 0.33C until the voltage reached 4.2V (vs. Li+ / LiIn). The specific capacity at this point is recorded as the 0.33C charging specific capacity. After resting for 5 minutes, it is discharged at a constant current rate of 0.33C until the voltage reaches 1.4V (vs. Li+ / LiIn). The specific capacity at this point is recorded as the 0.33C first-cycle discharge specific capacity. Then, the rate performance = 0.33C first-cycle discharge specific capacity / first-cycle discharge specific capacity × 100%. The discharge specific capacity is recorded on the 50th cycle after 50 cycles at 0.33C. The capacity retention rate = 50th-cycle discharge specific capacity / 0.33C first-cycle discharge specific capacity × 100%.

[0152] The results are shown in the table below:

[0153] As shown in the table above, the positive electrode active material prepared using the method provided in this application, due to the coating with Se and S, exhibits significantly improved first-cycle charge specific capacity, first-cycle discharge specific capacity, first-cycle coulombic efficiency, and capacity retention compared to the comparative example. This is presumably because coating with Li₂SO₄ and Li₂SeO₄, which have high ionic conductivity, effectively increases the overall ionic conductivity of the material, resulting in a higher ion diffusion coefficient and thus constructing a rapid ion transport network. Simultaneously, the uniform coating of Li₂SO₄ and Li₂SeO₄ on the surface inhibits direct contact between the lithium-rich manganese-based positive electrode material and the solid electrolyte, thereby effectively improving interface stability. The excellent ion transport and interfacial chemical compatibility enable this material to exhibit good specific capacity, first-cycle efficiency, and capacity retention in all-solid-state batteries.

[0154] Comparison of data from Examples 1-5, 8-9, 11, and Comparative Examples 2-5 shows that when the Se concentration is 1000-3000 ppm, the S concentration is 1000-3000 ppm, and the Se / S molar ratio is 0.2-0.4, good specific capacity, initial efficiency, and capacity retention can be achieved. When Se is absent or the Se / S molar ratio is too high, the lithium-ion diffusion coefficient of the lithium-rich manganese-based cathode material is low, which is detrimental to performance. It is speculated that this may be due to the inability to form Li₂Se with high ionic conductivity. x S 1- xO4 solid solution is the cause. When the concentrations of Se and S are too high, the volatilization of Se and S promotes the volatilization of Li salt, resulting in a lower lithium content and weakened performance of lithium-rich manganese-based cathode materials.

[0155] A comparison of the data from Examples 2, 6, 7, and 12 reveals that when the calcination temperature is too high, the discharge specific capacity, initial efficiency, and capacity retention decrease. It is speculated that the high calcination temperature accelerates the volatilization of SeO2 and SO2, resulting in greater Li salt volatilization and a reduction in lithium equivalence.

[0156] A comparison of the data from Example 1 and Comparative Example 6 shows that the sintering of sulfur and selenium sources with the precursor, as well as the different valence states of sulfur in the sulfur source, will affect the composition of the final product. If manganese sulfide with a negative valence state is used as the sulfur source and mixed with the selenium source and precursor for sintering, it is difficult to form a product containing Li2SO4 and Li2Se. x S 1-x O4 coating layer.

[0157] A comparison of the data from Examples 1 and 13 to 14 shows that controlling the particle size and specific surface area of ​​the positive electrode active material within a specific range can result in good performance.

[0158] A comparison of the data from Examples 1 and 15 to 16 shows that doping other elements into the positive electrode active material can result in better performance, especially doping with F, which can significantly improve the electrical performance of the positive electrode active material.

[0159] Figure 3 and Figure 4 Detailed explanation: Figure 3 The XRD diffraction patterns of the positive electrode active materials provided in Examples 2, 3, and Comparative Example 1 of this application are shown in the figures. As can be seen from the figures, there are no significant differences in the XRD patterns among the three, indicating that elements such as Se and S did not significantly affect the crystal structure of the lithium-rich manganese-based active material in the core. The improved electrical performance in Examples 2 and 3 mainly comes from the modification of the coating layer (i.e., the shell).

[0160] Figure 4 The XPS spectrum of the positive electrode active material provided in Example 2 of this application shows that the positive electrode active material contains SeO4. 2- SO4 2- / Se x S 1-x O4 2- At least two of them.

[0161] Figure 6 The image shows the EDS diagram of the positive electrode active material provided in Embodiment 2 of this application. As can be seen from the image, the positive electrode active material is doped with Se.

[0162] The above are merely specific embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material has a core-shell structure, wherein the core of the core-shell structure comprises a lithium-rich manganese-based active material, and the shell layer comprises Li₂SO₄, Li₂SeO₄, and Li₂Se. x S 1-x At least two of O4, where 0 < x < 1.

2. The positive electrode active material according to claim 1, characterized in that, The lithium-rich manganese-based active material is doped with at least one of the elements Se or S.

3. The positive electrode active material according to claim 1 or 2, characterized in that, The molar ratio of Se to S in the positive electrode active material is 0.2 to 0.

4.

4. The positive electrode active material according to any one of claims 1 to 3, characterized in that, In the positive electrode active material, the mass percentage of Se element is 1000ppm~3000ppm; and / or In the positive electrode active material, the mass percentage of sulfur element is 1000ppm~4000ppm.

5. The positive electrode active material according to any one of claims 1 to 4, characterized in that, The positive electrode active material includes Li[Li] a Ni x Co y Mn z M b O 2-e-f D e E f Where a+x+y+z+b=1, 0.1≤a≤0.25, 0.12≤x≤0.4, 0≤y≤0.15, 0.5≤z≤0.75, 0≤b≤0.1, 0<e≤0.1, 0≤f≤0.05, M is a metallic element, which includes at least one of Fe, Cr, Mo, W, Ta, Ti, Nb, Sb, Hf, Ce, Zr, Sn, V, Ca, La, Al, Mg, K or Na, and D includes SO4. 2- and SeO4 2- E includes at least one of F, P or Cl.

6. The positive electrode active material according to any one of claims 1 to 5, characterized in that, The positive electrode active material is a secondary particle formed by the agglomeration of primary particles, and the Dv50 of the positive electrode active material is 1μm~7μm; and / or The specific surface area of ​​the positive electrode active material is 0.5 m². 2 / g~3.5m 2 / g.

7. A method for preparing a positive electrode active material according to any one of claims 1 to 6, characterized in that, The method includes: The lithium-rich manganese-based active material precursor and lithium source are subjected to a first calcination to obtain an intermediate. The intermediate, the first Se source, and the first S source are subjected to a second calcination to obtain the positive electrode active material.

8. The method for preparing the positive electrode active material according to claim 7, characterized in that, The first Se source includes at least one of selenium powder, selenium dioxide, lithium selenate, sodium selenate, sodium perselenate, sodium selenite, ammonium selenate, or selenourea; and / or The first S source includes at least one of sulfur powder, lithium sulfate, sodium sulfate, sodium persulfate, sodium sulfite, ammonium sulfate, ammonium persulfate, sodium thiosulfate, or thiourea.

9. The method for preparing the positive electrode active material according to claim 7 or 8, characterized in that, The first calcination process includes: mixing a dopant source, a lithium-rich manganese-based active material precursor, and a lithium source; optionally, the dopant source includes at least one of a second Se source or a second S source; optionally, the second Se source includes at least one of selenium powder, selenium dioxide, lithium selenate, sodium selenate, sodium perselenate, sodium selenite, ammonium selenate, or selenourea; and the second S source includes at least one of sulfur powder, lithium sulfate, sodium sulfate, sodium persulfate, sodium sulfite, ammonium sulfate, ammonium persulfate, sodium thiosulfate, or thiourea; and / or The atmosphere for the first calcination is an oxygen-containing atmosphere; and / or The first calcination includes a first-stage calcination and a second-stage calcination. The holding temperature of the first-stage calcination is 300℃~600℃, the holding time is 3h~6h, and the heating rate is 1℃ / min~10℃ / min. The holding temperature of the second-stage calcination is 800℃~900℃, the holding time is 10h~24h, and the heating rate is 1℃ / min~10℃ / min; and / or The second calcination holding temperature is 500℃~700℃, and the second calcination holding time is 8h~15h.

10. A battery, characterized in that, The battery includes a positive electrode sheet, the positive electrode sheet includes a positive active material layer, the positive active material layer includes a positive active material, and the positive active material includes the positive active material prepared by any one of claims 1 to 6 or the positive active material prepared by any one of claims 7 to 9.

11. The battery according to claim 10, characterized in that, The battery is a solid-state battery.

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