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

Abstract

This invention provides a positive electrode active material, its preparation method, a positive electrode sheet, and a battery. The positive electrode active material includes an active material and a fast ion conductor material layer disposed on at least a portion of the surface of the active material. The chemical composition of the fast ion conductor material layer includes: xLi₂O·ySiO₂·mM·nR, wherein M and R independently include at least one selected from WO₃, Nb₂O₅, Ta₂O₅, Al₂O₃, Ga₂O₃, MgO, AlF₃, P₂O₅, and TiO₂, x+y+m+n=1, x>0, y>0, m>0, and n>0. The fast ion conductor material layer comprises an amorphous fast ion conductor material. By introducing a fast ion conductor material and utilizing it to construct a conductive network on the surface of the active material, this positive electrode active material can significantly improve the rate performance of high-compact positive electrode active materials.

Description

Technical Field

[0001] This invention relates to the field of battery materials, and more particularly to a positive electrode active material and its preparation method, a positive electrode sheet, and a battery. Background Technology

[0002] With the increasing demands for battery energy density and cycle life from new energy vehicles, energy storage systems, and consumer electronics, lithium iron phosphate (LiFePO4) cathode materials have become a core material in the power battery field due to their high safety, long cycle stability, and low cost. However, as the compaction density increases, the lithium-ion diffusion rate inside the material decreases significantly, leading to a decline in battery rate performance and an increase in internal resistance, which severely restricts its application in high-power scenarios.

[0003] To improve interfacial ion transport in lithium iron phosphate (LFP) cathode materials, current technologies mainly employ surface coating or doping modification strategies. Common coating materials include metal oxides and phosphates. These coating materials can suppress side reactions in the cathode material and improve its cycle stability to some extent, but their effect on improving the rate performance of high-pump cathode materials is limited. Therefore, how to improve the lithium-ion diffusion capability of cathode materials while maintaining high pump density is a key technological bottleneck in current cathode material development. Summary of the Invention

[0004] This invention provides a positive electrode active material, which incorporates a fast ion conductor material with a certain composition and an amorphous structure. The fast ion conductor material is used to construct a conductive network on the surface of the active material, thereby simultaneously increasing its electronic conductivity and ion conductivity, which can significantly improve the rate performance of the high-pressure positive electrode active material.

[0005] The present invention also provides a method for preparing the above-mentioned positive electrode active material, which can prepare the above-mentioned positive electrode active material and has a simple process.

[0006] The present invention also provides a positive electrode sheet, which, since includes the above-mentioned positive electrode active material, is used in a battery to help improve the battery's charge and discharge stability at high rates.

[0007] The present invention also provides a battery that, because it includes the above-mentioned positive electrode, has excellent rate performance.

[0008] In a first aspect, the present invention provides a positive electrode active material, comprising: an active substance and a fast ion conductor material layer disposed on at least a portion of the surface of the active substance; the chemical composition of the fast ion conductor material layer comprises: xLi2O·ySiO2·mM·nR, wherein M and R independently comprise at least one of WO3, Nb2O5, Ta2O5, Al2O3, Ga2O3, MgO, AlF3, P2O5, and TiO2, x+y+m+n=1, x+y+m+n=1, x>0, y>0, m>0, n>0, and the fast ion conductor material layer comprises a fast ion conductor material with an amorphous structure.

[0009] In an alternative implementation, 0.5 <x<0.6,0.20<y<0.30,0.10<m+n<0.30。

[0010] In an optional embodiment, M includes at least one of WO3, Nb2O5, Ta2O5, and TiO2, and R includes at least one of MgO, AlF3, Al2O3, and Ga2O3.

[0011] In an alternative embodiment, the thickness of the fast ion conductor material layer is 0.5 nm to 3 nm.

[0012] In an optional embodiment, the fast ion conductor material layer further includes nanoparticles of the fast ion conductor material;

[0013] More preferably, the average particle size of the nanoparticles of the fast ion conductor material is 0.5 nm to 3 nm.

[0014] In an optional embodiment, the positive electrode active material further includes a carbon layer disposed on at least a portion of the surface of the active material; the fast ion conductor material layer is disposed on at least a portion of the surface of the carbon layer.

[0015] In one alternative embodiment, the thickness of the carbon layer is 2nm-5nm.

[0016] In an optional embodiment, the active material includes at least one of lithium iron phosphate material, lithium manganese iron phosphate, and nickel-cobalt-manganese ternary oxide cathode material;

[0017] And / or, the compaction density of the positive electrode active material is greater than or equal to 2.6 g / cm³. 3 ;

[0018] And / or, the Dv50 of the positive electrode active material is 0.5μm-2μm.

[0019] And / or, the specific surface area of ​​the positive electrode active material is 5m². 2 / g-15m 2 / g.

[0020] Secondly, the present invention provides a method for preparing the above-mentioned positive electrode active material, comprising the following steps:

[0021] A gel-like mixture containing silicon source, M source, lithium source, R source and chelating agent is subjected to a heat preservation treatment at 350℃-400℃ to obtain a fast ion conductor material precursor.

[0022] The mixture comprising the fast ion conductor material precursor and the active material is subjected to a second heat treatment at 400℃-700℃, and then cooled to 100℃-300℃ at a cooling rate of 20℃ / min-50℃ / min, and subjected to a third heat treatment to obtain the positive electrode active material.

[0023] In one optional embodiment, the duration of the first heat preservation treatment is 2h-6h; the duration of the second heat preservation treatment is 30min-180min; and / or, the duration of the third heat preservation treatment is 30min-150min.

[0024] Thirdly, the present invention provides a positive electrode sheet, comprising a current collector and a positive electrode active layer disposed on at least one side of the current collector; the positive electrode active layer comprises the positive electrode active material described in the first aspect.

[0025] Fourthly, the present invention provides a battery comprising the above-described positive electrode.

[0026] The positive electrode active material provided by the present invention can construct a three-dimensional ion transport network with high ionic conductivity, high electronic conductivity and stable structure on the surface of the active material by setting a multi-element modified amorphous fast ion conductor material layer on the surface of the active material, thereby significantly improving the rate performance of the positive electrode active material, especially the rate performance of the high-compact positive electrode active material. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] Figure 1 The images shown are TEM and EDS images of the positive electrode active material in Example 1 of the present invention; where a is the TEM image of the positive electrode active material and b is the EDS image of the positive electrode active material.

[0029] Figure 2 This is an HRTEM image of the positive electrode active material of Example 1 of the present invention;

[0030] Figure 3 This is a TEM image of the positive electrode active material of Comparative Example 1 of the present invention;

[0031] Figure 4 This is an HRTEM image of the positive electrode active material of Comparative Example 2 of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In this application, the terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0034] In this application, references to "an embodiment," "an example," or "an example" mean that a specific feature, structure, or characteristic described in connection with that embodiment, example, or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination.

[0035] Common coating materials include metal oxides (such as Al2O3, ZrO2), phosphates (such as Li3PO4), or fast ion conductors (such as LLZO, LATP). These coating materials have limited effect on improving rate performance, mainly because: (1) Imbalance between ionic conductivity and electronic conductivity: Most coating materials are ionic conductors but electronic insulators (or vice versa), forming a single transport channel on the surface of the active material, which cannot synergistically promote the rapid conduction of ions and electrons, thus limiting the electrochemical reaction kinetics at high rates. (2) Insufficient structural rigidity and interface stability: Traditional crystalline coating materials are prone to side reactions with the electrolyte or cracks due to lattice mismatch during long-term battery cycling, especially during high-voltage charging and discharging, leading to coating material failure and damage to the ion transport network. (3) Failure to construct an effective three-dimensional permeation network: The simple surface coating of crystalline coating materials usually forms a dense or isolated two-dimensional layered structure, which cannot form a continuous and efficient ion transport pathway inside the high-pressure electrode, and has little effect on improving the bulk ion transport of the electrode.

[0036] It is evident that the existing technologies described above are insufficient to construct a composite interface layer with both high ionic conductivity and high electronic conductivity, and with a stable structure, on the surface of high-pressure positive electrode active material. Consequently, they cannot fundamentally solve the bottleneck of ion transport dynamics in high-pressure positive electrodes.

[0037] Therefore, the present invention aims to construct a stable, three-dimensional interconnected ion-electron hybrid conductive network in situ on the surface of active materials, so as to significantly improve the rate performance and fast charging capability of the battery without sacrificing energy density, thereby overcoming the above-mentioned defects.

[0038] In detail, in a first aspect, the present invention provides a positive electrode active material, comprising: an active substance and a fast ion conductor material layer disposed on at least a portion of the surface of the active substance; the chemical composition of the fast ion conductor material layer comprises: xLi2O·ySiO2·mM·nR, wherein M and R independently comprise at least one of WO3, Nb2O5, Ta2O5, Al2O3, Ga2O3, MgO, AlF3, P2O5, and TiO2, x+y+m+n=1, x>0, y>0, m>0, n>0, and the fast ion conductor material layer comprises amorphous fast ion conductor material.

[0039] By disposing a fast ion conductor material layer with a multi-element modified amorphous structure on at least a part of the surface of the active material, a three-dimensional ion transport network with high ionic conductivity, high electronic conductivity and stable structure can be constructed on the surface of the active material, thereby significantly improving the rate performance of the high-compaction cathode active material. The main reasons include: SiO2, as a network former, combines with Li2O to form a lithium silicate glass matrix, providing a basic ion conduction framework; while the two functional oxides M and R introduced play key multiple roles. On the one hand, as network intermediates or modifiers, their different ionic radii, coordination requirements and bonding capabilities restrict each other, effectively disrupting the long-range order of the silicon-oxygen network, significantly promoting complete vitrification, and forming a highly disordered and isotropic amorphous structure. This structure eliminates grain boundaries and provides a continuous and energy-uniform three-dimensional diffusion channel for lithium ions. On the other hand, M and R themselves have certain electronic conductivity or can introduce electronic carriers through doping. Their uniform incorporation embeds an electron transport path in the ionic conduction network, thus realizing the unique "dual conductor" (mixed ion-electron conductor) property. This amorphous dual-conducting network can be uniformly and continuously disposed on at least a part of the surface of the cathode active particles (such as the surface and grain boundaries), constructing a three-dimensional fast transport grid throughout the electrode inside the high-compaction electrode. During the electrochemical process, this three-dimensional fast transport network first serves as a high-speed lithium ion exchange interface, greatly reducing the interfacial charge transfer impedance; more importantly, its high ionic conductivity ensures that lithium ions can quickly enter and exit the active material bulk through the coating layer, and its moderate electronic conductivity at the same time ensures the equilibrium of the surface potential of the active particles, avoiding local polarization.

[0040] By way of example and not limitation, the chemical composition of the fast ion conductor material can be tested by the following method:

[0041] Clean and prepare the cathode active material to be tested. Subsequently, send the sample into the ultra-high vacuum analysis chamber of XPS and detect it at the set excitation energy. First, scan the full spectrum to obtain the element composition, and then perform a high-resolution scan of the relevant elements' fine spectra; during the test, it is necessary to calibrate the binding energy using known elements, and finally analyze the position, intensity and shape of the spectral peaks to obtain the chemical state, relative content and chemical bond information of each element in the sample.

[0042] In some embodiments, x + y + m + n = 1, 0.5 < x < 0.6, 0.20 < y < 0.30, 0.10 < m + n < 0.30. By precisely controlling the molar ratios of SiO2, Li2O and the doping elements (M, R), the fast ion conductor material of this embodiment can further balance the ionic conductivity and electronic conductivity, ensuring that the material still has good electronic transport ability under high-compaction conditions.

[0043] In some embodiments, M includes at least one of WO3, Nb2O5, Ta2O5, and TiO2, and R includes at least one of MgO, AlF3, Al2O3, and Ga2O3.

[0044] In the above embodiments, WO3, Nb2O5, Ta2O5, and TiO2, as oxides containing high-valence elements, can further distort the structure of the fast ion conductor material, promote the formation of lithium ion vacancies, and thus construct more lithium ion transport channels. MgO, AlF3, Al2O3, and Ga2O3, as oxides or glass forgings containing low-valence elements, can further stabilize the glass network structure of the fast ion conductor material and prevent dopant elements from precipitating out as crystals during cycling.

[0045] In addition, AlF3 also promotes the formation of an interface layer (CEI) rich in LiF components on the surface of the positive electrode active material, further ensuring the high efficiency and stability of the ion transport network.

[0046] When fast ion conductor materials include a fast ion conductor material layer, the fast ion conductor material can form a complete coating layer on the surface of the active material, ensuring that lithium ions can diffuse rapidly and isotropically in the bulk phase at the interface, fundamentally reducing the interface impedance and providing a stable and consistent reaction interface for electrochemical reactions. Furthermore, the amorphous structure layer also has excellent mechanical toughness and electrochemical stability, which can effectively buffer cyclic stress and suppress side reactions, thereby ensuring the long-term integrity of the network backbone.

[0047] In an optional embodiment, the fast ion conductor material layer further includes nanoparticles of the fast ion conductor material.

[0048] When fast ion conductor materials include nanoparticles, they can be embedded or attached to the fast ion conductor material layer. On the one hand, this further increases the node density of ion transport, fills in possible microscopic covering defects, and makes the network more compact. On the other hand, some nanoparticles with mixed conductivity properties can also act as "conductive bridges" to enhance electron percolation within the network and achieve synergistic optimization of ion and electron transport.

[0049] In some implementations, the thickness of the fast ion conductor material layer is 0.5 nm to 3 nm.

[0050] The fast ion conductor material layer of the above thickness not only ensures a thermodynamically stable and defect-free continuous coverage on the surface of the active material, preventing direct contact between the electrolyte and the active material, but also further improves the ion conduction efficiency, shortening the physical diffusion path of lithium ions across the interface layer to its limit.

[0051] For example, the thickness of the fast ion conductor material layer is any value or a range of any combination of 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, etc.

[0052] In some embodiments, the average particle size of the fast ion conductor material nanoparticles is 0.5 nm to 3 nm.

[0053] The fast ion conductor nanoparticles with the above particle size can be precisely embedded and firmly anchored in the ultrathin fast ion conductor material layer or at the lattice defects on the surface of the active material, thereby achieving chemical bonding and structural fusion of "particle-coating layer-matrix" at the atomic scale. This not only eliminates the new impedance caused by poor interfacial contact of traditional nanoparticles, but also significantly improves the mechanical stability and interfacial bonding force of the overall coating layer through bonding.

[0054] For example, the average particle size of the nanoparticles in the fast ion conductor material layer is any value or a range of any combination of 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, etc.

[0055] In some embodiments, the positive electrode active material further includes a carbon layer disposed on at least a portion of the surface of the active material; a fast ion conductor material layer is disposed on at least a portion of the surface of the carbon layer.

[0056] The above implementation method employs a sandwich interface structure of "active material-carbon layer-fast ion conductor material," which constructs an advanced interface system with clearly defined functions and synergistic effects at the physical and electrochemical levels. The inner carbon layer directly coats the active material, firstly constructing a continuous high electronic conductivity network to ensure rapid charge accumulation and uniform distribution during electrochemical reactions. At the same time, its good toughness and chemical inertness effectively buffer the volume expansion of the active material during cycling, providing a stable substrate for the outer fast ion conductor material structure. On this basis, the outer fast ion conductor material can be uniformly and firmly attached, focusing on building efficient lithium-ion transport channels, thereby further improving the rate performance of the battery.

[0057] In some implementations, the thickness of the carbon layer is 2nm-5nm.

[0058] The carbon layer of this thickness can construct an efficient and uniform electronic conduction pathway, thereby eliminating the contact resistance between active material particles and realizing rapid charge transport and uniform distribution. At the same time, the carbon layer of this thickness has excellent mechanical flexibility and chemical stability, which can effectively buffer the volume change stress of the active material during the lithium insertion / extraction process.

[0059] For example, the thickness of the carbon layer is any value or a range of any two of the following: 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, etc.

[0060] In some embodiments, the active material includes at least one of lithium iron phosphate, lithium manganese iron phosphate, and nickel-cobalt-manganese ternary oxide cathode materials.

[0061] Lithium iron phosphate materials have advantages such as high safety, long cycle stability and low cost, and they contain the fast ion conductor material of the present invention. Therefore, they can enable the battery to achieve good rate performance under high pressure.

[0062] In some embodiments, the compaction density of the positive electrode active material is greater than or equal to 2.6 g / cm³. 3 .

[0063] The above-mentioned compacted positive electrode active material has close contact between active material particles, which gives the electrode a higher volumetric energy density, meeting the rigid requirements for battery capacity in limited spaces such as electric vehicles.

[0064] For example, the compaction density of the positive electrode active material is 2.6 g / cm³. 3 2.7 g / cm 3 2.8 g / cm 3 2.9 g / cm 3 3.0 g / cm 3 The range consisting of any value in, etc., or any combination of both.

[0065] In some implementations, the Dv50 of the positive electrode active material is 0.5 μm-2 μm.

[0066] The Dv50 of the positive electrode active material is 0.5μm-2μm, which enables the positive electrode active material to achieve dense and uniform particle packing, effectively reducing macroscopic pores and contact unevenness caused by irregular particle arrangement. This is beneficial to increasing the active sites in the lithium ion insertion and extraction process, and can provide an ideal microscopic geometric basis for constructing a continuous and efficient "electron-ion" three-dimensional hybrid conductive network that runs through the entire electrode.

[0067] For example, the Dv50 of the positive electrode active material is any value or a range of any combination of 0.5 μm, 0.7 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.7 μm, 2.0 μm, etc.

[0068] The Dv50 of the aforementioned positive electrode active material refers to the particle size value corresponding to 50% (by volume) of the cumulative amount in the particle size distribution curve. It can be regarded as the median particle size of the material and is generally obtained by laser diffraction particle size distribution instrument.

[0069] In some embodiments, the specific surface area of ​​the positive electrode active material is 5 m². 2 / g-15 m 2 / g.

[0070] The specific surface area of ​​the positive electrode active material is 5 m². 2 / g-15 m 2 Within the range of / g, under high compaction density (≥2.6g / cm³) 3 When the positive electrode active material is packed with more compact and uniform particles, it is more conducive to increasing the active sites in the lithium ion insertion and extraction process, providing a more ideal microscopic geometric basis for constructing a continuous and efficient three-dimensional hybrid conductive network of "electron-ion" throughout the entire electrode.

[0071] For example, the specific surface area of ​​the positive electrode active material is 5 m². 2 / g、6 m 2 / g、7 m 2 / g、8 m 2 / g、9 m 2 / g, 10m 2 / g、11 m 2 / g、12 m 2 / g、13 m 2 / g、14 m 2 / g、15 m 2 Any value in / g, or a range consisting of any two of them.

[0072] The above-mentioned positive electrode active materials can create a highly developed "surface-to-surface" contact network at the microscale between the positive electrode active material particles, effectively compensating for the electrolyte wetting path lost due to extremely low porosity. This allows the composite conductive layers constructed on the particle surface to be interconnected, forming a highly efficient three-dimensional composite conductive framework that runs through the entire electrode thickness. This further ensures the high rate capability of the battery.

[0073] Secondly, the present invention provides a method for preparing the above-mentioned positive electrode active material, comprising the following steps:

[0074] In an inert atmosphere, a gel-like mixture containing silicon source, M source, lithium source, R source and chelating agent is subjected to a heat treatment at 350℃-400℃ to obtain a fast ion conductor material precursor.

[0075] A mixture of fast ion conductor material precursor and active material is subjected to a second heat treatment at 400℃-700℃, and then cooled to 100℃-300℃ at a cooling rate of 20℃ / min-50℃ / min, followed by a third heat treatment to obtain the positive electrode active material.

[0076] The above preparation method first provides a gel-state mixture, which is then subjected to a heat treatment at 350℃-400℃ to obtain a fast ion conductor material precursor. At this time, the precursor is a metal-organic hybrid, and no or incomplete metal oxide has been formed. Subsequently, an active material is added, and a second heat treatment is performed at 400℃-700℃ to combine the fast ion conductor material precursor with the active material. The cooling rate is then controlled to be higher than the critical cooling rate of the fast ion conductor material, which can reduce the time of the fast ion conductor in the suitable crystallization temperature range and avoid the formation of a large number of crystal particles during the cooling process, thus ensuring the amorphous state of the fast ion conductor material. Finally, three heat treatments are performed to obtain an active material with a fast ion conductor material having high ionic conductivity, high electronic conductivity, and a stable structure. This can significantly improve the rate performance of the high-pressure positive electrode active material, mainly due to the positive electrode active material.

[0077] For example, the temperature for the first insulation treatment is any value or a range of any two of 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, etc. The temperature for the second insulation treatment is any value or a range of any two of 400℃, 500℃, 600℃, 700℃, etc. The temperature for the third insulation treatment is any value or a range of any two of 100℃, 150℃, 200℃, 250℃, 300℃, etc.

[0078] In some embodiments, the M source and R source each independently include two or more of ammonium metatungstate, niobium oxide, tantalum ethoxide, aluminum fluoride, gallium nitrate, magnesium nitrate, aluminum nitrate, ammonium fluoride, phosphoric acid, and tetrabutyl titanate; the chelating agent includes one or more of citric acid, ethylene glycol, and ethylenediaminetetraacetic acid (EDTA); the silicon source includes one or more of tetraethyl orthosilicate and tetramethoxysilane; and the lithium source includes one or more of lithium hydroxide, lithium nitrate, lithium oxide, lithium carbonate, and lithium chloride.

[0079] In some embodiments, the gel-state mixture further includes a template agent, which may include one or more of ammonium carbonate, ammonium bicarbonate, or urea. Introducing a template agent can introduce more porous structures into the fast-ion conductor material in the finished product, thereby further increasing the specific surface area of ​​the positive electrode active material and increasing lithium-ion transport channels.

[0080] In some embodiments, the gel mixture is prepared by the following process: mixing silicon source, M source, lithium source, R source, chelating agent and solvent, and drying in air at 60-90°C to obtain the gel mixture.

[0081] In some embodiments, a mixture comprising a fast ion conductor material precursor and an active substance is prepared by the following process: the fast ion conductor material precursor and the active substance are mixed in a solvent, a dispersant is added, the mixture is ball-milled in a ball mill, and then dried to obtain the mixture.

[0082] The dispersant includes, but is not limited to, water, alcohol, or ethylene glycol; the ball milling speed is 400 rpm-600 rpm, and the ball milling time is 2h-8h.

[0083] In some embodiments, at least a portion of the surface of the active material includes a carbon layer, and the active material including the carbon layer can be purchased directly or prepared according to existing processes.

[0084] In some embodiments, a heat treatment is performed at 350°C-400°C, preceded by a temperature rise from room temperature to 350°C-400°C at a rate of 2°C / min-5°C / min. Exemplarily, the temperature rise rate is any value or a range of any combination of 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4.0°C / min, 4.5°C / min, 5.0°C / min, etc.

[0085] In some embodiments, a secondary heat preservation treatment is performed at 400°C-700°C, preceded by a temperature rise from room temperature to 350°C-400°C at a rate of 2°C / min-5°C / min. Exemplarily, the temperature rise rate is any value or a range of any combination of 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4.0°C / min, 4.5°C / min, 5.0°C / min, etc.

[0086] In an optional embodiment, the first heat treatment lasts for 2-6 hours; the second heat treatment lasts for 30-180 minutes; and / or the third heat treatment lasts for 30-150 minutes. These heat treatment times ensure a more complete reaction and improve the yield of the target product.

[0087] For example, the duration of the first heat treatment is any value or a range of any two of the following: 2 h, 3 h, 4 h, 5 h, 6 h. The duration of the second heat treatment is any value or a range of any two of the following: 30 min, 50 min, 60 min, 70 min, 80 min, 100 min, 120 min, 140 min, 160 min, 180 min. The duration of the third heat treatment is any value or a range of any two of the following: 0 min, 50 min, 60 min, 70 min, 80 min, 100 min, 120 min, 140 min, 150 min.

[0088] In some embodiments, the lithium source includes, but is not limited to, lithium carbonate, lithium hydroxide, lithium nitrate, etc.

[0089] In some embodiments, the M-source precursor includes, but is not limited to, carbonates, hydroxides, etc. of M.

[0090] Thirdly, the present invention provides a positive electrode sheet, including a current collector and a positive electrode active layer disposed on at least one side of the current collector, the positive electrode active layer including the positive electrode active material of the first aspect.

[0091] Exemplarily, the current collector and a positive electrode active layer disposed on at least one functional surface of the current collector; the positive electrode active layer includes a positive electrode active material, a conductive agent, and a binder, wherein the positive electrode active material includes the positive electrode active material of the first aspect; the material of the current collector is not specifically limited in this invention, for example, it can be selected from any one or more of aluminum, nickel, titanium, stainless steel, etc.; the conductive agent can be selected from at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, metal powder, and graphene; the binder can be selected from at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0092] Fourthly, the present invention provides a battery comprising the above-described positive electrode.

[0093] In some implementations, the battery also includes a negative electrode and a separator.

[0094] The present invention does not specifically limit the composition and material of the positive electrode, negative electrode, and separator of the battery. Exemplarily, the negative electrode includes a current collector and a negative electrode active material layer located on at least one surface of the current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material includes one or more of graphite, hard carbon, soft carbon, silicon-based negative electrode, titanium-based material, nitride, tin compound, and lithium metal. The negative electrode current collector can be a conventional negative electrode current collector in the art, such as copper foil. The conductive agent can be selected from at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotube, metal powder, and graphene. The binder can be selected from at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0095] In some embodiments, the negative electrode active material layer further includes a dispersant, which may be selected from at least one of sodium carboxymethyl cellulose, triethylhexyl phosphate, and sodium dodecyl sulfate.

[0096] The battery of the present invention can be manufactured according to conventional methods in the art. For example, the positive electrode, separator and negative electrode can be stacked in sequence and assembled into a cell by winding or stacking process. After packaging and baking, electrolyte is injected and then the battery is manufactured by hot pressing and other processes.

[0097] Exemplarily, the present invention does not particularly limit the material of the diaphragm described above, and any known porous diaphragm with electrochemical and chemical stability can be selected, for example, it can be at least one of glass fiber, non-woven fabric, polyethylene, polypropylene or polyvinylidene fluoride. The diaphragm can be single-layer or multi-layer.

[0098] This invention does not impose any particular limitation on the electrolyte mentioned above. For example, an electrolyte comprising an organic solvent and an electrolyte salt may be selected. The organic solvent, as the medium for transporting ions in the electrochemical reaction, may be one or more organic solvents known in the art for use in battery electrolytes, such as fluorocarbonates, fluorocarboxylic acid esters, non-fluorocarbonates, fluorocarbonates, non-fluorocarboxylic acid esters, fluorocarboxylic acid esters, fluoroethers, non-fluoroethers, and tetrahydrofuran. The electrolyte salt, as the ion source, may be one or more electrolyte salts known in the art for use in battery electrolytes, such as lithium hexafluorophosphate, bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0099] The present invention will be further described below with reference to specific embodiments:

[0100] Example 1

[0101] This example provides a positive electrode active material, comprising the active material lithium iron phosphate and a carbon layer and a fast ion conductor material layer sequentially disposed on the surface of the lithium iron phosphate. The chemical composition of the fast ion conductor material layer is: 0.5Li₂O·0.2SiO₂·0.15WO₃·0.15TiO₂. The fast ion conductor material layer comprises an amorphous fast ion conductor material. Other parameters are shown in Table 1.

[0102] Its preparation method includes the following steps:

[0103] 1) A 2M tetraethyl orthosilicate ethanol solution, a 1M ammonium metatungstate solution, a tetrabutyl titanate liquid, a 3M lithium nitrate aqueous solution, and a 4M citric acid aqueous solution were gradually mixed in a molar ratio of Li:Ti:Si:W:C6H8O7 = 1.0:0.15:0.2:0.15:0.80 and dried in air at 60°C for 12 hours. The resulting gel mixture powder was then pre-calcined at 350°C for 3 hours at a rate of 2°C / min and pulverized to obtain a fast ion conductor material precursor.

[0104] 2) The fast ion conductor material precursor and the carbon-coated lithium iron phosphate were mixed in alcohol and ball-milled at 600 rpm for 6 hours. After drying, the resulting mixed powder was heated to 500°C at a rate of 5°C / min and calcined for 120 min in a nitrogen atmosphere. Then, it was rapidly cooled to 200°C at a rate of 20°C / min and held at that temperature for 90 min before being cooled down in the furnace to finally obtain the positive electrode active material.

[0105] Figure 1 The images shown are TEM and EDS images of the positive electrode active material in Example 1; where a is the TEM image of the positive electrode active material and b is the EDS image of the positive electrode active material. Figure 2 Here is an HRTEM image of the positive electrode active material of Example 1, from... Figure 2 As can be seen, fast ion conductor materials have an amorphous, non-crystalline structure.

[0106] Example 2

[0107] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0108] The preparation method differs from that in Example 1 in that the ratio of precursor elements in the synthesis of fast ion conductor materials is modified to Li:Ti:Si:W:C6H8O7=0.80:0.20:0.20:0.20:0.80.

[0109] Example 3

[0110] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0111] The preparation method differs from that in Example 1 in that the tetrabutyl titanate liquid is replaced with aluminum nitrate, and the ratio of precursor elements in the synthesis of lithium fast ion conductor is modified to Li:Al:Si:W:C6H8O7=1.0:0.10:0.30:0.10:0.8.

[0112] Example 4

[0113] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0114] The preparation method differs from that in Example 1 in that the calcination regime of the mixed powder of fast ion conductor material precursor and lithium iron phosphate is modified to increase the temperature at a rate of 5°C / min to 550°C and calcinate for 150 min, followed by cooling.

[0115] Example 5

[0116] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0117] The preparation method differs from that in Example 1 in that the ratio of precursor elements in the synthesis of fast ion conductor materials is modified to Li:Ti:Si:W:C6H8O7=1.0:0.15:0.2:0.15:1.20.

[0118] Example 6

[0119] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0120] The preparation method differs from that in Example 1 in that 2M tetraethyl orthosilicate ethanol solution, 1M ammonium metatungstate solution, tetrabutyl titanate, 3M lithium nitrate aqueous solution and 4M citric acid aqueous solution are gradually mixed according to the final molar ratio Li:Ti:Si:W:C6H8O7=1.0:0.15:0.2:0.15:0.80. Ammonium carbonate is added as a template agent, accounting for 5% of the total system mass. After mixing, the mixture is dried in air at 60°C for 12 hours. The powder of the obtained gel mixture is heated to 350°C at a rate of 2°C / min for 3 hours and then pulverized to obtain the fast ion conductor material precursor.

[0121] Example 7

[0122] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0123] The preparation method differs from that in Example 1 in that: 1) 2M tetraethyl orthosilicate ethanol solution, 1M tantalum ethoxide solution, 1M magnesium nitrate, 3M lithium nitrate aqueous solution and 4M citric acid aqueous solution are gradually mixed according to the final molar ratio Li:Mg:Si:Ta:C6H8O7=1.0:0.15:0.2:0.15:0.80 and dried in air at 60°C for 12h. The powder of the obtained gel mixture is heated to 350°C at a rate of 2°C / min for 3h and then pulverized to obtain the fast ion conductor material precursor.

[0124] 2) The fast ion conductor material precursor and lithium iron phosphate coated with carbon layer were mixed in alcohol and ball-milled at 600 rpm for 6 hours. After drying, the resulting mixed powder was heated to 550°C at a rate of 5°C / min and calcined for 90 min in a nitrogen atmosphere. Then, it was rapidly cooled to 200°C at a rate of 20°C / min and held at that temperature for 90 min before being cooled down in the furnace to finally obtain the positive electrode active material.

[0125] Example 8

[0126] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0127] The preparation method differs from that in Example 1 in that, in step 1), the powder of the obtained gel mixture is heated to 350°C at a rate of 2°C / min for 6 hours and then pulverized to obtain a fast ion conductor material precursor.

[0128] Example 9

[0129] This example provides a positive electrode active material, the differences from Example 1 are shown in Table 1.

[0130] The preparation method differs from that in Example 1 in that, in step 2), the fast ion conductor material precursor and lithium iron phosphate are mixed in alcohol and ball-milled at 600 rpm for 6 hours, then dried. The resulting mixed powder is heated to 500°C at a rate of 5°C / min and calcined for 360 min in a nitrogen atmosphere, and then rapidly cooled to 200°C at a rate of 20°C / min. After holding at this temperature for 90 min, the temperature is lowered with the furnace to finally obtain the positive electrode active material.

[0131] Example 10

[0132] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0133] The preparation method differs from that in Example 1 in that, in step 2), the fast ion conductor material precursor and lithium iron phosphate are mixed in alcohol and ball-milled at 600 rpm for 6 hours, then dried. The resulting mixed powder is heated to 700°C at a rate of 5°C / min and calcined for 15 minutes in a nitrogen atmosphere, and then rapidly cooled to 200°C at a rate of 20°C / min. After holding at this temperature for 90 minutes, the temperature is lowered with the furnace to finally obtain the positive electrode active material.

[0134] Example 11

[0135] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0136] The preparation method differs from that in Example 1 in that, in step 2), the fast ion conductor material precursor and lithium iron phosphate are mixed in alcohol and ball-milled at 600 rpm for 6 hours, then dried. The resulting mixed powder is heated to 500°C for 120 minutes in a nitrogen atmosphere at a rate of 5°C / min, and then rapidly cooled to 100°C at a rate of 30°C / min. After holding at this temperature for 150 minutes, the temperature is lowered with the furnace to finally obtain the positive electrode active material.

[0137] Example 12

[0138] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0139] The preparation method differs from that in Example 1 in that, in step 2), the fast ion conductor material precursor and lithium iron phosphate are mixed in alcohol and ball-milled at 600 rpm for 6 hours, then dried. The resulting mixed powder is heated to 500°C at a rate of 5°C / min and calcined for 120 minutes in a nitrogen atmosphere, and then rapidly cooled to 300°C at a rate of 50°C / min. After holding at this temperature for 30 minutes, the temperature is lowered with the furnace to finally obtain the positive electrode active material.

[0140] Example 13

[0141] This example provides a positive electrode active material, the differences of which are shown in Table 1.

[0142] The preparation method differs from that in Example 1 in that, in step 2), the fast ion conductor material precursor and lithium manganese iron phosphate are mixed in alcohol and ball-milled at 600 rpm for 6 hours, then dried. The resulting mixed powder is heated to 500°C at a rate of 5°C / min and calcined for 120 minutes in a nitrogen atmosphere, and then rapidly cooled to 200°C at a rate of 20°C / min. After holding at this temperature for 90 minutes, the temperature is lowered with the furnace to finally obtain the positive electrode active material.

[0143] Comparative Example 1

[0144] This example provides a positive electrode active material, which differs from Example 1 in that it does not include a fast ion conductor material.

[0145] The preparation method differs from that in Example 1 in that no fast ion conductor material precursor is added in step 2).

[0146] Figure 3 TEM image of the positive electrode active material in Comparative Example 1; from Figure 3 It can be seen that without the addition of fast ion conductors, only a thinner amorphous carbon coating layer can be observed at the outermost edge of lithium iron phosphate.

[0147] Comparative Example 2

[0148] This example provides a positive electrode active material, which differs from Example 1 in that the fast ion conductor material has a crystalline structure and does not include amorphous structures.

[0149] The preparation method differs from Example 1 in that step 1) is omitted and step 2) is modified by mixing nano-silica, ammonium metatungstate, titanium dioxide, and lithium carbonate in a molar ratio of Li:Ti:Si:W:C6H8O7 = 1.0:0.15:0.2:0.15 with an appropriate amount of water. The mixture is then ball-milled at 600 rpm for 6 hours and dried. Subsequently, it is mixed with lithium iron phosphate material, and an appropriate amount of water is added to maintain a solid-liquid ratio of 35%. After thorough stirring, the mixture is spray-dried. The resulting mixed powder is calcined at 600°C for 6 hours under a nitrogen atmosphere at a rate of 5°C / min, and then cooled to room temperature at a rate of 5°C / min to finally obtain the positive electrode active material.

[0150] Figure 4 Here is an HRTEM image of the positive electrode active material in Comparative Example 2; from Figure 4 It can be seen that the fast ion conductor is not distributed on the material surface in the form of a coating layer, but is a mixture of unevenly distributed crystal particles and lithium iron phosphate. The figure shows not only a mixed region of 0.5Li2O·0.2SiO2·0.15WO3·0.15TiO2 and lithium iron phosphate, but also a separate lithium iron phosphate region, as well as Li2SiO3 crystal particles formed by some elements forming their own phases.

[0151] Comparative Example 3

[0152] This example provides a positive electrode active material, which differs from Example 1 in that the fast ion conductor material has a crystalline structure and does not include amorphous structures.

[0153] The preparation method differs from that in Example 1 in that, in step 2), the fast ion conductor material precursor and lithium iron phosphate are mixed in alcohol and ball-milled at 600 rpm for 6 hours, then dried. The resulting mixed powder is heated to 800°C at a rate of 5°C / min and calcined for 120 minutes in a nitrogen atmosphere, and then rapidly cooled to 200°C at a rate of 20°C / min. After holding at this temperature for 90 minutes, the temperature is lowered with the furnace to finally obtain the positive electrode active material.

[0154] Comparative Example 4

[0155] This example provides a positive electrode active material, which differs from Example 1 in that the fast ion conductor material does not contain silicon, as shown in Table 1.

[0156] The preparation method differs from that in Example 1 in that an ethanol solution of tetraethyl orthosilicate is not added in step 1).

[0157] Comparative Example 5

[0158] This example provides a positive electrode active material that differs from Example 13 in that it does not contain a fast ion conductor, as shown in Table 1.

[0159] The preparation method differs from that in Example 1 in that an ethanol solution of tetraethyl orthosilicate is not added in step 1).

[0160] Experimental Example 1

[0161] The preparation of a positive electrode sheet using the positive electrode active materials of the above embodiments and comparative examples includes the following steps:

[0162] Under normal temperature (25℃) and normal pressure (0.1 MPa) conditions, the positive electrode active material, conductive carbon black and polyvinylidene fluoride (PVDF) of each embodiment and comparative example were accurately weighed at a mass ratio of 90:5:5 and placed in N-methylpyrrolidone (NMP) solvent. The mixture was then subjected to high-speed shearing and stirring to form a uniform and stable positive electrode slurry. Subsequently, the slurry was uniformly coated onto a carbon-coated aluminum foil current collector, and the solvent was removed by segmented drying in an oven. After precision cold pressing, the positive electrode sheet was finally obtained.

[0163] Experimental Example 2

[0164] Assemble a battery using the above-mentioned positive electrode plates:

[0165] In a glove box filled with argon and with water and oxygen content both below 0.1 ppm, the obtained positive electrode sheet was punched into a 12 mm diameter disc and vacuum dried at 120 °C for 12 hours to completely remove moisture. Subsequently, using a lithium metal sheet as the counter electrode and reference electrode, a polypropylene membrane as the separator, and a 1.0 M LiPF6 EC / DEC (volume ratio 1:1) solution as the electrolyte, a coin cell was assembled and finally sealed under rated pressure using a sealing machine.

[0166] Test Example 1

[0167] The following tests were performed on the positive electrode active materials of the examples and comparative examples:

[0168] 1. Composition test of positive electrode active material:

[0169] Approximately 5-10 mg of the powder sample to be tested was evenly adhered to the conductive adhesive, and a brief argon ion sputtering was performed to clean the surface; subsequently, the sample was placed in a vacuum with a vacuum level better than 5.0 × 10⁻⁶. -8 The mbar ultra-high vacuum analysis chamber uses a monochromatic Al Kα ray source (hv=1486.6 eV) as the excitation source, and conducts detection under the conditions of an analyzer pass energy of 20 eV and a scan step size of 0.1 eV: first, the full spectrum is scanned in the range of 0-1200 eV to obtain the surface elemental composition, and then the relevant core elements are scanned with high resolution fine scan; throughout the test, the charge calibration is performed with the standard peak position of contaminating carbon C 1s (284.8 eV) as a reference, and finally, the spectral peaks are analyzed by professional software to obtain quantitative information such as the chemical state, relative atomic concentration and chemical bonding environment of each element on the sample surface.

[0170] 2. Morphological testing includes dimensional testing:

[0171] 1) Fast ion conductor layer thickness test: 20g of positive electrode active material sample was calcined at 550°C for 2 hours in air atmosphere to completely remove the carbon layer. Then, the treated sample was ultrasonically dispersed in ethanol for 10 minutes and dropped onto an ultrathin carbon support film copper grid to prepare an HRTEM observation sample. Using a high-resolution transmission electron microscope, by adjusting the objective lens focal length and astigmatism, a high-resolution transmission electron microscopy image was obtained that clearly showed the interface structure between the lattice fringes (corresponding to the crystalline phase of the active material) and the external amorphous region (corresponding to the fast ion conductor layer). Finally, at least 10 different positions were selected in the image along the direction perpendicular to the coating layer. According to the clear boundary line between the crystalline and amorphous regions, the total thickness from the surface of the active material to the outside of the amorphous layer was measured. The average value was calculated as the thickness of the fast ion conductor material layer.

[0172] 2) Carbon layer thickness test:

[0173] Untreated high-pressure lithium iron phosphate material was ultrasonically dispersed in ethanol for 10 minutes and then dropped onto an ultrathin carbon support film copper grid to prepare an HRTEM observation sample. Using a high-resolution transmission electron microscope, by adjusting the objective lens focal length and astigmatism, a high-resolution transmission electron microscopy image was obtained that clearly showed the interface structure between the lattice fringes (corresponding to the crystalline phase of the active material) and the external amorphous region (corresponding to the fast ion conductor layer). Finally, at least 10 different positions were selected in the image along the direction perpendicular to the coating layer, and the total thickness from the surface of the active material to the outer side of the amorphous layer was measured according to the clear boundary between the crystalline and amorphous regions. The thickness of the carbon layer was obtained by subtracting the thickness of the fast ion conductor material layer.

[0174] 3) Average particle size test of fast ion conductor material nanoparticles:

[0175] The positive electrode active material is taken as the test sample. A high-resolution transmission electron microscope (TEM) image of the ion conductor material on the test sample is obtained. Then, energy dispersive spectroscopy (EDS) is performed to observe individual particles without Fe element distribution. The particle size is then measured. At least 50 particles are randomly measured and the average value is calculated, which is the average particle size of the fast ion conductor material nanoparticles.

[0176] 3. Compaction, particle size, and specific surface area testing of the positive electrode active material:

[0177] Compaction test: The positive electrode active material was taken as the test sample. 2.000 g of the sample was weighed and filled into a clean hard alloy mold with an inner diameter of 13.0 mm. The mold was placed on an electric powder press and uniaxially pressed at 500 MPa for 30 seconds to form a dense cylindrical compact. Then, the diameter and height of the compact were measured multiple times at different positions using a digital vernier caliper with an accuracy of 0.01 mm. The volume of the compact was calculated, and then the compaction density of the material under the specified pressure was calculated. The final result was the average of at least three parallel experiments.

[0178] Particle size testing: Using the positive electrode active material as the sample, weigh approximately 0.1g of the sample and add it to a beaker containing 20 mL of 0.1% sodium hexametaphosphate aqueous solution. Initially stir and wet the sample with a glass rod. Then, place the beaker in a 40 kHz ultrasonic cleaning tank and mix thoroughly. After dispersion, immediately use a dropper to aspirate the uniform upper layer of the suspension and import it into the circulation chamber of a Malvern Mastersizer 3000 particle size analyzer. Turn on the magnetic stirrer and circulation pump. After the background signal stabilizes, start the instrument to perform laser diffraction measurements within the measurement range of 0.01-3500 μm. Set the instrument to automatically and continuously acquire 10 sets of data, with a 5-second interval between each set. Remove outliers and calculate the volume average particle size (Dv50) and particle size distribution width. The results are considered stable when the Dv50 deviation of three consecutive measurements is less than 2%, and the final data is recorded.

[0179] Specific surface area test: The positive electrode active material was used as the sample to be tested. Approximately 0.15 g of the dried sample was accurately weighed using a clean, dry sample tube. Subsequently, the sample tube containing the sample was installed in the degassing station of the Micro ASAP 2460 specific surface area analyzer and tested under high vacuum (<10). -3 Under a relative pressure of -196°C (Pa), the sample tube was heated to 200°C at a rate of 5°C / min and held at this temperature for 4 hours for degassing. After degassing, the sample tube was transferred to the analysis station, where nitrogen adsorption-desorption isotherms were measured by the instrument at a constant temperature of -196°C (liquid nitrogen bath). At least 15 uniformly distributed data points were collected within a relative pressure range of 0.05 to 0.30. Finally, the instrument automatically performed linear fitting on the adsorption data to calculate the specific surface area of ​​the material.

[0180] Summarize at least some of the test results in Table 1 or Table 2.

[0181] Test Example 2

[0182] Ratio Performance Test

[0183] First, activate the battery by performing 2-3 charge-discharge cycles at a low current of 0.1C, with a voltage range of 2.00-3.75V. Record the charge-discharge specific capacity of the battery at 0.1C. After activation, charge the battery to 3.75V under constant current charging at a rate of 1C, and then charge it at a constant voltage until the current is less than 0.05C. Record the charging capacity at this point as the first charge capacity. After resting for 5 minutes, discharge the battery to 2V under constant current charging at a rate of 1.0C. Record the discharge capacity at this point as the first discharge specific capacity at 1.0C. Then, adjust the rate to 1C and 5C and test using the same procedure.

[0184] At least some of the test results are summarized in Table 2.

[0185] Table 1:

[0186]

[0187] Table 2

[0188]

[0189] As can be seen from the test results in Table 1-2 above, compared with Comparative Examples 1-4, the positive electrode active material of Examples 1-13 can construct a three-dimensional ion transport network with high ionic conductivity, high electronic conductivity and stable structure by setting a multi-element modified amorphous fast ion conductor material layer on the surface of the active material, which helps to further improve the rate performance of the battery.

[0190] 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 active material, characterized in that, The positive electrode active material includes: an active substance and a fast ion conductor material layer disposed on at least a portion of the surface of the active substance; the chemical composition of the fast ion conductor material layer includes: xLi2O·ySiO2·mM·nR, wherein M and R independently include at least one of WO3, Nb2O5, Ta2O5, Al2O3, Ga2O3, MgO, AlF3, P2O5, and TiO2, x+y+m+n=1, x>0, y>0, m>0, n>0, and the fast ion conductor material layer includes amorphous fast ion conductor material.

2. The positive electrode active material according to claim 1, characterized in that, 0.5 <x<0.6,0.20<y<0.30,0.10<m+n<0.30; Preferably, M includes at least one of WO3, Nb2O5, Ta2O5, and TiO2, and R includes at least one of MgO, AlF3, Al2O3, and Ga2O3.

3. The positive electrode active material according to claim 2, characterized in that, The thickness of the fast ion conductor material layer is 0.5 nm to 3 nm; Preferably, the fast ion conductor material layer further includes nanoparticles of the fast ion conductor material; More preferably, the average particle size of the nanoparticles of the fast ion conductor material is 0.5 nm to 3 nm.

4. The positive electrode active material according to any one of claims 1-3, characterized in that, The positive electrode active material further includes a carbon layer disposed on at least a portion of the surface of the active material; the fast ion conductor material layer is disposed on at least a portion of the surface of the carbon layer; preferably, the thickness of the carbon layer is 2nm-5nm.

5. The positive electrode active material according to claim 4, characterized in that, The active material includes at least one of lithium iron phosphate, lithium manganese iron phosphate, and nickel-cobalt-manganese ternary oxide cathode materials.

6. The positive electrode active material according to any one of claims 1-5, characterized in that, The compaction density of the positive electrode active material is greater than or equal to 2.6 g / cm³. 3 ; And / or, the Dv50 of the positive electrode active material is 0.5μm-2μm; And / or, the specific surface area of ​​the positive electrode active material is 5m². 2 / g-15m 2 / g.

7. A method for preparing a positive electrode active material as described in any one of claims 1-6, characterized in that, Includes the following steps: A gel-like mixture containing silicon source, M source, lithium source, R source and chelating agent is subjected to a heat preservation treatment at 350℃-400℃ to obtain a fast ion conductor material precursor. The mixture comprising the fast ion conductor material precursor and the active material is subjected to a second heat treatment at 400℃-700℃, and then cooled to 100℃-300℃ at a cooling rate of 20℃ / min-50℃ / min, and subjected to a third heat treatment to obtain the positive electrode active material.

8. The preparation method according to claim 7, characterized in that, The duration of the first heat preservation treatment is 2h-6h; and / or, the duration of the second heat preservation treatment is 30min-180min; and / or, the duration of the third heat preservation treatment is 30min-150min.

9. A positive electrode plate, characterized in that, It includes a current collector and a positive electrode active layer disposed on at least one side of the current collector; the positive electrode active layer includes the positive electrode active material according to any one of claims 1-7.

10. A battery, characterized in that, Includes the positive electrode sheet as described in claim 9.

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