CN115020678A - Positive electrode active material, electrochemical device, and electronic device - Google Patents
Positive electrode active material, electrochemical device, and electronic device Download PDFInfo
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- CN115020678A CN115020678A CN202210822314.4A CN202210822314A CN115020678A CN 115020678 A CN115020678 A CN 115020678A CN 202210822314 A CN202210822314 A CN 202210822314A CN 115020678 A CN115020678 A CN 115020678A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a positive active material, an electrochemical device and electronic equipment, wherein the positive active material comprises lithium manganese iron phosphate, the lithium manganese iron phosphate comprises doped ions, the content gradient of manganese elements and the content gradient of the doped ions in the lithium manganese iron phosphate is reduced from inside to outside along the particles of the lithium manganese iron phosphate, and the content gradient of iron elements is increased. The anode active material contains specific element distribution, so that the dissolution of metal manganese in a circulation process is relieved, the electronic/ionic conductivity of the material is improved, the interface resistance is reduced, and the capacity, the rate capability and the stability of an electrochemical device are improved.
Description
Technical Field
The invention belongs to the technical field of batteries, and relates to a positive electrode active material, an electrochemical device and electronic equipment.
Background
The lithium iron phosphate has the advantages of good structural stability, good thermal stability, good safety performance, long cycle life, rich raw material sources and the like, and can be used in energy storage batteries and electricityBatteries for automobiles are increasingly used. However, the plateau voltage of lithium iron phosphate is only 3.4V vs. Li/Li + Resulting in a limitation of its energy density. The lithium manganese phosphate has an olivine structure identical to that of lithium iron phosphate, and has a higher plateau voltage compared with lithium iron phosphate, but has a low intrinsic lithium ion solid phase migration rate and a large charge polarization.
In the prior art, partial iron doping or replacement is mainly performed on a manganese site of lithium manganese phosphate to obtain lithium manganese iron phosphate, so that the energy density and the conductivity of the lithium manganese phosphate or the lithium iron phosphate are improved, and the polarization problem caused by manganese is still serious. In addition, manganese in the lithium manganese iron phosphate is easy to separate out in the charging and discharging process, manganese fluoride is formed on the surface of the positive electrode, or the lithium manganese iron phosphate is dissolved in electrolyte and separated out from the negative electrode, so that energy loss in the battery cycle process is caused. Therefore, the preparation of the lithium iron manganese phosphate material with high capacity, small internal resistance and good stability has important significance for the research and development of electrochemical devices.
Disclosure of Invention
In view of the disadvantages of the prior art, an object of the present invention is to provide a positive electrode active material, an electrochemical device, and an electronic apparatus. The cathode active material comprises the manganese lithium iron phosphate containing doped ions, the doped ions and manganese elements in the manganese lithium iron phosphate are reduced in a gradient manner from inside to outside, the iron element gradient is increased, the dissolution of metal manganese in a circulation process is relieved, the electron/ion conductivity of the material is improved, the interface resistance is reduced, the rate capability of the material is improved, and the capacity, the rate capability and the stability of an electrochemical device are further improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a positive active material, which includes lithium manganese iron phosphate, where the lithium manganese iron phosphate includes doped ions, and the content gradient of manganese and doped ions in the lithium manganese iron phosphate is reduced and the content gradient of iron is increased from inside to outside along particles of the lithium manganese iron phosphate.
According to the invention, the lithium manganese iron phosphate with a special structure is used as the positive active material, the manganese element content gradient is decreased progressively and the iron element content gradient is increased progressively in the lithium manganese iron phosphate particles from inside to outside, so that the problem of dissolution of manganese metal in the lithium manganese iron phosphate circulation process is favorably solved, the internal resistance related to the interface can be improved, and the rate capability of the positive active material is improved. Meanwhile, the manganese lithium iron phosphate contains doping elements, the content of the doping elements is consistent with the content change of the manganese element, and the doping elements are all gradually decreased from inside to outside in a gradient manner, so that the electronic/ionic conductivity of the manganese lithium iron phosphate is improved, the problem of reduction of the lithium ion transmission rate caused by excessive manganese is solved, and the specific gradient distribution structures of the manganese element, the iron element and the doping ions act in a synergistic manner to reduce the direct current resistance of the positive active material and improve the capacity, the multiplying power performance and the stability of the material.
Preferably, the chemical formula of the lithium manganese iron phosphate is Li x Mn y Fe 1-y-z M z PO 4 Wherein 0.9. ltoreq. x.ltoreq.1.1, such as 0.1, 0.3, 0.5, 0.7, 0.9 or 0.9, etc., 0.5. ltoreq. y.ltoreq.0.95, such as 0.5, 0.6, 0.7, 0.8, 0.9 or 0.95, etc., 0.0005. ltoreq. z.ltoreq.0.01, such as 0.0005, 0.001, 0.002, 0.004, 0.006, 0.008 or 0.01, etc., and M includes any one or a combination of at least two of Mg, Co, Ni, Ti, V, Cr and Zr, such as a combination of Mg and Co, a combination of Ni and Ti, a combination of Cr and Zr, a combination of Co, Ni and Ti, a combination of V, Cr and Zr, or the like.
According to the invention, specific doping ions such as Mg, Co, Ni, Ti, V, Cr and Zr are adopted and matched with a certain doping proportion, so that the electronic/ionic conductivity of the positive active material is further improved, and the capacity and the rate capability of the material are improved.
Preferably, the surface of the lithium iron manganese phosphate is further coated with carbon.
Preferably, the content of carbon is 1 wt% to 3 wt%, for example, may be 1 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt%, 3 wt%, or the like, based on 100 wt% of the total mass of the lithium iron manganese phosphate and carbon. The surface of the lithium iron manganese phosphate is coated with a certain content of carbon, so that the conductivity and the cycle performance of the material can be further improved, the comprehensive electrochemical performance of the material is improved,
preferably, the lithium manganese iron phosphate comprises lithium manganese iron phosphate in a primary particle form and/or lithium manganese iron phosphate in a secondary particle form.
Preferably, the particle diameter Dmin of the lithium iron manganese phosphate in the primary particle form is 0.1 μm to 0.3 μm, and may be, for example, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, or the like; d10 is 0.3 μm to 0.6. mu.m, and may be, for example, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm or 0.6 μm; d50 is 0.7 μm to 3 μm, and may be, for example, 0.7 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm or the like; d90 is 3.0 μm to 12 μm, and may be, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or 12 μm.
Preferably, the particle diameter Dmin of the lithium iron manganese phosphate in the form of secondary particles is 0.2 μm to 0.4 μm, and may be, for example, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, or 0.4 μm; d10 is 1 μm to 3 μm, and may be, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or the like; d50 is 7 μm to 11 μm, and may be, for example, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, or the like; d90 is 15 μm to 25 μm, and may be, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm or 25 μm.
Preferably, the particle diameter D50 of the primary particles in the lithium iron manganese phosphate in the secondary particle form is 30nm to 200nm, and may be, for example, 30nm, 50nm, 80nm, 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, or the like.
According to the invention, lithium manganese iron phosphate with proper primary particle size and secondary particle size is adopted, certain doping ions and the distribution of manganese element and iron element are matched, and the particle size and the element distribution structure of the material act together to realize synergistic interaction, so that the capacity, the rate capability and the stability of the positive active material are further improved.
In a second aspect, the present invention provides an electrochemical device comprising the positive electrode active material according to the first aspect in a positive electrode thereof.
The invention selects the lithium manganese iron phosphate containing specific doped ions and element distribution as the anode active material, thereby improving the capacity, rate capability and stability of the electrochemical device.
In an alternative embodiment, the present invention provides a method for detecting whether a sample of an electrochemical device contains a positive electrode active material according to the present invention, the method comprising:
the method comprises the steps of splitting an electrochemical device sample to obtain a positive electrode, washing and drying the positive electrode by using a solvent, blade-coating the surface of the positive electrode to obtain active substance powder, scanning the active substance powder through ICP, SEM and EDS, observing elements and element distribution contained in the active substance powder, and determining that the positive electrode of the electrochemical device sample contains the positive electrode active material disclosed by the invention, wherein the active substance powder contains lithium manganese phosphate doped with ions such as Mg, Co, Ni, Ti, V, Cr, Zr and the like, the content gradient of the doped ions and the manganese elements is reduced from inside to outside, and the content gradient of the iron element is increased.
In an alternative embodiment, the electrochemical device is a lithium ion battery.
In an alternative embodiment, the positive electrode of the electrochemical device includes a positive electrode active material, a conductive agent, and a binder.
Preferably, the conductive agent includes conductive carbon black (SP) and/or Carbon Nanotubes (CNT).
Preferably, the binder comprises polyvinylidene fluoride (PVDF).
Preferably, the mass ratio of the positive electrode active material, the SP, the CNT and the PVDF is (90 to 99):1:0.5:2, and may be, for example, 90:1:0.5:2, 92:1:0.5:2, 94:1:0.5:2, 96:1:0.5:2 or 99:1:0.5:2, or the like.
In an alternative embodiment, the negative electrode of the electrochemical device comprises graphite, SP, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a mass ratio of (90 to 99):1:1.5:2, for example, 90:1:1.5:2, 92:1:1.5:2, 94:1:1.5:2, 96:1:1.5:2, 98:1:1.5:2 or 99:1:1.5:2, etc.
In an alternative embodiment, the electrolyte of the electrochemical device includes a lithium salt and a solvent.
In an alternative embodiment, the lithium salt comprises LiPF 6 。
In an alternative embodiment, the lithium salt is present in an amount of 4 wt% to 24 wt%, for example 4 wt%, 8 wt%, 10 wt%, 15 wt%, 20 wt%, or 24 wt%, etc., based on 100 wt% of the mass of the electrolyte.
In an alternative embodiment, the solvent comprises at least one of Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC) and Polycarbonate (PC) or a combination of any two thereof, for example, a combination of EC and EMC, a combination of DMC and PC, a combination of EC, EMC and DMC, or a combination of EC, EMC, DMC and PC, or the like.
In an alternative embodiment, the mass ratio of EC, EMC, DMC and PC in the solvent is (2 to 4): (3 to 5): (2 to 4): (0 to 1), the selection range of EC (2 to 4) may be, for example, 2, 2.5, 3, 3.5, or 4, etc., the selection range of EMC (3 to 5) may be, for example, 3, 3.5, 4, 4.5, or 5, etc., the selection range of DMC (2 to 4) may be, for example, 2, 2.5, 3, 3.5, or 4, etc., the selection range of PC (0 to 1) may be, for example, 0, 0.1, 0.2, 0.3, 0.5, 0.7, or 1, etc., and when PC is 0, it means that PC is not contained in the solvent.
In the present invention, a method of assembling an electrochemical device using the cathode, the anode and the separator is a prior art, and a person skilled in the art can assemble the electrochemical device by referring to the methods disclosed in the prior art. Taking a lithium ion battery as an example, a positive electrode, a diaphragm and a negative electrode are sequentially wound or stacked to form a battery core, the battery core is placed in a battery case, electrolyte is injected, formation and packaging are performed, and the electrochemical device is obtained.
In a third aspect, the present invention provides an electronic device comprising the electrochemical device according to the third aspect.
The electronic device according to the present invention may be, for example, a mobile computer, a portable phone, a memory card, a liquid crystal television, an automobile, a motorcycle, a motor, a timepiece, a camera, or the like.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the lithium manganese iron phosphate with a special structure is used as the positive active material, the manganese element content gradient is decreased progressively and the iron element content gradient is increased progressively in the lithium manganese iron phosphate particles from inside to outside, so that the problem of dissolution of manganese metal in the lithium manganese iron phosphate circulation process is favorably solved, the internal resistance related to the interface can be improved, and the rate capability of the positive active material is improved. Meanwhile, the manganese-iron lithium phosphate contains doping elements, the content of the doping elements is consistent with the content change of the manganese element, and the doping elements are gradually decreased from inside to outside in a gradient manner, so that the electronic/ionic conductivity of the manganese-iron lithium phosphate is improved, the problem of reduction of the lithium ion transmission rate caused by excessive manganese is solved, and the specific gradient distribution structures of the manganese element, the iron element and the doping ions act in a synergistic manner to reduce the direct current resistance of the positive active material and improve the capacity, the multiplying power performance and the stability of the material.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments.
Example 1
The present embodiment provides a positive active material including vanadium-doped lithium iron manganese phosphate LiMn 0.6 Fe 0.395 Ni 0.005 PO 4 The content of Mn and Ni is reduced in a gradient manner along the particles of the lithium manganese iron phosphate from inside to outside, the content of Fe is increased in a gradient manner, the total mass of the lithium manganese iron phosphate and carbon is 100 wt%, the surface of the lithium manganese iron phosphate is further coated with carbon with the content of 2 wt%, and the positive active material is recorded as LiMn 0.6 Fe 0.395 Ni 0.005 @C。
The manganese lithium iron phosphate is in a secondary particle form, the particle size Dmin is 0.3 mu m, the D10 is 2 mu m, the D50 is 8 mu m, and the D90 is 20 mu m. The size of the primary particle in the lithium manganese iron phosphate in the form of the secondary particle is 100 nm.
The embodiment also provides a preparation method of the positive electrode active material, which comprises the following steps:
manganese sulfate, nickel sulfate, ferric sulfate and ammonium oxalate in stoichiometric ratio are mixed and precipitated in water to obtain the manganese iron nickel oxalate precursor. It should be noted that manganese phosphate and sulfuric acid are controlledThe relative addition rates of nickel and ferric sulfate enable the precursor end iron to be distributed outside the particles and the manganese and nickel to be distributed inside the particles. Then, the manganese iron nickel oxalate precursor is mixed and sintered with lithium carbonate, ammonium dihydrogen phosphate and glucose to obtain the positive active material LiMn 0.6 Fe 0.395 Ni 0.005 @C。
Assembling of lithium ion battery
(1) Preparation of the positive electrode: mixing the positive electrode active material prepared in the embodiment and the comparative example, SP, PVDF and N-methyl pyrrolidone (NMP) according to the mass ratio of 99:1.5:1:40, stirring at a high speed for 2h to obtain positive electrode slurry, uniformly coating the positive electrode slurry on an aluminum foil by using a scraper, placing the aluminum foil on a blast drying box, drying at 120 ℃ for 20min, rolling and cutting a dried electrode plate, and preparing a positive electrode;
(2) preparation of a negative electrode: mixing graphite, SP, CMC and SBR according to a mass ratio of 95.5:1:1.5:2 to prepare slurry, coating the slurry on a copper foil, and rolling to obtain a negative electrode;
(3) preparing a lithium ion battery: 1M LiPF using the above positive and negative electrodes 6 And (3) assembling an electrolyte, wherein the solvent in the electrolyte is Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and dimethyl carbonate (DMC) electrolyte in a mass ratio of 1:1:1, and a PE (polyethylene) base film to obtain the 1Ah soft package battery.
Second, performance test
(1) Gram capacity test at 0.33C and 1C magnification:
adopting a battery performance testing system (equipment model: BTS05/10C8D-HP) of Honghong electric appliance GmbH to test the capacity of 0.33C gram and the capacity of 3C gram of the soft package battery;
the actual capacity of the cell was defined after one charge and discharge (current density 0.33C, voltage window 2.0V to 4.3V) of the pouch cell at 25C, which was grown and aged. And performing a rate discharge test, namely charging to 4.3V at a constant current of 0.33C, then charging to 0.05C at a constant voltage to obtain a capacity of 0.33C, then discharging to 2.0V at 3C to obtain a capacity of 3C, and dividing the capacity of 3C by the capacity of 0.33C to obtain a capacity retention rate of 3C.
(2) Direct Current Resistance (DCR) testing
Adopting a battery performance testing system (the equipment model is BTS05/10C8D-HP) of the Shenghong electric appliance component electric company Limited to carry out DCR test on the soft package battery;
at 25 ℃, the state of charge (SOC) of the soft package battery is adjusted to 50% SOC, then the battery is discharged for 30s at a current density of 4C, and the voltage difference value before and after the discharge is divided by the current density to obtain the discharge direct current resistance value (discharge DCR) of the battery at the state of charge, and the discharge DCR is characterized by the internal resistance of the battery cell.
(3) And (3) stability testing:
a 30-day storage capacity retention rate test is carried out on the soft package battery by adopting a battery performance test system (equipment model: BTS05/10C8D-HP) of the Shenghong electric appliance component electric company Limited;
storing the battery cell in a constant temperature box at 60 ℃, taking out the battery cell at intervals of 30 days, testing the capacity of the battery cell at a rate of 0.33C, and dividing the capacity of the battery cell at 30 days by the actual capacity to obtain a 30-day storage capacity retention rate; the capacity retention rate corresponds to the stability of the positive electrode material.
Examples 2 to 7 were modified based on the procedure of example 1, and the parameters and test results of the modification are shown in tables 1 to 3, and the test results of comparative examples 1 to 2 are shown in table 4.
TABLE 1
TABLE 2
As can be seen from comparison between example 1 and examples 4 to 5 in table 2, in the present invention, the gram volume exertion, the multiplying power and the storage performance of the positive electrode active material can be improved by adding the dopant ions with a specific content and matching with a specific element gradient distribution structure; in example 4, the content of doped ions is too large, the inactive sites are increased, and the capacity exertion of the cathode material is affected, and in example 5, the content of doped elements is too small, so that the lithium ion migration rate of the lithium manganese phosphate is not obviously improved, the internal resistance is large, the dynamics is poor, and the electrical performance cannot be exerted. Thus, the overall performance of example 1 is better.
TABLE 3
As can be seen from comparison between example 1 and examples 6 to 7 in table 3, in the present invention, the capacity, rate capability, and stability of the positive electrode active material can be further improved by doping with lithium manganese iron phosphate in the form of secondary particles having an appropriate primary particle size and controlling the content distribution of the dopant ions, manganese element, and iron element. When the size of the primary particles of the lithium manganese iron phosphate is too large, the melting among the particles is serious, the lithium ion transmission distance is too long, and both the gram capacity and the rate capability are poor. When the size of the primary particles of the lithium manganese iron phosphate is too small, the crystallinity of the lithium manganese iron phosphate is low, the capacity and the rate performance of the whole material are poor, the specific surface of the material is large, the side reactions are more, and the stability is poor; therefore, the positive active material in example 1 had higher capacity, lower DCR, and better capacity retention rate.
Comparative example 1
The procedure was as in example 1 except that Ni was not doped.
Comparative example 2
The same as in example 1, except that the Ni content was constant along the lithium iron manganese phosphate particles from the inside to the outside.
TABLE 4
As can be seen from comparison between example 1 and comparative examples 1 to 2 in table 4, when no ion is doped in the lithium manganese iron phosphate, the solid phase diffusion rate of the lithium manganese iron phosphate is limited, and thus both gram-capacity exertion and rate capability are poor. Meanwhile, no doped ions stabilize the crystal lattice, and the stability of the material is poor. When the manganese iron phosphate is doped with ions, but the content of the doped ions does not change along with the content gradient of the manganese element, the synergistic effect of the doped ions and the manganese element is not exerted, and the problem of the reduction of the lithium ion transmission rate cannot be better improved, so that the gram capacity and the rate capability of the comparative examples 1 to 2 are inferior to those of the example 1.
In conclusion, the positive active material provided by the invention comprises the lithium manganese iron phosphate containing the doped ions, the doped ions and manganese elements in the lithium manganese iron phosphate are reduced in a gradient manner from inside to outside, and the iron element gradient is increased, so that the dissolution of metal manganese in a circulation process is relieved, the electronic/ionic conductivity of the material is improved, the interface resistance is reduced, the rate capability of the material is improved, and the capacity, rate capability and stability of an electrochemical device are further improved.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The utility model provides a positive active material, its characterized in that, positive active material includes the lithium manganese iron phosphate, including the doping ion in the lithium manganese iron phosphate, follow lithium manganese iron phosphate's granule is from inside to outside, the content gradient of manganese element and doping ion reduces in the lithium manganese iron phosphate, and the content gradient of iron element increases.
2. The positive electrode active material according to claim 1, wherein the lithium iron manganese phosphate has a chemical formula of Li x Mn y Fe 1-y-z M z PO 4 Wherein x is more than or equal to 0.9 and less than or equal to 1.1, y is more than or equal to 0.5 and less than or equal to 0.95, z is more than or equal to 0.0005 and less than or equal to 0.01, and M comprises any one or the combination of at least two of Mg, Co, Ni, Ti, V, Cr and Zr.
3. The positive electrode active material according to claim 1, wherein the surface of the lithium iron manganese phosphate is further coated with carbon.
4. The positive electrode active material according to claim 3, wherein the carbon is contained in an amount of 1 to 3 wt% based on 100 wt% of the total mass of the lithium iron manganese phosphate and the carbon.
5. The positive electrode active material according to claim 1, wherein the lithium manganese iron phosphate comprises a primary particle form of lithium manganese iron phosphate and/or a secondary particle form of lithium manganese iron phosphate.
6. The positive electrode active material according to claim 5, wherein Dmin of the lithium iron manganese phosphate in the primary particle form is 0.1 μm to 0.3 μm, D10 is 0.3 μm to 0.6 μm, D50 is 0.7 μm to 3 μm, and D90 is 3.0 μm to 12 μm.
7. The positive electrode active material according to claim 5, wherein the lithium manganese iron phosphate in the secondary particle form has a particle diameter Dmin of 0.2 to 0.4 μm, D10 of 1 to 3 μm, D50 of 7 to 11 μm, and D90 of 15 to 25 μm.
8. The positive electrode active material according to claim 5, wherein the particle diameter D50 of the primary particle in the lithium iron manganese phosphate in the secondary particle form is 30nm to 200 nm.
9. An electrochemical device, characterized in that a positive electrode of the electrochemical device comprises the positive electrode active material according to any one of claims 1 to 8.
10. An electronic device, characterized in that the electrochemical device according to claim 9 is included in the electronic device.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116646518A (en) * | 2023-07-25 | 2023-08-25 | 深圳海辰储能控制技术有限公司 | Positive electrode active material, preparation method, pole piece, energy storage device and power utilization device |
| CN116914087A (en) * | 2023-09-13 | 2023-10-20 | 中创新航科技集团股份有限公司 | Lithium iron manganese phosphate battery |
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| CN116914087B (en) * | 2023-09-13 | 2023-11-24 | 中创新航科技集团股份有限公司 | Lithium iron manganese phosphate battery |
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