CN111816851B - Hierarchical porous LiMnxFe1-xPO4Template-free hydrothermal preparation method of/C composite microsphere cathode material - Google Patents

Hierarchical porous LiMnxFe1-xPO4Template-free hydrothermal preparation method of/C composite microsphere cathode material Download PDF

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CN111816851B
CN111816851B CN202010572289.XA CN202010572289A CN111816851B CN 111816851 B CN111816851 B CN 111816851B CN 202010572289 A CN202010572289 A CN 202010572289A CN 111816851 B CN111816851 B CN 111816851B
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lithium
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孙福根
李亚辉
丁国彧
景鑫国
严奉乾
朱振
徐国军
李晓敏
岳之浩
周浪
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Nanchang University
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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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • 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
    • 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
    • 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
    • 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 belongs to the technical field of electrochemical energy storage materials, and discloses hierarchical porous LiMnxFe1‑xPO4A template-free hydrothermal preparation method of a/C composite microsphere cathode material. The method comprises the steps of forming and self-assembling nano particles, performing a dissolving-precipitating process in a hydrothermal reaction process, and obtaining the porous LiMn after simple carbon coatingxFe1‑xPO4the/C microsphere is of a hierarchical porous microsphere structure and is prepared from nano-scale LiMn with higher crystallinityxFe1‑xPO4The main grain consists of a uniform carbon coating inside. The hierarchical porous LiMn obtained by the inventionxFe1‑xPO4The unique structure of the/C composite microsphere cathode material simultaneously combines the design principles of structure, morphology and components, and has excellent structural stability and conduction advantages on electrons and lithium ions.

Description

Hierarchical porous LiMnxFe1-xPO4Template-free hydrothermal preparation method of/C composite microsphere cathode material
Technical Field
The invention relates to an electrochemical energy storage materialThe technical field of materials, in particular to a hierarchical porous LiMnxFe1- xPO4A template-free hydrothermal preparation method of a/C composite microsphere cathode material.
Background
Olivine-type transition metal phosphate LiMPO4(M ═ Fe, Mn, Ni, or Co) is considered a potential positive electrode material for rechargeable lithium ion batteries because of its good cycling stability, heat resistance, and safety. In which LiFePO is used4(LFP) has been most successful and has been used on a large scale in electric vehicles. However, LiFePO4The conductivity difference is low, the theoretical specific energy is low, and the requirement of higher energy density which is increased day by day in practical application is difficult to meet. In this respect, LiMnPO4(LMP) is more attractive because it has a higher affinity than LiFePO4Higher energy density and higher operating voltage (-4.1V vs. Li)+/Li), can provide a specific LiFePO4(～3.4V vs.Li+/Li) is about 20% higher. Unfortunately, due to LiMnPO4Having relatively low electron and Li+The conductivity, and its inherent John-teller distortion during charging and discharging, results in poor electrochemical performance. By adding in LiFePO4LiMn obtained by medium doping of MnxFe1-xPO4Solid solution systems are believed to incorporate LiFePO4And LiMnPO4Advantageous candidate positive electrode materials.
To further increase LiMnxFe1-xPO4The electrochemical performance of the cathode material, and the reasonable design of the microstructure and morphology thereof have been recognized as an effective method. Currently in the preparation of nano-sized LiMnxFe1-xPO4The particle (such as nanosphere, nano-plate and nano-rod) has achieved wide effect. Due to LiMnxFe1-xPO4The nano-particles have high specific surface area and short mobile charge transport length, and can provide a large active surface, a rapid interface and solid-state diffusion kinetics for lithium ion intercalation/deintercalation. However, although the specific capacity was improved to some extent, LiMn was presentxFe1-xPO4Nanoparticles and electrolysisThe contact surface of the material is enlarged, inevitably resulting in poor side reactions, low thermal stability and poor cycle performance. Further, LiMnxFe1-xPO4Tap density of nanoparticles (0.3-0.8g cm)-3) Compared with the traditional commercial oxide cathode material (LiCoO)2，2.6g cm-3) Much lower, resulting in lower volumetric energy density, which is not suitable for use in electric vehicles and other electronic devices. Further, LiMn having high interfacial energyxFe1-xPO4The nano particles are easy to aggregate, the operation difficulty of electrode manufacturing is greatly increased, and the electrochemical performance of the lithium ion battery is seriously influenced.
Porous LiMn formed by interconnecting nanoparticles, as compared to nanoparticlesxFe1-xPO4Microspheres are receiving increasing attention due to their high tap density, good flowability and porous structure. Porous LiMnxFe1-xPO4LiMn in microspheresxFe1-xPO4The good microspherical flow characteristics enable the electrode to be tightly packaged in the electrode, and the high volume energy density is guaranteed by combining with the high tap density. Meanwhile, LiMnxFe1-xPO4The porous structure of the microsphere can permeate electrolyte and is Li+The intercalation/deintercalation of (a) provides a sufficiently large active surface area. Further, LiMnxFe1-xPO4The micro-nano structure of the microsphere can inherit the advantages of short electron and ion transfer path of the original nano particles, and is beneficial to improving solid phase diffusion dynamics and electrochemical performance.
However, the prior art reports LiMnxFe1-xPO4The synthesis method of the microspheres is time-consuming and complex, and needs to use hard/soft templates to synthesize LiMn in advancexFe1-xPO4Microspheres or other methods are used to synthesize nanostructured precursors. Therefore, the method for preparing the high-performance lithium ion battery porous LiMn simply and economically is developedxFe1-xPO4The microsphere method is particularly important and urgent.
Disclosure of Invention
The object of the present invention is to overcome the above-mentioned drawbacks of the background art,provides a hierarchical porous LiMnxFe1- xPO4A template-free hydrothermal preparation method of a/C composite microsphere cathode material comprises the steps of forming and self-assembling nano particles, carrying out a dissolving-precipitating process in a hydrothermal reaction process, and obtaining porous LiMn after simple carbon coatingxFe1-xPO4the/C microsphere is of a hierarchical porous microsphere structure and is prepared from nano-scale LiMn with higher crystallinityxFe1-xPO4The main grain consists of a uniform carbon coating inside. The hierarchical porous LiMn obtained by the inventionxFe1-xPO4The unique structure of the/C composite microsphere cathode material simultaneously combines the design principles of structure, morphology and components, and has excellent structural stability and conduction advantages on electrons and lithium ions.
The composite microsphere anode material is prepared from LiMnxFe1-xPO4And (3) graded porous microspheres assembled by nano particles, wherein the diameter of the microspheres is not more than 8 microns.
To achieve the purpose of the invention, the invention grades porous LiMnxFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material comprises the following steps of:
(1) preparation of LiMnxFe1-xPO4Materials: sequentially adding a lithium source, a manganese source, an iron source, a phosphorus source and a reducing agent into deionized water, and fully and uniformly stirring; transferring the obtained mixed solution into a high-pressure reaction kettle, sealing, carrying out hydrothermal reaction for 6-12h at 160-200 ℃, naturally cooling to room temperature, carrying out suction filtration on a product, washing with deionized water, and drying the obtained solid precipitate to obtain LiMnxFe1-xPO4Precursor powder, and calcining the precursor powder in a protective atmosphere to obtain LiMnxFe1- xPO4A material;
(2) preparation of LiMnxFe1-xPO4material/C: the LiMn prepared in the step (1)xFe1-xPO4Dispersing the precursor powder in an organic carbon source aqueous solution, fully and uniformly stirring the solution, drying the solution,calcining the dried product in a protective atmosphere to obtain LiMnxFe1-xPO4a/C material;
wherein 0< x <1, the microspheres are no greater than 8 microns in diameter.
Further, in the step (1), the molar ratio of the lithium source, the manganese source, the iron source and the phosphorus source is Li: mn: fe: p is 1: x: 1-x: 1.
further, in the step (1), the lithium source is one or more of lithium hydroxide, lithium oxalate, lithium acetate, lithium carbonate, lithium nitrate and lithium oxide, and is preferably lithium hydroxide.
Further, in the step (1), the manganese source is one or more of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate, and preferably manganese nitrate.
Further, in the step (1), the iron source is one or more of ferric nitrate, ferric chloride, ferric sulfate and ferric citrate, and is preferably ferric nitrate.
Further, in the step (1), the phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate and lithium dihydrogen phosphate, and is preferably ammonium dihydrogen phosphate.
Further, the reducing agent in the step (1) is one or more of citric acid, glucose and ascorbic acid, and glucose is preferred.
Further, the protective atmosphere in steps (1) and (2) is one or more of nitrogen, argon, nitrogen-hydrogen mixed gas and argon-hydrogen mixed gas, preferably argon-hydrogen mixed gas.
Further, LiMn in the step (2)xFe1-xPO4The mass ratio of the precursor powder to the organic carbon source is 4-5: 1.
further, the organic carbon source in step (2) is one or more of sucrose, glucose, pitch, phenolic resin and PVP, and is preferably glucose.
Further, the calcination in the steps (1) and (2) is carried out at 4-6 ℃ for min-1The temperature rising rate is increased to 640-660 ℃, and the temperature is kept for 9-11 h.
Compared with the prior art, the invention has the following advantages:
(1) in the invention, the lithium source, the manganese source, the iron source, the phosphorus source and the reducing agent are all low-cost raw materials, in particular LiOH and Mn (NO) in the raw materials3)2、Fe(NO3)3、NH4H2PO4And glucose.
(2) Hierarchical porous LiMn prepared by the inventionxFe1-xPO4the/C composite microsphere positive electrode material ensures sufficient active contact area between an electrode and electrolyte, and in addition, the carbon coating on the surface of the material can also greatly improve the electronic conductivity inside the microsphere and between the microspheres, so that the material shows excellent electrochemical performance.
(3) The hierarchical porous LiMn of the inventionxFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material has the advantages of easily controlled conditions, simple process flow and contribution to industrial large-scale production, and the obtained hierarchical porous LiMnxFe1-xPO4the/C composite microsphere cathode material has faster electronic conductivity and Li+The conductivity is improved, so that the energy density of the lithium ion battery is improved, and the lithium ion battery has a good application prospect in the field of high-energy lithium ion batteries.
Drawings
FIG. 1 is LiMn synthesized in the examples0.1Fe0.9PO4Scanning Electron Micrographs (SEM) of microspheres;
FIG. 2 is LiMn synthesized in examples of the present invention0.1Fe0.9PO4Microspheres and LiMn0.1Fe0.9PO4Comparing charge and discharge curves of button cells assembled by using/C microspheres as raw materials at 0.2C and 1C, wherein four curves are arranged at the upper part and the lower part in the figure, and the four curves at the right side are represented by LiMn0.1Fe0.9PO4The charge-discharge curve of the button cell assembled by the C microspheres as raw materials; the four left-hand curves are represented by LiMn0.1Fe0.9PO4The microspheres are used as a charging and discharging curve of the button cell assembled by raw materials;
FIG. 3 is LiMn synthesized in examples of the present invention0.1Fe0.9PO4Microspheres and LiMn0.1Fe0.9PO4Button cell assembled by using/C microspheres as raw materials and having cycle performance comparison diagram at 0.2C, wherein the lowest part is LiMn synthesized in the embodiment of the invention0.1Fe0.9PO4The microspheres are button cells assembled by raw materials;
FIG. 4 is LiMn synthesized in examples of the present invention0.1Fe0.9PO4Microspheres and LiMn0.1Fe0.9PO4Button cell assembled by using/C microspheres as raw materials and a cycle performance comparison chart under 1C, wherein the lowest part is LiMn synthesized in the embodiment of the invention0.1Fe0.9PO4The microspheres are button cells assembled by raw materials.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. It is to be understood that the following description is only illustrative of the present invention and is not to be construed as limiting the present invention.
The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.
When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.
The indefinite articles "a" and "an" preceding an element or component of the invention are not intended to limit the number requirement (i.e., the number of occurrences) of the element or component. Thus, "a" or "an" should be read to include one or at least one, and the singular form of an element or component also includes the plural unless the number clearly indicates the singular.
Furthermore, the description below of the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Further, the technical features of the embodiments of the present invention may be combined with each other as long as they do not conflict with each other.
Example 1
One, LiMn0.1Fe0.9PO4Preparing a microsphere material:
(1) 0.587g of LiOH. H2O，0.5g Mn(NO3)2Solution (Mn (NO)3)250%) of 5.08g Fe (NO)3)39H2O，1.61g NH4H2PO4Adding 1.26g of glucose into 75ml of deionized water, and under the condition of continuous stirring, obtaining a gray green suspension;
(2) transferring the suspension obtained in the step (1) into a 100ml stainless steel high-pressure reaction kettle for hydrothermal reaction, and keeping the temperature at 180 ℃ for 9 hours;
(3) after the hydrothermal reaction is finished, naturally cooling the reaction kettle to room temperature, carrying out suction filtration on the product, washing the product with deionized water, and drying the product in a vacuum drying oven at 60 ℃ for 12 hours to obtain LiMn0.1Fe0.9PO4Precursor powder;
(4) LiMn obtained in the step (3)0.1Fe0.9PO4Placing the precursor powder in Ar/H2(H2Of 5%) at 5 ℃ for a period of time-1Raising the temperature to 650 ℃ at the temperature raising rate, and preserving the heat for 10 hours to obtain the LiMn0.1Fe0.9PO4A microsphere material.
II, LiMn0.1Fe0.9PO4Preparation of the/C microsphere material:
the LiMn prepared in the step (3) is added0.1Fe0.9PO4Dispersing the precursor powder in glucose aqueous solution (mass ratio of precursor powder to glucose is 4:1), stirring for 4H to ensure uniform dispersion, evaporating the dispersion in 80 deg.C water bath, collecting evaporated material, grinding into powder, and placing in Ar/H2(H2Of 5%) at 5 ℃ for a period of time-1Raising the temperature to 650 ℃ at the temperature raising rate, and preserving the heat for 10 hours to obtain the LiMn0.1Fe0.9PO4a/C microsphere material.
Preparation of positive electrode slice
LiMn prepared as described above respectively0.1Fe0.9PO4Microsphere material and LiMn0.1Fe0.9PO4Mixing the/C microsphere material, conductive carbon black Super P and a binder LA133 in a mass ratio of 8:1:1 in a penicillin bottle, using deionized water and absolute ethyl alcohol as dispersing agents, stirring the mixture by magnetic force to enable the slurry to be mixed uniformly, then coating the coating slurry on the surface of a pre-cut aluminum foil by using a scraper coating method to prepare a positive electrode plate, and drying the positive electrode plate in a vacuum drying oven at 120 ℃ for 12 hours for later use.
Fourthly, assembling the battery
LiMn prepared as described above respectively0.1Fe0.9PO4Microsphere material and LiMn0.1Fe0.9PO4The electrode plate of the/C microsphere material is a positive electrode, the PP polymer diaphragm (celgard 2500) is a battery diaphragm, the metal lithium sheet is a negative electrode, and the electrolyte contains 1mol L- 1LiFP6A mixed solution of Ethylene Carbonate (EC)/dimethyl carbonate (DMC) (volume ratio 1: 1). The cell being filled with high-purity argonThe glove box is thus assembled. And testing the charge and discharge performance of the assembled button battery at room temperature by adopting a LandCT2001A battery testing system and a CH1760E electrochemical workstation, wherein the charge and discharge termination voltage range is 2.5-4.5V.
LiMn in this example0.1Fe0.9PO4The scanning electron micrograph of the microsphere material is shown in FIG. 1.
LiMn in this example0.1Fe0.9PO4Microsphere material and LiMn0.1Fe0.9PO4The charge and discharge curves of the cell assembled with the/C microsphere material at 0.2C and 1C current densities are compared and shown in FIG. 2.
LiMn in this example0.1Fe0.9PO4Microsphere material and LiMn0.1Fe0.9PO4The cycling profile of a cell assembled with the/C microsphere material at a current density of 0.2C is shown in fig. 3. LiMn0.1Fe0.9PO4The discharge specific capacities of the battery assembled by the microsphere material after 100,200,300,500 cycles are 122.2,118.1,119.7 mAh g and 117.4mAh g respectively-1。LiMn0.1Fe0.9PO4The discharge specific capacity of the battery assembled by the/C microsphere material after 100,200,300,500 cycles is 147.8,144.2,138.6 mAh g and 134.9mAh g-1。
LiMn in this example0.1Fe0.9PO4Microsphere material and LiMn0.1Fe0.9PO4The cycling profile at 1C current density for a cell assembled with/C microsphere material is shown in fig. 4. LiMn0.1Fe0.9PO4The discharge specific capacities of the batteries assembled by the microsphere materials after 100,200,300,500 cycles are respectively 92.8,85.6,88.1 and 87.2mAh g-1。LiMn0.1Fe0.9PO4The discharge specific capacities of the batteries assembled by the/C microsphere material after 100,200,300,500 cycles are 133.8,127.3,125.5 mAh g and 114.8mAh g respectively-1。
Example 2
One, LiMn0.2Fe0.8PO4Preparation of microsphere materials
(1) 0.587g of LiOH. H2O，0.423g MnSO4，1.7g FeSO4，1.61g NH4H2PO4Adding 1.26g of glucose into 75ml of deionized water, and under the condition of continuous stirring, obtaining a gray green suspension;
(2) transferring the suspension obtained in the step (1) into a 100ml stainless steel high-pressure reaction kettle for hydrothermal reaction, and keeping the temperature at 180 ℃ for 9 hours;
(3) after the hydrothermal reaction is finished, naturally cooling the reaction kettle to room temperature, carrying out suction filtration on the product, washing the product with deionized water, and drying the product in a vacuum drying oven at 60 ℃ for 12 hours to obtain LiMn0.2Fe0.8PO4Precursor powder;
(4) LiMn obtained in the step (3)0.2Fe0.8PO4Placing the precursor powder in Ar/H2(H2Of 5%) at 5 ℃ for a period of time-1Raising the temperature rise rate to 650 ℃ and preserving the temperature for 10 hours to obtain LiMn0.2Fe0.8PO4A microsphere material.
II, LiMn0.2Fe0.8PO4Preparation of/C microsphere material
The LiMn prepared in the step (3) is added0.2Fe0.8PO4Dispersing the precursor powder in glucose aqueous solution (mass ratio of precursor powder to glucose is 4:1), stirring for 4H to ensure uniform dispersion, evaporating the dispersion in 80 deg.C water bath, collecting the evaporated material, grinding into powder, and placing in Ar/H2(H2Of 5%) at 5 ℃ for a period of time-1Raising the temperature rise rate to 650 ℃ and preserving the temperature for 10 hours to obtain LiMn0.2Fe0.8PO4a/C microsphere material.
Preparation of positive electrode slice
LiMn prepared as described above respectively0.2Fe0.8PO4Microsphere material and LiMn0.2Fe0.8PO4Mixing the/C microsphere material, conductive carbon black Super P and a binder LA133 in a penicillin bottle according to the mass ratio of 8:1:1, using deionized water and absolute ethyl alcohol as dispersing agents, stirring the materials by magnetic force to uniformly mix the slurry, and then coating the coating slurry on the product by a scraper coating methodFirstly, preparing a positive electrode plate on the surface of the cut aluminum foil, and drying the positive electrode plate in a vacuum drying oven at 120 ℃ for 12 hours for later use.
Fourthly, assembling the battery
LiMn prepared as described above respectively0.2Fe0.8PO4Microsphere material and LiMn0.2Fe0.8PO4The electrode plate of the/C microsphere material is a positive electrode, a PP polymer diaphragm (celgard 2500) is a battery diaphragm, a metal lithium sheet is a negative electrode, and the electrolyte contains 1mol L- 1LiFP6The volume ratio of Ethylene Carbonate (EC) to dimethyl carbonate (DMC) is 1: 1. The cell was assembled in a glove box filled with high purity argon. And testing the charge and discharge performance of the assembled button battery at room temperature by adopting a LandCT2001A battery testing system and a CH1760E electrochemical workstation, wherein the charge and discharge termination voltage range is 2.5-4.5V.
Example 3
One, LiMn0.5Fe0.5PO4Preparation of microsphere materials
(1) 0.587g of LiOH. H2O，0.88g MnCl2，1.135g FeCl3，1.61g NH4H2PO4Adding 1.26g of glucose into 75ml of deionized water, and under the condition of continuous stirring, obtaining a gray green suspension;
(2) transferring the suspension obtained in the step (1) into a 100ml stainless steel high-pressure reaction kettle for hydrothermal reaction, and keeping the temperature at 180 ℃ for 9 hours;
(3) after the hydrothermal reaction is finished, naturally cooling the reaction kettle to room temperature, carrying out suction filtration on the product, washing the product with deionized water, and drying the product in a vacuum drying oven at 60 ℃ for 12 hours to obtain LiMn0.5Fe0.5PO4Precursor powder;
(4) LiMn obtained in the step (3)0.5Fe0.5PO4Placing the precursor powder in Ar/H2(H2In a 5%) atmosphere at 5 deg.C for 5 min-1Raising the temperature rise rate to 650 ℃ and preserving the temperature for 10 hours to obtain LiMn0.5Fe0.5PO4A microsphere material.
II, LiMn0.5Fe0.5PO4Preparation of/C microsphere material
The LiMn prepared in the step (3) is added0.5Fe0.5PO4Dispersing the precursor powder in glucose aqueous solution (mass ratio of precursor powder to glucose is 4:1), stirring for 4H to ensure uniform dispersion, evaporating the dispersion in 80 deg.C water bath, collecting evaporated material, grinding into powder, and placing in Ar/H2(H2In a 5%) atmosphere at 5 deg.C for 5 min-1Raising the temperature rise rate to 650 ℃ and preserving the temperature for 10 hours to obtain LiMn0.5Fe0.5PO4a/C microsphere material.
Preparation of positive electrode slice
LiMn prepared as described above respectively0.5Fe0.5PO4Microsphere material and LiMn0.5Fe0.5PO4Mixing the/C microsphere material, conductive carbon black Super P and a binder LA133 in a penicillin bottle according to a mass ratio of 8:1:1, using deionized water and absolute ethyl alcohol as dispersing agents, stirring the mixture by magnetic force to uniformly mix the slurry, then coating the coating slurry on the surface of an aluminum foil cut in advance by using a scraper coating method to prepare a positive electrode plate, and drying the positive electrode plate in a vacuum drying oven at 120 ℃ for 12 hours for later use.
Fourthly, assembling the battery
LiMn prepared as described above respectively0.5Fe0.5PO4Microsphere material and LiMn0.5Fe0.5PO4The electrode plate of the/C microsphere material is a positive electrode, the PP polymer diaphragm (celgard 2500) is a battery diaphragm, the metal lithium sheet is a negative electrode, and the electrolyte contains 1mol L- 1LiFP6The volume ratio of Ethylene Carbonate (EC) to dimethyl carbonate (DMC) is 1: 1. The cell was assembled in a glove box filled with high purity argon. And testing the charge and discharge performance of the assembled button battery at room temperature by adopting a LandCT2001A battery testing system and a CH1760E electrochemical workstation, wherein the charge and discharge termination voltage range is 2.5-4.5V.
It will be understood by those skilled in the art that the foregoing is only exemplary of the present invention, and is not intended to limit the invention, which is intended to cover any variations, equivalents, or improvements therein, which fall within the spirit and scope of the invention.

Claims (8)

1. Hierarchical porous LiMnxFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized by comprising the following steps of:
(1) preparation of LiMnxFe1-xPO4Materials: sequentially adding a lithium source, a manganese source, an iron source, a phosphorus source and a reducing agent into deionized water, and fully and uniformly stirring; transferring the obtained mixed solution into a high-pressure reaction kettle, sealing, carrying out hydrothermal reaction for 6-12h at 160-200 ℃, naturally cooling to room temperature, carrying out suction filtration on a product, washing with deionized water, and drying the obtained solid precipitate to obtain LiMnxFe1-xPO4Precursor powder, and calcining the precursor powder in a protective atmosphere to obtain LiMnxFe1-xPO4A material;
(2) preparation of LiMnxFe1-xPO4material/C: the LiMn prepared in the step (1)xFe1-xPO4Dispersing the precursor powder in an organic carbon source aqueous solution, fully and uniformly stirring, drying the solution, and calcining the dried solution in a protective atmosphere to obtain LiMnxFe1-xPO4a/C material;
wherein 0< x <1, the microspheres are no greater than 8 microns in diameter;
the reducing agent in the step (1) is one or more of citric acid, glucose and ascorbic acid;
in the step (1), the iron source is one or more of ferric nitrate, ferric chloride, ferric sulfate and ferric citrate.
2. The hierarchical porous LiMn of claim 1xFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized in that in the step (1), the molar ratio of the components of the lithium source, the manganese source, the iron source and the phosphorus source is Li: mn: fe: p is 1:x: 1-x: 1; in the step (1), the lithium source is one or more of lithium hydroxide, lithium oxalate, lithium acetate, lithium carbonate, lithium nitrate and lithium oxide.
3. The hierarchical porous LiMn of claim 1xFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized in that the manganese source in the step (1) is one or more of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.
4. The hierarchical porous LiMn of claim 1xFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized in that in the step (1), the phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate and lithium dihydrogen phosphate.
5. The hierarchical porous LiMn of claim 1xFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized in that the reducing agent in the step (1) is glucose.
6. The hierarchical porous LiMn of claim 1xFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized in that the protective atmosphere in the steps (1) and (2) is one or more of nitrogen, argon, nitrogen-hydrogen mixed gas and argon-hydrogen mixed gas.
7. The hierarchical porous LiMn of claim 1xFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized in that LiMn in the step (2)xFe1-xPO4The mass ratio of the precursor powder to the organic carbon source is 4-5: 1; and (3) the organic carbon source in the step (2) is one or more of sucrose, glucose, asphalt, phenolic resin and PVP.
8. The hierarchical porous LiMn of claim 1xFe1-xPO4The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized in that the calcination in the steps (1) and (2) is carried out at 4-6 ℃ for min-1The temperature rising rate is increased to 640-660 ℃, and the temperature is kept for 9-11 h.
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