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

Abstract

The invention belongs to the technical field of electrochemical energy storage materials, and discloses hierarchical porous LiMn_xFe_1‑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 coating_xFe_1‑xPO₄the/C microsphere is of a hierarchical porous microsphere structure and is prepared from nano-scale LiMn with higher crystallinity_xFe_1‑xPO₄The main grain consists of a uniform carbon coating inside. The hierarchical porous LiMn obtained by the invention_xFe_1‑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 LiMn_xFe_{1- x}PO₄A 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 Mn_xFe_1-xPO₄Solid solution systems are believed to incorporate LiFePO₄And LiMnPO₄Advantageous candidate positive electrode materials.

To further increase LiMn_xFe_1-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 LiMn_xFe_1-xPO₄The particle (such as nanosphere, nano-plate and nano-rod) has achieved wide effect. Due to LiMn_xFe_1-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 present_xFe_1-xPO₄Nanoparticles and electrolysisThe contact surface of the material is enlarged, inevitably resulting in poor side reactions, low thermal stability and poor cycle performance. Further, LiMn_xFe_1-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 energy_xFe_1-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 nanoparticles_xFe_1-xPO₄Microspheres are receiving increasing attention due to their high tap density, good flowability and porous structure. Porous LiMn_xFe_1-xPO₄LiMn in microspheres_xFe_1-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, LiMn_xFe_1-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, LiMn_xFe_1-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 LiMn_xFe_1-xPO₄The synthesis method of the microspheres is time-consuming and complex, and needs to use hard/soft templates to synthesize LiMn in advance_xFe_1-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 developed_xFe_1-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 LiMn_xFe_{1- x}PO₄A 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 coating_xFe_1-xPO₄the/C microsphere is of a hierarchical porous microsphere structure and is prepared from nano-scale LiMn with higher crystallinity_xFe_1-xPO₄The main grain consists of a uniform carbon coating inside. The hierarchical porous LiMn obtained by the invention_xFe_1-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 LiMn_xFe_1-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 LiMn_xFe_1-xPO₄The template-free hydrothermal preparation method of the/C composite microsphere cathode material comprises the following steps of:

(1) preparation of LiMn_xFe_1-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 LiMn_xFe_1-xPO₄Precursor powder, and calcining the precursor powder in a protective atmosphere to obtain LiMn_xFe_{1- x}PO₄A material;

(2) preparation of LiMn_xFe_1-xPO₄material/C: the LiMn prepared in the step (1)_xFe_1-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 LiMn_xFe_1-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)_xFe_1-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 invention_xFe_1-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 invention_xFe_1-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 LiMn_xFe_1-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 examples_0.1Fe_0.9PO₄Scanning Electron Micrographs (SEM) of microspheres;

FIG. 2 is LiMn synthesized in examples of the present invention_0.1Fe_0.9PO₄Microspheres and LiMn_0.1Fe_0.9PO₄Comparing 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 LiMn_0.1Fe_0.9PO₄The charge-discharge curve of the button cell assembled by the C microspheres as raw materials; the four left-hand curves are represented by LiMn_0.1Fe_0.9PO₄The 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 invention_0.1Fe_0.9PO₄Microspheres and LiMn_0.1Fe_0.9PO₄Button 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 invention_0.1Fe_0.9PO₄The microspheres are button cells assembled by raw materials;

FIG. 4 is LiMn synthesized in examples of the present invention_0.1Fe_0.9PO₄Microspheres and LiMn_0.1Fe_0.9PO₄Button 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 invention_0.1Fe_0.9PO₄The 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, LiMn_0.1Fe_0.9PO₄Preparing 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 LiMn_0.1Fe_0.9PO₄Precursor powder;

(4) LiMn obtained in the step (3)_0.1Fe_0.9PO₄Placing 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 LiMn_0.1Fe_0.9PO₄A microsphere material.

II, LiMn_0.1Fe_0.9PO₄Preparation of the/C microsphere material:

the LiMn prepared in the step (3) is added_0.1Fe_0.9PO₄Dispersing 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 LiMn_0.1Fe_0.9PO₄a/C microsphere material.

Preparation of positive electrode slice

LiMn prepared as described above respectively_0.1Fe_0.9PO₄Microsphere material and LiMn_0.1Fe_0.9PO₄Mixing 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 respectively_0.1Fe_0.9PO₄Microsphere material and LiMn_0.1Fe_0.9PO₄The 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^{- 1}LiFP₆A 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 example_0.1Fe_0.9PO₄The scanning electron micrograph of the microsphere material is shown in FIG. 1.

LiMn in this example_0.1Fe_0.9PO₄Microsphere material and LiMn_0.1Fe_0.9PO₄The 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 example_0.1Fe_0.9PO₄Microsphere material and LiMn_0.1Fe_0.9PO₄The cycling profile of a cell assembled with the/C microsphere material at a current density of 0.2C is shown in fig. 3. LiMn_0.1Fe_0.9PO₄The 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。LiMn_0.1Fe_0.9PO₄The 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 example_0.1Fe_0.9PO₄Microsphere material and LiMn_0.1Fe_0.9PO₄The cycling profile at 1C current density for a cell assembled with/C microsphere material is shown in fig. 4. LiMn_0.1Fe_0.9PO₄The 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。LiMn_0.1Fe_0.9PO₄The 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, LiMn_0.2Fe_0.8PO₄Preparation 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 LiMn_0.2Fe_0.8PO₄Precursor powder;

(4) LiMn obtained in the step (3)_0.2Fe_0.8PO₄Placing 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 LiMn_0.2Fe_0.8PO₄A microsphere material.

II, LiMn_0.2Fe_0.8PO₄Preparation of/C microsphere material

The LiMn prepared in the step (3) is added_0.2Fe_0.8PO₄Dispersing 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 LiMn_0.2Fe_0.8PO₄a/C microsphere material.

Preparation of positive electrode slice

LiMn prepared as described above respectively_0.2Fe_0.8PO₄Microsphere material and LiMn_0.2Fe_0.8PO₄Mixing 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 respectively_0.2Fe_0.8PO₄Microsphere material and LiMn_0.2Fe_0.8PO₄The 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^{- 1}LiFP₆The 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, LiMn_0.5Fe_0.5PO₄Preparation 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 LiMn_0.5Fe_0.5PO₄Precursor powder;

(4) LiMn obtained in the step (3)_0.5Fe_0.5PO₄Placing 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 LiMn_0.5Fe_0.5PO₄A microsphere material.

II, LiMn_0.5Fe_0.5PO₄Preparation of/C microsphere material

The LiMn prepared in the step (3) is added_0.5Fe_0.5PO₄Dispersing 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 LiMn_0.5Fe_0.5PO₄a/C microsphere material.

Preparation of positive electrode slice

LiMn prepared as described above respectively_0.5Fe_0.5PO₄Microsphere material and LiMn_0.5Fe_0.5PO₄Mixing 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 respectively_0.5Fe_0.5PO₄Microsphere material and LiMn_0.5Fe_0.5PO₄The 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^{- 1}LiFP₆The 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 LiMn_xFe_1-xPO₄The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized by comprising the following steps of:

(1) preparation of LiMn_xFe_1-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 LiMn_xFe_1-xPO₄Precursor powder, and calcining the precursor powder in a protective atmosphere to obtain LiMn_xFe_1-xPO₄A material;

(2) preparation of LiMn_xFe_1-xPO₄material/C: the LiMn prepared in the step (1)_xFe_1-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 LiMn_xFe_1-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 1_xFe_1-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 1_xFe_1-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 1_xFe_1-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 1_xFe_1-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 1_xFe_1-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 1_xFe_1-xPO₄The template-free hydrothermal preparation method of the/C composite microsphere cathode material is characterized in that LiMn in the step (2)_xFe_1-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 1_xFe_1-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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