CN111092209A

CN111092209A - Composite material and preparation method and application thereof

Info

Publication number: CN111092209A
Application number: CN201911369280.2A
Authority: CN
Inventors: 汪伟文; 王丽平; 郑杰允; 李泓; 李立飞
Original assignee: Tianmu Lake Institute of Advanced Energy Storage Technologies Co Ltd
Current assignee: Tianmu Lake Institute of Advanced Energy Storage Technologies Co Ltd
Priority date: 2019-12-26
Filing date: 2019-12-26
Publication date: 2020-05-01

Abstract

The invention provides a composite material and a preparation method and application thereof, wherein the chemical composition of the composite material is FeS_2‑x@ C, wherein the value range of x is 0-1. A method for preparing a composite material comprising reacting FeS₂Calcining the carbon source mixture powder at 400-1000 ℃ in an inert gas atmosphere, and cooling along with the furnace to obtain the composite material. The composite material of the invention can effectively improve FeS₂The electronic conductivity of the raw material can effectively relieve FeS₂The active material pulverization causes the problems of capacity rapid attenuation and the like, so that the prepared composite material is preparedThe battery has better cycle performance.

Description

Composite material and preparation method and application thereof

Technical Field

The invention belongs to the field of material synthesis and chemical power supply, and particularly relates to FeS_2-xThe @ C composite material, the lithium battery positive electrode, the button battery and the preparation method and application of the button battery.

Background

So far, there has been a conventional graphite negative electrode and LiMO₂The energy and power density of commercial lithium ion batteries for (M ═ transition metal) positive electrodes have approached practical upper limits. Over the past two decades, great progress has been made in finding various negative electrode materials for lithium ion batteries, such as alloyed Si, Ge, Sb and Sn and conversion metal oxides. However, the research on the cathode material is much slower, mainly due to the LiMO₂The rigid structure of the oxide. Generally, suitable cathode materials for lithium ion batteries should combine the advantages of high energy density, long cycle life and low cost.

Over the past decade, a wide variety of Fe-based sulfide cathode materials (e.g., sulfide FeS)₂) Has attracted intensive attention from researchers to replace the typical LiMO₂Positive electrode materials because of their higher theoretical energy density and low cost characteristics. Especially pyrite FeS with rich content₂The theoretical capacity is up to 894mAh g^-1LiNi, the best intercalation cathode material than the current_xCo_yMn_zO₂Much higher (less than 300mAh g)^-1). In the discharge process, high-reactivity nano Fe powder and high-insulation Li₂FeS through which S passes₂Is formed by the conversion reaction of (a). Due to Li₂The insulation property of S, the severe agglomeration of nano Fe, and the dissolution of polysulfide converted from sulfur generated in situ, etc., are problems, and it is generally observed that the battery capacity is rapidly deteriorated and the cycle performance is poor.

Disclosure of Invention

In view of the above, the present invention is directed to a composite material, which overcomes the drawbacks of the prior art and can effectively improve FeS₂Electronic conductivity of the starting material, mitigation of FeS during cell cycling₂Active material dusting leads to problems such as rapid capacity fade.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a composite material has a chemical composition of FeS_2-x@ C, wherein the value range of x is 0-1.

Preferably, FeS in the composite material_2-xThe mass percentage of the component (A) is 40-99%.

The second object of the present invention is to propose a process for the preparation of a composite material as described above, by subjecting FeS to₂The raw materials are subjected to high-temperature desulfurization and carbon coating modification treatment to prepare the composite material.

a method for preparing a composite material, the method comprising subjecting FeS to₂Calcining the carbon source mixture powder at 400-1000 ℃ in an inert gas atmosphere, and cooling along with the furnace to obtain the composite material.

Preferably, FeS₂The mass ratio of the carbon source to the carbon source is (1-9): 1.

Preferably, the carbon source is one or more of ascorbic acid, glucose, fructose, maltose, phenol formaldehyde resin glucose, sucrose, soluble starch, polyacrylonitrile, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polyvinylidene fluoride, sodium carboxymethylcellulose, polypyrrole, and phenol formaldehyde resin.

Preferably, FeS₂The method for obtaining the powder mixed with the carbon source is to adopt a ball milling method to mix FeS with the carbon source₂Mixing with a carbon source.

Preferably, the ball milling speed is 100-400 r/min, and the ball milling time is 0.5-24 h;

and/or the inert gas is nitrogen and/or argon.

The invention also relates to the application of the composite material in a lithium battery to overcome the defects of the prior art, and the battery prepared by the composite material has high specific capacity and excellent cycling stability.

a lithium battery positive electrode comprises a conductive agent, a binder and an active material, and also comprises the composite material.

Preferably, in the lithium battery positive electrode, FeS_2-xThe content of the @ C composite material, the content of the conductive agent and the content of the adhesive are 40-99 wt%, 0-40 wt% and 0-30 wt%, respectively.

Preferably, in the lithium battery positive electrode, the conductive agent is one or more of acetylene black, graphite, ketjen black, graphene and a CNT conductive agent; the adhesive is one of polyvinylidene fluoride and polytetrafluoroethylene.

Preferably, the active material is a metal current collector, preferably Al;

preferably, the FeS in the composite material in the lithium battery positive electrode_2-xThe mass percentage is 40-99%.

The invention also relates to a lithium battery, which comprises a positive electrode, a diaphragm and a negative electrode, wherein the positive electrode is the positive electrode of the lithium battery, and the negative electrode is preferably a metallic lithium negative electrode.

The button cell is assembled by the lithium battery anode, the metal lithium cathode, the conventional lithium battery diaphragm and the conventional lithium battery electrolyte, and electrochemical test is carried out. The solvent in the preferred electrolyte is composed of 1, 2-Dimethoxyethane (DME) and 1, 3-Dioxolane (DOL) in a volume ratio of 1:1, and the lithium salt is lithium bis (trichloromethylsulfonate) imide (i.e., lithium bis (trifluoromethyl) sulfonylimide, LiTFSI) at a concentration of 1 mol/L. The constant current charge and discharge test is carried out on a NEWARE battery test system, and the cut-off potential of the lithium battery is 1.0-3.0V. All tests were performed at room temperature.

Compared with the prior art, the composite material has the following advantages:

(1) can effectively improve FeS₂Electronic conductivity of the starting material, mitigation of FeS during cell cycling₂Active material dusting leads to problems such as rapid capacity fade.

(2) The lithium ion battery anode material has good stability, high specific capacity, excellent cycling stability and good rate performance.

The preparation method of the composite material has the following advantages:

(1) low cost, abundant and cheap raw materials, easy acquisition and environmental protection.

(2) Simple operation, good repeatability and high product purity.

Compared with the prior art, the advantages of the lithium battery anode and the lithium battery are the same as those of the composite material, and are not described again.

Drawings

FIG. 1 shows FeS in example 1 of the present invention_2-xSEM picture of @ C composite;

FIG. 2 shows FeS in example 1 of the present invention_2-xTEM image of @ C composite;

FIG. 3 shows FeS in example 1 of the present invention_2-xThe XRD pattern of the @ C composite;

FIG. 4 shows FeS in example 1 of the present invention_2-xThe charging and discharging curve chart of the @ C composite material;

FIG. 5 shows FeS in example 1 of the present invention_2-xA plot of the cycling performance of the @ C composite;

FIG. 6 shows FeS in example 2 of the present invention_2-xThe XRD pattern of the @ C composite;

FIG. 7 shows FeS in example 2 of the present invention_2-xA plot of the cycling performance of the @ C composite;

FIG. 8 shows FeS in example 3 of the present invention_2-xThe XRD pattern of the @ C composite;

FIG. 9 shows FeS in example 3 of the present invention_2-xA plot of the cycling performance of the @ C composite;

FIG. 10 is a graph of the cycle performance of the sample of comparative example 1 of the present invention.

FIG. 11 is a graph of the cycle performance of the sample of comparative example 2 of the present invention.

Detailed Description

Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.

The present invention will be described in detail with reference to the following examples and accompanying drawings.

In order to embody the chemical composition, the chemical composition of the composite material is used in the following examples to define the name, i.e. "composite material" is written as "FeS_2-x@ C composite ". In addition, "FeS" is_2-xIn @ C "@" denotes a coating, in particular FeS_2-xThe material @ C is that in FeS_2-xThe surface of the material is coated with a layer of carbon material.

Example 1

FeS_2-xThe preparation method of the @ C composite material comprises the following specific steps:

(1) FeS is prepared₂Mixing the raw materials with a carbon source (glucose) according to a mass ratio of 9:1, and ball-milling at a rotating speed of 400r/min for 4 h;

(2) calcining the composite material obtained by ball milling for 8 hours at the temperature of 600 ℃ in an inert gas atmosphere, and cooling along with the furnace to obtain FeS_2-x@ C composite material. Measuring Fe content in the composite material by adopting an inductively coupled plasma emission spectrometer (ICP-OES), and measuring carbon and sulfur content in the composite material by adopting an element analyzer (UNICUBE, elementary), thus obtaining FeS_2-x0.86% of x in @ C composite material, FeS_2-xThe mass percentage of (B) is 94.8%.

In the preparation process, the carbon source adopts glucose, and the inert gas adopts nitrogen.

A lithium battery positive electrode containing the FeS_2-x@ C composite, acetylene black (20 wt%), polyvinylidene fluoride (PVDF), Al foil current collector, FeS_2-xThe mass ratio of the @ C composite material to the acetylene black (20 wt%) to the polyvinylidene fluoride (PVDF) is 8:1: 1.

The method for preparing the lithium battery anode comprises the following steps: the FeS is treated_2-xThe @ C composite, acetylene black (20 wt%), and polyvinylidene fluoride (PVDF) were dispersed in N-methylpyrrolidone (NMP) solvent and ground until mixed to give a slurry. And then coating the slurry on an Al foil current collector, and transferring the Al foil current collector into a vacuum oven at 80 ℃ for drying for 12 hours to obtain the lithium battery anode.

A lithium battery comprises the positive electrode, the negative electrode, electrolyte 1M LiTFSI-DOL/DME (v: v is 1:1) and a PP diaphragm, wherein the positive electrode, the negative electrode, the electrolyte and the PP diaphragm are assembled in a glove box filled with argon to form the button battery. The assembling mode is the conventional assembling mode.

And testing the performance of the battery in the button battery testing system. The charge-discharge current density is set to be 200mA/g, and the charge-discharge cut-off voltage limit is 1.0-3.0V.

This example is FeS_2-xThe SEM image of the @ C composite material is shown in FIG. 1, and from FIG. 1, it is clear that FeS_2-xThe @ C composite material has different particle sizes ranging from about 300nm to 5 microns.

This example is FeS_2-xThe TEM image of the @ C composite is shown in FIG. 2, and it is clear from FIG. 2 that FeS is produced_2-xVery even cladding of carbon layer in @ C composite material is at FeS_2-xThe surface of the material.

This example is FeS_2-xThe XRD pattern of the @ C composite material is shown in FIG. 3, and from FIG. 3, it is understood that FeS_2-xEach diffraction peak and Fe of @ C composite material₇S₈The standard card PDF #29-0723 is consistent with the result that x is approximately equal to 0.86 in the obtained composite material, and the result is consistent with the result of the element analysis.

This example is FeS_2-xThe charge-discharge curve of the @ C composite material is shown in FIG. 4, and from FIG. 4, it is clear that FeS_2-xThe primary discharge plateau for the @ C composite is about 1.45V;

this example is FeS_2-xThe charge-discharge cycle chart of the @ C composite material is shown in FIG. 5, and from FIG. 5, it is clear that FeS_2-x@ C composite material is subjected to charge-discharge cycle at a current density of 200mA/g according to FeS_2-xThe specific discharge capacity is kept at 610mAh/g and the coulombic efficiency is 99.9 percent by calculation of the @ C composite material.

Example 2

The preparation method is the same as example 1, only the composite material obtained by calcining and ball-milling at 600 ℃ is calcined at 400 ℃ for 12h, the rest steps are the same as example 1, and the FeS is obtained_2-x0 in @ C composite, FeS_2-xIs 95.8 percent by mass, namely the obtained material isFeS₂The specific XRD results for the @ C composite are shown in FIG. 6. This example is FeS_2-xThe charge-discharge cycle chart of the @ C composite material is shown in FIG. 6, and it can be seen from FIG. 6 that compared with the uncoated sample of comparative example 1, the FeS of the present example is caused by the fact that the electron conductivity of the material is improved after coating, and the volume expansion change of the material in the charge-discharge process can be effectively relieved by the carbon coating layer_2-xThe first-turn discharge capacity of the @ C composite material is high, and the capacity decay is relatively slow.

Example 3

The preparation method is the same as example 1, only the composite material obtained by calcining and ball-milling at 600 ℃ is calcined at 1000 ℃ for 0.5h, the rest steps are the same as example 1, and the obtained FeS_2-xX ═ 1, FeS in @ C composite_2-xThe mass percent of (a) is 94.7%, that is, the obtained material is the FeS @ C composite material, and the specific result is shown in an XRD (X-ray diffraction) diagram of figure 8. This example is FeS_2-xThe charge-discharge cycle chart of the @ C composite material is shown in FIG. 9.

Example 4

The preparation method is the same as example 1, only FeS₂The raw material and the carbon source (glucose) are mixed according to the mass ratio of 9:1 instead of 1:1, the rest steps are the same as the example 1, and the FeS is obtained_2-x@ C composite where x is 0.86, FeS_2-xThe mass percentage of (B) was 67.5%. This example is FeS_2-xThe discharge properties of the @ C composite are shown in Table 1.

Example 5

The preparation method is the same as example 1, only FeS₂The raw material and the carbon source (glucose) are mixed according to the mass ratio of 9:1 instead of 3:1, the rest steps are the same as the example 1, and the obtained FeS_2-x@ C composite where x is 0.86, FeS_2-xThe mass percentage of (B) is 86.1%. This example is FeS_2-xThe discharge properties of the @ C composite are shown in Table 1.

Example 6

The preparation method is the same as example 1, only FeS₂The raw material and the carbon source (glucose) were mixed in a mass ratio of 9:1, the mixture was changed to 5:1, the rest of the procedure was the same as in example 1, and the obtained FeS_2-x@ C composite materialWhere x is 0.86, FeS_2-xThe mass percentage of (B) is 91.2%. This example is FeS_2-xThe discharge properties of the @ C composite are shown in Table 1.

Example 7

The preparation method is the same as example 1, only FeS₂The raw material and the carbon source (glucose) were mixed at a mass ratio of 9:1, changed to 7:1, and the rest of the procedure was the same as in example 1 to obtain FeS_2-x@ C composite where x is 0.86, FeS_2-xThe mass percentage of (B) is 93.6%. This example is FeS_2-xThe discharge properties of the @ C composite are shown in Table 1.

Table 1 examples FeS_2-xDischarge performance of @ C composite

As can be seen from the table, when the amount of the carbon source in the raw material is high, the obtained composite material has good cycle performance and high capacity retention rate, but FeS is caused by high carbon content_2-xAn increase in the carbon content of the inactive substance in the @ C composite, i.e. corresponding to the active substance FeS_2-xIs reduced, resulting in FeS_2-xThe discharge capacity of the @ C composite is relatively low.

Example 8

The preparation method is the same as example 1, only the composite material obtained by calcining and ball-milling at 600 ℃ is calcined at 500 ℃ for 0.5h, the rest steps are the same as example 1, and the obtained FeS_2-x0.06 x in @ C composite, FeS_2-xThe mass percentage of (B) is 95.7%.

Example 9

The preparation method is the same as example 1, only the composite material obtained by calcining and ball milling at 600 ℃ is calcined for 8 hours at 500 ℃ for 5 hours, the rest steps are the same as example 1, and the obtained FeS_2-x0.23 in @ C composite, FeS_2-xThe mass percentage of (B) is 95.5%.

Example 10

The preparation method is the same as that of example 1, and the composite material obtained by calcining and ball milling at the temperature of 600 ℃ is only used for 8hCalcination was carried out at 550 ℃ for 5 hours, and the rest steps were the same as in example 1 to obtain FeS_2-x0.58 in @ C composites, FeS_2-xThe mass percentage of (B) is 95.2%.

Example 11

The preparation method is the same as example 1, only the composite material obtained by calcining and ball-milling at 600 ℃ is calcined at 550 ℃ for 10h, the rest steps are the same as example 1, and the FeS is obtained_2-x0.74 of x in @ C composite material, FeS_2-xThe mass percentage of (B) is 95.1%.

Comparative example 1

The preparation method is the same as example 1, except that no carbon source is added in the ball milling process, and the rest steps are the same as example 1, so that the obtained material experiment test result is quite poor, and the cycling stability is poor. The capacity was low, and the specific results are shown in FIG. 10.

Comparative example 2

The preparation method is the same as that of example 1, only 8 hours of the composite material obtained by calcining and ball-milling at 600 ℃ is changed into 12 hours of calcining at 300 ℃, the rest steps are the same as those of example 1, compared with example 2, the obtained material has lower electron conductivity due to too low carbonization temperature, so that the discharge capacity is lower, and the specific charge-discharge cycle result is shown in fig. 11.

Comparative example 3

The preparation method is the same as example 1, only the composite material obtained by calcining and ball milling at 600 ℃ is calcined for 8 hours and is changed into calcining at 1100 ℃ for 0.5 hour, the rest steps are the same as example 1, and FeS is caused due to too high calcining temperature₂The composite material obtained by decomposing the raw materials is FeS_2-x+ Fe + C.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A composite material characterized by: the chemical composition is FeS_2-x@ C, wherein the value range of x is 0-1.

2. The composite material of claim 1, wherein: FeS in composite material_2-xThe mass percentage of the component (A) is 40-99%.

3. A method of preparing a composite material according to claim 1 or 2, characterized in that: comprises FeS₂Calcining the carbon source mixture powder at 400-1000 ℃ in an inert gas atmosphere, and cooling along with the furnace to obtain FeS_2-x@ C composite material.

4. A method for preparing a composite material according to claim 3, characterized in that: FeS₂The mass ratio of the carbon source to the carbon source is (1-9): 1.

5. A method for preparing a composite material according to claim 3 or 4, characterized in that: the carbon source is one or more of ascorbic acid, glucose, fructose, maltose, phenolic resin glucose, sucrose, soluble starch, polyacrylonitrile, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polyvinylidene fluoride, sodium carboxymethylcellulose, polypyrrole and phenolic resin.

6. The method for preparing a composite material according to any one of claims 3 to 5, characterized in that: FeS₂The method for obtaining the powder mixed with the carbon source is to adopt a ball milling method to mix FeS with the carbon source₂Mixing with a carbon source;

and/or the inert gas is nitrogen and/or argon.

7. The method for preparing a composite material according to claim 6, characterized in that: the ball milling speed is 100-400 r/min, and the ball milling time is 0.5-24 h.

8. Use of a composite material according to claim 1 or 2 in a lithium battery.

9. A lithium battery positive electrode comprises an active material, a conductive agent and a binder, and is characterized in that: further comprising the composite material according to claim 1 or 2.

10. A lithium battery comprises a positive electrode, a diaphragm and a negative electrode, and is characterized in that: the positive electrode is the positive electrode for a lithium battery according to claim 9.