CN110729481A - Lithium ion battery negative active material MnxFe1-xC2O4Synthetic method and application - Google Patents

Lithium ion battery negative active material MnxFe1-xC2O4Synthetic method and application Download PDF

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CN110729481A
CN110729481A CN201911018251.1A CN201911018251A CN110729481A CN 110729481 A CN110729481 A CN 110729481A CN 201911018251 A CN201911018251 A CN 201911018251A CN 110729481 A CN110729481 A CN 110729481A
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lithium ion
active material
ion battery
negative electrode
negative active
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王石泉
贾艳梅
刘建文
陈文�
吴慧敏
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Hubei 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
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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
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    • 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

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Abstract

The invention discloses a cathode active material Mn of a lithium ion batteryxFe1‑xC2O4And a synthetic method and application thereof. The invention adopts a hydrothermal or solvothermal method to prepare the manganese oxalate with a rod-shaped structure. In addition, a series of manganese iron oxalate Mn with different morphologies after the manganese oxalate is modified is obtained by doping ferrous salt with a proper proportion and adopting the same methodxFe1‑xC2O4A material. Tests in application in lithium ion batteries show that: mn synthesized by the inventionxFe1‑xC2O4The material is used as a negative active material, and compared with pure-phase manganese oxalate, the reversible specific capacity is obviously improved; the cycling stability is also obviously improved. For exampleMn prepared by doping0.8Fe0.2C2O4The capacity of the lithium ion battery can be remarkably improved, and the most excellent cycle performance and rate capability are shown. Thus, Mn of the present inventionxFe1‑ xC2O4Is a potential lithium ion negative electrode material.

Description

Lithium ion battery negative active material MnxFe1-xC2O4Synthetic method and application
Technical Field
The invention relates to the technical field of new energy material synthesis, in particular to a lithium ion battery cathode active material MnxFe1-xC2O4A synthetic method and application.
Background
Lithium Ion Batteries (LIBs) have wide application in the fields of electric vehicles, hybrid electric vehicles, smart grids, renewable energy sources and the like, and electrode materials of lithium ions are the hot spots of research of people all the time.
Graphite has a low operating voltage and a stable cycle capacity as a commercially used negative electrode material for lithium ion batteries, but as the demand for high-energy and high-power-density LIBs increases, the capacity of graphite is low (theoretical capacity: 372mAh g)-1Corresponds to LiC6) Poor performance kinetics of lithium intercalation and deintercalation become factors restricting practical application, and the increasingly high requirements on the performance of the lithium ion battery are difficult to meet. Therefore, efforts are being made to develop a negative electrode material having high performance instead of industrial graphite.
Through a great deal of previous research, many materials such as fluoride, oxide, nitride, phosphide and oxysalt can be used as the negative electrode material of the lithium ion battery with good electrochemical performance. Among them, among the oxo acid salts, oxalate such as cobalt oxalate, ferrous oxalate, manganese oxalate, etc. are widely noticed by people due to their advantages of easy preparation and low cost. Of these, manganese oxalate is of interest to researchers in that it has a specific stoichiometric composition and a small grain size. However, in the past researches, the oxalate is generally prepared by a reverse micelle method, and the oxalate prepared by the method has low capacity and poor circulation stability. Therefore, the manganese oxalate prepared by the reverse micelle method has poor electrochemical performance and is not suitable for being used as a lithium ion battery material.
For the above reasons, the present application has been made.
Disclosure of Invention
In view of the problems or defects of the prior art, the present invention is directed to a negative active material Mn for lithium ion batteriesxFe1-xC2O4A synthetic method and application. The method adopts a hydrothermal or solvothermal method to prepare the manganese oxalate, so that the crystallinity of the product can be improved, the structural stability of the manganese oxalate is improved, and the capacity is lower. In addition, the invention also relates to Fe2+Mixed oxalate Mn prepared by doping ions into the crystal lattice of manganese oxalatexFe1-xC2O4The capacity and the circulation stability of the manganese oxalate can be obviously improved, the prepared mixed oxalate has a smaller size structure, the contact area of the material and electrolyte can be improved, the diffusion path of lithium ions is shortened, and the electrochemical performance is better.
In order to achieve the first object of the present invention, the present invention adopts the following technical solutions:
lithium ion battery negative active material MnxFe1-xC2O4Wherein: x is more than or equal to 0.5 and less than or equal to 1.
Further, in the above technical solution, the Mn isxFe1-xC2O4The value of x is preferably equal to 0.8.
The second purpose of the invention is to provide the negative active material Mn of the lithium ion batteryxFe1-xC2O4The method specifically comprises the following steps:
(1) raw material dissolution: according to the molar metering ratio of 5-10: 0-5: 10 adding soluble manganese salt, ferrous salt and oxalic acid into a uniform medium, and stirring and mixing uniformly to obtain a mixed reaction solution;
(2) hydrothermal or solvothermal synthesis: transferring the mixed reaction liquid obtained in the step (1) into a polytetrafluoroethylene reaction kettle, sealing, heating the reaction kettle to 100-180 ℃ for constant-temperature reaction for 24 hours, cooling to room temperature after the reaction is finished, taking out the obtained product, centrifuging, washing for several times, and finally vacuum dryingObtaining MnxFe1-xC2O4A precursor;
(3) annealing treatment: mn obtained in the step (2)xFe1-xC2O4Placing the precursor in a tube furnace, heating for 1-3h under the protection of inert gas to remove crystal water, and obtaining the cathode active material Mn of the lithium ion batteryxFe1-xC2O4。
Further, in the above technical solution, the ratio of the number of moles of oxalic acid in step (1) to the sum of the number of moles of the manganese salt and the ferrous salt is 1.
Further, in the above technical scheme, the soluble manganese salt in step (1) may be any one or more of manganese acetate, manganese chloride, manganese sulfate, manganese nitrate, and the like.
Preferably, in the above technical solution, the manganese acetate is manganese acetate tetrahydrate (mn (ac))2·4H2O)。
Further, in the above technical solution, the ferrous salt in the step (1) may be ferrous sulfate (e.g., FeSO)4·7H2O), ferrous chloride, and the like, or combinations thereof.
Further, in the above technical scheme, the chemical formula of oxalic acid in the step (1) is H2C2O4·2H2O。
Further, in the above technical solution, the homogeneous medium in step (1) is any one of water and Ethylene Glycol (EG), or a combination thereof, wherein: the ratio of the water to the ethylene glycol is not limited as long as the reaction is not affected.
Further, in the above technical solution, the vacuum drying process in step (2) is preferably: drying at 60 deg.C for 12 h.
Further, in the above technical solution, the inert gas in the step (3) is preferably argon gas.
Further, in the above technical solution, the heating temperature in the step (3) is 180-; the heating time is preferably 2 h.
The third purpose of the invention is to provide the lithium ion battery prepared by the methodNegative electrode active material MnxFe1-xC2O4The lithium ion battery anode material can be used as a lithium ion battery anode material.
The negative electrode material of the lithium ion battery comprises a negative electrode active material, a binder and a conductive additive, wherein the negative electrode active material is the negative electrode active material Mn of the lithium ion batteryxFe1-xC2O4。
A lithium ion battery negative electrode comprising a current collector and a negative electrode material coated and/or filled on the current collector, wherein: the negative electrode material is the lithium ion battery negative electrode material.
A lithium ion battery comprising a pole core and a nonaqueous electrolytic solution, the pole core and the nonaqueous electrolytic solution being sealed in a battery case, the pole core comprising a positive electrode, a negative electrode and a separator, wherein: the negative electrode is the negative electrode of the lithium ion battery.
Compared with the prior art, the invention relates to a lithium ion battery cathode active material MnxFe1-xC2O4The preparation method and the application have the following beneficial effects:
(1) the synthesis method is simple and easy to operate, and the prepared cathode active material Mn of the lithium ion batteryxFe1-xC2O4The lithium ion battery material is used for a lithium ion battery performance test, can remarkably improve the capacity of the lithium ion battery, has a low charge and discharge platform, shows excellent cycle performance and rate capability, and is a very potential lithium ion negative electrode material.
(2) The invention adopts a hydrothermal or solvothermal method and takes water and glycol as solvents to prepare the manganese oxalate with a rod-shaped structure. By doping ferrous salt with proper proportion, a series of manganese iron oxalate Mn with different morphologies after the manganese oxalate is modified is obtained by the same preparation methodxFe1-xC2O4A material. Mn synthesized by the inventionxFe1-xC2O4As a negative active material of the lithium ion battery, compared with pure-phase manganese oxalate, the material has smaller particle size and obvious reversible specific capacitySignificantly improved, e.g. Mn prepared by doping with a multi-layered nano-platelet structure0.8Fe0.2C2O4The contact area of the material and the electrolyte is obviously increased, the capacity of the lithium ion battery can be obviously improved, and the optimal cycle performance and rate performance are shown.
Drawings
FIG. 1 shows separately synthesized negative active materials MnC of Li-ion batteries according to examples 1-7 of the present invention2O4、Mn0.9Fe0.1C2O4、Mn0.85Fe0.15C2O4、Mn0.8Fe0.2C2O4、Mn0.75Fe0.25C2O4、Mn0.67Fe0.33C2O4、Mn0.5Fe0.5C2O4XRD contrast patterns of the samples;
in FIG. 2, (a) to (g) are sequentially the negative electrode active materials MnC of the lithium ion batteries synthesized in examples 1 to 7 of the present invention2O4、Mn0.9Fe0.1C2O4、Mn0.85Fe0.15C2O4、Mn0.8Fe0.2C2O4、Mn0.75Fe0.25C2O4、Mn0.67Fe0.33C2O4、Mn0.5Fe0.5C2O4SEM comparison of samples;
FIG. 3 shows a lithium ion battery negative active material MnC synthesized in examples 1-7 of the present invention2O4、Mn0.9Fe0.1C2O4、Mn0.85Fe0.15C2O4、Mn0.8Fe0.2C2O4、Mn0.75Fe0.25C2O4、Mn0.67Fe0.33C2O4、Mn0.5Fe0.5C2O4The sample had a current density of 100mA · g-1A graph comparing the cycling stability for 100 cycles under the conditions;
FIG. 4 shows a lithium ion battery negative active material MnC synthesized in examples 1-7 of the present invention2O4、Mn0.9Fe0.1C2O4、Mn0.85Fe0.15C2O4、Mn0.8Fe0.2C2O4、Mn0.75Fe0.25C2O4、Mn0.67Fe0.33C2O4、Mn0.5Fe0.5C2O4A graph comparing the rate performance curves of the half cells of the samples;
FIGS. 5(a) - (g) are respectively a lithium ion battery negative active material MnC synthesized in examples 1-7 of the present invention2O4、Mn0.9Fe0.1C2O4、Mn0.85Fe0.15C2O4、Mn0.8Fe0.2C2O4、Mn0.75Fe0.25C2O4、Mn0.67Fe0.33C2O4、Mn0.5Fe0.5C2O4The charge and discharge curves of the samples are compared.
Detailed Description
The present invention will be described in further detail below with reference to examples. The present invention is implemented on the premise of the technology of the present invention, and the detailed embodiments and specific procedures are given to illustrate the inventive aspects of the present invention, but the scope of the present invention is not limited to the following embodiments.
Various modifications to the precise description of the invention will be readily apparent to those skilled in the art from the information contained herein without departing from the spirit and scope of the appended claims. It is to be understood that the scope of the invention is not limited to the procedures, properties, or components defined, as these embodiments, as well as others described, are intended to be merely illustrative of particular aspects of the invention. Indeed, various modifications of the embodiments of the invention which are obvious to those skilled in the art or related fields are intended to be covered by the scope of the appended claims.
For a better understanding of the invention, and not as a limitation on the scope thereof, all numbers expressing quantities, percentages, and other numerical values used in this application are to be understood as being modified in all instances by the term "about". Accordingly, unless expressly indicated otherwise, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
The electrochemical performance test method related in the following embodiments of the invention is concretely as follows:
the following examples synthesize negative electrode materials Mn for lithium ion batteriesxFe1-xC2O4Electrochemical detection was performed at 25 ℃ using button cells of the CR2025 type. The working electrode was prepared using 70% active material, 20% acetylene black as a conductive additive, and 10% polyvinylidene fluoride (PVDF) as a binder, wherein the active material was the sample obtained in each example. In the preparation process of the electrode, the mixture is uniformly dispersed on a copper foil through related processes, and is placed under vacuum at 125 ℃ for 10 hours. The electrolyte adopted in the battery assembling process is 1mol L-1LiPF6A mixture of Ethylene Carbonate (EC) and dimethyl carbonate (DMC). The counter electrode and the reference electrode are both made of lithium foil, the type of the diaphragm is a porous polypropylene film (Celgard 2400), and a lithium sheet is used as the counter electrode and the reference electrode. The battery is assembled in a glove box filled with argon and oxygen and humidity are less than 1 ppm. An automatic battery test system (Neware, China) with a voltage range of 0.01-3.0V is adopted in the charge and discharge test.
Example 1
The lithium ion battery cathode active material MnC of the embodiment2O4The method specifically comprises the following steps:
2.45g of Mn (Ac) were weighed in order2·4H2O, 1.26g of H2C2O4·2H2O into a 100mL beaker, 60mL total EG and water were addedSolvent (V)EG:VH2O3: 1) and placed on a magnetic stirrer and stirred for 30 minutes to uniformly mix all samples together. The resulting mixture was transferred to a 100ml stainless steel reaction kettle of polytetrafluoroethylene, which was then placed in an oven and heated to 180 ℃ for 24 h. And after the reaction is finished, cooling the reaction kettle to room temperature, washing the obtained sample with deionized water and ethanol for three times, performing centrifugal separation, and then placing the separated sample in a vacuum oven for drying at 60 ℃ for 12 hours. Finally, the dried sample is heated in a tube furnace for 2 hours under the protection of argon gas at 180 ℃ (the heating rate is 5 ℃ per minute) to remove crystal water to obtain anhydrous MnC2O4I.e. sample 1 to be synthesized.
And respectively carrying out X-diffraction (XRD) test on the product structure, Scanning Electron Microscope (SEM) test on the product morphology and lithium battery performance test on the sample 1. The XRD test results are shown in fig. 1, the SEM test results are shown in fig. 2, the cycle measurement results of the lithium battery are shown in fig. 3, the rate performance is shown in fig. 4, and the charge and discharge performance is shown in fig. 5.
Example 2
The negative active material Mn of the lithium ion battery of the embodiment0.9Fe0.1C2O4The method specifically comprises the following steps:
2.20g of Mn (Ac) were weighed in order2·4H2O, 0.278g of FeSO4·7H2O and 1.26g of H2C2O4·2H2O into a 100mL beaker, a total of 60mL EG and water were added as solvent (V)EG:VH2O3: 1) and placed on a magnetic stirrer and stirred for 30 minutes to uniformly mix all samples together. The resulting mixture was transferred to a 100ml stainless steel reaction kettle of polytetrafluoroethylene, which was then placed in an oven and heated to 180 ℃ for 24 h. And after the reaction is finished, cooling the reaction kettle to room temperature, washing the obtained sample with deionized water and ethanol for three times, performing centrifugal separation, and then placing the separated sample in a vacuum oven for drying at 60 ℃ for 12 hours. Finally, the dried sample is heated to 2 hours (heating rate) in a tube furnace under the protection of argon gas at 180 DEG CAt 5 ℃ per minute) to remove the crystal water and obtain anhydrous Mn0.9Fe0.1C2O4I.e. sample 2 to be synthesized.
The sample 2 obtained in this example was subjected to XRD test for product structure, SEM test for product morphology, and lithium battery performance test, respectively. The XRD test results are shown in fig. 1, the SEM test results are shown in fig. 2, the cycle measurement results of the lithium battery are shown in fig. 3, the rate performance is shown in fig. 4, and the charge-discharge curve is shown in fig. 5.
Example 3
The negative active material Mn of the lithium ion battery of the embodiment0.85Fe0.15C2O4The method specifically comprises the following steps:
2.08g of Mn (Ac) were weighed in order2·4H2O, 0.417g of FeSO4·7H2O and 1.26g of H2C2O4·2H2O into a 100mL beaker, a total of 60mL EG and water were added as solvent (V)EG:VH2O3: 1) and placed on a magnetic stirrer and stirred for 30 minutes to uniformly mix all samples together. The resulting mixture was transferred to a 100ml stainless steel reaction kettle of polytetrafluoroethylene, which was then placed in an oven and heated to 180 ℃ for 24 h. And after the reaction is finished, cooling the reaction kettle to room temperature, washing the obtained sample with deionized water and ethanol for three times, performing centrifugal separation, and then placing the separated sample in a vacuum oven for drying at 60 ℃ for 12 hours. Finally, the dried sample is heated to 180 ℃ in a tube furnace under the protection of argon, the temperature is kept constant for 2 hours (the heating rate is 5 ℃ per minute), and crystal water is removed to obtain anhydrous Mn0.85Fe0.15C2O4I.e. sample 3 to be synthesized.
The sample 3 obtained in this example was subjected to XRD test for product structure, SEM test for product morphology, and lithium battery performance test, respectively. The XRD test results are shown in fig. 1, the SEM test results are shown in fig. 2, the cycle measurement results of the lithium battery are shown in fig. 3, the rate performance is shown in fig. 4, and the charge-discharge curve is shown in fig. 5.
Example 4
The negative active material Mn of the lithium ion battery of the embodiment0.8Fe0.2C2O4The method specifically comprises the following steps:
1.96g of Mn (Ac) were weighed in order2·4H2O, 0.556g of FeSO4·7H2O and 1.26g of H2C2O4·2H2O into a 100mL beaker, a total of 60mL EG and water were added as solvent (V)EG:VH2O3: 1) and placed on a magnetic stirrer and stirred for 30 minutes to uniformly mix all samples together. The resulting mixture was transferred to a 100ml stainless steel reaction kettle of polytetrafluoroethylene, which was then placed in an oven and heated to 180 ℃ for 24 h. And after the reaction is finished, cooling the reaction kettle to room temperature, washing the obtained sample with deionized water and ethanol for three times, performing centrifugal separation, and then placing the separated sample in a vacuum oven for drying at 60 ℃ for 12 hours. Finally, the dried sample is heated to 180 ℃ in a tube furnace under the protection of argon, the temperature is kept constant for 2 hours (the heating rate is 5 ℃ per minute), and crystal water is removed to obtain anhydrous Mn0.8Fe0.2C2O4I.e. sample 4 to be synthesized.
The sample 4 obtained in this example was subjected to XRD test for product structure, SEM test for product morphology, and lithium battery performance test, respectively. The XRD test results are shown in fig. 1, the SEM test results are shown in fig. 2, the cycle measurement results of the lithium battery are shown in fig. 3, the rate performance is shown in fig. 4, and the charge-discharge curve is shown in fig. 5.
Example 5
The negative active material Mn of the lithium ion battery of the embodiment0.75Fe0.25C2O4The method specifically comprises the following steps:
1.83g of Mn (Ac) were weighed in order2·4H2O, 0.695g of FeSO4·7H2O and 1.26g of H2C2O4·2H2O into a 100mL beaker, a total of 60mL EG and water were added as solvent (V)EG:VH2O3: 1) is placed on a magnetic stirrer for stirring 3All samples were mixed together uniformly for 0 min. The resulting mixture was transferred to a 100ml stainless steel reaction kettle of polytetrafluoroethylene, which was then placed in an oven and heated to 180 ℃ for 24 h. And after the reaction is finished, cooling the reaction kettle to room temperature, washing the obtained sample with deionized water and ethanol for three times, performing centrifugal separation, and then placing the separated sample in a vacuum oven for drying at 60 ℃ for 12 hours. Finally, the dried sample is heated to 180 ℃ in a tube furnace under the protection of argon, the temperature is kept constant for 2 hours (the heating rate is 5 ℃ per minute), and crystal water is removed to obtain anhydrous Mn0.75Fe0.25C2O4I.e. the sample 5 to be synthesized.
The sample 5 obtained in this example was subjected to XRD test for product structure, SEM test for product morphology, and lithium battery performance test, respectively. The XRD test results are shown in fig. 1, the SEM test results are shown in fig. 2, the cycle measurement results of the lithium battery are shown in fig. 3, the rate performance is shown in fig. 4, and the charge-discharge curve is shown in fig. 5.
Example 6
The negative active material Mn of the lithium ion battery of the embodiment0.67Fe0.33C2O4The method specifically comprises the following steps:
1.64g of Mn (Ac) were weighed in order2·4H2O, 0.917g of FeSO4·7H2O and 1.26g of H2C2O4·2H2O into a 100mL beaker, a total of 60mL EG and water were added as solvent (V)EG:VH2O3: 1) and placed on a magnetic stirrer and stirred for 30 minutes to uniformly mix all samples together. The resulting mixture was transferred to a 100ml stainless steel reaction kettle of polytetrafluoroethylene, which was then placed in an oven and heated to 180 ℃ for 24 h. And after the reaction is finished, cooling the reaction kettle to room temperature, washing the obtained sample with deionized water and ethanol for three times, performing centrifugal separation, and then placing the separated sample in a vacuum oven for drying at 60 ℃ for 12 hours. Finally, heating the dried sample in a tube furnace under the protection of argon to 180 ℃, keeping the temperature for 2 hours (the heating rate is 5 ℃ per minute), and removing crystal water to obtain the productAnhydrous Mn0.67Fe0.33C2O4I.e. sample 6 to be synthesized.
The sample 6 obtained in this example was subjected to XRD test for product structure, SEM test for product morphology, and lithium battery performance test, respectively. The XRD test results are shown in fig. 1, the SEM test results are shown in fig. 2, the cycle measurement results of the lithium battery are shown in fig. 3, the rate performance is shown in fig. 4, and the charge-discharge curve is shown in fig. 5.
Example 7
The negative active material Mn of the lithium ion battery of the embodiment0.5Fe0.5C2O4The method specifically comprises the following steps:
1.23g of Mn (Ac) were weighed in order2·4H2O, 1.39g of FeSO4·7H2O and 1.26g of H2C2O4·2H2O into a 100mL beaker, a total of 60mL EG and water were added as solvent (V)EG:VH2O3: 1) and placed on a magnetic stirrer and stirred for 30 minutes to uniformly mix all samples together. The resulting mixture was transferred to a 100ml stainless steel reaction kettle of polytetrafluoroethylene, which was then placed in an oven and heated to 180 ℃ for 24 h. And after the reaction is finished, cooling the reaction kettle to room temperature, washing the obtained sample with deionized water and ethanol for three times, performing centrifugal separation, and then placing the separated sample in a vacuum oven for drying at 60 ℃ for 12 hours. Finally, the dried sample is heated to 180 ℃ in a tube furnace under the protection of argon, the temperature is kept constant for 2 hours (the heating rate is 5 ℃ per minute), and crystal water is removed to obtain anhydrous Mn0.5Fe0.5C2O4I.e. sample 7 to be synthesized.
The sample 7 obtained in this example was subjected to XRD test for product structure, SEM test for product morphology, and lithium battery performance test, respectively. The XRD test results are shown in fig. 1, the SEM test results are shown in fig. 2, the cycle measurement results of the lithium battery are shown in fig. 3, the rate performance is shown in fig. 4, and the charge-discharge curve is shown in fig. 5.
In conclusion, the invention successfully prepares the anhydrous manganese oxalate and uses Fe2+Successfully doped into manganese oxalate crystal lattices to prepare a series of negative active materials Mn of the lithium ion batteryxFe1-xC2O4And the synthesized sample has no impurity phase in the XRD pattern shown in figure I. Mn synthesized by the inventionxFe1-xC2O4As shown in fig. 2, the SEM image of the material shows that the particle size is smaller, which can increase the contact area between the material and the electrolyte and shorten the diffusion path of lithium ions. The synthesized negative electrode material is subjected to electrochemical performance test, and assembled into a lithium ion half cell, the voltage is set in a range of 0.01-3V, and 100 mA.g-1The current density was measured. As shown in fig. 3, each sample after doping has good cycling stability compared to the pure phase in 100 charge/discharge cycles. Then, the assembled lithium ion half cell was subjected to rate capability test at 100, 200, 500, 1000, 2000mA · g-1Under the discharge current, the obtained curve is shown in fig. 4, and all the samples after doping modification have good rate performance. Wherein sample 4 exhibited the best rate performance at 100, 200, 500, 1000, 2000mA · g-1The specific capacities were 680,760,720,650 and 565mAh g, respectively, at discharge current-1. The current density is recovered to 100mA g-1The capacity is restored to 950mAh g-1And excellent rate performance is shown. And all samples have good charge and discharge platforms after doping modification as shown in figure 5, and have good market potential.

Claims (10)

1. Lithium ion battery negative active material MnxFe1-xC2O4The method is characterized in that: the Mn isxFe1-xC2O4In the formula, x is more than or equal to 0.5 and less than or equal to 1.
2. The negative active material Mn of claim 1 for lithium ion batteriesxFe1-xC2O4The method is characterized in that: the Mn isxFe1-xC2O4The value of x is preferably equal to 0.8.
3. The negative active material Mn for lithium ion batteries according to claim 1xFe1-xC2O4The synthesis method is characterized in that: the method specifically comprises the following steps:
(1) raw material dissolution: according to the molar metering ratio of 5-10: 0-5: 10 adding soluble manganese salt, ferrous salt and oxalic acid into a uniform medium, and stirring and mixing uniformly to obtain a mixed reaction solution;
(2) hydrothermal or solvothermal synthesis: transferring the mixed reaction liquid obtained in the step (1) into a polytetrafluoroethylene reaction kettle, sealing, heating the reaction kettle to 100-180 ℃ for constant-temperature reaction for 24 hours, cooling to room temperature after the reaction is finished, taking out the obtained product, centrifuging, washing for a plurality of times, and finally performing vacuum drying to obtain MnxFe1-xC2O4A precursor;
(3) annealing treatment: mn obtained in the step (2)xFe1-xC2O4Placing the precursor in a tube furnace, heating for 1-3h under the protection of inert gas to remove crystal water, and obtaining the cathode active material Mn of the lithium ion batteryxFe1-xC2O4。
4. The negative active material Mn of claim 3 for lithium ion batteriesxFe1-xC2O4The synthesis method is characterized in that: the ratio of the mole number of the oxalic acid in the step (1) to the sum of the mole numbers of the manganese salt and the ferrous salt is 1.
5. The negative active material Mn of claim 3 for lithium ion batteriesxFe1-xC2O4The synthesis method is characterized in that: the soluble manganese salt in the step (1) is any one or more of manganese acetate, manganese chloride, manganese sulfate or manganese nitrate; the ferrous salt is any one or combination of ferrous sulfate and ferrous chloride.
6. The negative active material Mn of claim 3 for lithium ion batteriesxFe1-xC2O4The synthesis method is characterized in that: the homogeneous medium in the step (1) is any one of water and ethylene glycol or the combination thereof.
7. The negative active material Mn for lithium ion batteries according to any of claims 1 to 2xFe1-xC2O4Or a negative active material Mn of the lithium ion battery synthesized by the method of any one of claims 3 to 6xFe1-xC2O4The application of (2), which is characterized in that: can be used as the cathode material of lithium ion battery.
8. A lithium ion battery negative electrode material comprises a negative electrode active material, a binder and a conductive additive, and is characterized in that: the negative active material is the negative active material Mn of any one of claims 1 to 2 for the lithium ion batteryxFe1-xC2O4Or a negative active material Mn of the lithium ion battery synthesized by the method of any one of claims 3 to 6xFe1-xC2O4。
9. A lithium ion battery negative electrode, the negative electrode comprises a current collector and a negative electrode material coated and/or filled on the current collector, and is characterized in that: the negative electrode material is the lithium ion battery negative electrode material of claim 8.
10. A lithium ion battery comprising a pole core and a nonaqueous electrolytic solution, the pole core and the nonaqueous electrolytic solution being sealed in a battery case, the pole core comprising a positive electrode, a negative electrode and a separator, characterized in that: the negative electrode is the lithium ion battery negative electrode of claim 9.
CN201911018251.1A 2019-10-24 2019-10-24 Lithium ion battery negative active material MnxFe1-xC2O4Synthetic method and application Pending CN110729481A (en)

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