CN114447290B - Modification method and application of lithium-rich manganese-based positive electrode material of lithium ion battery - Google Patents

Modification method and application of lithium-rich manganese-based positive electrode material of lithium ion battery Download PDF

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CN114447290B
CN114447290B CN202111570863.9A CN202111570863A CN114447290B CN 114447290 B CN114447290 B CN 114447290B CN 202111570863 A CN202111570863 A CN 202111570863A CN 114447290 B CN114447290 B CN 114447290B
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lithium
positive electrode
electrode material
rich manganese
ion battery
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CN114447290A (en
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李喜飞
郝猷琛
刘�文
王晶晶
***
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Xian University of Technology
Shaanxi Coal and Chemical Technology Institute Co Ltd
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Shaanxi Coal and Chemical Technology Institute Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • 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
    • H01M2004/028—Positive 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
    • 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 discloses a method for modifying a lithium-rich manganese-based positive electrode material of a lithium ion battery, which comprises the steps of dissolving a complexing agent in deionized water under certain conditions to obtain a complexing solution; adding a proper amount of positive electrode material into the solution, fully stirring and dispersing, sealing at normal temperature and keeping for a period of time at constant temperature, thus obtaining the in-situ growth, compact and thin-layer Prussian-blue-like coated and modified lithium ion battery positive electrode material which has good cycle stability, excellent rate performance and reliable safety, and the preparation method has the characteristics of low cost, simple operation, environmental friendliness and the like, and can be applied to industrial production on a large scale; the invention also discloses an application of the Prussian-like blue coating modified lithium-rich manganese-based positive electrode material of the lithium ion battery prepared by the modification method of the lithium-rich manganese-based positive electrode material in the aspect of preparing the lithium ion battery.

Description

Modification method and application of lithium-rich manganese-based positive electrode material of lithium ion battery
Technical Field
The invention belongs to the technical field of energy storage and conversion, and mainly relates to a method for modifying a lithium-rich manganese-based positive electrode material of a lithium ion battery.
The invention also relates to the application of the lithium-rich manganese-based cathode material of the lithium ion battery in the aspect of preparing the lithium ion battery.
Background
The lithium ion battery as an efficient energy storage device plays an important role in utilization and popularization of clean energy, and especially becomes a hot spot for disputed research and development of countries in the world under the background of 'double carbon'. The energy-saving battery has the characteristics of small volume, light weight, high specific energy, no memory effect, long cycle life and the like, and is widely applied to the fields of mobile equipment, electric automobiles and the like. As a power source of various electric equipment, the performance of the lithium ion battery directly determines the service life and the endurance mileage of the equipment. In order to further develop the electric automobile with long endurance, the lithium-rich manganese-based anode with higher theoretical specific capacity becomes a core and a key material which need to be overcome for the next generation of high-performance lithium ion battery.
Aiming at the problem of rapid capacity attenuation of a lithium-rich manganese-based positive electrode, coating modification is a common technical scheme, and the method is mainly a protection method for forming a uniform coating layer on the surface of target material particles, wherein the coating modification is a material with excellent physical and chemical properties. Researchers coat the anode material by using the prussian-like blue, and the result shows that the prussian-like blue coating modified anode material has higher capacity, good rate performance and excellent cycle performance.
The existing preparation method of the coated modified lithium-rich manganese-based positive electrode material of the lithium ion battery mainly comprises a high-energy ball milling method, a sol-gel method and the like, for example, chinese patent CN202010847189.3 has the problems of rough coating effect, complex process steps and the like, and although the rate performance of the positive electrode material is improved, the positive electrode material does not show good effect in the aspect of cycle life. Therefore, the development of a preparation method which is low in cost, simple in process, environment-friendly and remarkably prolonged in cycle life is imperative.
Disclosure of Invention
The invention aims to provide a method for modifying a lithium-rich manganese-based positive electrode material of a lithium ion battery, which solves the problem of capacity attenuation caused by different inducements of the lithium-rich manganese-based positive electrode material of the lithium ion battery under high multiplying power and low multiplying power.
The invention also aims to provide a modification method of the lithium-rich manganese-based cathode material of the lithium ion battery, and application of the obtained prussian blue-like coated modified lithium-rich manganese-based cathode material of the lithium ion battery in preparation of the lithium ion battery.
The technical scheme adopted by the invention is that the method for modifying the lithium-rich manganese-based anode material of the lithium ion battery is implemented by the following steps:
step 1, dispersing a complexing agent in deionized water, and fully stirring and dissolving to obtain a complexing solution;
step 2, adding the lithium-rich manganese-based positive electrode material into the solution in a dosage ratio, stirring to disperse positive electrode particles, and then sealing and maintaining the complexing solution soaked with the positive electrode material at a constant temperature;
and 3, filtering the product obtained in the step 2, washing the product for multiple times by using deionized water and absolute ethyl alcohol, and then preserving the heat of a filter cake in a vacuum drying oven to obtain the Prussian-like blue coated lithium ion battery anode material.
The first technical scheme of the invention is also characterized in that:
wherein the complexing agent in the step 1 is ferrocyanide;
wherein the complexing agent is K 4 Fe(CN) 6 、Na 4 Fe(CN) 6 、Li 4 Fe(CN) 6 Or at least one of its corresponding hydrates;
wherein the lithium-rich manganese-based positive electrode material in the step 2 is as follows: xLi with a layered structure 2 MnO 3 -(1-x)LiMO 2 A material;
wherein the mol ratio of the complexing agent to the lithium-rich manganese-based positive electrode material in the step 2 is 1:10 to 1:1; the concentration of the complexing solution is 0.05-0.5 mol/L;
wherein the stirring is carried out for 3-10 min in the step 2, the constant temperature is 20-60 ℃, and the sealing is carried out for 6-24 h;
wherein in the step 3, deionized water and absolute ethyl alcohol are washed for at least 3 times, the temperature in the vacuum drying oven is 60 ℃, and the temperature is kept for 6-12 h;
wherein the thickness of the Prussian-like blue coating layer in the step 3 is 0.5-5 nm, and the molar ratio of substances is 0.01-0.10% of the amount of the substances of the positive electrode material.
The second technical scheme of the invention is that the Prussian-like blue coated modified lithium-rich manganese-based positive electrode material of the lithium ion battery prepared by the method is applied to the preparation of the lithium ion battery.
The method comprises the following steps: prussian blue-like coating modified lithium ion lithium-rich manganese-based positive electrode material and conductive carbon black (conductive agent)) Grinding and fully mixing the electrolyte, polyvinylidene fluoride (PVDF binder) and a small amount of N-methyl pyrrolidone (NMP) to form uniform slurry, coating the uniform slurry on an aluminum foil substrate to be used as a test electrode, wherein the electrolyte is 1M LiPF 6 DMC: EC: EMC (V: V = 1); the experimental results show that: prussian blue-like coated lithium-rich manganese-based positive electrode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 After 100 times of charge and discharge tests under low multiplying power (50 mA/g), the capacity can still reach 220mA h/g, and the capacity retention rate is 91.4%; after 300 times of charge and discharge tests under high multiplying power (250 mA/g), the capacity is kept at 155mA h/g, and the capacity retention rate is 87.8%;
the invention has the advantages that
The coating layer in the functional Prussian-blue-like coated lithium ion battery lithium-rich manganese-based positive electrode material prepared by the invention is compact and uniform and has good stability, on one hand, the overflow of lattice oxygen and the side reaction of an electrolyte and a positive electrode interface can be effectively inhibited under low multiplying power, and on the other hand, the functional Prussian-blue-like coated lithium ion battery lithium-rich manganese-based positive electrode material is also effective for capacity attenuation caused by electrochemical polarization behavior under high multiplying power. Under different multiplying powers, the interface stability can be effectively optimized, the cycle life of the lithium ion battery is prolonged, and the electrochemical performance of the lithium ion battery is improved;
the method for preparing the functional Prussian-blue-like coated lithium ion battery lithium-rich manganese-based anode material fully utilizes the strong complexation between the complexing agent and metal ions, and takes metal atoms on the surface of the lithium-rich manganese-based anode as a metal source to perform in-situ complexation with the complexing agent to construct a conformal interface film. On one hand, a compact, uniform and good-stability Prussian-blue-like coating layer is formed on the surface of the lithium-rich manganese-based positive electrode material, so that the side reaction of an electrolyte and a positive electrode interface can be effectively reduced under low multiplying power, meanwhile, the overflow of oxygen is inhibited, and the reversibility of lattice oxygen is improved; on the other hand, the electrochemical polarization behavior of the lithium-rich manganese-based anode under high multiplying power is weakened, the cycle reversibility of the lithium-rich manganese-based anode material under high multiplying power and low multiplying power is obviously improved, the cycle life of the battery is greatly prolonged, and the electrochemical performance of the lithium-rich manganese-based anode of the lithium ion battery under different multiplying power is improved;
the Prussian blue-like coating modified lithium ion battery lithium-rich manganese-based positive electrode material is synthesized in one step through in-situ complexation, the method is simple in process, low in cost, environment-friendly and suitable for large-scale application, and the defects of complex process, high cost, rough coating effect, poor controllability and the like in the traditional coating modification method are overcome;
the Prussian-blue-like coated and modified lithium-rich manganese-based positive electrode material of the lithium ion battery is synthesized in one step through in-situ complexing reaction, and the spontaneous complexing reaction at the contact interface of positive electrode particles and a complexing solution simplifies the process, mildens the conditions and realizes large-scale preparation;
the Prussian-like blue coated modified lithium-rich manganese-based positive electrode material for the lithium ion battery, which is prepared by the invention, is applied to the lithium ion battery, shows higher reversible capacity, good rate performance and excellent cycle performance, and greatly prolongs the cycle life of the lithium ion battery under different rates.
Drawings
FIG. 1 shows Li before and after Prussian-like blue coating modification in an embodiment of a method for modifying a lithium-rich manganese-based cathode material of a lithium ion battery 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 Scanning electron microscope images of the anode material;
FIG. 2 shows modified Li coated with Prussian-like blue in an embodiment of a method for modifying a lithium-rich manganese-based positive electrode material of a lithium ion battery according to the present invention 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 XPS fine images of Fe 2p and Mn 2p of the positive electrode material under different potentials;
FIG. 3 shows an example of a method for modifying a lithium-rich manganese-based positive electrode material for a lithium ion battery according to the present invention, in which Prussian-like blue is coated and modified to obtain Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 A high-resolution scanning transmission electron microscope image of the anode material;
FIG. 4 shows Li before and after Prussian-like blue coating modification in an embodiment of a method for modifying a lithium-rich manganese-based cathode material of a lithium ion battery according to the present invention 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 A cycle performance diagram of the anode material under low multiplying power;
FIG. 5 shows Li before and after Prussian-like blue coating modification in an embodiment of a method for modifying a lithium-rich manganese-based positive electrode material of a lithium ion battery according to the present invention 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 A cycle performance diagram of the anode material under high magnification;
FIG. 6 shows Li before and after Prussian-like blue coating modification in an embodiment of a method for modifying a lithium-rich manganese-based cathode material of a lithium ion battery according to the present invention 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 And cycling the corresponding polarization diagram of the anode material under high magnification.
Detailed Description
The invention is described in detail below with reference to the drawings and the detailed description.
According to the technical scheme, a certain amount of complexing agent is dispersed in a certain amount of deionized water, the lithium-rich manganese-based positive electrode material is immersed in the solution, the complexing agent can be fully contacted with the lithium-rich manganese-based positive electrode, and then metal elements contained in the lithium-rich manganese-based positive electrode are used as metal centers for complexing, so that a Prussian blue-like coating layer is obtained;
the invention mainly researches the Prussian-like blue coated anode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 The preparation method and the application mainly solve the problems of short cycle life and poor rate capability of the lithium-rich manganese-based anode of the lithium ion battery.
Example 1
Step 1, adding K 4 Fe(CN) 6 Dispersing in deionized water with concentration controlled at 0.1mol/L, stirring for 10min to dissolve completely to obtain potassium ferrocyanide solution;
step 2, taking 0.3g of lithium-rich manganese-based positive electrode material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 Adding the solution (the molar ratio of the complexing agent to the anode is 1:5), stirring for 5min to enable the solution to be fully contacted with the anode particles, and then placing the complexing solution soaked with the anode material at a constant temperature of 20 ℃ for standing for 24h to obtain the Prussian-blue-like coated modified lithium-rich manganese-based anode materialFeeding;
step 3, filtering the product obtained in the step 2, washing the product for 3 times by using absolute ethyl alcohol, and then preserving the heat of a filter cake in a vacuum drying box at the temperature of 60 ℃ for 12 hours to obtain the prussian blue-like coated lithium-rich manganese-based positive electrode material;
0.64g of Prussian-blue-like coated modified Li prepared as described above was weighed 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 Adding 0.08g of conductive carbon black serving as a conductive agent and 0.08g of PVDF serving as a binder into a positive electrode material, dropwise adding a small amount of NMP, grinding and uniformly mixing to form uniform slurry, coating the uniform slurry on an aluminum foil to serve as a test electrode, and using 1M LiPF 6 DMC: EC: EMC (V: V = 1), charge and discharge performance (current densities of 50mA/g and 250mA/g, respectively) was tested;
coating modified Li prepared in this example 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 The material characteristics and electrochemical properties of the cathode material are shown in the following figures 1-6:
FIG. 1 is a scanning electron micrograph from which it can be seen that Li has not been modified by coating 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 The anode material has a sphere-like structure consisting of primary particles with the size of 200-500nm, and particles with fine surfaces are generally considered as residual lithium. Li after in-situ complexing treatment 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 The shape and the size of the anode material particles are not obviously changed, the characteristic of conformal coating of a coating layer is verified, and meanwhile, the disappeared tiny residual lithium particles are caused by water washing;
FIG. 2 is an XPS fine spectrum of Fe 2p and Mn 2p at different potentials after Prussian-like blue coating modification, from which it can be seen that [ Fe (CN) in Prussian-like blue coating layer after in-situ complexation 6 ] 4- The lithium manganese oxide can participate in redox reaction, and the potential of the reaction is consistent with that of the lithium manganese oxide-based anode, so that part of overload current can be shared in the reaction process of the anode, and the problem of polarization under high multiplying power is further relieved;
FIG. 3 shows modified Prussian-like blue Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 A high-resolution transmission electron microscope image of the cathode material indicates that the amorphous Prussian blue-like ultrathin, compact and uniform coating is carried out on the surface of the cathode material;
FIG. 4 shows Li before and after coating modification 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 The long cycle performance diagram of the cathode material under low multiplying power shows that the modified Li is coated by the Prussian-like blue 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 When the anode material is discharged at a constant current at room temperature (50 mA/g), the specific capacity can still be kept at 220mA h/g after 100 times of circulation, and the capacity retention rate of the anode material is up to 91.2 percent and is obviously superior to that of an unmodified material (78 percent);
FIG. 5 shows Li before and after coating modification 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 The long cycle performance diagram of the anode material under high multiplying power shows that the modified Li is coated by prussian-like blue 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 When the anode material discharges at a constant current (250 mA/g) at room temperature, the specific capacity can still be kept at 155mA h/g after the cycle is carried out for 300 times, the corresponding capacity retention rate is 87.8%, and the capacity retention rate of an unmodified material under the same condition is only 50.5%;
FIG. 6 shows Li before and after coating modification 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 The polarization patterns corresponding to long circulation of the anode material under high magnification are obviously different before and after 50-week circulation of the anode material is modified, the polarization of the unmodified material is continuously enlarged, and Prussian-blue-like coated and modified Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 The anode material is maintained at a lower polarization level, which shows that the existence of the Prussian-like blue coating layer obviously reduces the polarization behavior under high rate, thereby keeping stable long-cycle performance;
example 2
Step 1, adding K 4 Fe(CN) 6 Dispersing in deionized water with concentration controlled at 0.5mol/L, stirring for 10min to dissolve completely to obtain potassium ferrocyanide solution;
step 2, 0.3g of lithium-rich manganese-based positive electrode is takenPolar material Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 Adding the solution (the molar ratio of the complexing agent to the anode is 1:1), stirring for 5min to enable the solution to be fully contacted with the anode particles, and then placing the complexing solution soaked with the anode material at a constant temperature of 40 ℃ for standing for 12h to obtain the Prussian-blue-like coated modified lithium-rich manganese-based anode material;
step 3, filtering the product obtained in the step 2, washing the product for 3 times by using absolute ethyl alcohol, and then keeping the temperature of a filter cake in a vacuum drying oven at 60 ℃ for 12 hours to obtain a Prussian-like blue coated lithium-rich manganese-based positive electrode material;
0.64g of Prussian-blue-like coated modified Li prepared as described above was weighed 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 Adding 0.08g of conductive carbon black serving as a conductive agent and 0.08g of PVDF serving as a binder into a positive electrode material, dropwise adding a small amount of NMP, grinding and uniformly mixing to form uniform slurry, coating the uniform slurry on an aluminum foil serving as a test electrode, and using 1M LiPF 6 DMC: EC: EMC (V: V = 1), charge and discharge performance (current densities of 50mA/g and 250mA/g, respectively) was tested;
in the embodiment, the concentration of the complexing agent and the constant temperature are improved, so that the complexing reaction is accelerated, and the thickness of the coating layer can be improved by the relatively large-dosage-ratio complexing agent. Tests prove that when the lithium-rich manganese-based positive electrode material coated and modified in the embodiment is subjected to constant current discharge at room temperature (50 mA/g), the specific capacity can still be kept at 212mAh/g after 100 times of circulation, which is better than 177.8mAh/g of an unmodified material; meanwhile, the capacity of the modified material after 300 times of circulation under high multiplying power (250 mA/g) is 132.4mAh/g, while the capacity of the unmodified material is 101.1mAh/g. The result shows that the amount of the complexing agent and the reaction temperature are controlled based on the complexation reaction of the complexing agent and the metal atom center, compared with example 1, the prussian blue-like coated modified lithium-rich manganese-based positive electrode in the embodiment has the effect of prolonging the cycle life, but the thickness of the coating layer has a great influence on the electrochemical performance, and the thicker the coating layer is, the better the coating layer is.
Comparative example 1
To illustrate the important role of the complexing agent, this comparative example is essentially the same as example 1, except thatIn the implementation process, no K is added 4 Fe(CN) 6 The other operations as a complexing agent were exactly the same as in example 1. And (4) carrying out suction filtration and drying on the lithium-rich manganese-based positive electrode material soaked in the deionized water to obtain the contrast material.
The morphology of the comparative material was similar to that of the sample obtained in example 1, and the clean surface indicated that the fine residual lithium particles on the surface of the unmodified material could be removed by washing with water.
The lithium-rich manganese-based positive electrode material obtained in comparative example 1 was subjected to the deionized water immersion treatment to prepare an electrode and tested in the same manner as in example 1. The lithium-rich manganese-based positive electrode without the prussian-like blue coating has a significant difference compared with example 1. Under low multiplying power (50 mA/g), the capacity of the comparative example material is 197.9mA h/g after the comparative example material is cycled for 100 times, the stability of the comparative example material is obviously weaker than that of the example 1 material, the capacity retention rate is only 81.6 percent and is slightly higher than 78 percent of that of an unmodified material, and the modification effect of pure deionized water cleaning on the lithium-rich manganese-based anode is very limited. More obviously, under a high multiplying power (250 mA/g), the capacity of the comparative example material is almost attenuated to 0 after being circulated for 300 times, which shows that the lithium-rich manganese-based cathode material soaked by pure deionized water has no great modification effect and is not beneficial to the performance of the material. The comparison example eliminates the modification influence of deionized water cleaning on the lithium-rich manganese-based positive electrode material, and proves that the Prussian-like blue coating layer formed through in-situ complexing reaction is the important reason for realizing long cycle life of the lithium-rich manganese-based positive electrode under high multiplying power and low multiplying power.
Comparative example 2
To illustrate the action of the complexing agent more visually, this comparative example is essentially identical to example 1, except that a small amount of K is added in step (1) of the process 4 Fe(CN) 6 The other operations as a complexing agent were exactly the same as in example 1. The specific process of the step (1) is as follows: will K 4 Fe(CN) 6 Dispersing in deionized water with concentration controlled at 0.025mol/L, stirring for 10min to dissolve completely to obtain potassium ferrocyanide solution. The procedure was then exactly the same as in example 1. And (3) carrying out suction filtration and drying on the lithium-rich manganese-based positive electrode material soaked in the deionized water to obtain the contrast material.
Comparative example 2 the greatest difference compared to comparative example 1 is the addition of a small amount of K 4 Fe(CN) 6 And constructing a Prussian blue-like coating layer on the surface of the lithium-rich manganese-based positive electrode as a complexing agent. Even if the amount of the complexing agent was only 1/5 of the amount of the complexing agent as compared to example 1, the difference was very significant as compared to comparative example 1 in which no complexing agent was added.
The material obtained in comparative example 2 was used to assemble a battery using the same procedure as in example 1, and the electrochemical properties thereof were tested. Compared with comparative example 1, the material of comparative example 2 has the modification effect basically the same as comparative example 1 at low rate, and is slightly better than the modified lithium-rich manganese-based positive electrode. The difference performance under high multiplying power is very outstanding, the capacity of the material in the comparative example is rapidly attenuated to 0 under high multiplying power, the specific capacity of 113mA h/g of the material in the comparative example 2 is kept after 300 cycles, the specific capacity is not attenuated to 0, the specific capacity is remarkably superior to 86.8mA h/g of an unmodified material, and the outstanding modification effect of the Prussian-like blue coating layer constructed by the in-situ complexation reaction on the attenuation of the lithium-rich manganese-based positive electrode under high multiplying power and low multiplying power is explained again.

Claims (5)

1. The method for modifying the lithium-rich manganese-based positive electrode material of the lithium ion battery is characterized by comprising the following steps of:
step 1, dispersing a complexing agent in deionized water, fully stirring and dissolving to obtain a complexing solution, wherein the complexing agent is K 4 Fe(CN) 6 、Na 4 Fe(CN) 6 、Li 4 Fe(CN) 6 Or at least one of its corresponding hydrates;
step 2, adding the lithium-rich manganese-based positive electrode material into the solution according to the dosage ratio, stirring to disperse the positive electrode material, and then sealing and maintaining the complexing solution soaked with the positive electrode material at a constant temperature; the lithium-rich manganese-based positive electrode material is xLi with a layered structure 2 MnO 3 -(1-x)LiMO 2 The molar ratio of the material, the complexing agent and the lithium-rich manganese-based positive electrode material is 1:10 to 1;
and 3, filtering the product obtained in the step 2, washing the product with deionized water and absolute ethyl alcohol for multiple times, and then keeping the temperature of a filter cake in a vacuum drying box to obtain the Prussian blue-like coated lithium ion battery cathode material, wherein the thickness of the Prussian blue-like coated layer is 0.5-5 nm, and the amount of the Prussian blue-like coated layer is 0.01-0.10% of the amount of the cathode material.
2. The method for modifying the lithium-rich manganese-based positive electrode material of the lithium ion battery according to claim 1, wherein the concentration of the complexing solution in the step 2 is 0.05 to 0.5mol/L.
3. The method for modifying the lithium-rich manganese-based positive electrode material of the lithium ion battery according to claim 1, wherein the stirring in the step 2 is carried out for 3 to 10min at a constant temperature of 20 to 60 ℃ and the sealing is carried out for 6 to 24h.
4. The method for modifying the lithium-rich manganese-based positive electrode material of the lithium ion battery according to claim 1, wherein the deionized water and the absolute ethyl alcohol are washed at least 3 times in the step 3, and the temperature in a vacuum drying oven is 60 ℃ and is kept for 6 to 12h.
5. The application of the Prussian-like blue coated modified lithium-rich manganese-based cathode material of the lithium ion battery, which is prepared by the method for modifying the lithium-rich manganese-based cathode material of the lithium ion battery of any one of claims 1~4, in the preparation of the lithium ion battery.
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