CN112993241B - Preparation method of single-crystal lithium manganate material - Google Patents
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Abstract
The invention discloses a preparation method of a single-crystal lithium manganate material, wherein a doping element M adopted in the method has two functions: the lithium manganate particles can be used as a fluxing agent, and can be formed at lower temperature or in heat preservation time, even can be formed into single-crystal lithium manganate particles with different shapes; and secondly, the doping element can reduce the Jahn-Teller effect in the lithium manganate circulation process, reduce the dissolution of manganese and stabilize the lattice structure, thereby improving the circulation and rate capability of the lithium manganate. The doped mangano-manganic oxide has the characteristics that secondary particles are formed by agglomeration of larger octahedral primary particles, doping elements are uniformly precipitated or adsorbed in gaps or surfaces of precursor particles, so that the consistency of the performance and the appearance of the lithium manganate can be greatly improved, in addition, the single crystal lithium manganate can be synthesized in a solid phase mode at lower temperature or in heat preservation time, and even single crystal lithium manganate particles with different appearances are formed, so that the single crystal lithium manganate material with both physical properties and electrochemical properties can be obtained.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery anode materials, and particularly relates to a preparation method of a single-crystal lithium manganate material.
Background
With the increasing environmental problems of exhaustion of fossil energy such as petroleum, air pollution and the like and the improvement of performance requirements of people on various aspects of secondary batteries, lithium ion batteries attract attention of people with the advantages of high energy density, long service life, small pollution and the like, and in the development process of nearly thirty years, the occupancy rate of the lithium ion batteries in the market by the advantages of multiple aspects of the lithium ion batteries gradually catches up and exceeds that of the traditional secondary batteries such as: lead-acid batteries, nickel-hydrogen batteries and nickel-cadmium batteries, and are widely applied to new energy automobiles, smart phones, notebook computers and other products.
At present, many reports have been made on positive electrode materials of lithium ion batteries, and particularly, lithium cobalt oxide has been used as a positive electrode material, and the lithium ion batteries have a relatively mature technology and are widely used, but with shortage of cobalt resources and soaring price, people gradually find new positive electrode materials which can be used for lithium ion batteries, and compared with lithium cobalt oxide, lithium manganese oxide positive electrode materials have an absolute advantage in price, and in addition, the lithium manganese oxide positive electrode materials have the characteristics of high discharge voltage, low pollution, high safety performance and the like, and are also greatly concerned. However, the cycle performance of lithium manganate needs to be improved, and the development of lithium manganate is greatly limited by the problem that the capacity of lithium manganate is rapidly attenuated particularly at high temperature (55 ℃).
The single crystal lithium manganate material has the characteristics of small specific surface area, good crystallinity, good lattice orientation consistency and the like, can effectively reduce the side reaction of the material with electrolyte when being used as an electrode active substance, and reduce the dissolution of manganese, thereby maintaining a stable lattice structure and improving the cycle performance; in addition, the compaction density and the tap density of the single-crystal lithium manganate are greatly higher than those of polycrystalline lithium manganate with serious primary particle agglomeration, so that the single-crystal lithium manganate has excellent physical properties and also improves the volume energy density; in addition, the condition that the particles are broken after rolling can be effectively avoided in the processing process of the single crystal lithium manganate with large-size primary particles, and the single crystal lithium manganate has good processing performance.
In order to improve the electrochemical performance of the lithium manganate anode material or to synthesize a single-crystal lithium manganate material more easily, doping elements are usually added in the process of synthesizing lithium manganate at a high temperature in the prior art, but only the doping elements are usually concerned to improve the cycle and rate performance of lithium manganate. The change of doping elements on the appearance of the lithium manganate material and the change of a preparation process of the lithium manganate material are not concerned; at present, solid-phase mixing is mainly adopted for doping elements, so that the doping elements are not uniformly mixed with a manganese source and a lithium source, and the consistency of the particle appearance and performance is directly influenced; therefore, how to ensure the uniformity of the doping elements is an urgent problem to be solved.
Disclosure of Invention
The invention aims to provide a preparation method of a single-crystal lithium manganate material, which can ensure the uniformity of doped elements, reduce the synthesis temperature and shorten the time.
The preparation method of the single-crystal lithium manganate material comprises the following steps:
A) adding ammonium salt and soluble doping element M into deionized water, continuously stirring and introducing oxidizing gas at a set temperature, adding manganese powder under the condition of keeping the gas introduction, continuously and slowly adding the manganese powder, continuing to react after the addition is finished, stopping the gas introduction after the reaction is finished, cooling to room temperature, then adding a precipitator, carrying out stirring and precipitation reaction, carrying out solid-liquid separation after the reaction is finished, and washing and drying the solid to obtain uniformly doped trimanganese tetroxide powder;
B) uniformly mixing the uniformly doped manganous-manganic oxide powder obtained in the step A) and a lithium source to obtain mixed powder;
C) and C), firstly roasting the mixed powder in the step B) at 400-550 ℃, then roasting at 600-680 ℃, finally roasting at 800-950 ℃ in a third stage, cooling and crushing to obtain the defective single crystal lithium manganate powder material.
D) And C), continuously roasting the defect type single crystal lithium manganate powder material in the step C) at 350-520 ℃ for the first time, then roasting at 580-650 ℃ for the second time, finally roasting at 700-850 ℃ for the third time, and cooling and crushing to obtain the single crystal lithium manganate powder material with a complete crystal structure.
In the step A), the ammonium salt is one or more of ammonium nitrate, ammonium chloride and ammonium sulfate; the doping element M is at least one of nitrate, sulfate, acetate and chloride of cobalt, nickel, calcium, tin, zirconium, chromium, titanium, lanthanum, barium, aluminum, magnesium, boron, strontium, niobium, samarium and cerium; the concentration of ammonium salt in deionized water is 5-100 g/L, and the concentration of doping element M in deionized water is 5-30 g/L; setting the temperature to be 50-90 ℃; the oxidizing gas is oxygen or air; the mass ratio of the manganese powder to the ammonium salt is (3-20): 1, the adding speed of the manganese powder is 20-30 g/h, and the continuous reaction time is 5-12 h; the precipitator is one or more of ammonium carbonate, ammonium bicarbonate, ammonia water, sodium carbonate and sodium hydroxide, and the precipitation reaction time is 1-12 h; in the reaction process, the stirring speed is 300-1000 r/min.
The doping element M adopted in the method has two functions: the lithium manganate particles can be used as a fluxing agent, and can be formed at lower temperature or in heat preservation time, even can be formed into single-crystal lithium manganate particles with different shapes; and secondly, the doping element can reduce the Jahn-Teller effect in the lithium manganate circulation process, reduce the dissolution of manganese and stabilize the lattice structure, thereby improving the circulation and rate capability of the lithium manganate.
Compared with the prior art, the uniformly doped manganous-manganic oxide obtained by the method has secondary particles formed by agglomeration of large octahedral primary particles, and can be used for solid-phase synthesis of a single-crystal lithium manganate material at lower temperature and with shorter heat preservation time, so that the energy consumption is reduced, the interior of the lithium manganate material is more complete, and the excellent electrochemical performance is obtained.
In the step B), the lithium source comprises one or more of lithium carbonate, lithium hydroxide, lithium acetate and lithium nitrate, and the uniformly doped manganous-manganic oxide powder and the lithium source are proportioned according to the structural formula of the doped lithium manganate.
In the step C), all heating rates are 1-8 ℃/min, the first-stage roasting time is 2-6 h, the second-stage roasting time is 4-9 h, and the third-stage roasting time is 8-16 h; and (3) crushing by adopting roller crushing or ball milling crushing, wherein the crushing time is 10-60 min, and sieving by using a 100-300-mesh sieve.
In the step D), all the heating rates are 1-6 ℃/min, the first-stage roasting time is 2-5 h, the second-stage roasting time is 4-8 h, and the third-stage roasting time is 8-14 h; and (3) crushing by adopting roller crushing or ball milling crushing, wherein the crushing time is 10-60 min, and sieving by using a 100-300-mesh sieve.
The method of the invention utilizes the defect type single crystal lithium manganate material with uniform particles, proper size and few defects obtained at the higher synthesis temperature of the step C), and utilizes the sintering at the lower synthesis temperature of the step D) to ensure that the lithium manganate material in the step D) has more complete and stable structure.
The single-crystal lithium manganate material is prepared according to the method.
The invention has the beneficial effects that:
1) the doped mangano-manganic oxide has the characteristics that secondary particles are formed by agglomeration of larger octahedral primary particles, doping elements are uniformly precipitated or adsorbed in gaps or surfaces of precursor particles, so that the consistency of the performance and the appearance of the lithium manganate can be greatly improved, in addition, the single crystal lithium manganate can be synthesized in a solid phase mode at lower temperature or in heat preservation time, and even single crystal lithium manganate particles with different appearances are formed, so that the single crystal lithium manganate material with both physical properties and electrochemical properties can be obtained.
2) The single crystal lithium manganate anode material is synthesized by two times of low-temperature sintering after high-temperature sintering and cooling, mainly comprises large single crystal primary particles, has the characteristics of uniform particles, proper size, small specific surface area, good crystallinity, difficult breakage during particle processing, complete and stable structure, can show larger tap density and compacted density when being used as an active substance, has small side reaction with electrolyte, can effectively inhibit the dissolution of divalent manganese in a circulating process, and is an energy storage material with excellent physical performance and electrochemical performance.
3) The preparation process of the manganous-manganic oxide doped and synthesized monocrystal lithium manganate material is simple, has low cost and is beneficial to large-scale production.
Drawings
FIG. 1 is an SEM photograph of Al-doped manganomanganic oxide in example 1 of the present invention.
FIG. 2 is an SEM photograph of trimanganese tetroxide in comparative example 1 of the present invention.
FIG. 3 is an SEM photograph of a single crystalline lithium manganate material according to example 1 of the present invention.
FIG. 4 is a comparison graph showing the normal temperature cycle of lithium manganate 1C according to example 1 of the present invention and comparative example 2.
FIG. 5 is a graph showing a comparison of high temperature (55 ℃ C.) cycles of lithium manganate 1C according to example 1 of the present invention and comparative example 2.
Detailed description of the invention
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the following examples and comparative examples, crushing was effected by roller crushing for a crushing time of 30 min.
The 100-300 mesh sieve used for sieving in the following examples and comparative examples.
In the roasting in the following examples and comparative examples, the temperature rise rate of the first high-temperature sintering is 1-8 ℃/min; the first-stage roasting time is 2-6 hours, the second-stage roasting time is 4-9 hours, and the third-stage roasting time is 8-16 hours. And after crushing and cooling, carrying out second-time lower-temperature sintering at a temperature rise rate of 1-6 ℃/min, wherein the first-stage roasting time is 2-5 h, the second-stage roasting time is 4-8 h, and the third-stage roasting time is 8-14 h.
The invention will be further illustrated with reference to the following specific examples and the accompanying drawings:
example 1
Preparation of Al-doped mangano-manganic oxide and LiMn synthesized by same1.9Al0.1O4A single-crystal lithium manganate material: adding 20g of ammonium chloride and 20g of aluminum nitrate into 1L of constant-temperature deionized water, keeping the water temperature at 65 ℃, continuously introducing oxygen, continuously stirring at 400r/min, uniformly and slowly adding 100g of manganese powder into the water within 4h, and adding the manganese powderAnd after continuously reacting for 10 hours, stopping introducing oxygen, cooling to room temperature, adding 10g of ammonia water, continuously reacting for 3 hours, carrying out solid-liquid separation, and washing and drying the obtained solid to obtain the uniform Al-doped manganous manganic oxide powder.
Weighing lithium carbonate and Al-doped manganous-manganic oxide according to a stoichiometric ratio, uniformly grinding to obtain a mixture, heating to 500 ℃ at the heating rate of 3 ℃/min, and roasting for a period of 4 hours; heating to 700 ℃ according to the heating rate of 3 ℃/min, and carrying out secondary roasting for 6 h; heating to 850 ℃ according to the heating rate of 3 ℃/min, carrying out three-stage roasting for 12h, crushing for 30min by adopting a crushing roller after roasting is finished, and then sieving by using a 200-mesh sieve to obtain the defective monocrystal lithium manganate powder. Finally, roasting the powder at a lower temperature for the second time, wherein the sintering system is to carry out first-stage roasting for 3h when the temperature is raised to 450 ℃ according to the temperature raising rate of 3 ℃/min, and carry out second-stage roasting for 5h when the temperature is raised to 600 ℃ according to the temperature raising rate of 3 ℃/min; heating to 770 ℃ at a heating rate of 3 ℃/min, and carrying out three-stage roasting for 8 h; crushing for 30min by adopting a crushing roller, sieving by using a 200-mesh sieve, and cooling to obtain the single crystal LiMn1.9Al0.1O4。
The charge and discharge performance test of the products obtained in all the examples and comparative examples was carried out according to the following method:
uniformly mixing the obtained lithium manganate, acetylene black and PVDF in a mass ratio of 8:1:1, adding NMP, grinding into uniform slurry, coating the uniform slurry on an aluminum foil, standing in a vacuum drying phase at 120 ℃ for 10 hours, and preparing the CR2025 button cell by taking a metal lithium sheet as a negative electrode and 1M LiPF6 as electrolyte. The electrochemical test voltage range is 3-4.3V, and 1C cycle is carried out after 2 cycles of 0.2C (1C: 148mAh/g) (NMP: N-methyl-2-pyrrolidone; PVDF: polyvinylidene fluoride).
In the embodiment 1, the 1C first discharge specific capacity of the single-crystal lithium manganate material at normal temperature is 115.7mAh/g, and the capacity retention rate after 200 cycles is 93.9%; under the condition of 1C at high temperature (55 ℃), the first discharge specific capacity is 117.4mAh/g, and the capacity retention rate after 200 cycles is 93.2%.
TABLE 1 electrochemical Performance test results of the positive electrode materials obtained in examples 1 to 2 and comparative examples 1 to 2
Example 2
Preparation of Al-doped mangano-manganic oxide and LiMn synthesized by same1.9Al0.1O4A single-crystal lithium manganate material: adding 20g of ammonium chloride and 20g of aluminum nitrate into 1L of constant-temperature deionized water, keeping the temperature of the water at 65 ℃, continuously introducing oxygen, continuously stirring at 400r/min, uniformly and slowly adding 100g of manganese powder into the water within 4h, continuously reacting for 10h after the manganese powder is added, stopping introducing the oxygen, cooling to room temperature, adding 10g of ammonia water, continuously reacting for 3h, performing solid-liquid separation, washing and drying the obtained solid to obtain the uniform Al-doped manganous manganic oxide powder.
Weighing lithium carbonate and Al-doped manganous-manganic oxide according to the stoichiometric ratio, grinding uniformly to obtain a mixture, heating to 500 ℃ according to the heating rate of 5 ℃/min, and roasting for a period of 5 hours; heating to 700 ℃ according to the heating rate of 5 ℃/min, and carrying out secondary roasting for 8 h; and heating to 950 ℃ according to the heating rate of 5 ℃/min, carrying out three-stage roasting for 14h, crushing for 30min by adopting a crushing roller after roasting is finished, and then sieving by using a 200-mesh sieve to obtain the defective monocrystal lithium manganate powder. Finally, roasting the powder at a lower temperature for the second time, wherein the sintering system is to perform first-stage roasting for 5 hours by heating to 450 ℃ according to the heating rate of 5 ℃/min, and perform second-stage roasting for 6 hours by heating to 600 ℃ according to the heating rate of 5 ℃/min; heating to 770 ℃ according to the heating rate of 5 ℃/min, and carrying out three-section roasting for 12 h; crushing for 30min by adopting a crushing roller, sieving by a 200-mesh sieve, and cooling to obtain the single crystal LiMn1.9Al0.1O4。
Example 2 the 1C first discharge specific capacity of the single-crystal lithium manganate material at normal temperature is 112.1mAh/g, and the capacity retention rate after 200 cycles of circulation is 92.3%; under the condition of 1C at high temperature (55 ℃), the first discharge specific capacity is 116.4mAh/g, and the capacity retention rate after 200 cycles is 88.4%.
Example 3
Preparation of Ba-doped mangano-manganic oxide and synthesized LiMn thereof1.9Ba0.1O4A single-crystal lithium manganate material: adding 20g of ammonium chloride and 13.12g of barium hydroxide into 1L of constant-temperature deionized water, keeping the water temperature at 65 ℃, continuously introducing oxygen, continuously stirring at 400r/min, and uniformly and slowly adding 100g of manganese powder within 4hAdding the mixture into water, continuously reacting for 10 hours after the manganese powder is added, stopping introducing oxygen, cooling to room temperature, adding 10g of ammonia water, continuously reacting for 3 hours, carrying out solid-liquid separation, washing and drying the obtained solid to obtain the mangano-manganic oxide powder uniformly doped with Ba.
Weighing lithium carbonate and Ba-doped manganous-manganic oxide according to a stoichiometric ratio, uniformly grinding to obtain a mixture, heating to 500 ℃ at a heating rate of 3 ℃/min, and roasting for a period of 4 hours; heating to 700 ℃ according to the heating rate of 3 ℃/min, and carrying out secondary roasting for 6 h; heating to 850 ℃ according to the heating rate of 3 ℃/min, carrying out three-stage roasting for 12h, crushing for 30min by adopting a crushing roller after roasting is finished, and then sieving by using a 200-mesh sieve to obtain the defective monocrystal lithium manganate powder. Finally, roasting the powder at a lower temperature for the second time, wherein the sintering system is to carry out first-stage roasting for 3h when the temperature is raised to 450 ℃ according to the temperature raising rate of 3 ℃/min, and carry out second-stage roasting for 5h when the temperature is raised to 600 ℃ according to the temperature raising rate of 3 ℃/min; heating to 770 ℃ at a heating rate of 3 ℃/min, and carrying out three-stage roasting for 8 h; crushing for 30min by adopting a crushing roller, sieving by a 200-mesh sieve, and cooling to obtain the single crystal LiMn1.9Ba0.1O4。
Example 3 the 1C first discharge specific capacity of the single crystal lithium manganate material at normal temperature is 112.2mAh/g, and the capacity retention rate after 200 cycles is 93.4%; under the condition of 1C at high temperature (55 ℃), the first discharge specific capacity is 116.8mAh/g, and the capacity retention rate after 200 cycles is 91.8%.
Example 4
Preparation of Ca-doped mangano-manganic oxide and LiMn synthesized by same1.9Ca0.1O4A single-crystal lithium manganate material: adding 20g of ammonium chloride and 10.7g of calcium chloride into 1L of constant-temperature deionized water, keeping the temperature of the water at 65 ℃, continuously introducing oxygen, continuously stirring at 400r/min, uniformly and slowly adding 100g of manganese powder into the water within 4h, continuously reacting for 10h after the manganese powder is added, stopping introducing the oxygen, cooling to room temperature, adding 10g of ammonium bicarbonate, continuously reacting for 3h, performing solid-liquid separation, washing and drying the obtained solid to obtain the uniform Ca-doped mangano-manganic oxide powder.
Then weighing lithium carbonate and Ca-doped manganous-manganic oxide according to the stoichiometric ratioUniformly grinding to obtain a mixture, heating to 500 ℃ according to the heating rate of 3 ℃/min, and roasting for a period of 4 hours; heating to 700 ℃ according to the heating rate of 3 ℃/min, and carrying out secondary roasting for 6 h; heating to 850 ℃ according to the heating rate of 3 ℃/min, carrying out three-stage roasting for 12h, crushing for 30min by adopting a crushing roller after roasting is finished, and then sieving by using a 200-mesh sieve to obtain the defective monocrystal lithium manganate powder. Finally, roasting the powder at a lower temperature for the second time, wherein the sintering system is to carry out first-stage roasting for 3h when the temperature is raised to 450 ℃ according to the temperature raising rate of 3 ℃/min, and carry out second-stage roasting for 5h when the temperature is raised to 600 ℃ according to the temperature raising rate of 3 ℃/min; heating to 770 ℃ at a heating rate of 3 ℃/min, and carrying out three-stage roasting for 8 h; crushing for 30min by adopting a crushing roller, sieving by using a 200-mesh sieve, and cooling to obtain the single crystal LiMn1.9Ca0.1O4. The electrochemical test method of the product is the same as that of the example 1.
Example 4, the 1C first discharge specific capacity of the single-crystal lithium manganate material at normal temperature is 112.4mAh/g, and the capacity retention rate after 200 cycles is 93.2%; under the condition of 1C at high temperature (55 ℃), the first discharge specific capacity is 116.3mAh/g, and the capacity retention rate after 200 cycles is 92.1%.
Comparative example 1
Preparation of mangano-manganic oxide and LiMn synthesized by same2O4Adding 20g of ammonium chloride into 1L of constant-temperature deionized water, keeping the temperature of the water at 65 ℃, continuously introducing oxygen, continuously stirring at 400r/min, uniformly and slowly adding 100g of manganese powder into the water within 4h, continuously reacting for 10h after the manganese powder is added, stopping introducing the oxygen, cooling to room temperature, adding 10g of ammonia water, continuously reacting for 3h, performing solid-liquid separation, washing and drying the obtained solid to obtain manganous oxide powder. Weighing lithium carbonate and Al-doped manganous-manganic oxide according to the stoichiometric ratio, uniformly grinding to obtain a mixture, heating to 500 ℃ at the heating rate of 3 ℃/min, and roasting for a period of 4 hours; heating to 700 ℃ according to the heating rate of 3 ℃/min, and carrying out secondary roasting for 6 h; heating to 850 ℃ according to the heating rate of 3 ℃/min, carrying out three-stage roasting for 12h, crushing for 30min by adopting a crushing roller after roasting is finished, and then sieving by using a 200-mesh sieve to obtain the defective monocrystal lithium manganate powder. Most preferablyThen, roasting the powder at a lower temperature for the second time, wherein the sintering system is to perform first-stage roasting for 3 hours when the temperature is raised to 450 ℃ according to the temperature-raising rate of 3 ℃/min, and perform second-stage roasting for 5 hours when the temperature is raised to 600 ℃ according to the temperature-raising rate of 3 ℃/min; heating to 770 ℃ at a heating rate of 3 ℃/min, and carrying out three-stage roasting for 8 h; crushing for 30min by adopting a crushing roller, sieving by a 200-mesh sieve, and cooling to obtain the single crystal LiMn2O4。
Comparative example 1A single-crystal lithium manganate material has a 1C first discharge specific capacity of 115.2mAh/g at normal temperature, and the capacity retention rate after 200 cycles of circulation is 87.1%; under high temperature (55 ℃), the first discharge specific capacity is 119.5mAh/g, and the capacity retention rate after 200 cycles of circulation is 85.8%.
Comparative example 2
Preparation of mangano-manganic oxide and LiMn synthesized by same2O4Adding 20g of ammonium chloride into 1L of constant-temperature deionized water, keeping the temperature of the water at 65 ℃, continuously introducing oxygen, continuously stirring at 400r/min, uniformly and slowly adding 100g of manganese powder into the water within 4h, continuously reacting for 10h after the manganese powder is added, stopping introducing the oxygen, cooling to room temperature, adding 10g of ammonia water, continuously reacting for 3h, performing solid-liquid separation, washing and drying the obtained solid to obtain manganous oxide powder. Weighing lithium carbonate and manganous manganic oxide according to the stoichiometric ratio, grinding uniformly, roasting at a second lower temperature, wherein the sintering system is to firstly roast at 450 ℃, secondly roast at 600 ℃, finally roast at 770 ℃, crush and cool to obtain the polycrystalline LiMn2O4(ii) a The electrochemical test method of the product is the same as that of the example 1.
Comparative example 2 the first discharge specific capacity of the polycrystalline lithium manganate material at room temperature under 1C is 115.1mAh/g, and the capacity retention rate after 200 cycles is 73.2%; under the condition of 1C at high temperature (55 ℃), the first discharge specific capacity is 116.4mAh/g, and the capacity retention rate after 200 cycles is 72.8%.
FIG. 1 is an SEM image of Al-doped manganous-manganic oxide in the embodiment of the invention, and it can be seen from FIG. 1 that the Al-doped manganous-manganic oxide is formed by more large octahedral primary particles, has uniform particle size, less agglomeration and smaller specific surface area, and the particle size is 0.2-0.5 μm.
Fig. 2 is an SEM image of manganomanganic oxide in a comparative example of the present invention, and it can be seen from fig. 2 that manganomanganic oxide is a secondary particle formed by agglomeration of primary particles, in which there are a small number of octahedral primary particles.
FIG. 3 is an SEM photograph of a single-crystal lithium manganate material of example 1 of the present invention, and from FIG. 3, it can be seen that synthesized LiMn1.9Al0.1O4The single crystal particle consists of primary single crystal particles with truncated octahedron shapes, and the particle size is approximately 0.5-2 mu m.
FIG. 4 is a comparison of the normal temperature cycle of lithium manganate 1C of example 1 of the present invention and comparative example 2, and from FIG. 4, it can be seen that single crystal LiMn1.9Al0.1O4The cycle performance of the material is superior to that of polycrystalline LiMn without doping Al element2O4And (3) a positive electrode material.
FIG. 5 is a comparison of high temperature (55 ℃ C.) cycles of lithium manganate 1C according to example 1 and comparative example 2 of the present invention, and it can be seen from FIG. 5 that single crystal LiMn1.9Al0.1O4The cycle performance of the material is superior to that of polycrystalline LiMn without doping Al element2O4And (3) a positive electrode material.
TABLE 1 electrochemical Performance test results of the positive electrode materials obtained in examples 1 to 2 and comparative examples 1 to 2
The above-mentioned application examples are only illustrative and the present invention is described in detail by examples, which are only used for further illustration of the present invention and are not intended to limit the scope of the present invention, and those skilled in the art can make some insubstantial modifications and adaptations of the present invention.
Claims (5)
1. The preparation method of the monocrystal doped lithium manganate material is characterized by comprising the following steps of:
A) adding ammonium salt and a soluble compound M containing doping elements into deionized water, continuously stirring and introducing oxidizing gas at a set temperature, adding manganese powder under the condition of keeping the condition of introducing gas, continuously and slowly adding the manganese powder, continuing to react after the addition is finished, stopping introducing gas after the reaction is finished, cooling to room temperature, then adding a precipitator, performing stirring and precipitation reaction, after the reaction is finished, performing solid-liquid separation, washing and drying the solid to obtain uniformly-doped manganous oxide powder, wherein the uniformly-doped manganous oxide powder has secondary particles formed by agglomeration of octahedral primary particles;
B) uniformly mixing the uniformly doped manganous-manganic oxide powder obtained in the step A) and a lithium source to obtain mixed powder;
C) performing primary roasting on the mixed powder in the step B) at 400-550 ℃, performing secondary roasting at 600-680 ℃, finally performing three-stage roasting at 800-950 ℃, cooling and crushing to obtain a defective monocrystal-doped lithium manganate powder material;
D) continuously roasting the defect type single crystal doped lithium manganate powder material obtained in the step C) at 350-520 ℃, then roasting at 580-650 ℃ for the second time, finally roasting at 700-850 ℃ for the third time, cooling and crushing to obtain a single crystal doped lithium manganate powder material with a complete crystal structure;
in the step A), the oxidizing gas is oxygen or air; the mass ratio of the manganese powder to the ammonium salt is (3-20): 1, the adding speed of the manganese powder is 20-30 g/h, and the continuous reaction time is 5-12 h; the precipitator is one or more of ammonium carbonate, ammonium bicarbonate, ammonia water, sodium carbonate and sodium hydroxide, and the precipitation reaction time is 1-12 h; in the reaction process, the stirring speed is 300-1000 r/min;
in the step A), the ammonium salt is one or more of ammonium nitrate, ammonium chloride and ammonium sulfate; the soluble compound M containing the doping elements is at least one of nitrates of cobalt, nickel, calcium, tin, zirconium, chromium, barium, aluminum, magnesium and strontium, chlorides of cobalt, calcium, tin, zirconium, chromium, lanthanum, barium, aluminum, magnesium and strontium, acetates of nickel, calcium, lanthanum, barium, magnesium and strontium and sulfates of cobalt, nickel, tin, zirconium, chromium, aluminum, magnesium and cerium; the concentration of ammonium salt in deionized water is 5-100 g/L, and the concentration of a compound M containing a doping element in deionized water is 5-30 g/L; the temperature is set to 50-90 ℃.
2. The method for preparing a single-crystal doped lithium manganate material according to claim 1, wherein in the step B), the lithium source comprises one or more of lithium carbonate, lithium hydroxide, lithium acetate and lithium nitrate, and the uniformly doped manganous manganic oxide powder and the lithium source are proportioned according to the structural formula of the doped lithium manganate.
3. The preparation method of the single-crystal doped lithium manganate material according to claim 1, characterized in that in the step C), all temperature rise rates are 1-8 ℃/min, the time of the first-stage roasting is 2-6 h, the time of the second-stage roasting is 4-9 h, and the time of the third-stage roasting is 8-16 h; and (3) crushing by adopting roller crushing or ball milling crushing, wherein the crushing time is 10-60 min, and sieving by using a 100-300-mesh sieve.
4. The preparation method of the single-crystal doped lithium manganate material according to claim 1, characterized in that in the step D), all the temperature rise rates are 1-6 ℃/min, the time of the first-stage roasting is 2-5 h, the time of the second-stage roasting is 4-8 h, and the time of the third-stage roasting is 8-14 h; and (3) crushing by adopting roller crushing or ball milling crushing, wherein the crushing time is 10-60 min, and sieving by using a 100-300-mesh sieve.
5. The single-crystal doped lithium manganate material prepared by the preparation method of any one of claims 1 to 4.
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