CN115224259A - Titanium-doped lithium nickel manganese oxide positive electrode material, preparation method and application thereof, and lithium ion battery - Google Patents
Titanium-doped lithium nickel manganese oxide positive electrode material, preparation method and application thereof, and lithium ion battery Download PDFInfo
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Abstract
The invention provides a titanium-doped lithium nickel manganese oxide positive electrode material, a preparation method and application thereof and a lithium ion battery. The preparation method comprises the following steps: (1) Under the stirring state, mixing titanium salt and dispersion liquid containing nickel-manganese precursor, and reacting to obtain precipitate containing nickel, manganese and titanium; the stirring speed is 150-900 r/min; the solvent in the dispersion liquid comprises alcohol, alkaline solution and water; the volume ratio of water to alcohol is (0.05-5): 100, respectively; the molar ratio of the titanium salt to the nickel-manganese precursor is (3-30): 100, respectively; (2) Mixing the precipitate containing nickel, manganese and titanium obtained in the step (1) with a lithium source to obtain an intermediate mixture, and calcining the intermediate mixture; the calcining temperature is 500-1000 ℃; the calcining time is 8-20 h. The preparation method has simple process and low cost, and is suitable for industrial production; the lithium ion battery assembled by the lithium ion battery has the advantages of high capacity, good rate capability, good cycle performance and the like.
Description
Technical Field
The invention relates to the field of new energy materials, and particularly relates to a titanium-doped lithium nickel manganese oxide positive electrode material, a preparation method and application thereof, and a lithium ion battery.
Background
Currently, lithium ion secondary batteries are becoming core energy storage devices of various power devices due to their advantages of high energy density, no obvious memory effect, little environmental pollution, long cycle life, etc., and development of lithium ion secondary batteries with excellent electrochemical properties is becoming the focus of current research. The positive electrode material is the key to ensure the excellent performance of the lithium ion secondary battery. At present, common cathode materials in lithium ion secondary batteries, such as lithium cobaltate, lithium manganate, lithium iron phosphate and the like, are difficult to meet the requirements of the market on high-performance lithium ion batteries, including high energy density, excellent rate performance, cycle performance and the like. Therefore, the research and development of the cathode material with excellent electrochemical performance have great significance.
The lithium nickel manganese oxide positive electrode material is concerned by the advantages of high working voltage, high energy density and low cost. However, under high operating voltage, lattice oxygen in the structure of the lithium nickel manganese oxide material is unstable, and the lattice oxygen will migrate to the surface in the repeated charging and discharging process to cause oxidative decomposition of the electrolyte, and the decomposition product hydrogen fluoride will corrode the active material, resulting in deterioration of capacity and cycle performance. In addition, after lattice oxygen is desorbed from the material bulk phase, the oxygen framework of the material and the diffusion channel stability of lithium ions are deteriorated, and rapid desorption of lithium ions cannot be achieved, thereby deteriorating rate performance.
Therefore, the key for improving the electrochemical performance of the lithium nickel manganese oxide cathode material is to enhance the stability of oxygen atoms in crystal lattices. Research shows that titanium element is introduced into the crystal structure of the material to effectively stabilize the lattice oxygen of the material, thereby stabilizing the crystal structure and improving the electrochemical performance (J.Zhang, Q.Li, C.Ouyang, et. Al, trace doping of multiple elements capable of standing crystal cycling of LiCoO) 2 at 4.6V, nature Energy 2019,4, 594-603). However, the diffusion rate of titanium ions in the cathode material is low, and a conventional doping modification method is easy to form a hetero phase on the surface of lithium nickel manganese oxide, which can hinder the insertion and extraction of lithium ions and influence the rate capability of the material.
For example, the electrochemical Performance of the material can be improved to a certain extent by Doping titanium, but titanium in the prepared material is doped into a bulk phase, but a mixed phase is formed on the Surface of the titanium, so that the rate Performance is not favorably improved (D.Kong, et. Al, ti-Gradient to stable layer Surface Structure for High Performance High-Ni Oxide of Li-Ion batteries, advanced Energy Materials,2019, 1901756).
Therefore, it is difficult and hot to find an effective modification means to dope titanium element to stabilize lattice oxygen and not introduce impurity phase on the surface. In addition, in order to further improve the electrochemical performance of the lithium nickel manganese oxide cathode material, reasonable structural design is necessary, wherein the large-particle cathode material is beneficial to improving the compaction density and the mechanical strength and improving the electrochemical performance of the cathode material.
Disclosure of Invention
The invention aims to overcome the defects that lattice oxygen in a lithium nickel manganese oxide material structure is unstable and a titanium ion is doped into the lithium nickel manganese oxide material structure to easily form a mixed phase on the surface so that the rate performance of the material is poor in the prior art, and provides a titanium-doped lithium nickel manganese oxide positive electrode material, a preparation method, application and a lithium ion battery. According to the titanium-doped lithium nickel manganese oxide cathode material prepared by the invention, titanium ions can effectively stabilize lattice oxygen, the stability of a crystal structure is improved, and meanwhile, the surface with lower impurity phase content and even without impurity phase is beneficial to realizing the rapid de-intercalation of lithium ions; the preparation method is simple, has low cost, can realize macro preparation of the active material, and is suitable for industrial production.
According to the invention, titanium salt is uniformly deposited on the surface of the precursor, and titanium ions are doped into a lithium nickel manganese oxide phase by combining high-temperature lithium insertion calcination, so that lattice oxygen is effectively stabilized without introducing surface impurity phases, and finally the titanium ion doped lithium nickel oxide cathode material is obtained.
The invention solves the technical problems through the following technical scheme:
the invention provides a preparation method of a titanium-doped lithium nickel manganese oxide positive electrode material, which comprises the following steps:
(1) Under the stirring state, mixing titanium salt and dispersion liquid containing nickel-manganese precursor, and reacting to obtain precipitate containing nickel, manganese and titanium; the stirring speed is 150-900 r/min; the solvent in the dispersion liquid comprises alcohol, alkaline solution and water; the volume ratio of the water to the alcohol is (0.05-5): 100, respectively; the molar ratio of the titanium salt to the nickel-manganese precursor is (3-30): 100, respectively;
(2) Mixing the precipitate containing nickel, manganese and titanium obtained in the step (1) with a lithium source to obtain an intermediate mixture, and calcining the intermediate mixture; the calcining temperature is 500-1000 ℃; the calcining time is 8-20 h.
In step (1), the titanium salt may be conventional in the art, and is preferably tetrabutyl titanate or titanium tetrachloride.
In the step (1), the molar ratio of the titanium salt to the nickel-manganese precursor can be (5-20): 100, e.g. 10.3:100.
in step (1), the mixing sequence may be conventional in the art, and preferably the titanium salt is added to the dispersion containing the nickel-manganese precursor.
Wherein, the titanium salt is preferably added dropwise.
In step (1), the nickel-manganese precursor can be conventional in the art, and is preferably prepared by the following method: dissolving nickel salt, manganese salt and a precipitator in a solvent according to a stoichiometric ratio, and carrying out hydrothermal reaction.
The nickel salt may be an inorganic nickel salt or an organic nickel salt, such as nickel sulfate, nickel chloride, nickel nitrate, or nickel acetate, which are conventional in the art.
The manganese salt may be an inorganic manganese salt or an organic manganese salt, such as manganese sulfate, manganese chloride, manganese nitrate or manganese acetate, which are conventional in the art.
Wherein the molar ratio of the nickel salt to the manganese salt may be 1:3.
wherein, the precipitant can be conventional in the art, and is preferably urea, urotropine or ammonium bicarbonate.
Wherein the amount of the precipitant may be conventional in the art, and is generally not less than the sum of the moles of the nickel salt and the manganese salt.
Wherein, the solvent can be one or more of water, glycol and glycerol.
Wherein, the total mass concentration of the nickel salt, the manganese salt and the precipitator can be 0.04-0.1 g/mL, preferably 0.05-0.08 g/mL, and more preferably 0.07g/mL.
Wherein the temperature of the hydrothermal reaction can be 150-200 ℃, for example 180 ℃.
Wherein, the time of the hydrothermal reaction can be 10-14 h, such as 12h.
In the step (1), the molecular expression of the nickel-manganese precursor can be Ni x Mn 2-x (CO 3 ) 2 Wherein x is more than or equal to 0.4 and less than or equal to 0.6.
In step (1), the concentration of the nickel-manganese precursor may be 0.5-2 mg/mL, preferably 0.8-1.2 mg/mL, for example 1mg/mL.
In step (1), the alcohol may be conventional in the art, preferably ethanol or ethylene glycol.
In the step (1), the volume ratio of the alcohol to the dispersion may be (90 to 99.9): 100, preferably (95 to 99.9): 100, e.g. 99.7.
In step (1), the alkaline solution may be conventional in the art, and is generally capable of controlling the pH of the dispersion to less than 12.5, such as ammonia or sodium hydroxide.
In step (1), the pH of the dispersion containing the nickel-manganese precursor may be 8 to 12.5, for example, 10.3, 10.7, or 12.1, preferably 9 to 11.5.
In step (1), the water may be conventional in the art, such as deionized water.
In the step (1), the volume ratio of the water to the alcohol may be (0.1 to 1): 100, e.g. 0.17:100.
in step (1), the temperature of the reaction may be 60 to 90 ℃, for example 80 ℃.
In step (1), the reaction time may be 4 to 10 hours, for example, 4 hours.
In the step (1), the rotation speed of the stirring can be 150r/min, 200r/min, 500r/min or 800r/min, preferably 500-800r/min.
In the step (1), the precipitate containing nickel, manganese and titanium may be Ni x Mn 2-x (CO 3 ) 2 And TiO 2 2 A mixture of (a).
In the step (1), after the reaction is finished, the precipitate containing nickel, manganese and titanium is generally subjected to suction filtration, washing and drying.
The washing operation and conditions can be conventional in the art, and the washing is generally performed by alternately washing with deionized water and ethanol. The number of washes is typically three.
Wherein, the drying can be conventional in the field, and preferably is vacuum drying.
The temperature of the drying may be conventional in the art, preferably 80 ℃.
In step (2), the lithium source may be conventional in the art, and is preferably lithium carbonate, lithium hydroxide, lithium acetate, lithium chloride or lithium nitrate.
In the step (2), the molar ratio of the lithium source and the precipitate containing nickel, manganese, and titanium may be 1.05:1 to 1.3:1, preferably 1.1:1 to 1.25:1, e.g. 1.1:1 or 1.25:1.
the precipitate containing nickel, manganese and titanium is a mixture, the main component of the precipitate is a nickel-manganese precursor, and the precipitate containing nickel, manganese and titanium can be considered as the nickel-manganese precursor when the addition amount of the lithium source is calculated.
In step (2), the mixing may be conventional in the art, and is typically a milling mixing.
In step (2), the calcination is generally carried out in a tube furnace.
In step (2), the atmosphere for the calcination is generally an oxygen-containing atmosphere, such as air or oxygen.
In step (2), the temperature of the calcination may be 800 to 1000 ℃, preferably 850 to 1000 ℃, for example 800 ℃ or 900 ℃.
In the step (2), the calcination time may be 9 to 20 hours, for example, 10 hours.
In the step (2), the calcination is usually followed by natural cooling.
The invention also provides the titanium-doped lithium nickel manganese oxide cathode material prepared by the preparation method.
The invention also provides a titanium-doped lithium nickel manganese oxide positive electrode material which comprises LiNi x Mn 2-x-y Ti y O 4 (ii) a Wherein x is more than or equal to 0.4 and less than or equal to 0.6, y is more than or equal to 0.0005 and less than or equal to 0.01, the titanium is doped in a bulk phase of the lithium nickel manganese oxide material, and the surface of the lithium nickel manganese oxide material is basically free of impurity phases.
In the invention, the property of the titanium-doped lithium nickel manganese oxide positive electrode material is not obviously changed due to the content of the heterogeneous phase, for example, the rate performance of the titanium-doped lithium nickel manganese oxide positive electrode material is not lower than that of the Chinese patent document CN 105280912A.
In the invention, the titanium-doped lithium nickel manganese oxide cathode material can be in a spinel structure.
In the present invention, the heterogeneous phase may be a titanium-containing phase different from spinel nickel manganese lithium titanate, such as TiMn 2 O 4 Or Li 2 TiO 3 And the like.
In the titanium-doped lithium nickel manganese oxide positive electrode material, the valence state of titanium is quadrivalent.
In the invention, the titanium-doped lithium nickel manganese oxide positive electrode material can be massive particles with the maximum diameter length within the range of 2-10 micrometers.
The invention also provides an application of the titanium-doped lithium nickel manganese oxide positive electrode material in a lithium ion battery as a positive electrode material.
The invention also provides a lithium ion battery which uses the titanium-doped lithium nickel manganese oxide cathode material.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
(1) A complete and uniform coating layer can be formed on the surface of the nickel-manganese precursor by controlling the hydrolysis rate of the titanium salt;
(2) Titanium ions can be fully diffused into a bulk phase by high-temperature treatment, so that the titanium-doped lithium nickel manganese oxide cathode material without impurity phases on the surface is obtained; the titanium ions can effectively improve the stability of oxygen atoms in crystal lattices, inhibit the oxygen atoms from migrating to the surface, relieve the occurrence of electrolyte decomposition side reactions, and meanwhile, the stable oxygen framework and the surface without impurity phases realize the rapid de-intercalation of lithium ions, thereby improving the multiplying power performance of the material;
(3) The large granular structure of the titanium-doped lithium nickel manganese oxide cathode material can improve the compaction density, inhibit the cracking of the material in circulation and remarkably improve the electrochemical performance of the titanium-doped lithium nickel manganese oxide cathode material;
(4) The method combining liquid phase coating and high-temperature calcination is adopted, the process is simple, the cost is low, the macro preparation of the active material can be realized, and the method is suitable for industrial production.
In a preferred embodiment, the titanium-doped lithium nickel manganese oxide cathode material of the invention shows excellent electrochemical performance after being assembled into a lithium ion battery: within the voltage range of 3.5-5.0V, the discharging specific capacity under 1C can be as high as 133mAh g -1 The capacity retention rate after 100 cycles at 1C can be 98%, and the battery can have 90mAh g at a large current density of 10C -1 The specific capacity of (A).
Drawings
FIG. 1 is an X-ray diffraction pattern of the product of example 1.
FIG. 2 is an electron micrograph of the product of example 1; FIG. 2a is a scanning electron micrograph of the product of example 1; FIG. 2b is a transmission electron micrograph of the product of example 1.
FIG. 3 shows the results of electrochemical performance tests of the positive electrode materials obtained in example 1 and comparative example 4; FIG. 3a is a result of rate capability test of the positive electrode materials obtained in example 1 and comparative example 4; fig. 3b is a result of cycle performance test of the positive electrode materials obtained in example 1 and comparative example 4.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the invention thereto. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
Example 1
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. 600mg of precursor (Ni) was taken 0.5 Mn 1.5 (CO 3 ) 2 ) Ultrasonically dispersed in 600mL of ethylene glycol, and 1mL of ammonia water and 1mL of deionized water were added to form a dispersion, the pH of which =10.3. 85 mu L of tetrabutyl titanate is added into the dispersion liquid drop by drop, the mixture is fully stirred, the rotating speed is 800r/min, and the mixture is reacted for 4 hours at the constant temperature of 80 ℃. Filtering the obtained precipitate (Ni) 0.5 Mn 1.5 (CO 3 ) 2 And TiO 2 2 Mixture of (d) was washed three times with deionized water and ethanol alternately and then dried under vacuum at 80 ℃. Lithium carbonate and dried precipitate are mixed in the molar ratio of n (Li) to n (Ni) 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials 1 and 1, calcining the materials at 900 ℃ for 10 hours in an air atmosphere, and cooling the materials to obtain the titanium-doped lithium nickel manganese oxide cathode material with a molecular expression of LiNi 0.5 Mn 1.495 Ti 0.005 O 4 。
Example 2
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. 600mg of precursor (Ni) was taken 0.5 Mn 1.5 (CO 3 ) 2 ) The dispersion was ultrasonically dispersed in 600mL of ethylene glycol and 1mL of ammonia and 1mL of deionized water were added to form a dispersion having a pH =10.3. 85 mu L of tetrabutyl titanate is added into the dispersion liquid drop by drop, the mixture is fully stirred, the rotating speed is 800r/min, and the mixture is reacted for 4 hours at the constant temperature of 80 ℃. And (4) washing the precipitate obtained by suction filtration with deionized water and ethanol for three times alternately, and then drying in vacuum at 80 ℃. Lithium carbonate and dried precipitate are mixed in the molar ratio of n (Li) to n (Ni) 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials 1 and 1, calcining the materials at 900 ℃ for 10 hours in an air atmosphere, and cooling the materials to obtain the titanium-doped lithium nickel manganese oxide cathode material, wherein the molecular expression is Li 1.15 Ni 0.5 Mn 1.495 Ti 0.005 O 4 。
Example 3
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. 600mg of precursor (Ni) was taken 0.5 Mn 1.5 (CO 3 ) 2 ) Ultrasonically dispersed in 600mL of ethanol, and added with 1mL of ammonia water and 1mL of deionized water to form a dispersion, wherein the pH of the dispersion is =10.7. 85 mu L of tetrabutyl titanate is added into the dispersion liquid drop by drop, the mixture is fully stirred, the rotating speed is 800r/min, and the mixture is reacted for 4 hours at the constant temperature of 80 ℃. And (4) alternately washing the precipitate obtained by suction filtration with deionized water and ethanol for three times, and then drying in vacuum at 80 ℃. Lithium carbonate and dried precipitate are mixed in the molar ratio of n (Li) to n (Ni) 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials in a ratio of =1.1, calcining the materials at 900 ℃ for 10 hours in an air atmosphere, and cooling the materials to obtain the titanium-doped lithium nickel manganese oxide cathode material, wherein the molecular expression is LiNi 0.5 Mn 1.495 Ti 0.005 O 4 。
Example 4
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. 600mg of precursor (Ni) was taken 0.5 Mn 1.5 (CO 3 ) 2 ) Ultrasonically dispersed in 600mL of ethylene glycol, and 1mL of NaOH solution (concentration of NaOH solution is 1m, pH = 14) and 1mL of deionized water were added to form a dispersion, pH of which =12.1. 85 mu L of tetrabutyl titanate is dropwise added into the dispersion liquid, the mixture is fully stirred at the rotation speed of 800r/min, and the mixture is reacted for 4 hours at the constant temperature of 80 ℃. And (4) alternately washing the precipitate obtained by suction filtration with deionized water and ethanol for three times, and then drying in vacuum at 80 ℃. Lithium carbonate and the dried precipitate are mixed according to the mol ratio of n (Li) to n (Ni) 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials 1 and 1, calcining the materials at 900 ℃ for 10 hours in an air atmosphere, and cooling the materials to obtain the titanium-doped lithium nickel manganese oxide cathode material with a molecular expression of LiNi 0.5 Mn 1.495 Ti 0.005 O 4 。
Example 5
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. 600mg of precursor (Ni) was taken 0.5 Mn 1.5 (CO 3 ) 2 ) The dispersion was ultrasonically dispersed in 600mL of ethylene glycol and 1mL of ammonia and 1mL of deionized water were added to form a dispersion having a pH =10.3. 85 mu L of tetrabutyl titanate is added into the dispersion liquid drop by drop, the mixture is fully stirred, the rotating speed is 150r/min, and the mixture is reacted for 4 hours at the constant temperature of 80 ℃. And (4) alternately washing the precipitate obtained by suction filtration with deionized water and ethanol for three times, and then drying in vacuum at 80 ℃. Lithium carbonate and the dried precipitate are mixed according to the mol ratio of n (Li) to n (Ni) 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials in a ratio of =1.1, calcining the materials at 900 ℃ for 10 hours in an air atmosphere, and cooling the materials to obtain the titanium-doped lithium nickel manganese oxide cathode material, wherein the molecular expression is LiNi 0.5 Mn 1.495 Ti 0.005 O 4 。
Example 6
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. 600mg of precursor (Ni) was taken 0.5 Mn 1.5 (CO 3 ) 2 ) The dispersion was ultrasonically dispersed in 600mL of ethylene glycol and 1mL of ammonia and 1mL of deionized water were added to form a dispersion having a pH =10.3. 85 mu L of tetrabutyl titanate is added into the dispersion liquid drop by drop, the mixture is fully stirred, the rotating speed is 800r/min, and the mixture is reacted for 4 hours at the constant temperature of 80 ℃. And (4) alternately washing the precipitate obtained by suction filtration with deionized water and ethanol for three times, and then drying in vacuum at 80 ℃. Lithium carbonate and dried precipitate are mixed in the molar ratio of n (Li) to n (Ni) 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials 1 and 1, calcining the materials at 800 ℃ for 10 hours in an air atmosphere, and cooling the materials to obtain the titanium-doped lithium nickel manganese oxide cathode material with a molecular expression of LiNi 0.5 Mn 1.495 Ti 0.005 O 4 。
Comparative example 1
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. 600mg of precursor (Ni) was taken 0.5 Mn 1.5 (CO 3 ) 2 ) The dispersion was ultrasonically dispersed in 600mL of ethylene glycol and 1mL of ammonia and 1mL of deionized water were added to form a dispersion having a pH =10.3. 340 mu L of tetrabutyl titanate is added into the dispersion liquid drop by drop, the mixture is fully stirred, the rotating speed is 800r/min, and the mixture is reacted for 4 hours at the constant temperature of 80 ℃. And (4) alternately washing the precipitate obtained by suction filtration with deionized water and ethanol for three times, and then drying in vacuum at 80 ℃. Lithium carbonate and dried precipitate are mixed in the molar ratio of n (Li) to n (Ni) 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials 1 and 1, calcining the materials at 900 ℃ for 10 hours in an air atmosphere, and cooling the materials to obtain the titanium-doped lithium nickel manganese oxide cathode material with a molecular expression of LiNi 0.5 Mn 1.48 Ti 0.02 O 4 。
Comparative example 2
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. 600mg of precursor (Ni) was taken 0.5 Mn 1.5 (CO 3 ) 2 ) Ultrasonically dispersed in 600mL of ethylene glycol, and 1mL of ammonia water and 1mL of deionized water were added to form a dispersion, the pH of which =10.3. 85 mu L of tetrabutyl titanate is added into the dispersion liquid drop by drop, the mixture is fully stirred, the rotating speed is 800r/min, and the mixture is reacted for 4 hours at the constant temperature of 80 ℃. And (4) alternately washing the precipitate obtained by suction filtration with deionized water and ethanol for three times, and then drying in vacuum at 80 ℃. Lithium carbonate and the dried precipitate are mixed according to the mol ratio of n (Li) to n (Ni) 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials in a ratio of =1.1, calcining the materials at 900 ℃ for 6 hours in an air atmosphere, and cooling the materials to obtain the titanium-doped lithium nickel manganese oxide cathode material, wherein the molecular expression is LiNi 0.5 Mn 1.495 Ti 0.005 O 4 。
Comparative example 3
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. Precursor (Ni) 0.5 Mn 1.5 (CO 3 ) 2 ) N (Li): n (Ni) in molar ratio to lithium carbonate 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials 1 and 1, calcining the materials at 900 ℃ for 10 hours in an air atmosphere, and cooling the calcined materials to obtain the lithium nickel manganese oxide cathode material LiNi 0.5 Mn 1.5 O 4 . 430mg of LiNi was taken 0.5 Mn 1.5 O 4 The dispersion was ultrasonically dispersed in 600mL of ethylene glycol and 1mL of ammonia and 1mL of deionized water were added to form a dispersion having a pH =10.3. 85 mu L of tetrabutyl titanate is added into the dispersion liquid drop by drop, the mixture is fully stirred, the rotating speed is 800r/min, and the mixture is reacted for 4 hours at the constant temperature of 80 ℃. After the reaction is finished, the precipitate is obtained by suction filtration, and is dried in vacuum at 80 ℃ after being washed for three times by deionized water and ethanol alternately. To be treatedThe product is calcined in an air atmosphere at 400 ℃ for 10h after being dried.
Comparative example 4
0.62g of nickel acetate, 1.83g of manganese acetate and 1.2g of urea are fully dissolved in 50mL of ethylene glycol, hydrothermal reaction is carried out for 12h at 180 ℃, and the obtained precipitate is filtered, washed and dried to obtain a precursor. Mixing the precursor (Ni) 0.5 Mn 1.5 (CO 3 ) 2 ) The molar ratio of the lithium carbonate to the lithium carbonate is n (Li) to n (Ni) 0.5 Mn 1.5 (CO 3 ) 2 Grinding and mixing the materials in a ratio of =1.1, calcining the materials at 900 ℃ for 10h in an air atmosphere, and cooling the materials to obtain the titanium-undoped lithium nickel manganese oxide cathode material with a molecular expression of LiNi 0.5 Mn 1.5 O 4 。
Effect example 1
1、XRD
FIG. 1 is an X-ray diffraction pattern of the product of example 1. As can be seen from the figure, the crystal structure of the lithium nickel manganese oxide positive electrode material is not damaged by titanium ion doping modification, and a mixed phase is not introduced, and the corresponding PDF card is as follows: 80-2162.
2. SEM and TEM
FIG. 2 is an electron micrograph of the product of example 1; FIG. 2a is a scanning electron micrograph of the product of example 1; FIG. 2b is a transmission electron micrograph of the product of example 1. From the figure, it can be seen that the titanium-doped lithium nickel manganese oxide cathode material has a large granular structure and no impurity phase on the surface.
3. Electrochemical performance test
The positive electrode materials prepared in examples 1 to 6 and comparative examples 1 to 4 were assembled into a half cell according to the following procedure: the prepared material is mixed with 10wt% of binder (4 wt% of N-methylpyrrolidone (NMP) solution of polyvinylidene fluoride (PVDF)) and 8wt% of conductive agent (SuperP conductive carbon black), and the mixture is coated on an aluminum foil after being uniformly stirred and is put into an oven to be dried at 60-80 ℃. And then punching the electrode plate by using a punch with the diameter of 10-16 mm, drying the electrode plate in a vacuum oven at the temperature of 60-120 ℃ for 4-12 h, and then transferring the electrode plate into a glove box filled with argon. Metal Li is used as a counter electrode, EC and DMC are adopted as electrolyte to assemble a CR2032 button cell, and constant current is carried out on a LAND cell test system (provided by Wuhanjinnuo electronics Co., ltd.)Testing the charge and discharge performance, wherein the charge and discharge cut-off voltage is relative to Li/Li + 3.5-5.0V, and the current density is 1-10c, 1c =147mA/g.
Electrochemical performance data for examples 1-6 and comparative examples 1-4 are shown in table 1. In the invention, the specific capacities are all obtained by testing at 25 ℃.
TABLE 1
FIG. 3 shows the results of electrochemical performance tests of the positive electrode materials obtained in example 1 and comparative example 4; FIG. 3a is the result of rate capability test of the positive electrode materials obtained in example 1 and comparative example 4; fig. 3b is a result of cycle performance test of the positive electrode materials obtained in example 1 and comparative example 4. In a voltage range of 3.5-5.0V, the discharge specific capacity of the cathode material prepared in example 1 at 1C is 133mAh/g, the reversible specific capacity at 10C is 90mAh/g, and the capacity retention rate is 98% after 100 cycles at 1C. The positive electrode material prepared in comparative example 4 has a specific discharge capacity of only 125mAh/g at 1C, a reversible specific capacity of 30mAh/g at 10C, and a capacity retention rate of only 74% after circulating for 100 circles at 1C.
Claims (10)
1. The titanium-doped lithium nickel manganese oxide cathode material is characterized in that the titanium-doped lithium nickel manganese oxide cathode material consists of LiNi x Mn 2-x-y Ti y O 4 (ii) a Wherein x is more than or equal to 0.4 and less than or equal to 0.6, y is more than or equal to 0.0005 and less than or equal to 0.01, and the titanium is doped in a bulk phase of the lithium nickel manganese oxide material and basically has no impure phase on the surface of the lithium nickel manganese oxide material.
2. The titanium-doped lithium nickel manganese oxide positive electrode material of claim 1, wherein the titanium-doped lithium nickel manganese oxide positive electrode material has a spinel structure;
and/or the heterogeneous phase is a titanium-containing phase different from the spinel nickel manganese lithium titanate, such as TiMn 2 O 4 Or Li 2 TiO 3 Etc.;
and/or in the titanium-doped lithium nickel manganese oxide positive electrode material, the valence state of titanium is quadrivalent;
and/or the titanium-doped lithium nickel manganese oxide cathode material is massive particles with the maximum diameter length within the range of 2-10 microns.
3. The preparation method of the titanium-doped lithium nickel manganese oxide cathode material is characterized by comprising the following steps of:
(1) Under the stirring state, mixing and reacting titanium salt and dispersion liquid containing nickel-manganese precursors to obtain precipitates containing nickel, manganese and titanium; the stirring speed is 150-900 r/min; the solvent in the dispersion comprises alcohol, alkaline solution and water; the volume ratio of the water to the alcohol is (0.05-5): 100, respectively; the molar ratio of the titanium salt to the nickel-manganese precursor is (3-30): 100, respectively;
(2) Mixing the precipitate containing nickel, manganese and titanium obtained in the step (1) with a lithium source to obtain an intermediate mixture, and calcining the intermediate mixture; the calcining temperature is 500-1000 ℃; the calcining time is 8-20 h.
4. The method for preparing the titanium-doped lithium nickel manganese oxide cathode material according to claim 3, wherein the titanium salt is tetrabutyl titanate or titanium tetrachloride;
and/or the molar ratio of the titanium salt to the nickel-manganese precursor is (5-20): 100, e.g. 10.3:100;
preferably, the mixing sequence is that the titanium salt is added into the dispersion liquid containing the nickel-manganese precursor;
and/or the nickel-manganese precursor is prepared by the following method: dissolving nickel salt, manganese salt and a precipitator in a solvent according to a stoichiometric ratio, and carrying out hydrothermal reaction.
5. The method for preparing the titanium-doped lithium nickel manganese oxide positive electrode material of claim 3, wherein the molecular expression of the nickel manganese precursor is Ni x Mn 2-x (CO 3 ) 2 Wherein x is more than or equal to 0.4 and less than or equal to 0.6;
and/or the concentration of the nickel-manganese precursor is 0.5-2 mg/mL, preferably 0.8-1.2 mg/mL, such as 1mg/mL;
and/or, the alcohol is preferably ethanol or ethylene glycol;
and/or the volume ratio of the alcohol to the dispersion is (90-99.9): 100, preferably (95 to 99.9): 100, e.g., 99.7;
and/or the alkaline solution is capable of controlling the pH value of the dispersion to be less than 12.5, such as ammonia water or sodium hydroxide;
and/or the pH of the dispersion containing the nickel manganese precursor is 8 to 12.5, such as 10.3, 10.7, or 12.1, preferably 9 to 11.5;
and/or the volume ratio of the water to the alcohol is (0.1-1): 100, e.g. 0.17:100, respectively;
and/or the temperature of the reaction is 60 to 90 ℃, for example 80 ℃;
and/or the reaction time is 4 to 10 hours, such as 4 hours;
and/or the rotation speed of the stirring is 150r/min, 200r/min, 500r/min or 800r/min, preferably 500-800r/min;
and/or the precipitate containing nickel, manganese and titanium is Ni x Mn 2-x (CO 3 ) 2 And TiO 2 A mixture of (a).
6. The method for preparing the titanium-doped lithium nickel manganese oxide cathode material according to claim 4, wherein the nickel salt is an inorganic nickel salt or an organic nickel salt, such as nickel sulfate, nickel chloride, nickel nitrate or nickel acetate;
and/or the manganese salt is an inorganic manganese salt or an organic manganese salt, such as manganese sulfate, manganese chloride, manganese nitrate or manganese acetate;
and/or the molar ratio of the nickel salt to the manganese salt is preferably 1:3;
and/or the precipitant is urea, urotropine or ammonium bicarbonate;
and/or the dosage of the precipitant is not less than the sum of the mole numbers of the nickel salt and the manganese salt;
and/or the solvent is one or more of water, glycol and glycerol;
and/or the total mass concentration of the nickel salt, the manganese salt and the precipitant is 0.04-0.1 g/mL, preferably 0.05-0.08 g/mL, and more preferably 0.07g/mL;
and/or the temperature of the hydrothermal reaction is 150-200 ℃, such as 180 ℃;
and/or the hydrothermal reaction time is 10-14 h, such as 12h.
7. The method for preparing the titanium-doped lithium nickel manganese oxide cathode material of claim 3, wherein the lithium source is lithium carbonate, lithium hydroxide, lithium acetate, lithium chloride or lithium nitrate;
and/or the molar ratio of the lithium source and the nickel, manganese and titanium containing precipitate is 1.05:1 to 1.3:1, preferably 1.1:1 to 1.25:1, e.g. 1.1:1 or 1.25:1;
and/or the temperature of the calcination is 800 to 1000 ℃, preferably 850 to 1000 ℃, such as 800 ℃ or 900 ℃;
and/or the calcination time is 9 to 20 hours, for example 10 hours.
8. The titanium-doped lithium nickel manganese oxide cathode material is prepared according to the preparation method of the titanium-doped lithium nickel manganese oxide cathode material as claimed in any one of claims 3 to 7.
9. Use of the titanium-doped lithium nickel manganese oxide positive electrode material according to any one of claims 1 to 2 and 8 as a positive electrode material in a lithium ion battery.
10. A lithium ion battery using the titanium-doped lithium nickel manganese oxide positive electrode material according to any one of claims 1 to 2 and 8.
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