CN110923801B - Preparation method and application of single crystal ternary material - Google Patents
Preparation method and application of single crystal ternary material Download PDFInfo
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- C30B9/04—Single-crystal growth from melt solutions using molten solvents by cooling of the solution
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- 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
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Abstract
The invention discloses a preparation method and application of a single crystal ternary material. The invention firstly prepares a single crystal precursor, adds a fluxing agent in the process of preparing the precursor, and prepares the single crystal ternary material after lithium is prepared and lithiated. The preparation steps are as follows: 1) weighing a certain amount of precursor A; 2) weighing the precursor A and the fluxing agent B according to the mass ratio of 1: 0.001-1, uniformly mixing, roasting in an oxygen-containing atmosphere, crushing a roasted product, washing with water to remove the fluxing agent, and drying to obtain a single crystal ternary precursor C; 3) and (3) mixing the single crystal ternary precursor C and a lithium source according to the molar ratio of 1: 1-1.1, uniformly mixing, performing secondary roasting in an oxygen-containing atmosphere, and crushing and demagnetizing the roasted product to obtain the single crystal ternary material product. The invention disassembles the traditional one-step synthesis method into two steps of synthesis of the single crystal precursor and lithium preparation and roasting, reduces Li/Ni mixed discharge and improves the capacity and the first effect of the single crystal ternary material compared with the single crystallization process for completing lithiation in one step.
Description
Technical Field
The invention relates to the field of lithium ion battery materials, in particular to a preparation method and application of a single crystal ternary material.
Background
With the continuous growth of new energy automobile industry at home and abroad, the demand for the anode material is increasing day by day, and higher requirements are also put forward on the performance of the anode material. Wherein, the layered ternary material LiNiaCobMcO2The lithium salt integrates the advantages of three transition metal oxide lithium salts, has high energy density, good cycle performance and low cost, and is regarded as one of the anode materials for the new energy automobile with the most application potential.
Traditional ternary materials are mostly aggregate ternary materials, are the secondary particle that is reunited by primary particle, and aggregate secondary particle is very easily powdered under manifold cycles and high voltage, leads to fresh interface to expose, directly leads to electrolyte side reaction to increase, and interface impedance increases, and polarization increases, and extreme dangerous phenomena such as circulation later stage capacity diving, battery gas expansion even explosion finally influence battery safety performance.
At present, the preparation of single crystal ternary materials is a main means for solving the problem of particle pulverization, and the methods for preparing single crystal materials in the prior art generally comprise two methods: 1. the sintering temperature after the precursor is mixed with lithium salt is increased to prepare the single crystal ternary material, but Ni is used2+With Li+The ionic radii of the Ni/Li single crystal ternary material are similar, and Ni occupies Li position more easily at high temperature, so that the single crystal ternary material prepared by the method has high Ni/Li mixed discharge and low specific capacity; 2. adding fluxing agent, reducing the baking temperature, and overcoming the defect of ion mixing caused by the high temperature condition of the method 1.
Chinese patent CN109378469A discloses a preparation method of a ternary material, which is to uniformly mix a ternary precursor, a lithium source and a fluxing agent, obtain a single-crystal-like anode material through one-time sintering, and then coat the single-crystal-like anode material to obtain the ternary material; chinese patent CN109216688A mixes the precursor, a lithium source, a fluxing agent, a doping element and polyvinyl alcohol, and presses after spray drying to obtain a block, and then the block is roasted, crushed and coated to obtain the single crystal-like ternary lithium battery material.
However, in the prior art, a method of mixing and roasting a lithium source, a fluxing agent and a precursor is adopted, the method has obvious defects, the optimal temperature of the fluxing agent for exerting the fluxing effect is not always completely consistent with the optimal synthesis temperature of the ternary material (i.e. Li ions enter crystal lattices and the crystallinity is increased to complete the lithiation process), and if the optimal synthesis temperature is higher than the optimal fluxing temperature of the fluxing agent, the fluxing agent is melted, so that partial anions and cations in the fluxing agent enter the crystal lattices of the ternary material, lattice defects are caused, the anions and cations are excessively doped, and the electrochemical performance of the material is reduced; on the contrary, the optimal synthesis temperature is lower than the optimal fluxing temperature of the fluxing agent, the fluxing effect of the fluxing agent is reduced, and the single crystal ternary material with good appearance cannot be obtained.
Therefore, the development of a single crystal ternary material with simple preparation steps, good electrochemical performance and high stability is a technical problem in the field of lithium ion battery materials.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method and application of a single crystal ternary material, and the defects of the prior art are overcome by adding a fluxing agent in the synthesis process of a precursor, so that the high-performance single crystal ternary material is prepared.
In order to solve the technical problems, the invention adopts the technical scheme that:
a preparation method of a single crystal ternary material comprises the following steps: firstly, uniformly mixing a ternary precursor and a fluxing agent, and roasting for one time to generate a single crystal ternary precursor; and washing and drying the single crystal ternary precursor, and adding a lithium source for secondary roasting to generate the single crystal ternary material.
A preparation method of a single crystal ternary material comprises the following steps:
1) weighing a certain amount of precursor A, wherein the chemical formula of the precursor A is Ni1-x-y CoxMy(OH)2Wherein, 0<x≤1/3，0<y is less than or equal to 1/3, M is one or more elements of Mn, Al, Mg, Zr, Ti and Sr, and D50 of the precursor A is 1-15 mu M;
2) weighing the precursor A and the fluxing agent B according to the mass ratio of 1: 0.001-1, uniformly mixing, roasting in an oxygen-containing atmosphere, crushing a roasted product, washing with water to remove the fluxing agent, and drying to obtain a single crystal ternary precursor C;
3) mixing a single crystal ternary precursor C and a lithium source according to a molar ratio of 1: 1-1.2, uniformly mixing the lithium source with the molar weight of pure lithium, roasting for the second time in an oxygen-containing atmosphere, and crushing and demagnetizing the roasted product to obtain the LiNi1-x-y CoxMyO2A single crystal ternary material product.
Preferably, the oxygen-containing atmosphere is an atmosphere having a pure oxygen volume fraction of more than 20%.
Preferably, the fluxing agent B in the step 2) is a two-phase composite fluxing agent B2O3+Bi2O3、 ZrO2+B2O3、Al2O3+B2O3At least one of LiF + AlF and KCl + MgCl and/or at least one of three-phase composite fluxing agents LiF + NaF + KF, LiF + AlF + CsF and KF + LiF + CsF.
Preferably, the fluxing agent B in step 2) is selected from one or more of the following: in terms of molar ratio, KCl and MgCl are 2: 1; KF, AlF, CsF ═ 0.515:0.225: 0.26; b is2O3：Bi2O3＝1:1。
Preferably, when the fluxing agent is used, the addition amount of the fluxing agent B is 5 to 20 percent of the mass of the precursor A.
Preferably, the temperature of primary roasting is 400-950 ℃, and the sintering time is 0.1-24 h.
Preferably, the temperature of the secondary roasting is 700-.
Preferably, the lithium source is one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, lithium phosphate, lithium fluoride, lithium nitrate, lithium dihydrogen phosphate, lithium tert-butoxide and lithium oxalate.
Preferably, the single crystal ternary material prepared by the preparation method of the single crystal ternary material provided by the invention is applied to a lithium ion battery.
Compared with the single crystal material synthesized by one step in the prior art, the invention changes the material preparation process, adds the fluxing agent in the synthesis process of the precursor, and obtains the single crystal ternary material by mixing and sintering the precursor and the lithium source.
The invention has the beneficial effects that:
1. under the action of a fluxing agent, the single crystallization temperature of a precursor is reduced, a secondary particle precursor is fused into a precursor with a single crystal morphology through low-temperature sintering, a single crystal ternary material precursor is independently synthesized, the precursor is subjected to lithium preparation and then low-temperature solid-phase sintering, and the single crystal ternary material is finally obtained.
2. The method adopts the method of low-temperature preparation of the molten salt, does not need higher temperature treatment in the preparation stage of the single crystal precursor or the lithiation stage, can achieve the effect that the precursor of the secondary particle agglomerate is fused into the precursor with the single crystal morphology and is fully lithiated, and successfully avoids the loss of transition metal caused by the high-temperature decomposition of the precursor oxide and the uneven element distribution caused by the atomic position rearrangement of the transition metal element in the precursor at high temperature.
Drawings
FIG. 1 is a graph comparing the cycle performance of the products obtained in example 1 and comparative examples 1 to 4;
FIG. 2 is an SEM image of a single crystal ternary precursor prepared in example 1;
FIG. 3 is an SEM image of a non-single crystal ternary precursor prepared in comparative example 3;
FIG. 4 is an SEM image of a single crystal-like ternary precursor prepared in comparative example 4;
FIG. 5 shows XRD diffraction patterns of the products obtained in example 1 and comparative examples 1 to 4.
Detailed Description
The invention provides a preparation method of a single crystal ternary material, which comprises the following steps: firstly, uniformly mixing a ternary precursor and a fluxing agent, and roasting for one time to generate a single crystal ternary precursor; and washing and drying the single crystal ternary precursor, and adding a lithium source for secondary roasting to generate the single crystal ternary material.
The method for preparing the single crystal ternary material in the prior art generally adopts high temperature or adds a fluxing agent to reduce the roasting temperature, however, in the prior art, the precursor, the fluxing agent and a lithium source are mixed and roasted together, and the method can cause anions and cations in part of the fluxing agent to enter the crystal lattice of a finished product, so that the crystal lattice defect is caused, the anions and cations are excessively doped, and the electrochemical performance of the material is reduced.
In order to overcome the defects in the prior art, the invention disassembles the one-step synthesis method into two steps of synthesis of a single crystal precursor and lithium-matched roasting, reduces Li/Ni mixed discharge and improves the capacity and the first effect of a single crystal ternary material compared with the single crystallization process for completing lithiation in one step at 800 ℃.
The invention provides a preparation method of a single crystal ternary material, which comprises the following steps:
1) weighing a certain amount of precursor A, wherein the chemical formula of the precursor A is Ni1-x-y CoxMy(OH)2Wherein, 0<x≤1/3，0<y is less than or equal to 1/3, M is one or more elements of Mn, Al, Mg, Zr, Ti and Sr, and D50 of the precursor A is 1-15 mu M;
2) weighing the precursor A and the fluxing agent B according to the mass ratio of 1: 0.001-1, uniformly mixing, roasting in an oxygen-containing atmosphere, crushing a roasted product, washing with water to remove the fluxing agent, and drying to obtain a single crystal ternary precursor C;
3) mixing a single crystal ternary precursor C and a lithium source according to a molar ratio of 1: 1-1.2, uniformly mixing the lithium source with the molar weight of pure lithium, roasting for the second time in an oxygen-containing atmosphere, and crushing and demagnetizing the roasted product to obtain the LiNi1-x-y CoxMyO2A single crystal ternary material product.
The oxygen-containing atmosphere selected by the invention is an atmosphere with pure oxygen volume fraction of more than 20%. The production of high nickel materials requires sintering in a high purity oxygen atmosphere as much as possible to convert the chemical reaction to LiNixCoyMnzO2The final resultant moves in the direction, the lithium oxide oxidized by the raw material lithium hydroxide is completely reacted, the residual alkali of the material is reduced, and the Ni is reduced2+The content is reduced, and Li/Ni mixed row is reduced, so that the high-nickel material with excellent performance is obtained.
The fluxing agent B selected in the invention is a two-phase composite fluxing agent B2O3+Bi2O3、ZrO2+B2O3、 Al2O3+B2O3At least one of LiF + AlF and KCl + MgCl and/or at least one of three-phase composite fluxing agents LiF + NaF + KF, LiF + AlF + CsF and KF + LiF + CsF.
Particularly preferably, the fluxing agent B in the present invention is selected from one or more of the following fluxing agents: in accordance with the moleKCl and MgCl are 2:1 in molar ratio; KF, AlF, CsF ═ 0.515:0.225: 0.26; b is2O3：Bi2O3＝1:1。
Wherein the adding amount of the fluxing agent B is 5-20% of the mass of the precursor A.
Because the traditional process is one-step lithiation roasting of a fluxing agent, a lithium source and a precursor material, when the disassembly is two steps, the selection of the fluxing agent is very important because no lithium salt participates in the synthesis of a single crystal precursor.
Lithium salt is an important eutectic salt, but Li is easy to break at high temperature due to weak Li-O bond+The radius is smaller than 0.076nm, and the lithium-oxygen (Li-O) octahedron is easily formed by inserting into octahedron transition metal layers of Ni-O, Co-O and Mn-O, and research shows that Li can be generated at 500 DEG C+Into the crystal lattice to cause [003 ]]The peak intensity was increased. Therefore, most of LiOH added in the process of synthesizing the ternary material is decomposed and bonded by Li-O, and Li+The ions split into the crystal lattice and do not act as a flux.
In the present invention, it is necessary to select a flux having a large atomic radius, a low melting point at which insertion into a transition metal layer does not easily occur, and no chemical bond with Li, as the most preferable flux. The fluxing agent with a single component generally has a higher melting point, generally needs to be added in a lithium preparation stage, and the required fluxing temperature is higher, while the fluxing agent is added before lithium preparation, the invention aims at synthesizing a single crystal precursor at a low temperature, so that the fluxing agent with a lower fluxing temperature is needed, and the composite fluxing agent with a eutectic point can greatly reduce the melting temperature, for example, when the molar ratio of KCl to MgCl is 1.5:1, the eutectic point is 600 ℃, and is far lower than the KCl melting point 770 ℃ and the MgCl melting point 720 ℃. The generation of the precursor with the single crystal morphology can be promoted at low temperature.
When the composite fluxing agent with specific components is selected, the invention can be used for preparing the flux, such as KCl, MgCl, and/or KCl, MgCl, and MgCl in molar ratio of 2: 1; KF, AlF, CsF ═ 0.515:0.225: 0.26; b is2O3：Bi2O3The 1:1 fluxing agent has proper component proportion, moderate crystal nucleus growth rate, synergistic effect between fluxing elements, better fluxing effect and better appearance of the generated precursor single crystal。
The temperature of primary roasting is 400-950 ℃, and the sintering time is 0.1-24 h.
The temperature of the secondary roasting is 700-1100 ℃, and the sintering time is 0.1-24 h.
The lithium source in the invention is one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, lithium phosphate, lithium fluoride, lithium nitrate, lithium dihydrogen phosphate, lithium tert-butoxide and lithium oxalate.
In addition to the selection of the flux, the selection of firing conditions is also an important factor. The roasting temperature is too low, the time is too short, the solid phase mass transfer rate is slow, and a single crystal structure cannot be formed; the roasting temperature is too high, the time is too long, and LiNiO is easily caused2The single crystal structure is broken down. The invention explores the best roasting condition through a large amount of experimental work and thermodynamic theoretical calculation.
Preferably, the single crystal ternary material prepared by the preparation method of the single crystal ternary material provided by the invention is applied to a lithium ion battery.
The invention finds a condition enough to generate perfect single crystal by a great amount of attempts of controlling the growth rate of crystal nucleus by thermodynamic calculation and matching with various proportioning modes and various roasting conditions of different fluxing agents. The invention creatively provides a preparation method of a single crystal ternary material, and the quality and the electrochemical performance of the single crystal ternary material are improved.
The technical solution of the present invention is described in detail below with reference to examples.
Example 1:
30mol of Ni are respectively weighed0.8Co0.1Mn0.1(OH)2(D50 is 5 mu m), 2mol of KCl and 1mol of MgCl are added into a high-speed mixer together, after uniform mixing, the mixture is sintered for 8h at 650 ℃ in an oxygen atmosphere, and after crushing, washing and drying, a single crystal ternary precursor is obtained; uniformly mixing a single crystal ternary precursor with 31.5mol of LiOH by using a high-speed mixer, and then sintering for 16h at 800 ℃ in an oxygen atmosphere; cooling, dissociating and sieving to obtain single crystal LiNi0.8Co0.1Mn0.1O2Three positive elementsA pole material.
Comparative example 1:
respectively weighing 30molNi0.8Co0.1Mn0.1(OH)2(D50 ═ 5 μm), 2mol of KCl and 1mol of MgCl were uniformly mixed with 31.5mol of LiOH in a high-speed mixer, and then secondary sintered at 800 ℃ for 16 hours in an oxygen atmosphere; cooling, dissociating and sieving to obtain single crystal LiNi0.8Co0.1Mn0.1O2A ternary positive electrode material.
Comparative example 2:
30mol of Ni are respectively weighed0.8Co0.1Mn0.1(OH)2(D50 ═ 15 μm) was uniformly mixed with 31.5mol of LiOH in a high-speed mixer, and then, secondary sintering was carried out at 800 ℃ for 16 hours in an oxygen atmosphere; cooling, dissociating and sieving to obtain LiNi of secondary particle aggregate0.8Co0.1Mn0.1O2A ternary positive electrode material.
Comparative example 3:
30mol of Ni are respectively weighed0.8Co0.1Mn0.1(OH)2(D50 is 5 mu m), 2mol of KCl are added into a high-speed mixer together, after uniform mixing, sintering is carried out for 8h at 650 ℃ in an oxygen atmosphere, and after crushing, water washing and drying, ternary precursor of the aggregate is obtained; uniformly mixing the ternary precursor of the aggregate with 31.5mol of LiOH by using a high-speed mixer, and then sintering for 16h at 800 ℃ in an oxygen atmosphere; cooling, dissociating and sieving to obtain the LiNi aggregate0.8Co0.1Mn0.1O2A ternary positive electrode material.
Comparative example 4:
30mol of Ni are respectively weighed0.8Co0.1Mn0.1(OH)2(D50 is 5 mu m), 2mol of KCl are added into a high-speed mixer together, after uniform mixing, sintering is carried out for 8h at 950 ℃ in an oxygen atmosphere, and after crushing, water washing and drying are carried out, a single crystal-like ternary precursor is obtained; uniformly mixing the mono-like ternary precursor with 31.5mol of LiOH by using a high-speed mixer, and then sintering for 16h at 800 ℃ in an oxygen atmosphere; cooling, dissociating and sieving to obtain similar monocrystal LiNi0.8Co0.1Mn0.1O2A ternary positive electrode material.
Example 2:
30mol of Ni are respectively weighed0.6Co0.2Mn0.2(OH)2(D50. mu.m) and 1mol of B2O3And 1mol of Bi2O3Adding the raw materials into a high-speed mixer, uniformly mixing, sintering for 6 hours at 800 ℃ in an oxygen atmosphere, crushing, washing with water, and drying to obtain a single crystal ternary precursor; mixing a single crystal ternary precursor with 15.75mol of Li2CO3After being uniformly mixed by a high-speed mixer, the mixture is sintered for 18 hours for the second time at 850 ℃ in the oxygen atmosphere; cooling, dissociating and sieving to obtain single crystal LiNi0.6Co0.2Mn0.2O2A ternary positive electrode material.
Comparative example 5:
30mol of Ni are respectively weighed0.6Co0.2Mn0.2(OH)2(D50. mu.m) and 2mol of B2O3And 1mol of Bi2O3Adding the raw materials into a high-speed mixer, uniformly mixing, sintering for 6 hours at 800 ℃ in an oxygen atmosphere, crushing, washing with water, and drying to obtain a single crystal ternary precursor; mixing a single crystal ternary precursor with 15.75mol of Li2CO3After being uniformly mixed by a high-speed mixer, the mixture is sintered for 18 hours for the second time at 850 ℃ in the oxygen atmosphere; cooling, dissociating and sieving to obtain single crystal LiNi0.6Co0.2Mn0.2O2A ternary positive electrode material.
Example 3:
30mol of Ni are respectively weighed0.8Co0.1Mn0.1(OH)2(D50 ═ 5 μm), 0.515mol of KF, 0.225mol of AlF, and 0.26mol of CsF were put together in a high-speed mixer, and after uniformly mixing, the mixture was sintered at 700 ℃ for 8 hours in an oxygen atmosphere, and after pulverizing, washing with water, and drying, the mixture was uniformly mixed with 31.5mol of LiOH in a high-speed mixer, and then, the mixture was sintered at 800 ℃ for a second time for 16 hours in an oxygen atmosphere; cooling, dissociating and sieving to obtain single crystal LiNi0.8Co0.1Mn0.1O2A ternary positive electrode material.
Comparative example 6:
30mol of Ni are respectively weighed0.8Co0.1Mn0.1(OH)2(D50 ═ 5 μm) was put into a high-speed mixer together with 0.515mol of KF and 0.225mol of AlF, and after mixing uniformly, the mixture was sintered at 700 ℃ for 8 hours in an oxygen atmosphere, and after grinding, washing with water, and drying, the mixture was mixed uniformly with 31.5mol of LiOH in a high-speed mixer, and then, after secondary sintering was carried out at 800 ℃ for 16 hours in an oxygen atmosphere; cooling, dissociating and sieving to obtain single crystal LiNi0.8Co0.1Mn0.1O2A ternary positive electrode material.
Example 4:
30mol of Ni are respectively weighed0.8Co0.15Al0.05(OH)2(D50 is 5 mu m), 2mol of KCl and 1mol of MgCl are added into a high-speed mixer together, after uniform mixing, the mixture is sintered for 8h at 650 ℃ in an oxygen atmosphere, and after crushing, washing and drying, a single crystal ternary precursor is obtained; uniformly mixing a single crystal ternary precursor with 31.5mol of LiOH by using a high-speed mixer, and then sintering for 16h at 650 ℃ in an oxygen atmosphere; cooling, dissociating and sieving to obtain single crystal LiNi0.8Co0.15Al0.05O2A ternary positive electrode material.
Experimental conditions:
the specific capacity of the first cycle discharge and the rate capability of the button cell prepared by using the lithium ion secondary battery anode materials prepared in the examples 1-4 and the comparative examples 1-5 are listed in the table 1, and the specific surface area and the compaction density of the material are tested.
And (3) electrochemical performance testing: the CT2001A LAND tester tests the capacity and the cycle performance of the battery, the charging voltage range is 3.0-4.3V, and the testing temperature is 25 ℃.
TABLE 1 electrochemical and physicochemical Properties of the materials
From table 1, it can be seen that the single crystal ternary materials prepared in examples 1 to 4 have high capacity and cycle performance and high compaction density.
As can be seen from Table 1, although the materials obtained in example 1 and comparative example 1 are single crystal materials, the specific capacity of example 1 is higher than that of comparative example 1 by 180mAh/g and is larger than that of comparative example 1 by more than 171 mAh/g. This is because although flux is added in both schemes, in example 1, flux is added before lithium preparation, the sintering temperature of flux is 650 ℃, and the anion and cation of flux are not or less doped into the crystal structure, while in comparative example 1, flux is added in the lithium preparation stage, the sintering temperature must be at the optimal lithiation temperature of 800 ℃, so that a ternary material with excellent electrochemical performance can be obtained, but 800 ℃ is also an optimal doping temperature for flux cations, so that adding flux during lithium preparation causes the doping of flux cations into the crystal structure, which causes Li/Ni mixing, reduces the first effect, and thus the material capacity is reduced. Therefore, compared with the one-step synthesis method, the flux stepwise synthesis method can avoid mixed discharge of the hetero ions, and the obtained product has better performance.
Comparative example 2 no flux was added, and single crystal material could not be synthesized at the same synthesis temperature, and synthesized was agglomerated material; comparative example 3 is a single component flux, and the flux effect cannot be exerted at 650 ℃, so that an aggregate is obtained, and the later performance is seriously attenuated. However, even with elevated firing temperatures, the effectiveness of the flux is still poor when a single component is used. Comparative example 4 also adopts a flux with a single component, although the sintering temperature is increased to 950 ℃, the flux effect is still not obvious, which shows that only the single-crystal-like precursor can be generated, and the sintering temperature is higher than that of Ni at 950 ℃ because the sintering temperature is higher2O3The decomposition temperature of (a) resulted in the formation of non-chemically active NiO, which was shown to decrease the capacity of the finished product (166mAh/g), much lower than the performance of example 1.
Compared with the examples, the proportion of the composite fluxing agent is changed in the comparative examples 5 and 6, and the performance is slightly reduced compared with the optimized proportion. The reason for this is probably that when the component proportion is optimal, the crystal nucleus growth rate is moderate, the fluxing elements generate a synergistic effect, the fluxing effect is better, the structure of the generated precursor single crystal is better, and the performance of the product is better.
FIG. 1 shows the cycle performance of a battery using a model LAND tester model CT2001A, with a charging voltage range of 3.0-4.3V and a test temperature of 25 ℃. From the cycle curves of the materials obtained in example 1, comparative example 2 and comparative example 4, it can be seen that the single crystal ternary cathode material prepared by preparing the single crystal precursor at a low temperature and then lithiating at a low temperature in example 1 has a small Li/Ni mixing and a high capacity because the sintering temperature does not exceed the optimal temperature for preparing the secondary particle agglomerates. Meanwhile, due to the existence of the single crystal morphology, the cycle performance of the material is excellent.
Fig. 2, 3 and 4 are graphs of the morphology of the sintered precursors in example 1, comparative example 3 and comparative example 4 by using a japanese electron JSM-6510 type scanning electron microscope, and the significant morphology difference can be seen in the graphs. As can be seen from the figure, in example 1, Ni0.8Co0.1M0.1(OH)2Mixing with two-phase fluxing agent, and sintering at 650 ℃ for 8h to obtain Ni with single crystal morphology0.8Co0.1M0.1O2In the comparative example 3, the precursor with the same components and particle size is sintered for 8 hours at 650 ℃ in a single fluxing agent to generate Ni with the appearance of secondary particle aggregates0.8Co0.1M0.1O2In comparative example 4, Ni with single crystal-like morphology could be obtained by increasing the sintering temperature of the precursor to 950 ℃0.8Co0.1M0.1O2. The appearance of an electron microscope shows that the addition of the composite molten salt can promote the formation of precursor single crystals and greatly reduce the single crystallization temperature of the precursor.
FIG. 5 is a crystal structure characterization of a sample using a UItima type IV X-ray diffractometer, under the following test conditions: the Cu target K α (λ ═ 0.15406 nm) rays, the scan rate was 12 °/min, the step size was 0.02 °, and the range was 10 ° to 80 °. From the XRD patterns of the materials obtained in example 1, comparative example 2, comparative example 3 and comparative example 4, it can be seen that a single crystal ternary material having alpha-NaFeO was obtained in example 12A layered structure, a hexagonal system of R-3m space point groups.
The composite fluxing agent stepwise synthesis method provided by the invention can synthesize the ternary material with the single crystal structure at a lower temperature, and compared with the one-step method in the prior art, the synthesized material has better performance because of no impurity doping problem. In addition, the invention finds a condition enough for generating perfect single crystal by controlling the growth rate of crystal nucleus by thermodynamic calculation and matching with a plurality of matching modes of different fluxing agents and a plurality of attempts of roasting conditions, and the synthesized material is a single crystal material with better performance.
In summary, the disclosure of the present invention is not limited to the above-mentioned embodiments, and persons skilled in the art can easily set forth other embodiments within the technical teaching of the present invention, but such embodiments are included in the scope of the present invention.
Claims (9)
1. The preparation method of the single crystal ternary material is characterized by comprising the following steps of:
1) weighing a precursor A, wherein the chemical formula of the precursor A is Ni1-x-yCoxMy(OH)2Wherein, 0<x≤1/3，0<y is less than or equal to 1/3, M is one or more elements of Mn, Al, Mg, Zr, Ti and Sr, and D50 of the precursor A is 1-15 mu M;
2) weighing the precursor A and the fluxing agent B according to the mass ratio of 1-1: 0.001, uniformly mixing, roasting in an oxygen-containing atmosphere, crushing a roasted product, washing with water to remove the fluxing agent, and drying to obtain a single crystal ternary precursor C;
3) mixing a single-crystal ternary precursor C and a lithium source according to a molar ratio of 1: 1-1.2, wherein the molar weight of the lithium source is calculated by the molar weight of pure lithium; after being mixed evenly, the mixture is roasted for the second time in the oxygen-containing atmosphere, and the roasted product is crushed and demagnetized to obtain the LiNi1-x- yCoxMyO2A single crystal ternary material product.
2. The method for producing a single-crystal ternary material according to claim 1, characterized in that: the oxygen-containing atmosphere is an atmosphere with pure oxygen volume fraction of more than 20%.
3. The method for producing a single-crystal ternary material according to claim 1, characterized in that: the fluxing agent B in the step 2) is a two-phase composite fluxing agent B2O3+Bi2O3、ZrO2+B2O3、Al2O3+B2O3At least one of LiF + AlF and KCl + MgCl and/or at least one of three-phase composite fluxing agents LiF + NaF + KF, LiF + AlF + CsF and KF + LiF + CsF.
4. The method for producing a single-crystal ternary material according to claim 1, characterized in that: the fluxing agent B in the step 2) is selected from one or more of the following fluxing agents: KCl MgCl 2:1, KF AlF CsF 0.515:0.225:0.26 and B2O3：Bi2O3＝1:1。
5. The method for producing a single-crystal ternary material according to claim 4, characterized in that: the mass of the fluxing agent B is 5-20% of that of the precursor A.
6. The method for producing a single-crystal ternary material according to claim 1, characterized in that: the temperature of the primary roasting in the step 2) is 400-950 ℃, and the roasting time is 0.1-24 h.
7. The method for producing a single-crystal ternary material according to claim 1, characterized in that: the temperature of the secondary roasting in the step 3) is 700-.
8. The method for producing a single-crystal ternary material according to claim 1, characterized in that: the lithium source adopted in the step 3) is one or more of lithium hydroxide, lithium carbonate, lithium phosphate, lithium fluoride, lithium nitrate, lithium dihydrogen phosphate, lithium tert-butoxide and lithium oxalate.
9. The use of a single-crystal ternary material prepared by the method of any one of claims 1 to 8 in a lithium ion battery.
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| CN113299905B (en) * | 2021-05-21 | 2023-05-16 | 湖北融通高科先进材料集团股份有限公司 | Preparation method of monocrystal nickel cobalt lithium manganate ternary material |
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| CN114314689B (en) * | 2021-12-09 | 2023-08-29 | 湖南桑瑞新材料有限公司 | Lithium battery anode material and preparation method thereof |
| CN114665090A (en) * | 2022-04-11 | 2022-06-24 | 中南大学 | Method for preparing large-particle-size single crystal ternary cathode material at low temperature in one step |
| CN114678525B (en) * | 2022-04-12 | 2023-08-18 | 浙江极氪智能科技有限公司 | Ternary positive electrode material, preparation method thereof and lithium ion battery |
| CN114804233A (en) * | 2022-05-17 | 2022-07-29 | 无锡零一未来新材料技术研究院有限公司 | High-nickel ternary cathode material for lithium battery and preparation method thereof |
| CN116177625A (en) * | 2023-04-19 | 2023-05-30 | 新乡天力锂能股份有限公司 | Method for reducing residual alkali on surface of nickel-based positive electrode material and application thereof |
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