CN115295748A - Method for preparing lithium ion Chi Shanjing ternary cathode material by using multi-metal MOF precursor and product thereof - Google Patents

Method for preparing lithium ion Chi Shanjing ternary cathode material by using multi-metal MOF precursor and product thereof Download PDF

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CN115295748A
CN115295748A CN202210088918.0A CN202210088918A CN115295748A CN 115295748 A CN115295748 A CN 115295748A CN 202210088918 A CN202210088918 A CN 202210088918A CN 115295748 A CN115295748 A CN 115295748A
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mof
source
precursor
cathode material
ternary cathode
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陆潇晓
单瑞浩
毛秦钟
王寅峰
吉同棕
蔡玉荣
姚菊明
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Zhejiang Haichuang Lithium Battery Technology Co ltd
Zhejiang Sci Tech University ZSTU
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Zhejiang Haichuang Lithium Battery Technology Co ltd
Zhejiang Sci Tech University ZSTU
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    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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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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    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a method for preparing a lithium ion Chi Shanjing ternary cathode material by using a multi-metal MOF precursor and a product thereof. Firstly, a multi-metal MOF single crystal precursor containing Ni, co and Mn elements in a specific proportion is synthesized, annealing is carried out to remove organic ligands in the multi-metal MOF single crystal precursor, the MOF precursor annealing product has the characteristics of nanoscale primary particles and secondary agglomerated particles with special space and pore structures, the multi-metal MOF single crystal precursor is fully mixed with a lithium source compound, and the mixture is placed in a muffle furnace to be calcined for a certain time under a certain atmosphere, so that the material is grown to have primary particlesTernary positive electrode material LiNi with single crystal morphology structure characteristics x Co y Mn z O 2 (x + y + z = 1) particles. The single crystal ternary anode material LiNi prepared by the invention x Co y Mn z O 2 (x + y + z = 1) has the advantages of uniform particle size, good thermal stability, good structural stability, good lithium storage cycle performance, long service life and the like.

Description

Method for preparing lithium ion Chi Shanjing ternary cathode material by using multi-metal MOF precursor and product thereof
Technical Field
The invention belongs to the technical field of material engineering, and relates to a method for preparing a lithium ion Chi Shanjing ternary cathode material by using multi-metal MOF and a product thereof.
Background
The lithium ion battery is used as a highly efficient clean power supply with great potential, has the advantages of high specific energy, long cycle life, stable performance, no waste discharge in the use process and the like, and is called as a green power supply. In recent 20 years, along with the gradual expansion of the application range of lithium ion batteries from small electronic products to large-scale energy storage devices such as new energy automobile power batteries and large-scale energy storage devices, the industry has put forward the requirements of lower cost, higher energy density and higher safety for next generation lithium ion batteries. Ternary positive electrode material LiNi x Co y Mn z O 2 (x + y + z = 1) has significant advantages of raw material cost and high energy density, is one of the electrode materials of lithium ion batteries which are intensively developed in recent years, and is also the main development direction of the current positive electrode material of energy storage power batteries. However, ternary materials suffer from a series of problems such as low cycle life, poor thermal stability, unstable chemical properties, and the like, and the problems are found in high-nickel ternary positive electrode materials (LiNi) x Co y Mn 1-x-y O 2 And x is not less than 0.5). The above problems can be mainly attributed to two aspects: the chemical activity of Ni element is low, the Ni-O binding force is weak, the stability of the material crystal structure is reduced along with the introduction of the Ni element, and the problems of cation mixed discharge, dissolution, oxygen vacancy defect and the like are easy to occur, so that the thermal decomposition temperature is reduced. 2. The ternary positive electrode material used on the commercial battery is generally spherical secondary particles, the structure is formed by agglomeration of nanoscale primary crystal grains, and due to uneven stress distribution, the spheres are broken due to the volume change of the primary crystal grains generated by the intercalation and deintercalation of lithium ions, so that the side reaction is increased, and the cycle capacity is quickly attenuated; in addition, the positive electrode material prepared from the spherical secondary agglomerated particles is low in compaction density, and is unfavorable for improving the energy density of the battery. In order to solve the series of problems of the ternary cathode material, the performance of the ternary cathode material is improved mainly by adopting methods such as chemical modification, surface modification and structural modification, and adopting a single crystal ternary material and the like.
The chemical modification method mainly adopts an ion doping mode and is implemented by doping Al into a ternary material crystal lattice 3+ ,Zr 4+ ,Ti 4+ And metal ions with stronger bonding force with oxygen can effectively improve the crystal structure stability of the ternary material. Chinese patent CN113410458A discloses a method for obtaining a cation-doped modified ternary cathode material by uniformly dispersing a nanoscale transition metal oxide in a solvent, uniformly and physically mixing the nanoscale transition metal oxide with a ternary material precursor to obtain a precursor material coated with the nanoscale transition metal oxide, drying the precursor material, mixing the dried precursor material with a lithium salt, and roasting the dried precursor material. But the method is complex, difficult to realize industrial production and high in cost.
The surface modification method mainly adopts a coating cladding means, and Chinese patent CN113753972A discloses a ternary anode material with a cladding surface coated with metal oxide, which is obtained by mixing sodium-potassium alloy and nickel-cobalt-manganese metal salt and then performing the steps of shearing, soaking and calcining, and the like.
Chinese patent CN 111129448A discloses a method for preparing a single crystal ternary cathode material by low-temperature sintering, which selects an NCM ternary precursor with the particle size D50 of 2.5-5.5 μm as a raw material to be mixed with lithium salt by a dry method, and repeats the steps of calcining, crushing, sieving and the like for multiple times.
Chinese patent CN 112573589A discloses a method for preparing a high-nickel type single crystal ternary cathode material by using a molten salt method, which comprises the steps of firstly preparing single crystal lithium cobaltate by using the molten salt method, then supplementing elements such as Ni, mn (Al) and the like and a certain amount of lithium salt, and synthesizing the single crystal ternary cathode material by high-temperature calcination again. The molten salt synthesis method used in the method has higher corrosion resistance requirement on equipment, has higher energy consumption and is not beneficial to green production. And the diffusion coefficients of elements such as Ni and Mn (Al) in the layered lithium cobaltate material have larger difference, and the synthesis method for supplementing transition metal elements through subsequent steps is easy to cause deviation of stoichiometric proportion of element compositions, thereby improving the difficulty of regulating and controlling the synthesis process.
Chinese patent CN113753971A discloses a method for preparing a single crystal ternary cathode material by mixing high nickel ternary material secondary agglomerated particles with an acid solution and performing acid etching. Although the method can keep the appearance and advantages of primary particles to the maximum extent, the loss of transition metal and lithium ions is inevitably caused in the acid etching process, and the waste of raw materials is caused. Meanwhile, the surface components of the ternary material can generate side reaction with the acid solution to cause surface inactivation of the material, and after the high-nickel ternary material is subjected to acid etching, lithium salt needs to be added again for lithium supplement calcination, so that a large amount of energy is consumed in the secondary calcination process, lithium element consumption is caused, and the production cost is increased.
Although multi-metal MOF is used as a precursor in the preparation process of the ternary cathode material of the lithium ion battery, for example, chinese patents: CN09585835A, but the MOF precursor contains organic ligands, and the direct mixing and calcination with a lithium source can hinder the diffusion of lithium ions to a certain extent, so that the generation of a heterogeneous phase is easy to cause, and the prepared ternary cathode material has small primary and secondary particles and large specific surface area, so that the practical single crystal ternary cathode material particles are difficult to prepare.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for preparing a lithium ion Chi Shanjing ternary cathode material LiNi by mixing and calcining a multi-metal ion MOF annealing product serving as a precursor and a lithium source x Co y Mn z O 2 (x + y + z = 1). Firstly, a multi-metal MOF single crystal precursor containing Ni, co and Mn elements in a specific proportion is synthesized, annealing is carried out to remove organic ligands in the multi-metal MOF single crystal precursor, the MOF precursor annealing product has the characteristics of nanoscale primary particles and secondary agglomerated particles with special space and pore structures, the MOF precursor annealing product is fully mixed with a lithium source compound, and the mixture is placed in a muffle furnace to be calcined for a certain time under a certain atmosphere, so that the material is grown into a ternary positive electrode material LiNi with the primary single crystal morphology structure characteristics x Co y Mn z O 2 (x + y + z = 1) particles.
The method comprises the following steps:
and (1) dissolving a certain amount of MOF organic ligand in a certain amount of deionized water, and stirring for 10-20 min to form a uniform milky MOF ligand solution.
Preferably, the MOF organic ligand in the step (1) adopts 4,4-biphenyldicarboxylic acid BPDC and 2-amino terephthalic acid NH 2 -BDC, isophthalic acid H 2 One or more of IPA.
Preferably, the molar ratio of the MOF organic ligand to deionized water in step (1) is 1: 400-1.
And (2) adding a certain amount of NaOH solution into the MOF ligand solution obtained in the step (1) until the solution is changed from turbid to clear.
Preferably, the concentration of the NaOH solution in the step (2) is 0.5-2 mol/L;
preferably, the volume ratio of the NaOH solution to the MOF ligand solution in the step (2) is 1.
Directly dispersing a Ni source, a Co source and a Mn source in a certain proportion in the solution obtained in the step (2), and stirring for 15-20 min until the Ni source, the Co source and the Mn source are completely dissolved; and transferring the solution to a liquid phase reaction kettle for heating reaction, after the reaction is finished, centrifugally washing, taking out precipitate, and drying to obtain the precursor of the polymetallic MOF.
Preferably, the Ni source in step (3) is: ni (NO) 3 ) 2 、Ni(CH 3 COO) 2 、NiCl 2 、Ni(C 5 H 7 O 2 ) 2 One or more of them.
Preferably, the Co source in step (3) is: co (NO) 3 ) 2 、Co(CH 3 COO) 2 、CoCl 2 、Co(C 5 H 7 O 2 ) 2 One or more of them.
Preferably, in the step (3), the Mn source is: mn (NO) 3 ) 2 、Mn(CH 3 COO) 2 、MnCl 2 、Mn(C 5 H 7 O 2 ) 2 One or more of them.
Preferably, the molar ratio of the Ni source to the Co source is 1:1-8, and the molar ratio of the Co source to the Mn source is 2:3-1:1.
Preferably, the liquid phase reaction temperature in the step (3) is 90-180 ℃, and the reaction time is 8-16 h.
Preferably, in the step (3), the centrifugal washing times of the multi-metal MOF precursor are 3-5 times, the drying temperature is 55-85 ℃, and the drying time is 12-24 h.
Step (4), placing the multi-metal MOF precursor prepared in the step (3) in a muffle furnace, and annealing at 400-500 ℃ for 2-3 h to remove organic matters in the precursor; mixing and grinding the annealed MOF precursor and a lithium source in a certain proportion, sequentially presintering and calcining in a certain atmosphere, and cooling to room temperature to obtain a single crystal ternary cathode material; wherein the molar ratio of lithium element in the lithium source to the total number of transition metal elements (Ni + Co + Mn) in the Ni source, the Co source and the Mn source is 1.05.
Preferably, the lithium source in step (4) is Li 2 CO 3 、LiNO 3 LiOH, acetic acidOne or more of lithium.
Preferably, the pre-burning and calcining atmosphere in the step (4) is pure oxygen or air; the presintering temperature is 500-600 ℃, and the presintering time is 3-6 h; the calcining temperature is 750-950 ℃, and the calcining time is 16-20 h.
The invention also aims to provide a lithium ion battery single crystal ternary positive electrode material LiNi x Co y Mn z O 2 (x + y + z = 1), prepared by the above method.
The invention has the beneficial effects that:
the invention utilizes a multi-metal ion MOF annealing product as a precursor, and the precursor is mixed with a lithium source and calcined to prepare the lithium ion Chi Shanjing ternary cathode material LiNi x Co y Mn z O 2 (x + y + z = 1). Firstly, a multi-metal MOF single crystal precursor containing Ni, co and Mn elements in a specific proportion is synthesized, and annealing is carried out to remove organic ligands in the precursor, so that subsequent solid-phase reaction with a lithium source can be fully mixed. Meanwhile, the MOF precursor annealing product is mixed with a lithium source compound by utilizing the characteristic that the primary particles with extremely small nano-scale and the secondary aggregates have special void structures, and the mixture is placed in a muffle furnace to be calcined in a certain atmosphere, so that the material is grown into a ternary positive electrode material LiNi with the primary single crystal morphology structure characteristics x Co y Mn z O 2 (x + y + z = 1) particles. Compared with the existing material preparation method, the method has the advantages of simple process steps, good compatibility with the existing production process, high production efficiency and relatively low cost, and the prepared single crystal ternary cathode material LiNi x Co y Mn z O 2 (x + y + z = 1) has the advantages of uniform particle size, good thermal stability, good structural stability, good lithium storage cycle performance, long service life and the like.
Drawings
FIG. 1 is an SEM image of the prepared Ni, co, mn multi-metal MOFs.
FIG. 2 is an XRD pattern of the prepared Ni, co, mn multimetallic MOFs.
FIG. 3 is an SEM image of the Ni, co, mn multimetallic MOF annealed products prepared.
Fig. 4 is an SEM image of the NCM333 type ternary cathode material prepared.
Fig. 5 is an XRD pattern of the prepared NCM333 type ternary cathode material.
Fig. 6 is a charge-discharge curve of the prepared NCM333 type single crystal ternary cathode material.
FIG. 7 is a cycle performance diagram of the prepared NCM333 type single crystal ternary cathode material.
Fig. 8 is an SEM image of the NCM333 type ternary cathode material prepared in comparative example 2.
Detailed Description
As described above, in view of the deficiencies of the prior art, the present inventors have made extensive studies and extensive practices, and propose a technical solution of the present invention, which is mainly based on at least: firstly, a multi-metal MOF single crystal precursor containing Ni, co and Mn elements in a specific proportion is synthesized, annealing is carried out to remove organic ligands in the multi-metal MOF single crystal precursor, the MOF precursor annealing product has the characteristics of nanoscale primary particles and secondary agglomerated particles with special space and pore structures, the MOF precursor annealing product is fully mixed with a lithium source compound, and the mixture is placed in a muffle furnace to be calcined for a certain time under a certain atmosphere, so that the material is grown into a ternary positive electrode material LiNi with the primary single crystal morphology structure characteristics x Co y Mn z O 2 (x + y + z = 1) particles.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. 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 addition, the technical features involved in the respective embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention discloses a method for preparing a lithium ion Chi Shanjing ternary cathode material by using a multi-metal MOF precursor, which comprises the following steps of:
step (1), dissolving a certain amount of MOF organic ligand in a certain amount of deionized water, and stirring for 10-20 min to form a uniform milky MOF ligand solution.
Preferably, the MOF organic ligands described in step (1)Adopting 4,4-biphenyldicarboxylic acid BPDC and 2-amino terephthalic acid NH 2 -BDC, isophthalic acid H 2 One or more of IPA.
Preferably, the molar ratio of the MOF organic ligand to deionized water in step (1) is 1: 400-1.
And (2) adding a certain amount of NaOH solution into the MOF ligand solution obtained in the step (1) until the solution is changed from turbid to clear.
Preferably, the concentration of the NaOH solution in the step (2) is 0.5-2 mol/L;
preferably, the volume ratio of the NaOH solution to the MOF ligand solution in the step (2) is 1.
Directly dispersing a Ni source, a Co source and a Mn source in a certain proportion in the solution obtained in the step (2), and stirring for 15-20 min until the Ni source, the Co source and the Mn source are completely dissolved; and transferring the solution to a liquid phase reaction kettle for heating reaction, after the reaction is finished, centrifugally washing, taking out precipitate, and drying to obtain the precursor of the polymetallic MOF.
Preferably, the Ni source in step (3) is: ni (NO) 3 ) 2 、Ni(CH 3 COO) 2 、NiCl 2 、Ni(C 5 H 7 O 2 ) 2 One or more of them.
Preferably, the Co source in step (3) is: co (NO) 3 ) 2 、Co(CH 3 COO) 2 、CoCl 2 、Co(C 5 H 7 O 2 ) 2 One or more of them.
Preferably, the Mn source in step (3) is: mn (NO) 3 ) 2 、Mn(CH 3 COO) 2 、MnCl 2 、Mn(C 5 H 7 O 2 ) 2 One or more of them.
Preferably, the molar ratio of the Ni source to the Co source is 1:1 to 8, and the molar ratio of the Co source to the Mn source is 2:3 to 1:1.
Preferably, the liquid phase reaction temperature of the step (3) is 90-180 ℃, and the reaction time is 8-16 h.
Preferably, in the step (3), the centrifugal washing times of the multi-metal MOF precursor are 3-5 times, the drying temperature is 55-85 ℃, and the drying time is 12-24 h.
Step (4), placing the multi-metal MOF precursor prepared in the step (3) in a muffle furnace, and annealing at 400-500 ℃ for 2-3 h to remove organic matters in the precursor; mixing and grinding the annealed MOF precursor and a lithium source in a certain proportion, sequentially presintering and calcining in a certain atmosphere, and cooling to room temperature to obtain a single crystal ternary cathode material; wherein the molar ratio of lithium element in the lithium source to the total number of transition metal elements (Ni + Co + Mn) in the Ni source, the Co source and the Mn source is 1.05.
Preferably, the lithium source in step (4) is Li 2 CO 3 、LiNO 3 One or more of LiOH and lithium acetate.
Preferably, the pre-burning and calcining atmosphere in the step (4) is pure oxygen or air; the presintering temperature is 500-600 ℃, and the presintering time is 3-6 h; the calcining temperature is 750-950 ℃, and the calcining time is 16-20 h.
The technical solutions of the present invention are further explained below with reference to some preferred embodiments, but the experimental conditions and the setting parameters should not be construed as limitations of the basic technical solutions of the present invention. And the scope of the present invention is not limited to the following examples.
Example 1-1: single crystal NCM333
6mmol of organic ligand BPDC is dissolved in 45ml of deionized water and stirred for 10min to form a uniform milky MOF ligand solution. Subsequently, 6ml of NaOH solution (2 mol/L) was added and the solution changed from turbid to clear. Mixing Ni (NO) 3 ) 2 ·6H 2 O(3mmol)、Co(NO 3 ) 2 ·6H 2 O(3mmol)、Mn(NO 3 ) 2 (3 mmol) was directly dispersed in the above ligand solution and stirred for 15min to completely dissolve. And transferring the solution into a reactor for heating, reacting for 12h at 95 ℃, and drying the precipitate in an oven at 60 ℃ to obtain the MOF precursor. Subsequently, the MOF precursor was calcined in a muffle furnace at 450 ℃ for 2h to remove organics from the precursor. Mixing Li 2 CO 3 Mixing and grinding with calcined MOF precursor, and controlling lithium element and transition metal elementThe molar ratio of the total (Ni + Co + Mn) was 1.05. And then placing the mixture in a muffle furnace in the air atmosphere to be pre-sintered for 5h at 500 ℃, then heating to 900 ℃ to be calcined for 20h, and cooling to room temperature to obtain the single crystal ternary cathode material.
Fig. 1 is an SEM image of Ni, co, mn multimetal MOF precursors obtained in example 1-1, which exhibit a pronounced rod-like crystal structure. FIG. 2 is an XRD pattern of the polymetallic MOF precursor obtained in example 1-1. The comparison of XRD patterns of the precursor and the organic ligand thereof can find that the diffraction peak of the MOF precursor is obviously different from that of the organic ligand, thereby proving the correct synthesis of MOF crystals. FIG. 3 is an SEM image of the Ni, co, mn multimetallic MOF annealed products prepared. As can be seen from the figure, the MOF precursor annealing product has primary particles of nanometer scale, and the secondary agglomerated particles have special morphology and void structure. FIG. 4 is a single crystal LiNi synthesized using multi-metal MOF precursors of example 1-1 1/3 Co 1/3 Mn 1/3 O 2 SEM photograph of (SC-NCM 333). It can be seen from the figure that the synthesized material is in a dispersed particle state, and the single particles show a single crystal morphology and exhibit α -NaFeO 2 The crystal has a specific polyhedral structure, and the average grain diameter of SC-NCM333 particles is about 400nm. FIG. 5 is an XRD pattern of SC-NCM333 synthesized using multi-metal MOF precursors in example 1-1. By comparison with the literature (J Power Sources 233 (2013) 121-130), the synthesized SC-NCM333 has typical alpha-NaFeO 2 The structure and the diffraction peak (108)/(110) near 65 degrees have obvious bifurcation, which proves that the material has good layered crystal structure. Further calculating the diffraction peak intensity ratio (I) of the (003) to (104) planes (003) /I (104) ) As a result, it was found that the synthesized SC-NCM333 material had I (003) /I (104) If the crystal lattice order degree of the material is more than 1.34, the nickel-lithium mixed-out degree of the material is proved to be smaller, and the crystal lattice order degree of the prepared material is higher.
Examples 1 to 2: lithium battery performance test
The single-crystal ternary positive electrode material prepared in example 1-1 was mixed with PVDF as a binder and the conductive agent, superP, in a mass ratio of 80Forming electrode slurry. Then, the slurry was coated on the surface of an aluminum foil, and after vacuum drying was carried out at 120 ℃ for 24 hours, the coated aluminum foil was cut into a wafer having a diameter of 15mm as an electrode sheet, which was connected to a metal lithium sheet, an electrolyte (EC: EMC: DMC =1 6 Concentration of 1 mol/L) are assembled into a RC2030 type button cell in a glove box. And carrying out constant current charge and discharge test in a Newware battery test system. The performance of the cell was evaluated by performing 50 charge-discharge cycles at a temperature of 25C, a rate of 0.5C, and a potential of 2.8-4.3V.
Fig. 6 is a graph showing charge and discharge curves of the test cells prepared in examples 1-2 at the 1 st, 20 th and 50 th times under the test conditions of a rate of 0.5C and a potential interval of 2.8-4.3V. As can be seen from the graph, the SC-NCM333 has an initial charge voltage of 3.65V and an initial discharge voltage of 4.27V. Fig. 6 is a graph of discharge capacity and coulombic efficiency for test cells prepared in examples 1-2 at a rate of 0.5C and a potential interval of 2.8-4.3V. As shown in the figure, the prepared lithium ion battery has the following charge and discharge performance: the first discharge capacity of SC-NCM333 is about 146mAh g -1 The first coulombic efficiency was about 92.1%; the capacity retention after 50 cycles was about 94.5% and the coulombic efficiency was close to 100%.
Example 2-1: single crystal NCM523
5mmol of organic ligand BPDC is dissolved in 45ml of deionized water and stirred for 10min to form a uniform milky MOF ligand solution. Subsequently, 5ml of NaOH solution (2 mol/L) was added and the solution changed from turbid to clear. Mixing Ni (NO) 3 ) 2 ·6H 2 O(2.5mmol)、Co(NO 3 ) 2 ·6H 2 O(1mmol)、Mn(NO 3 ) 2 (1.5 mmol) was directly dispersed in the above ligand solution and stirred for 15min to completely dissolve. And transferring the solution into a reactor for heating, reacting for 12h at 95 ℃, and drying the precipitate in an oven at 60 ℃ to obtain the MOF precursor. Subsequently, the MOF precursor was calcined in a muffle furnace at 450 ℃ for 2h to remove organics from the precursor. Mixing Li 2 CO 3 Mixing and grinding the mixture with a calcined MOF precursor, and controlling the molar ratio of lithium element to the total number of transition metal elements (Ni + Co + Mn) to be 1.05. Followed byAnd pre-burning the mixture in a muffle furnace at 500 ℃ for 5h under the pure oxygen atmosphere, then heating to 900 ℃ and calcining for 20h, and cooling to room temperature to obtain the single crystal ternary cathode material (SC-NCM 523).
The Ni, co, mn multimetal MOF precursors obtained in example 2-1 exhibited a pronounced rod-like crystal structure. The comparison of XRD patterns of the precursor and the organic ligand thereof can find that the diffraction peak of the MOF precursor is obviously different from that of the organic ligand, thereby proving the correct synthesis of MOF crystals. By observing the synthesized SC-NCM523 by using SEM, the synthesized material is seen to be in a dispersed particle state, and single particles show single crystal morphology and show alpha-NaFeO 2 The crystal has a characteristic polyhedral structure, and the average grain diameter of the single crystal ternary cathode material particles is about 350nm. Compared with the literature (J Power Sources 233 (2013) 121-130), the synthesized single crystal ternary cathode material has typical a-NaFeO 2 The structure and the diffraction peak (108)/(110) near 65o have obvious bifurcation, which proves that the material has good layered crystal structure. Further calculating the diffraction peak intensity ratio (I) of the (003) to (104) planes (003) /I (104) ) Then, the synthesized single crystal ternary cathode material I can be found (003) /I (104) More than 1.31, the material is proved to have smaller nickel-lithium mixed-out degree, and the prepared material has higher lattice order degree.
Example 2-2: lithium battery performance test
The single-crystal ternary positive electrode material prepared in example 2-1 was mixed with PVDF as a binder and the super p as a conductive agent in a mass ratio of 80. The slurry was then coated on the surface of an aluminum foil, and after vacuum drying at 120 ℃ for 24 hours, the coated aluminum foil was cut into a wafer having a diameter of 15mm as an electrode sheet, which was connected to a lithium metal sheet, an electrolyte (EC: EMC: DMC =1 6 Concentration of 1 mol/L) were assembled into a button cell of the RC2030 type in a glove box. And carrying out constant current charge and discharge test in a Newware battery test system. The performance of the cell was evaluated at a temperature of 25C, a rate of 0.5C, and a potential of 2.8-4.3V, with 50 charge-discharge cycles.
The prepared lithium ion battery has the following charge and discharge performances: the first discharge capacity of SC-NCM523 is about 152mAh g -1 First coulombic efficiency was about 92.5%; the capacity retention after 50 cycles was about 94.3% and the coulombic efficiency was close to 100%.
Example 3-1: single crystal NCM622
5mmol of organic ligand BPDC is dissolved in 45ml of deionized water and stirred for 10min to form a uniform milky MOF ligand solution. Subsequently, 5ml of NaOH solution (2 mol/L) was added and the solution changed from turbid to clear. Mixing Ni (NO 3 ) 2 ·6H 2 O(3mmol)、Co(NO 3 ) 2 ·6H 2 O(1mmol)、Mn(NO 3 ) 2 (1 mmol) was directly dispersed in the above ligand solution and stirred for 15min to complete dissolution. And transferring the solution into a reactor for heating, reacting for 12h at 95 ℃, and drying the precipitate in an oven at 60 ℃ to obtain the MOF precursor. Subsequently, the MOF precursor was calcined in a muffle furnace at 450 ℃ for 2h to remove organics from the precursor. Mixing Li 2 CO 3 Mixing and grinding with the calcined MOF precursor, and controlling the molar ratio of lithium element to the total number of transition metal elements (Ni + Co + Mn) to be 1.05. And then placing the mixture in a muffle furnace under pure oxygen atmosphere to be calcined for 5h at 500 ℃, then heating to 950 ℃ to be calcined for 20h, and cooling to room temperature to obtain the single crystal ternary cathode material (SC-NCM 622).
The Ni, co, mn multimetal MOF precursors obtained in example 3-1 exhibited a pronounced rod-like crystal structure. The comparison of XRD patterns of the precursor and the organic ligand thereof can find that the diffraction peak of the MOF precursor is obviously different from that of the organic ligand, thereby proving the correct synthesis of MOF crystals. By observation of SC-NCM622 using SEM, it can be seen that the synthesized material is in the state of dispersed particles, and the individual particles exhibit single crystal morphology and exhibit alpha-NaFeO 2 The crystal has a characteristic polyhedral structure, and the average grain diameter of the single crystal ternary cathode material grains is about 300nm. Compared with the literature (J Power Sources 233 (2013) 121-130), the synthesized single-crystal ternary cathode material has typical a-NaFeO 2 The structure is shown, and diffraction peaks (108)/(110) in the vicinity of 65 DEG are quite obviousThe material has a good layered crystal structure. The ratio (I) of the diffraction peak intensities of the (003) and (104) planes was further calculated (003) /I (104) ) Then, the synthesized single crystal ternary cathode material I can be found (003) /I (104) More than 1.27, the material is proved to have smaller nickel-lithium mixed-out degree, and the prepared material has higher lattice order degree.
Example 3-2: lithium battery performance test
The single-crystal ternary positive electrode material prepared in example 2-1 was mixed with PVDF as a binder and the super p as a conductive agent in a mass ratio of 80. The slurry was then coated on the surface of an aluminum foil, and after vacuum drying at 120 ℃ for 24 hours, the coated aluminum foil was cut into a wafer having a diameter of 15mm as an electrode sheet, which was connected to a lithium metal sheet, an electrolyte (EC: EMC: DMC =1 6 Concentration of 1 mol/L) were assembled into a button cell of the RC2030 type in a glove box. And carrying out constant current charge and discharge test in a Newware battery test system. The performance of the cell was evaluated by performing 50 charge-discharge cycles at a temperature of 25C, a rate of 0.5C, and a potential of 2.8-4.3V.
The prepared lithium ion battery has the following charge and discharge performance: the first discharge capacity of SC-NCM622 is about 169mAh g -1 The first coulombic efficiency was about 91.2%; the capacity retention after 50 cycles was about 95.1% and the coulombic efficiency was close to 100%.
Comparative example 1
The single crystal high nickel ternary materials prepared in examples 1, 2, 3 were compared with the documents electrochim. Acta 232 (2017) 123-13, j electroanal. Chem.838 (2019) 94-100 and Nano lett.2020,20,12,8832-8840 for lithium battery cycle performance. Electrochemical performance test is referred to electrolyte used in the above literature (EC: DMC: EMC =1 6 ) And test conditions (MCN 333,2.7-4.3V; MCN523,3-4.3V; MCN622, 2.8-4.5V) and is charged and discharged at a multiplying power of 1C, the prepared single crystal ternary material is respectively circulated for 100 circles, and the capacity retention rate is inspected. The test results are shown in table 1.
Table 1 lithium battery cycling performance of the single crystal ternary positive electrode material synthesized in the example and the ternary material of the comparative example
Figure BDA0003488370020000111
As can be seen from table 1, the discharge capacity and capacity retention rate of the single crystal ternary cathode material prepared by the present embodiment are improved to a certain extent compared with those reported in the literatures electrochim. Acta 232 (2017) 123-13, j electrical company. Chem.838 (2019) 94-100 and Nano lett.2020,20,12,8832-8840, so that the preparation method can make up for the deficiencies of the existing methods to a certain extent, and becomes a more effective preparation method of the single crystal ternary cathode material.
Comparative example 2
6mmol of organic ligand BPDC is dissolved in 45ml of deionized water and stirred for 10min to form a uniform milky MOF ligand solution. Subsequently, 6ml of NaOH solution (2 mol/L) was added and the solution changed from turbid to clear. Ni (NO 3) 2.6H 2O (3 mmol), co (NO 3) 2.6H 2O (3 mmol), mn (NO 3) 2 (3 mmol) in a molar ratio of 1. And transferring the solution into a reactor for heating, reacting for 12h at 95 ℃, and drying the precipitate in an oven at 60 ℃ to obtain the MOF precursor. Subsequently, the MOF precursor and Li2CO3 were directly mixed and ground, and the molar ratio of lithium element to the total number of transition metal elements (Ni + CO + Mn) was controlled to 1.05. And then placing the mixture in a muffle furnace in air atmosphere to be calcined for 5h at 500 ℃, then heating to 900 ℃, calcining for 20h, and cooling to room temperature to obtain the ternary cathode material.
Fig. 8 is an SEM image of the NCM 333-type ternary cathode material prepared in comparative example 2. As can be seen from the figure, the grains of the primary particles of the ternary cathode material prepared by directly mixing and calcining the polymetallic MOF with the lithium source are smaller, and the secondary particles present a random agglomeration morphology, which indicates that the grain growth of the NCM material is influenced by the presence of the organic ligand, so that the single-crystal ternary cathode material cannot be prepared by using the comparative example method.
The above embodiments are not intended to limit the present invention, and the present invention is not limited to the above embodiments, and all embodiments are within the scope of the present invention as long as the requirements of the present invention are met.

Claims (10)

1. A method for preparing a lithium ion Chi Shanjing ternary cathode material by using a multi-metal MOF precursor is characterized by comprising the following steps:
dissolving a certain amount of MOF organic ligand in a certain amount of deionized water, and stirring for 10-20 min to form a uniform milky MOF ligand solution;
step (2), adding a certain amount of NaOH solution into the MOF ligand solution obtained in the step (1) until the solution is changed from turbid to clear;
directly dispersing a Ni source, a Co source and a Mn source in a certain proportion in the solution obtained in the step (2), and stirring for 15-20 min until the Ni source, the Co source and the Mn source are completely dissolved; transferring the solution to a liquid phase reaction kettle for heating reaction, after the reaction is finished, centrifugally washing, taking out precipitate, and drying to obtain a multi-metal MOF precursor;
step (4), placing the precursor of the multi-metal MOF prepared in the step (3) in a muffle furnace, and annealing at 400-500 ℃ for 2-3 h to remove organic matters in the precursor; mixing and grinding the annealed MOF precursor and a lithium source in a certain proportion, sequentially presintering and calcining in a certain atmosphere, and cooling to room temperature to obtain a single crystal ternary cathode material; wherein the molar ratio of lithium element in the lithium source to the total number of transition metal elements (Ni + Co + Mn) in the Ni source, the Co source and the Mn source is 1.05.
2. The method for preparing the ternary cathode material of lithium ion Chi Shanjing by using the precursor of multi-metal MOF as claimed in claim 1, wherein the MOF organic ligand in step (1) is 4,4-Biphenyl dicarboxylic acid BPDC, 2-amino terephthalic acid NH 2 -BDC, isophthalic acid H 2 One or more of IPA.
3. The method for preparing the lithium ion Chi Shanjing ternary cathode material from the polymetallic MOF precursor of claim 1, wherein the molar ratio of MOF organic ligand to deionized water in step (1) is 1: 400-1.
4. The method for preparing the lithium ion Chi Shanjing ternary cathode material by using the multi-metal MOF precursor as claimed in claim 1, wherein the concentration of the NaOH solution in the step (2) is 0.5-2 mol/L; the volume ratio of the NaOH solution to the MOF ligand solution is 1.
5. The method for preparing the lithium ion Chi Shanjing ternary cathode material from multi-metal MOF precursor of claim 1 wherein in step (3) the Ni source is: ni (NO) 3 ) 2 、Ni(CH 3 COO) 2 、NiCl 2 、Ni(C 5 H 7 O 2 ) 2 One or more of the above; the Co source is: co (NO) 3 ) 2 、Co(CH 3 COO) 2 、CoCl 2 、Co(C 5 H 7 O 2 ) 2 One or more of the above; the Mn source is: mn (NO) 3 ) 2 、Mn(CH 3 COO) 2 、MnCl 2 、Mn(C 5 H 7 O 2 ) 2 One or more of the above; in the step (4), the lithium source is Li 2 CO 3 、LiNO 3 One or more of LiOH and lithium acetate.
6. The method for preparing the ternary cathode material of lithium ion Chi Shanjing by using the precursor of the polymetallic MOF as claimed in claim 1, wherein the molar ratio of the Ni source to the Co source is 1:1-8, and the molar ratio of the Co source to the Mn source is 2:3-1:1.
7. The method for preparing the lithium ion Chi Shanjing ternary cathode material by using the multi-metal MOF precursor as claimed in claim 1, wherein the liquid phase reaction temperature in step (3) is 90-180 ℃ and the reaction time is 8-16 h.
8. The method for preparing the lithium ion Chi Shanjing ternary cathode material by using the multi-metal MOF precursor according to claim 1, wherein the multi-metal MOF precursor is centrifugally washed for 3-5 times in the step (3), the drying temperature is 55-85 ℃, and the drying time is 12-24 hours.
9. The method for preparing the lithium ion Chi Shanjing ternary cathode material from the multi-metal MOF precursor as claimed in claim 1, wherein the pre-sintering and calcining atmosphere in step (4) is pure oxygen or air; the presintering temperature is 500-600 ℃, and the presintering time is 3-6 h; the calcining temperature is 750-950 ℃, and the calcining time is 16-20 h.
10. Lithium ion battery single crystal ternary positive electrode material LiNi x Co y Mn z O 2 (x + y + z = 1) prepared by the method of any one of claims 1-9.
CN202210088918.0A 2022-01-25 2022-01-25 Method for preparing lithium ion Chi Shanjing ternary cathode material by using multi-metal MOF precursor and product thereof Pending CN115295748A (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116102079A (en) * 2022-12-08 2023-05-12 中南大学 Li (Ni) 1/2 Mn 3/2 ) 1-x M x O 4-y N y And preparation and application thereof

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