CN110350185B - Fluorine-doped lithium-rich cathode material and preparation method and application thereof - Google Patents
Fluorine-doped lithium-rich cathode material and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of lithium ion batteries, and discloses a fluorine-doped lithium-rich cathode material and a preparation method and application thereof. The chemical formula of the fluorine-doped lithium-rich cathode material is Li1.19Mn0.56‑x‑ yCo0.12Ni0.12ZrxNbyO2‑zFzWherein, 0<x<0.06，0<y<0.02，0<z<0.6. Mixing metal salt with 2,3,5, 6-tetrafluoroterephthalic acid and 4, 4' -bipyridine, ball-milling, presintering and roasting to obtain a fluorine-doped lithium-rich cathode material; wherein the metal salt is composed of lithium salt, nickel salt, cobalt salt, manganese salt, zirconium salt and niobium salt. The fluorine-doped lithium-rich cathode material provided by the invention has the advantages of high cycle stability, stable discharge platform, high coulombic efficiency in the first cycle, high rate capability, high specific capacity, uniform particle size and the like, can be used for preparing a lithium ion battery cathode, and has wide application prospect.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a fluorine-doped lithium-rich cathode material and a preparation method and application thereof.
Background
The lithium ion battery is a recyclable high-efficiency clean new energy, is an effective technical way for comprehensively relieving energy and environmental problems, is widely applied to the fields of various portable electronic products, new energy automobiles and the like, and is indispensable energy storage equipment in the current society. The development of a new generation of high energy lithium battery is a goal continuously pursued by the industry, and the main bottleneck limiting the energy density of the lithium ion battery is the anode material. At present, lithium ions have been commercializedThe battery anode material is lithium cobaltate, lithium iron phosphate, ternary anode material and the like, but the specific capacity of the materials is low, so that the urgent requirements of future electronic products on high-energy-density lithium ion batteries are difficult to meet, the development requirements of electric automobiles are particularly difficult to meet, and the further development of the lithium ion batteries is hindered. The lithium-rich manganese-based positive electrode material has the advantages of high capacity, high discharge plateau and the like, and is considered to have the most potential to become the next generation of high-energy density lithium ion battery positive electrode material. However, the positive electrode material has the problems of low cycle stability, low coulombic efficiency in the first cycle, rapid attenuation of a discharge platform, poor discharge rate performance, large particle size, uneven distribution and the like. Relevant research shows that the solid phase method is adopted to synthesize the Li with the salt rock structure2Mn2/3Nb1/3O2F, under the current of 0.1C (20mAh g-1), the first discharge specific capacity reaches 277mAh g-1However, after 25 cycles, the specific capacity dropped to about 220mAh g-1The capacity retention rate was about 79.4% (Lee J, Kitchaev D A, Kwon D H, et al. Nature,2018,556(7700): 185.); li synthesized by coprecipitation method1.2[Mn0.7Ni0.2Co0.1]0.8O2The first discharge capacity reaches 235 mAh.g-1But the first turn of coulombic efficiency is only 66% (Q.Ma et al. journal of Power Sources 331(2016) (112-); li prepared by sol-gel method1.2Mn0.56Ni0.16Co0.08O2-xFxThe stability of the cycle performance is obviously improved (the capacity retention rate of the material is up to 79.2 percent after the material is cycled for 500 times under the current density of 125 mAh/g), the attenuation of a discharge platform is greatly inhibited (after the material is cycled for 500 times under the multiplying power of 0.5C, the obvious discharge platform still exists), but the specific capacity is lower (the specific capacity under the multiplying power of 0.5C is lower than 161 mAh.g)-1) (Zhang Shilong et al kinetic energy material 4 th phase 04164-. Therefore, the preparation of the lithium ion battery cathode material which has high cycle stability, stable discharge platform, high coulombic efficiency in the first circle, high rate capability, high specific capacity and uniform particle size is one of the key directions of the current research.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide the fluorine-doped lithium-rich cathode material which has the advantages of high cycle stability, stable discharge platform, high coulombic efficiency in the first cycle, high rate capability, high specific capacity and uniform particle size.
The invention also aims to provide a preparation method of the fluorine-doped lithium-rich cathode material.
The invention further aims to provide application of the fluorine-doped lithium-rich cathode material.
In order to achieve the purpose, the invention is realized by the following technical scheme: a fluorine-doped lithium-rich cathode material with a chemical formula of Li1.19Mn0.56-x-yCo0.12Ni0.12ZrxNbyO2-zFzWherein x is>0，y>0，0<x+y<0.54，0<z<0.6。
Said x is preferably 0< x < 0.06; more preferably 0.03. ltoreq. x.ltoreq.0.05.
Said y is preferably 0< y < 0.02; more preferably 0.01.
Z is preferably 0.1-0.5.
The preparation method of the fluorine-doped lithium-rich cathode material comprises the following steps: mixing metal salt with 2,3,5, 6-tetrafluoroterephthalic acid and 4, 4' -bipyridyl, ball-milling, presintering and roasting to obtain a fluorine-doped lithium-rich cathode material; wherein the metal salt is composed of lithium salt, nickel salt, cobalt salt, manganese salt, zirconium salt and niobium salt.
The metal salt is preferably prepared from lithium salt, nickel salt, cobalt salt, manganese salt, zirconium salt and niobium salt according to a stoichiometric ratio of 1.19: 0.12: 0.12: 0.5-0.52: 0.03-0.05: 0.01.
The lithium salt is preferably at least one of lithium hydroxide, lithium carbonate and lithium acetate.
The nickel salt is preferably one or two of nickel nitrate and nickel acetate.
The cobalt salt is preferably one or two of cobalt nitrate and cobalt acetate.
The manganese salt is preferably one or two of manganese nitrate and manganese acetate.
The zirconium salt is preferably one or both of zirconium nitrate and zirconium acetate.
The niobium salt is preferably one or two of niobium oxalate and niobium ethoxide.
The dosage of the 2,3,5, 6-tetrafluoroterephthalic acid is preferably in a ratio of 0.1-4.0: 1 according to the molar ratio of the 2,3,5, 6-tetrafluoroterephthalic acid to metal ions; more preferably, the molar ratio of the metal ions to the metal ions is 0.1-0.25: 1.
The dosage of the 4, 4' -bipyridyl is preferably 0-1: 1 molar ratio of the bipyridyl to the 2,3,5, 6-tetrafluoroterephthalic acid, and the dosage of the bipyridyl does not contain 0 endpoint; more preferably, the molar ratio of the compound to 2,3,5, 6-tetrafluoroterephthalic acid is 0.5-1: 1.
the conditions of the ball milling are preferably as follows: ball milling for 10-14 hours at a rotating speed of 400-500 r/min; more preferably: ball milling is carried out for 12 hours at the rotating speed of 450 r/min.
The conditions for the pre-firing are preferably as follows: heating at 400-600 ℃ for 4-8 hours; more preferably, the heating is carried out at 450 ℃ for 6 to 8 hours.
The roasting conditions are preferably as follows: heating at 600-950 ℃ for 6-24 hours; more preferably, the heating is carried out at 850-950 ℃ for 12-20 hours.
The fluorine-doped lithium-rich cathode material is applied to the preparation of the lithium ion battery cathode.
A lithium ion battery anode contains the fluorine-doped lithium-rich anode material.
The positive electrode of the lithium ion battery also contains conductive agent acetylene black and binder PVDF.
The positive electrode of the lithium ion battery preferably comprises the following components: the fluorine-doped lithium-rich cathode material, the conductive agent acetylene black and the binder PVDF are mixed according to the mass ratio of 75-85: 5-15: 5-15 parts by weight; more preferably, the weight ratio of the components is 80:10: 10.
The preparation method of the lithium ion battery anode comprises the following steps:
(A) fully stirring and uniformly mixing acetylene black serving as a conductive agent and the fluorine-doped lithium-rich cathode material, adding PVDF serving as an adhesive after dry mixing and stirring uniformly, adding N-methylpyrrolidone after dry mixing and stirring uniformly, and mixing uniformly to obtain cathode slurry;
(B) and coating the anode slurry on an aluminum foil, rolling on a rolling roller, and punching to obtain the lithium ion battery anode.
The dosage of the N-methyl pyrrolidone in the step (A) is calculated according to the solid content of the anode slurry of 40-50% and the viscosity of the slurry of 5000-6000 cps; preferably, the solid content of the anode slurry is 45%, and the viscosity of the slurry is 5050 cps.
Compared with the prior art, the invention has the following advantages and effects:
(1) when the fluorine-doped lithium-rich cathode material provided by the invention is charged and discharged at 0.1C (20mA/g), the specific discharge capacity is greater than 270mAh/g, the first-turn coulombic efficiency is 90.4%, the discharge specific capacity is greater than 150mAh/g at the current density of 2C (400mA/g), the capacity retention rate reaches 97.5% after 100 turns of 1C multiplying power charge-discharge cycle, and the specific capacity is greatly higher than that of a commercial unitary lithium cobaltate material (LiCoO)2) And ternary NCM material (LiMn)0.6Co0.2Ni0.2O2) The cycling stability is greatly higher than that of a typical lithium-rich manganese-based positive electrode material (Li)1.2Mn0.56Ni0.12Ni0.12O2) And has wide application prospect.
(2) The preparation method of the fluorine-doped lithium-rich cathode material adopts 2,3,5, 6-tetrafluoroterephthalic acid, 4' -bipyridine and transition metal to coordinate to generate a Metal Organic Framework (MOF) compound with a specific structure, synthesizes the lithium-rich fluorinated cathode material through a ball-milling synthesis method, the tetrafluoroterephthalic acid and the 4, 4' -bipyridyl can generate coordination with metal ions in the process of high-speed ball milling, so that the metal ions can be uniformly distributed at the atomic level, simultaneously, the fluorine source is used for providing fluorine element required in synthesis, the prepared anode material is a nano-grade material, the lithium ion diffusion path is short, therefore, the anode material has excellent rate performance, the particle size distribution is concentrated, the elements are uniformly distributed, and the problems of large particle size, non-uniform particle size distribution and poor rate performance of the anode material after the anode material is fluorinated are solved.
(3) Properties obtained by substitution modification between lithium-rich modified non-simple Transition Metals (TM) in the present inventionThe improvement is realized by the following specific principle: doped Nb5+The ions enter the Li layer through the Li layer and combine the O-TM (Li) -O plates nearby the Li layer into a whole; zr4+Ions are fixed on the TM layer and keep inertia in the circulating process, so that oxygen precipitation between O layers is prevented, and the stability of the structure is ensured; fluoride ions preferentially bind to cobalt and manganese ions and substitution of O with F induces partial reduction of TM ions by a charge compensation process; in the lithium-rich material granular crystal, the doping positions and the improvement principle of each atom are different, but have a synergistic effect, and a phenomenon of inhibiting the reduction of a discharge voltage platform caused by the change of a crystal structure can be generated, so that the fluorine-doped lithium-rich anode material has the characteristic of stable discharge platform.
Drawings
FIG. 1 is a SEM photograph provided in example 1.
Fig. 2 is an SEM image at different magnifications provided in comparative example 1.
FIG. 3 is a graph showing the rate capability test of examples 1, 2,3 and comparative example 1.
FIG. 4 is a graph showing the cycle performance test of example 1 and comparative example 1.
Fig. 5 is a graph of the median voltage (average discharge potential) as a function of the number of cycles in example 1, comparative example 2 and comparative example 3.
FIG. 6 is a graph showing the rate capability test of example 1 and comparative example 4.
Fig. 7 is a first-turn charge-discharge curve chart of example 1 and comparative example 1.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Example 1
(1) Preparing a positive electrode material:
1.214g (1.19mmol) of lithium acetate dihydrate, 0.299g (0.12mmol) of nickel acetate tetrahydrate, 0.299g (0.12mmol) of cobalt acetate tetrahydrate, 1.274g (0.52mmol) of manganese acetate tetrahydrate, 0.129g (0.03mmol) of zirconium nitrate pentahydrate, 0.054g (0.01mmol) of niobium oxalate, 0.476g (0.2mmol) of 2,3,5, 6-tetrafluoroterephthalic acid, 0.156g of 4, 4' -bipyridine(0.1mmol) and added into a ball milling pot (the molar ratio of the added components is lithium acetate dihydrate: nickel acetate tetrahydrate: cobalt acetate tetrahydrate: manganese acetate tetrahydrate: zirconium nitrate pentahydrate: niobium oxalate: 2,3,5, 6-tetrafluoroterephthalic acid: 4, 4' -bipyridine is 1.19: 0.12: 0.12: 0.52: 0.03: 0.01: 0.2: 0.1), and the ball milling is carried out for 12 hours at the rotating speed of 450 r/min; putting the product into a muffle furnace after ball milling, presintering for 6 hours at 450 ℃, grinding uniformly, roasting for 20 hours at 850 ℃, cooling along with the furnace to obtain the fluorine-doped lithium-rich cathode material, analyzing and quantifying by ICP (inductively coupled plasma spectrometer), EDS (X-ray energy spectrum analysis) and XPS (X-ray photoelectron spectroscopy) to determine that the structural formula is Li1.19Mn0.52Co0.12Ni0.12Zr0.03Nb0.01O1.9F0.1。
(2) Preparing a positive electrode:
the positive electrode material is used as a positive electrode active substance, and is respectively weighed with acetylene black serving as a conductive agent and PVDF serving as a binder according to a mass ratio of 80:10: 10; and then fully stirring and uniformly mixing the conductive agent acetylene black and the positive electrode material, adding the adhesive PVDF after dry mixing and stirring uniformly, adding N-methyl pyrrolidone after dry mixing and stirring uniformly to form slurry, and controlling the solid content of the slurry to be 45% and the viscosity of the slurry to be 5500cps to obtain the positive electrode slurry.
And coating the anode slurry on an aluminum foil, rolling on a rolling roller, and punching to obtain the anode material anode electrode. The electrode is used as a positive electrode, metal lithium is used as a negative electrode, the electrolyte adopts 1.0mol/LLIPF6-EC + DMC (the volume ratio of EC to DMC is 1:1), and a button cell is assembled in a dry glove box filled with argon.
Example 2
(1) Preparing a positive electrode material:
1.214g (1.19mmol) of lithium acetate dihydrate, 0.299g (0.12mmol) of nickel acetate tetrahydrate, 0.299g (0.12mmol) of cobalt acetate tetrahydrate, 1.225g (0.5mmol) of manganese acetate tetrahydrate, 0.215g (0.05mmol) of zirconium nitrate pentahydrate, 0.054g (0.01mmol) of niobium oxalate, 1.190g (0.5mmol) of 2,3,5, 6-tetrafluoroterephthalic acid and 0.781g of 4, 4' -bipyridine (0.5mmol) were weighed, and addedBall milling in a ball milling pot (the molar ratio of the added components is lithium acetate dihydrate to nickel acetate tetrahydrate to cobalt acetate tetrahydrate to manganese acetate tetrahydrate to zirconium nitrate pentahydrate to niobium oxalate 1.19: 0.12: 0.12: 0.5: 0.05: 0.01: 0.5: 0.5), and ball milling is carried out at the rotating speed of 450r/min for 12 hours; putting the product into a muffle furnace after ball milling, presintering for 6 hours at 450 ℃, grinding uniformly, roasting for 12 hours at 850 ℃, cooling along with the furnace to obtain the fluorine-doped lithium-rich cathode material, analyzing and quantifying by ICP (inductively coupled plasma spectrometer), EDS (X-ray energy spectrum analysis) and XPS (X-ray photoelectron spectroscopy) to determine that the structural formula is Li1.19Mn0.5Co0.12Ni0.12Zr0.05Nb0.01O1.5F0.5。
(2) Preparing a positive electrode:
the positive electrode material is used as a positive electrode active substance, and is respectively weighed with acetylene black serving as a conductive agent and PVDF serving as a binder according to a mass ratio of 80:10: 10; and then fully stirring and uniformly mixing the conductive agent acetylene black and the positive electrode material, adding the adhesive PVDF after dry mixing and stirring uniformly, adding N-methyl pyrrolidone after dry mixing and stirring uniformly to form slurry, and controlling the solid content of the slurry to be 45% and the viscosity of the slurry to be 5500cps to obtain the positive electrode slurry.
And coating the anode slurry on an aluminum foil, rolling on a rolling roller, and punching to obtain the anode material anode electrode. The electrode is used as a positive electrode, metal lithium is used as a negative electrode, the electrolyte adopts 1.0mol/LLIPF6-EC + DMC (the volume ratio of EC to DMC is 1:1), and a button cell is assembled in a dry glove box filled with argon.
Example 3
(1) Preparing a positive electrode material:
1.214g (1.19mmol) of lithium acetate dihydrate, 0.299g (0.12mmol) of nickel acetate tetrahydrate, 0.299g (0.12mmol) of cobalt acetate tetrahydrate, 1.225g (0.5mmol) of manganese acetate tetrahydrate, 0.215g (0.05mmol) of zirconium nitrate pentahydrate, 0.054g (0.01mmol) of niobium oxalate, 1.190g (0.5mmol) of 2,3,5, 6-tetrafluoroterephthalic acid and 0.781g of 4, 4' -bipyridine (0.5mmol) were weighed and charged into a ball mill pot (each of which was charged withThe molar ratio of the added components is lithium acetate dihydrate: nickel acetate tetrahydrate: cobalt acetate tetrahydrate: manganese acetate tetrahydrate: zirconium nitrate pentahydrate: niobium oxalate: 2,3,5, 6-tetrafluoroterephthalic acid: the molar ratio of the added 4, 4' -bipyridine is 1.19: 0.12: 0.12: 0.5: 0.05: 0.01: 0.5: 0.5) and ball milling for 12 hours at the rotating speed of 450 r/min; putting the product into a muffle furnace after ball milling, presintering for 8 hours at 450 ℃, grinding uniformly, roasting for 16 hours at 950 ℃, cooling along with the furnace to obtain the fluorine-doped lithium-rich cathode material, analyzing and quantifying by ICP (inductively coupled plasma spectrometer), EDS (X-ray energy spectrum analysis) and XPS (X-ray photoelectron spectroscopy), and determining that the structural formula is Li1.19Mn0.52Co0.12Ni0.12Zr0.03Nb0.01O1.5F0.5。
(2) Preparing a positive electrode:
the positive electrode material is used as a positive electrode active substance, and is respectively weighed with acetylene black serving as a conductive agent and PVDF serving as a binder according to a mass ratio of 80:10: 10; and then fully stirring and uniformly mixing the conductive agent acetylene black and the positive electrode material, adding the adhesive PVDF after dry mixing and stirring uniformly, adding N-methyl pyrrolidone after dry mixing and stirring uniformly to form slurry, and controlling the solid content of the slurry to be 45% and the viscosity of the slurry to be 5500cps to obtain the positive electrode slurry.
And coating the anode slurry on an aluminum foil, rolling on a rolling roller, and punching to obtain the anode material anode electrode. The electrode is used as a positive electrode, metal lithium is used as a negative electrode, the electrolyte adopts 1.0mol/LLIPF6-EC + DMC (the volume ratio of EC to DMC is 1:1), and a button cell is assembled in a dry glove box filled with argon.
Comparative example 1
A typical fluorine doping (lithium fluoride as fluorine source) procedure was used to prepare a lithium rich material with the same composition as in example 1 for comparison, as follows:
(1) 0.704g (0.69mmol) of lithium acetate dihydrate, 0.299g (0.12mmol) of nickel acetate tetrahydrate, 0.299g (0.12mmol) of cobalt acetate tetrahydrate, 1.274g (0.52mmol) of manganese acetate tetrahydrate, 0.129g (0.03mmol) of zirconium nitrate pentahydrate and 0.054g (0.054 mmol) of niobium oxalate were weighed01mmol), 0.130g (0.5mmol) of lithium fluoride is added into a ball milling pot and ball milled for 12 hours at the rotating speed of 450 r/min; putting the product into a muffle furnace after ball milling, presintering for 6 hours at 450 ℃, grinding uniformly, calcining for 20 hours at 850 ℃, cooling along with the furnace to obtain the fluorine-doped lithium-rich material, analyzing and quantifying by ICP (inductively coupled plasma spectrometer), EDS (X-ray energy spectrum analysis) and XPS (X-ray photoelectron spectroscopy) to determine that the structural formula is Li1.19Mn0.52Co0.12Ni0.12Zr0.03Nb0.01O1.5F0.5。
(2) Preparing a positive electrode:
the positive electrode material is used as a positive electrode active substance, and is respectively weighed with acetylene black serving as a conductive agent and PVDF serving as a binder according to a mass ratio of 80:10: 10; and then fully stirring and uniformly mixing the conductive agent acetylene black and the positive electrode material, adding the adhesive PVDF after dry mixing and stirring uniformly, adding N-methyl pyrrolidone after dry mixing and stirring uniformly to form slurry, and controlling the solid content of the slurry to be 45% and the viscosity of the slurry to be 5500cps to obtain the positive electrode slurry.
And coating the anode slurry on an aluminum foil, rolling on a rolling roller, and punching to obtain the anode material anode electrode. The electrode is used as a positive electrode, metal lithium is used as a negative electrode, the electrolyte adopts 1.0mol/LLIPF6-EC + DMC (the volume ratio of EC to DMC is 1:1), and a simulated battery is assembled in a dry glove box filled with argon. And after the mixture is placed aside for 12 hours, carrying out magnification performance tests of 0.1C, 0.5C, 1C, 2C, 3C, 5C and 10C, cycle performance tests under 1C current and appearance analysis.
Comparative example 2
Another typical fluorine doping (ammonium fluoride as the fluorine source) procedure was used to prepare a lithium rich material with the same composition as in example 1 for comparison, as follows:
(1) preparing a positive electrode material:
1.214g (1.19mmol) of lithium acetate dihydrate, 0.299g (0.12mmol) of nickel acetate tetrahydrate, 0.299g (0.12mmol) of cobalt acetate tetrahydrate, 1.274g (0.52mmol) of manganese acetate tetrahydrate, 0.129g (0.03mmol) of zirconium nitrate pentahydrate, 0.054g (0.01mmol) of niobium oxalate, ammonium fluoride were weighedAdding 0.148g (2.0mmol) of the mixture into a ball milling tank, and carrying out ball milling for 12 hours at the rotating speed of 450 r/min; putting the product into a muffle furnace after ball milling, presintering for 6 hours at 450 ℃, grinding uniformly, roasting for 20 hours at 850 ℃, cooling along with the furnace to obtain the fluorine-doped lithium-rich material, analyzing and quantifying by ICP (inductively coupled plasma spectrometer), EDS (X-ray energy spectrum analysis) and XPS (X-ray photoelectron spectroscopy) to determine that the structural formula is Li1.19Mn0.52Co0.12Ni0.12Zr0.03Nb0.01O1.5F0.5。
(2) Preparing a positive electrode:
the positive electrode material is used as a positive electrode active substance, and is respectively weighed with acetylene black serving as a conductive agent and PVDF serving as a binder according to a mass ratio of 80:10: 10; and then fully stirring and uniformly mixing the conductive agent acetylene black and the positive electrode material, adding the adhesive PVDF after dry mixing and stirring uniformly, adding N-methyl pyrrolidone after dry mixing and stirring uniformly to form slurry, and controlling the solid content of the slurry to be 45% and the viscosity of the slurry to be 5500cps to obtain the positive electrode slurry.
And coating the anode slurry on an aluminum foil, rolling on a rolling roller, and punching to obtain the anode material anode electrode. The electrode is used as a positive electrode, metal lithium is used as a negative electrode, the electrolyte adopts 1.0mol/LLIPF6-EC + DMC (volume ratio is 1:1), and a simulated battery is assembled in a dry glove box filled with argon for testing.
Comparative example 3
Preparation of Li by typical fluorine doping method1.2Mn0.56Co0.12Ni0.12O2-xFxThe lithium-rich cathode material is prepared from three transition metals of Mn, Co and Ni, and comprises the following steps:
(1) preparing a positive electrode material:
1.224g (1.20mmol) of lithium acetate dihydrate, 0.299g (0.12mmol) of nickel acetate tetrahydrate, 0.299g (0.12mmol) of cobalt acetate tetrahydrate, 1.373g (0.56mmol) of manganese acetate tetrahydrate and 0.130g (0.5mmol) of lithium fluoride are weighed according to the required proportion and added into a ball milling pot to be ball milled for 12 hours at the rotating speed of 450 r/min; after ball milling, the product is put into a muffle furnace at 450 DEG CAfter pre-sintering for 6 hours, grinding uniformly, roasting at 850 ℃ for 20 hours, then cooling along with the furnace to obtain the required anode material, analyzing and quantifying by ICP (inductively coupled plasma spectrometer), EDS (X-ray energy spectrum analysis) and XPS (X-ray photoelectron spectroscopy), and determining that the structural formula is Li1.20Mn0.56Co0.12Ni0.12O1.5F0.5。
(2) Preparing a positive electrode:
weighing the layered lithium-rich manganese-based material serving as a positive electrode active material, a conductive agent acetylene black and a binder PVDF according to a mass ratio of 80:10: 10; and then fully stirring and uniformly mixing the conductive agent acetylene black, the adhesive PVDF and the lithium-rich cathode material, adding N-methyl pyrrolidone to form slurry after dry mixing and stirring uniformly, and controlling the solid content of the slurry to be 40% and the viscosity of the slurry to be 4500cps to obtain the cathode slurry.
And coating the positive electrode slurry on an aluminum foil, rolling on a rolling roller, and punching to obtain the lithium-rich material positive electrode. The electrode is used as a positive electrode, metal lithium is used as a negative electrode, the electrolyte adopts 1.0mol/LLIPF6-EC + DMC (the volume ratio of EC to DMC is 1:1), and a button cell is assembled in a dry glove box filled with argon for testing.
Comparative example 4
The preparation method of comparative example 4 is the same as that of example 1 except that the niobium oxalate is changed to vanadium pentoxide to obtain Li1.19Mn0.56-x-yCo0.12Ni0.12ZrxVyO2-zFzAnalyzing and quantifying by ICP (inductively coupled plasma spectrometer), EDS (X-ray energy spectrum analysis) and XPS (X-ray photoelectron spectroscopy), and determining that the structural formula is Li1.19Mn0.52Co0.12Ni0.12Zr0.03V0.01O1.9F0.1。
Effects of the embodiment
(1) Detection by Scanning Electron Microscope (SEM): an SEM image of the cathode material prepared in example 1 is shown in fig. 1, and it can be seen that the material is a nano material, has a diameter of 100 to 200nm, is irregular particles, and has a uniform particle size; the SEM image of the cathode material prepared in comparative example 1 is shown in fig. 2, and it can be seen from the figure that the particle size is not uniform, the particle size is large, and the particle size is not uniform, which varies from 200nm to 2 μm.
(2) And (3) rate performance test: the batteries prepared in examples 1-3 and comparative example 1 were subjected to rate performance tests of 0.1C, 0.5C, 1C, 2C, 3C, 5C, and 10C after being left for 12 hours, and the results are shown in fig. 3: under the current density of 0.1C (20mA/g), the specific discharge capacity of the batteries prepared in the embodiments 1 to 3 is 296.1mAh/g, 293.5mAh/g and 277.4mAh/g respectively, which are all larger than 270mAh/g, while the specific discharge capacity of the battery prepared in the comparative example 1 is only 242.3 mAh/g; charging and discharging at the multiplying power of 0.5C, wherein the specific capacity of the embodiments 1-3 is more than 200mAh/g, and the specific capacity of the embodiment 1 can reach 246.1 mAh/g; under the heavy current of 10C (2A/g), the specific discharge capacity of the examples 1-3 is more than 50mAh/g (wherein the specific discharge capacity of the example 1 is as high as 110.2mAh/g), and the specific discharge capacity of the comparative example 1 is only 0.2 mAh/g; the results show that: with the increase of the multiplying power, the discharge capacity of the embodiment is larger than that of the comparative example, which shows that the multiplying power performance of the anode material synthesized by the technical scheme of the invention is obviously improved.
(3) And (3) testing the cycle performance: the batteries prepared in example 1 and comparative example 1 were subjected to cycle performance test at a current of 1C after being left for 12 hours, and the results are shown in fig. 4: after the battery prepared in the embodiment 1 is cycled for 100 circles, the specific discharge capacity is 240.9mAh/g, and the capacity retention rate reaches 97.5%; after the battery prepared in the comparative example 1 is cycled for 100 circles, the discharge specific capacity is 126.1mAh/g, and the capacity retention rate is 77.3%; the result shows that the capacity retention rate and the discharge specific capacity of the anode material synthesized by the technical scheme of the invention are obviously greater than those of the anode material synthesized by the comparative example 1.
(4) Average discharge potential test: the batteries prepared in example 1 and comparative examples 1, 2 and 3 were left for 12 hours and then charged and discharged for 100 cycles at 1C, and the discharge median potential was recorded for each cycle. The curve of the change of the discharge median potential (average discharge potential) with the cycle number is shown in fig. 5, and it can be seen that the discharge potential of the lithium-rich material synthesized by the method of example 1 is maintained; the lithium-rich materials synthesized by the methods of comparative examples 1, 2 and 3 have no inhibition of the decrease of the average discharge potential. The anode material synthesized by the technical scheme of the invention has the effect of inhibiting the voltage platform from dropping.
(5) And (3) rate performance test: the batteries prepared in example 1 and comparative example 4 were subjected to rate performance tests of 0.1C, 0.5C, 1C, 2C, 3C, 5C, 10C after being left for 12 hours, and the results are shown in fig. 6. It can be seen that the fluorine-doped lithium-rich cathode material with the elemental composition of example 1 has better rate performance than comparative example 4.
(6) And (3) first-turn coulomb efficiency test: the batteries prepared in example 1 and comparative example 1 were left for 12 hours and then charged and discharged at 0.1C, and the results are shown in fig. 7: the coulombic efficiency of the first circle of the battery prepared in the embodiment 1 is 90.4%; the coulombic efficiency of the first turn of the battery prepared in comparative example 1 was 69.5%; the anode material synthesized by the technical scheme of the invention has higher first-turn coulombic efficiency.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (11)
1. A fluorine-doped lithium-rich cathode material is characterized in that: has a chemical formula of Li1.19Mn0.56-x-yCo0.12Ni0.12ZrxNbyO2- zFzWherein, 0<x<0.06，0<y<0.02，0<z<0.6；
The fluorine-doped lithium-rich cathode material is prepared by the following steps:
mixing metal salt with 2,3,5, 6-tetrafluoroterephthalic acid and 4, 4' -bipyridyl, ball-milling, presintering and roasting to obtain a fluorine-doped lithium-rich cathode material; wherein the metal salt is composed of lithium salt, nickel salt, cobalt salt, manganese salt, zirconium salt and niobium salt.
2. The method for preparing the fluorine-doped lithium-rich cathode material according to claim 1, comprising the steps of: mixing metal salt with 2,3,5, 6-tetrafluoroterephthalic acid and 4, 4' -bipyridyl, ball-milling, presintering and roasting to obtain a fluorine-doped lithium-rich cathode material; wherein the metal salt is composed of lithium salt, nickel salt, cobalt salt, manganese salt, zirconium salt and niobium salt.
3. The method for preparing the fluorine-doped lithium-rich cathode material according to claim 2, wherein:
the metal salt is prepared from lithium salt, nickel salt, cobalt salt, manganese salt, zirconium salt and niobium salt according to the stoichiometric ratio of 1.19: 0.12: 0.12: 0.5-0.52: 0.03-0.05: 0.01;
the dosage of the 2,3,5, 6-tetrafluoroterephthalic acid is 0.1-4.0: 1 according to the molar ratio of the 2,3,5, 6-tetrafluoroterephthalic acid to metal ions;
the using amount of the 4, 4' -bipyridyl is 0-1: 1 molar ratio of the using amount to the 2,3,5, 6-tetrafluoroterephthalic acid, and the using amount does not contain 0 endpoint.
4. The method for preparing the fluorine-doped lithium-rich cathode material according to claim 3, wherein:
the dosage of the 2,3,5, 6-tetrafluoroterephthalic acid is 0.1-0.25: 1 according to the molar ratio of the 2,3,5, 6-tetrafluoroterephthalic acid to metal ions;
the dosage of the 4, 4' -bipyridyl is 0.5-1 proportion according to the molar ratio of the bipyridyl to the 2,3,5, 6-tetrafluoroterephthalic acid.
5. The method for preparing the fluorine-doped lithium-rich cathode material according to any one of claims 2 to 4, wherein:
the lithium salt is at least one of lithium carbonate and lithium acetate;
the nickel salt is one or two of nickel nitrate and nickel acetate;
the cobalt salt is one or two of cobalt nitrate and cobalt acetate;
the manganese salt is one or two of manganese nitrate and manganese acetate;
the zirconium salt is one or two of zirconium nitrate and zirconium acetate;
the niobium salt is one or two of niobium oxalate and niobium ethoxide.
6. The method for preparing the fluorine-doped lithium-rich cathode material according to claim 2, wherein:
the ball milling conditions are as follows: ball milling for 10-14 hours at a rotating speed of 400-500 r/min;
the pre-burning conditions are as follows: heating at 400-600 ℃ for 4-8 hours;
the roasting conditions are as follows: heating at 600-950 ℃ for 6-24 hours.
7. The use of the fluorine-doped lithium-rich cathode material of claim 1 in the preparation of a lithium ion battery cathode.
8. A lithium ion battery positive electrode, characterized in that: a fluorine-doped lithium-rich cathode material according to claim 1.
9. The lithium ion battery positive electrode of claim 8, wherein: the conductive agent acetylene black and the binder PVDF are also contained; the fluorine-doped lithium-rich cathode material as claimed in claim 1, a conductive agent acetylene black and a binder PVDF in a mass ratio of 75-85: 5-15: 5-15.
10. The lithium ion battery positive electrode of claim 9, wherein: the fluorine-doped lithium-rich cathode material as claimed in claim 1, the conductive agent acetylene black and the binder PVDF are mixed according to a mass ratio of 80:10: 10.
11. The method for preparing the positive electrode of the lithium ion battery according to claim 8, comprising the steps of:
(A) fully stirring and uniformly mixing acetylene black serving as a conductive agent and the fluorine-doped lithium-rich cathode material according to claim 1, adding PVDF serving as an adhesive after dry mixing and stirring uniformly, adding N-methylpyrrolidone after dry mixing and stirring uniformly, and uniformly mixing to obtain cathode slurry;
(B) and coating the anode slurry on an aluminum foil, rolling and punching to obtain the anode of the lithium ion battery.
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