A high-voltage composite positive electrode coated with an organic-inorganic composite medium, and its preparation method and application

Abstract

The present invention discloses a high-voltage composite positive electrode coated with an organic-inorganic composite medium, and its preparation method and application. The preparation method is to form a metal-based organic-inorganic composite film on the surface of the high-voltage positive electrode material by molecular layer deposition of an inorganic metal source precursor and an organic non-metallic source precursor. This method can effectively improve the capacity and cycle stability of the high-voltage positive electrode material, and at 250mAg ‑1 The current density can reach 263mAhg ‑1 The discharge capacity of the battery is as high as 94% after 200 cycles (the voltage range is 2.0-4.8V). It can also effectively improve the contact impedance and stability of the electrode / solid electrolyte interface in all-solid-state batteries. ‑1 The current density can reach 180mAhg ‑1 The discharge specific capacity is 100W, and the capacity retention rate after 20 cycles is 95%.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a high-voltage composite positive electrode coated with an organic-inorganic composite medium, and a preparation method and application thereof. Background Art

[0002] As a highly efficient and environmentally friendly energy storage device, lithium-ion batteries have been widely used in consumer electronics, transportation, and large-scale energy storage. However, the widespread adoption of electric vehicles has placed more stringent requirements on lithium-ion batteries, including energy density, safety, lifespan, and cost.

[0003] As one of the main components, cathode materials significantly impact the production cost and performance of lithium-ion batteries. Increasing the charge cutoff voltage of cathode materials can effectively increase their capacity. However, side reactions under high voltage can increase the generation of irreversible reaction capacity, reduce the initial coulombic efficiency, and hinder capacity retention during cycling. Therefore, it is urgent to explore and develop a convenient, efficient, and low-cost method to optimize the interfacial stability of high-voltage cathode materials, improve their overall electrochemical performance, and thus prepare lithium-ion batteries with excellent performance. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a high-voltage composite positive electrode coated with an organic-inorganic composite medium and a preparation method and application thereof, thereby solving the problems in the above-mentioned background technology.

[0005] One of the technical solutions employed by the present invention to solve its technical problems is to provide a high-voltage composite positive electrode coated with an organic-inorganic composite dielectric, comprising a high-voltage positive electrode material and a metal-based organic-inorganic composite thin film. The metal-based organic-inorganic composite thin film, acting as a dielectric and coated on the surface of the high-voltage positive electrode material, is prepared by molecular layer deposition of an inorganic metal source precursor and an organic non-metallic source precursor, with 1 to 200 layers. The thickness of the metal-based organic-inorganic composite thin film is determined by the number of coating layers and the deposition material. The voltage range of the high-voltage composite positive electrode is between 2.0 and 4.8V.

[0006] In a preferred embodiment of the present invention, the high voltage positive electrode material is Li 1+x MO2, wherein x≥0, M is one or a combination of Ni, Co, Mn, Fe, Al, W, Nb, Ti, Zr, Fe, Mg, Ti, Ru, Sn, Ir, Te.

[0007] In a preferred embodiment of the present invention, the inorganic metal source precursor is one or more of trimethylaluminum Al(CH3)3, diethylzinc Zn(CH3CH2)2, lithium tert-butoxide LiOC(CH3)3, tert-butyl lithium LiC(CH3)3, tetrakis(ethylmethylamino)zirconium Zr[N(CH3CH2)(CH3)]4, and zirconium tert-butoxide Zr[OC(CH3)3]4.

[0008] In a preferred embodiment of the present invention, the organic non-metallic precursor source precursor is ethylene glycol (CH2OH)2, glycerol (CH2OH)2CH(OH), hydroquinone One or more of fumaric acid HOOC-CH=CH-COOH.

[0009] In a preferred embodiment of the present invention, the metal-based organic-inorganic composite thin film is coated on the surface of primary particles or secondary particles of the high-voltage positive electrode active material.

[0010] The second technical solution adopted by the present invention to solve the technical problem is: providing a method for preparing a high-voltage composite positive electrode coated with an organic-inorganic composite medium, comprising the following steps:

[0011] S201: placing the high voltage cathode material in a molecular layer deposition system reaction chamber;

[0012] S202: Setting the growth parameters of the molecular layer deposition system;

[0013] S203: After the inorganic metal precursor source pulse is introduced into the reaction chamber of the molecular layer deposition system, high-purity argon gas is used for cleaning to flush out the reaction byproducts and residual inorganic metal precursor source;

[0014] S204: After the organic non-metallic precursor source pulse is introduced into the reaction chamber of the molecular layer deposition system, high-purity argon gas is used for cleaning to flush out reaction byproducts and residual organic non-metallic precursor source;

[0015] S205: Repeat steps S203 to S204 in sequence to obtain a high-voltage composite positive electrode material coated with an organic-inorganic composite medium.

[0016] In a preferred embodiment of the present invention, in S202, the growth parameters are a deposition temperature of 25-300°C and a deposition pressure of 0.01-200 Torr.

[0017] The third technical solution adopted by the present invention to solve its technical problem is: providing the application of the above-mentioned high-voltage composite positive electrode coated with an organic-inorganic composite medium in a liquid / solid-state lithium-ion battery.

[0018] A fourth technical solution adopted by the present invention to solve its technical problems is: to provide a liquid lithium-ion battery, which employs a high-voltage composite cathode coated with the above-mentioned organic-inorganic composite medium; and the electrolyte components include one or several of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC).

[0019] A fifth technical solution adopted by the present invention to solve its technical problems is: to provide a solid-state lithium-ion battery, which employs a high-voltage composite cathode coated with the above-mentioned organic-inorganic composite medium; and the solid electrolyte is one or several of inorganic solid electrolytes, polymer solid electrolytes, and composite polymer solid electrolytes.

[0020] In a preferred embodiment of the present invention, the inorganic solid electrolyte is Li7La3Zr2O 12 、Li 1.4 Al 0.4 Ti 1.6 (PO4)3、Li 1+x Al x Ge 2-x (PO4)3(0 < x < 1), Li 3x La 2 / 3-x TiO3(0 < x < 0.16), or one or several of them.

[0021] In a preferred embodiment of the present invention, the polymer solid electrolyte is one or several of polyethylene oxide (PEO), polyethylene glycol (PEG), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), or polyvinylidene fluoride - hexafluoropropylene (PVDF-HFP), or derivatives of the above polymers.

[0022] In a preferred embodiment of the present invention, the polymer solid electrolyte is composed of a composite of a polymer, a lithium salt, and inorganic ceramic particles. Among them, the polymer can be one or several of polyethylene oxide (PEO), polyethylene glycol (PEG), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), or polyvinylidene fluoride - hexafluoropropylene (PVDF-HFP), or derivatives of the above polymers; the lithium salt is one or several of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), and lithium hexafluorophosphate (LiPF6); the inorganic ceramic particles are Li7La3Zr2O 12 、Li 1.4 Al 0.4 Ti 1.6 (PO4)3、Li 1+x Alx Ge 2-x (PO4)3(0 < x < 1), Li 3x La 2 / 3-x TiO3(0 < x < 0.16), or one or more of them.

[0023] Compared with the background technology, this technical solution has the following advantages:

[0024] In this invention, by coating a coating layer prepared by molecular layer deposition on the surface of the high-voltage lithium-ion cathode material, the side reactions between the electrode material and the electrolyte under high voltage, and between the electrode material and the solid electrolyte under high voltage are effectively inhibited, the stability of the interface between the electrode material / electrolyte (or solid electrolyte) is improved, and the interface contact between the electrode material and the solid electrolyte is improved, thereby obtaining a high-performance high-voltage lithium-ion cathode material with high capacity and high cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the X-ray diffraction pattern of sample 1 after molecular layer deposition in Example 1.

[0026] Figure 2 is the SEM image of the micron-sized spherical particles assembled from sample 1 after molecular layer deposition in Example 1.

[0027] Figure 3 is the cycling performance of the liquid coin-type half-cell of sample 1 after molecular layer deposition in Example 1.

[0028] Figure 4 is the cycling performance of the all-solid-state battery of sample 1 after molecular layer deposition in Example 2.

[0029] Figure 5 is the cycling performance of the liquid coin-type half-cell of sample 2 after molecular layer deposition in Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Example 1

[0031] This example includes the following steps:

[0032] (1) Preparation of the lithium-rich manganese-based cathode material: Place 1 g of Ni 1 / 6 Co 1 / 6 Mn 2 / 3 CO3 in a muffle furnace, with a heating rate of 5 °C / min, and calcine in air at 500 °C for 5 h to obtain an oxide precursor. After cooling with the furnace, grind and mix the oxide precursor with 0.75 g of LiOH evenly, and then place the mixture in a muffle furnace and calcine in air at 850 °C for 12 h with a heating rate of 5 °C / min. After cooling with the furnace, a cathode material with the molecular formula 0.5Li(Ni 1 / 3 Co1 / 3 Mn 1 / 3 )O2·0.5Li2MnO3 lithium-rich manganese-based positive electrode material.

[0033] (2) Modification treatment: a certain amount of lithium-rich manganese-based cathode material was measured and placed in the reaction chamber of the molecular layer deposition system. The chamber temperature was 150°C, the chamber pressure was 0.1-200 torr, the chamber volume was 200 mL, and the carrier gas during the deposition process was argon with a flow rate of 10-1500 sccm, preferably 25 sccm;

[0034] (3) Aluminum glycolate was deposited using molecular layer deposition technology: the first pulse of trimethylaluminum vapor chemically adsorbed on the surface of the primary / secondary particles of the lithium-rich manganese-based cathode material, and the physically adsorbed portion was removed by evacuation and purging; the second pulse of ethylene glycol vapor semi-reacted with trimethylaluminum to form an aluminum glycol compound, and the unreacted ethylene glycol was removed by evacuation and purging; the multiple composite deposition times were trimethylaluminum / reaction / purge / ethylene glycol / reaction / purge = 0.1s / 3s / 30s / 1s / 3s / 30s. The temperature of the trimethylaluminum raw material was 25°C, and the temperature of the ethylene glycol raw material was 80°C. This was repeated for 5 cycles to obtain an aluminum glycolate inorganic-organic composite film on the surface of the lithium-rich manganese-based cathode material particles. The resulting material was named Sample 1.

[0035] like Figure 1 As shown in the XRD spectrum of sample 1, the characteristic diffraction peaks of sample 1 are sharp and are consistent with those of 0.5Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O2·0.5Li2MnO3, indicating that the material after molecular layer deposition does not change the crystallinity of lithium-rich manganese-based materials.

[0036] like Figure 2 As shown in the SEM image, sample 1 is composed of nanoparticles assembled into micron-shaped spherical particles with a diameter of about 15 μm.

[0037] First, sample 1, conductive carbon and binder are mixed to form a uniform slurry. Then the slurry is coated on aluminum foil for drying, rolling and cutting. Finally, it is assembled with the separator and lithium metal sheet into a liquid button half-cell.

[0038] like Figure 3 As shown in the cycling curve of sample 1, the voltage range of sample 1 is 2.0~4.8V and the cycle time of sample 1 is 250mAg. -1 The discharge capacity can reach 263 mAh g when cycling at the current density -1 After 200 cycles, the discharge capacity is 246 mAh g -1 , the capacity retention rate is as high as 94%, showing high discharge specific capacity and excellent cycle stability.

[0039] Example 2

[0040] (1) Sample 1, conductive carbon, and a binder are mixed to form a uniform slurry. The slurry is then coated on aluminum foil for drying, rolling, and cutting. Finally, the slurry is assembled with a lithium metal sheet to form an all-solid-state battery.

[0041] (2) Figure 4 As shown in the cycle curve, the all-solid-state battery assembled by sample 1 has a voltage range of 2.0 to 4.6 V and a cycle time of 50 mA g. -1 The discharge capacity can reach 180 mAh g when cycling at the current density -1 After 20 cycles, the discharge capacity is 171 mAh g -1 , the capacity retention rate is as high as 95%, showing high discharge specific capacity and excellent cycle stability.

[0042] Example 3

[0043] This embodiment includes the following steps:

[0044] (1) Preparation of cobalt-free lithium-rich manganese-based cathode materials: 1g Ni 0.25 Mn 0.75 CO3 was placed in a muffle furnace, heated at a rate of 5°C / min, and calcined in air at 500°C for 5 hours to obtain an oxide precursor. After cooling in the furnace, the oxide precursor was ground and mixed with 0.8g LiOH. The mixture was then placed in a muffle furnace and calcined in air at 850°C for 12 hours at a rate of 5°C / min. After cooling in the furnace, a 0.5Li(Ni 0.5 Mn 0.5 )O2·0.5Li2MnO3 cobalt-free lithium-rich manganese-based cathode material.

[0045] (2) Modification treatment: a certain amount of cobalt-free lithium-rich manganese-based cathode material is measured and placed in the reaction chamber of the molecular layer deposition system. The chamber temperature is 150°C, the chamber pressure is 0.1-200 torr, the chamber volume is 200 ml, and the carrier gas during the deposition process is argon with a flow rate of 10-1500 sccm, preferably 25 sccm;

[0046] (3) Aluminum glycolate was deposited using molecular layer deposition technology: the first pulse of trimethylaluminum vapor was chemically adsorbed on the surface of the primary / secondary particles of the lithium-rich manganese-based positive electrode material, and the physically adsorbed part was removed by vacuuming and purging; the second pulse of ethylene glycol vapor semi-reacted with trimethylaluminum to form an aluminum glycolate compound, and the unreacted ethylene glycol was removed by vacuuming and purging; the multiple composite deposition times were trimethylaluminum / reaction / purge / ethylene glycol / reaction / purge = 0.1s / 3s / 30s / 1s / 3s / 30s. The temperature of the trimethylaluminum raw material was 25°C, and the temperature of the ethylene glycol raw material was 80°C. This was repeated for 5 cycles to obtain an inorganic-organic composite film of aluminum glycolate on the surface of the lithium-rich manganese-based positive electrode material particles. The resulting material was named Sample 2.

[0047] Sample 2, conductive carbon and binder were mixed to form a uniform slurry, which was then coated on aluminum foil for drying, rolling and cutting. 0.33 La 0.55 TiO3 assembled into all-solid-state batteries.

[0048] like Figure 5 As shown in the cycling curve, the all-solid-state battery assembled by sample 2 has a voltage range of 2.0-4.8V and a cycling rate of 250mAg. -1 The discharge capacity is 211 mAh g after 200 cycles at the current density -1 , showing excellent electrochemical performance.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-voltage composite positive electrode coated with an organic-inorganic composite dielectric, characterized by: The invention comprises a high voltage positive electrode material and a metal-based organic-inorganic composite film; the metal-based organic-inorganic composite film is coated on the surface of the high voltage positive electrode material as a medium, and is prepared by molecular layer deposition of an inorganic metal source precursor and an organic non-metal source precursor; the high voltage positive electrode material is Li 1+x MO2, wherein x≥0, M is one or more of Ni, Co, Mn, Fe, Al, W, Nb, Ti, Zr, Mg, Ru, Sn, Ir, Te; the inorganic metal source precursor is one or more of trimethylaluminum, diethylzinc, lithium tert-butoxide, tert-butyl lithium, tetrakis(ethylmethylamino)zirconium, zirconium tert-butoxide; the organic non-metallic source precursor is one or more of ethylene glycol, propylene glycol, hydroquinone, and fumaric acid.

2. The high-voltage composite positive electrode coated with an organic-inorganic composite dielectric according to claim 1, characterized in that: The metal-based organic-inorganic composite film is coated on the surface of the primary particles or the surface of the secondary particles of the high-voltage positive electrode active material, and the number of layers is 1 to 200.

3. The method for preparing a high-voltage composite positive electrode coated with an organic-inorganic composite dielectric according to claim 1, characterized in that: The steps include: S201: placing a high voltage cathode material in a molecular layer deposition system reaction chamber; S202: Setting the growth parameters of the molecular layer deposition system; S203: After an inorganic metal precursor source pulse is introduced into the reaction chamber of the molecular layer deposition system, high-purity argon gas is used for cleaning to flush out reaction byproducts and residual inorganic metal precursor source; S204: After a pulse of an organic non-metallic precursor source is introduced into the reaction chamber of the molecular layer deposition system, the reaction chamber is purged with high-purity argon gas to flush out reaction byproducts and residual organic non-metallic precursor source; S205: Repeat steps S203 to S204 in sequence to obtain a high-voltage composite positive electrode material coated with an organic-inorganic composite medium.

4. The method for preparing a high-voltage composite positive electrode coated with an organic-inorganic composite dielectric according to claim 3, characterized in that: In S202 , the growth parameters are a deposition temperature of 25 to 300° C. and a deposition pressure of 0.01 to 200 torr.

5. Use of a high-voltage composite positive electrode coated with an organic-inorganic composite medium as claimed in claim 1 or 2 in a liquid / solid-state lithium-ion battery.

6. A liquid lithium-ion battery, characterized in that: A high-voltage composite positive electrode coated with an organic-inorganic composite medium as described in claim 1 or 2 is used; and the electrolyte components include one or more of LiPF6, LiClO4, EC, DMC, and DEC.

7. A solid-state lithium-ion battery, characterized in that: A high-voltage composite positive electrode coated with an organic-inorganic composite medium as described in claim 1 or 2 is used; and the solid electrolyte coats one or more of an inorganic solid electrolyte, a polymer solid electrolyte, and a composite polymer solid electrolyte.

8. A solid-state lithium-ion battery according to claim 7, characterized in that: The inorganic solid electrolyte is Li7La3Zr2O 12 , Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li 1+x Al x Ge 2-x (PO4)3 (0 < x < 1), Li 3x La 2 / 3-x TiO3 (0 < x < 0.16), or one or more of them.

9. The solid-state lithium-ion battery according to claim 7, characterized in that: The polymer solid electrolyte is one or more of polyethylene oxide, polyethylene glycol, polyvinyl chloride, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene or derivatives of the above polymers.

10. The solid-state lithium-ion battery according to claim 7, characterized in that: The polymer solid electrolyte is composed of a polymer, a lithium salt, and inorganic ceramic particles. The polymer can be one or several of polyethylene oxide, polyethylene glycol, polyvinyl chloride, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene, or derivatives of the above polymers; the lithium salt is one or several of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, and lithium hexafluorophosphate; the inorganic ceramic particles are one or several of Li7La3Zr2O 12 、Li 1.4 Al 0.4 Ti 1.6 (PO4)3、Li 1+x Al x Ge 2-x (PO4)3(0 < x < 1), Li 3x La 2 / 3-x TiO3(0 < x < 0.16).

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