CN113851622A - Protective layer of battery system and electrochemical device - Google Patents

Protective layer of battery system and electrochemical device Download PDF

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Publication number
CN113851622A
CN113851622A CN202111074448.4A CN202111074448A CN113851622A CN 113851622 A CN113851622 A CN 113851622A CN 202111074448 A CN202111074448 A CN 202111074448A CN 113851622 A CN113851622 A CN 113851622A
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lithium
selenium
positive electrode
protective layer
electrolyte
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Inventor
郑建明
符昂
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Xiamen University
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Xiamen University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides an electrochemical device, wherein a positive electrode of the electrochemical device is provided with a protective layer, the protective layer can be modified by selenium-containing substances on the surface of the positive electrode in an ex-situ mode, and can also be formed in situ on the surface of the positive electrode in the charging and discharging process of a battery in a mode of introducing a selenium-containing additive into an electrolyte; the protective layer contains selenium element, fluorine element and phosphorus element; in a battery system, the protective layer has the functions of stabilizing the structure of a positive electrode material and the stability of an interface under a high voltage condition, and improving the stability of a layered structure of an electrode after circulation, particularly, the I (003)/I (104) peak ratio is higher, and the oxygen release of the positive electrode under the high voltage condition can be reduced, so that the cycle performance of the battery is improved.

Description

Protective layer of battery system and electrochemical device
Technical Field
The invention provides a battery anode protective layer which can be used for a battery system.
Background
In recent years, green energy is vigorously advocated in the country, and new energy systems represented by solar energy, wind energy, electric energy, and the like are gradually replacing conventional energy. Among them, electric energy is the most mature energy storage system at present, and plays an important role in people's daily life. Meanwhile, the battery system with higher energy density also becomes a great challenge for energy storage in the future, and the development of the battery system with high energy density is urgent.
Based on the current commercial anode material, there are two main ways to improve the energy density of the battery: firstly, the discharge capacity of the positive electrode is improved; second, the discharge voltage of the positive electrode is increased. For the layered positive electrode material, the discharge voltage of the battery is improved, and the discharge capacity of the positive electrode is further improved. However, as the discharge voltage of the battery increases, the cycle stability of the battery is also severely impaired: on one hand, the layered positive electrode material is easy to generate phenomena of oxygen release, transition metal ion dissolution and the like under high voltage, and generate irreversible phase change to destroy the structure of the positive electrode; on the other hand, the conventional electrolyte is unstable at high voltage and easily reacts with the surface of the positive electrode, further deteriorating the positive electrode.
Therefore, it is an effective solution to introduce a protective layer, especially a protective layer containing selenium, on the surface of the positive electrode. However, pure elemental selenium has poor ionic conductivity, and the use of pure elemental selenium as a protective layer is not conducive to ion transport. The protective layer containing selenium instead of pure selenium is used, so that the transmission of ions is ensured, the side reaction of the interface of the anode and the electrolyte can be effectively reduced, and the effect of stabilizing the anode structure is achieved, so that the stability of the anode material under the high-voltage condition is improved, and the cycle life of the battery under the high-voltage charging and discharging condition is prolonged
Related background information before filing date:
1.J.Power Sources,2020,460,228062
2.Chem.Soc.Rev.,2018,47,6505
disclosure of Invention
The invention provides a selenium-containing anode protective layer, which can be modified on the surface of an anode in an ex-situ mode, and can also be formed on the surface of the anode in an in-situ mode when a battery is charged and discharged by introducing a selenium-containing additive into electrolyte; in a battery system, the protective layer has the function of stabilizing the structure of the positive electrode material and the interface stability under the high-voltage condition.
The weight ratio of the protective layer to the positive electrode is 0.01-1 wt%;
the protective layer contains selenium (Se) element;
the content of selenium in the protective layer is 0.01-99.5 wt%.
The positive electrode material comprises LiCoO2、NixCoyMn1-x-y(0＜x＜1，0＜y＜1)、NixCoyAl1-x-y(0＜x＜1， 0＜y＜1)、LiMn2O4、LiNiO2、LiCoPO4、LiFePO4(ii) a The positive electrode can be pre-modified by means of doping, cladding and the like, and doping elements include but are not limited to one or more of lithium, boron, nitrogen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, gallium, germanium, arsenic, selenium, zirconium, niobium, molybdenum, silver, indium, tin, antimony, tellurium, iodine, tantalum, tungsten, lead, astatine and the like; coating materials include, but are not limited to, lithium, boron, nitrogen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, gallium, germanium, arsenic, selenium, zirconium, niobium, molybdenum, silver, indium, tin, antimony, tellurium, iodine, tantalum, tungsten, lead, astatine, and like elements of fluoride, oxide, nitride, phosphide, sulfide, chloride, phosphate, vanadate, borate, titanate, zirconate, metaaluminate, carbonate, such as one or more of lithium fluoride, sodium fluoride, magnesium fluoride, aluminum fluoride, lithium oxide, boron oxide, sodium oxide, magnesium oxide, aluminum oxide, silicon oxide, titanium oxide, manganese oxide, iron oxide cobalt oxide, nickel oxide, zinc oxide, zirconium oxide, tin oxide, aluminum phosphate, lithium phosphate, sodium phosphate, aluminum phosphate, lithium vanadate, lithium borate, lithium metaaluminate, lithium carbonate, lithium zirconate, sodium aluminate, lithium carbonate, lithium aluminate, lithium titanate, lithium zirconate, lithium aluminate, lithium carbonate, lithium aluminate, and the like, Barium titanate, and the like.
In the electrolyte, the solute is a lithium salt, including but not limited to lithium hexafluorophosphate (LiPF)6) Lithium difluorophosphate (LiPF)2O2) Lithium difluorobis (oxalato) phosphate, lithium tetrafluorooxalato phosphate, lithium difluoroxantheimide (LiFSI), lithium bistrifluorosulfonylimide (LiTFSI), lithium trifluoromethanesulfonate, lithium tetrafluoroborate (LiBF)4) One or more of lithium perchlorate, lithium nitrate, lithium oxalate, lithium formate, lithium chloride, lithium bromide and lithium iodide;
the solvent can be ester solvent, ether solvent, sulfone solvent, etc., and the ester solvent includes but is not limited to one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), Ethylene Carbonate (EC), Propylene Carbonate (PC), methyl acetate, ethyl acetate, methyl propionate, methyl butyrate, ethyl propionate, propyl propionate, gamma-butyrolactone; the ether solvent includes but is not limited to one or more of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, 15-5 crown ether, Tetrahydrofuran (THF) and 2-methyl tetrahydrofuran; in addition, the solvent can also be one or more of 1-methylimidazole, acetonitrile, dimethyl sulfoxide, sulfolane, ethyl vinyl sulfone and methyl isopropyl sulfone.
The second additive may be lithium tetrafluoroborate (LiBF)4) At least one of vinyl sulfate (DTD), fluoroethylene carbonate (FEC), Vinylene Carbonate (VC), 1, 3-Propane Sultone (PS), 1, 4-butane sultone, 2, 4-butane sultone, propane sulfonic anhydride, succinic anhydride, lithium difluorophosphate, succinonitrile, adiponitrile, fumarodinitrile, glutaronitrile, 1,3, 6-hexane trinitrile or 1,2, 3-tris (2-cyanato) propane, lithium bis (oxalato) borate, and lithium difluoro (oxalato) borate.
In some embodiments, the ex-situ protection layer provided by the invention is formed by wrapping a selenium simple substance, a selenium alloy and a selenium-containing compound on the surface of a positive electrode material; selenium alloys include, but are not limited to, lithium selenium alloys, selenium iron alloys, selenium zinc alloys, selenium aluminum alloys, selenium magnesium alloys, selenium silver alloys, and the like; selenium-containing compounds include, but are not limited to, magnesium selenide, aluminum selenide, potassium selenide, cobalt selenide, copper selenide, cuprous selenide, zinc selenide, tellurium selenide, indium selenide, tin selenide, lithium selenate, sodium selenate, potassium selenate, and the like;
the coating method includes but is not limited to one or more of grinding, ball milling, liquid phase coating, evaporation method, melting method, coprecipitation method, atomic layer deposition and magnetron sputtering.
In some embodiments, the in-situ protection layer provided by the invention is formed by introducing a selenium-containing additive into an electrolyte to promote the electrolyte additive to react in the battery charging and discharging process and form an effective protection layer on a positive electrode interface;
the content of the additive containing selenium in the electrolyte is 0.01-10 wt%;
the weight ratio of the protective layer to the positive electrode is 0.01-1 wt%;
the protective layer contains selenium (Se) element;
the content of selenium in the protective layer is 0.01-99.5 wt%.
The selenium-containing electrolyte additive has a structure shown as the following formula:
Figure BDA0003261607060000031
the structure may be a structure of formula 1, in particular, a structure of formula 2; or a structure of formula 3; wherein the content of the first and second substances,
Figure BDA0003261607060000032
represents a binding site to an adjacent atom; the bonded objects include hydrogen atoms, halogen atoms, functional groups containing oxygen atoms, and also include alkylene, alkenylene, alkynylene, arylene, cycloalkyl, and also include alkyl, alkenylene, alkynylene, arylene, cycloalkyl which are partially or fully substituted by halogen atoms;
some of the structures of formula 1 are shown below, including but not limited to A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, etc.;
Figure BDA0003261607060000033
the partial structure of formula 2 is shown in the following formula, including but not limited to B1, B2, B3, B4, B5, B6, B7, etc.;
Figure BDA0003261607060000041
some of the structures of formula 3 are shown below, including but not limited to C1, C2, C3, etc.;
Figure BDA0003261607060000042
in some embodiments, the battery system is a positive electrode modification system, and comprises an electrolyte, a modified positive electrode sheet, a negative electrode sheet and a separation film;
the electrolyte and the modified positive electrode sheet are as described above;
the active material of the negative plate is metallic lithium, metallic sodium, artificial graphite, natural graphite, hard carbon, silicon carbon negative electrode, silicon negative electrode and the like, the metallic lithium negative electrode comprises but is not limited to lithium alloy and pure metallic lithium, and the alloy element comprises one or more of nickel, cobalt, manganese, aluminum, magnesium and zirconium;
the isolating film includes, but is not limited to, polyethylene isolating film, polypropylene/polyethylene/polypropylene composite isolating film, cellulose isolating film, PET non-woven fabric isolating film, and polyethylene isolating film, polypropylene/polyethylene/polypropylene composite isolating film, cellulose isolating film, PET non-woven fabric isolating film modified by surface coating, grafting and the like.
A separator coating or graft modification on at least one surface of the separator, the coating comprising inorganic particles selected from alumina (Al) and a binder2O3) Silicon oxide (SiO)2) Magnesium oxide (MgO), titanium oxide (TiO)2) Tin oxide (SnO)2) Cerium oxide (CeO)2) Nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (Y)2O3) At least one of silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, manganese carbonate, calcium carbonate, aluminum borate, and magnesium borate; the binder is selected from at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene; the grafting modification is mainly to crosslink and polymerize the surface of the isolating membrane in a chemical bonding mode, and comprises polydopamine, polyethylene glycol dimethacrylate and the like; the surface modification of the isolating membrane can improve the heat resistance, the oxidation resistance and the electrolyte infiltration performance of the isolating membrane and enhance the adhesion between the isolating membrane and the pole pieceAnd (4) sex.
In some embodiments, the battery system is an electrolyte modifying system, and comprises a modified electrolyte, a positive plate, a negative plate and a separation film;
the modified electrolyte and the positive plate are as described above;
the active material of the negative plate is metallic lithium, metallic sodium, artificial graphite, natural graphite, hard carbon, silicon carbon negative electrode, silicon negative electrode and the like, the metallic lithium negative electrode comprises but is not limited to lithium alloy and pure metallic lithium, and the alloy element comprises one or more of nickel, cobalt, manganese, aluminum, magnesium and zirconium;
the isolating film includes, but is not limited to, polyethylene isolating film, polypropylene/polyethylene/polypropylene composite isolating film, cellulose isolating film, PET non-woven fabric isolating film, and polyethylene isolating film, polypropylene/polyethylene/polypropylene composite isolating film, cellulose isolating film, PET non-woven fabric isolating film modified by surface coating, grafting and the like.
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Detailed Description
The present invention will be specifically described below by way of examples.
Example 1:
step 1, preparing electrolyte:
the solute of the electrolyte is lithium hexafluorophosphate, and the concentration is 1mol L-1The solvent is EC and DEC, and the volume ratio of the solvent is 1: 1;
step 2, preparing the anode material and the slurry:
the method is characterized in that cobaltosic oxide, lithium carbonate, titanium oxide, magnesium oxide and aluminum oxide with certain mass are used as raw materials, and the weight ratio of lithium: cobalt: titanium: magnesium: the molar ratio of aluminum is 1.05: 0.97: 0.01: 0.01: 0.01, grinding for 30 minutes; then sintering at 900 ℃ for 20h, and grinding for 30 min; sintering at 750 ℃ for 20h, and grinding for 30 minutes to obtain a titanium, magnesium and aluminum doped lithium cobaltate positive electrode material; and then mixing the positive electrode material with a selenium simple substance and silver powder (the mass ratio of the protective layer to the positive electrode is 0.2 wt%, the mass ratio of the silver powder to the selenium is 0.2: 0.8 (the mass ratio of the selenium in the protective layer is 80 wt%), grinding for 30 minutes, and sintering at 800 ℃ for 12 hours to obtain the titanium, magnesium and aluminum element doped and selenium/silver compound surface modified lithium cobaltate positive electrode material.
The modified positive electrode is taken as a raw material, N-methyl pyrrolidone (NMP) is taken as a solvent, polyvinylidene fluoride (PVDF) is taken as a binder, acetylene black is taken as a conductive agent, positive electrode slurry is prepared and coated on an aluminum foil, and the coating mass is 5mg cm-2Left and right;
step 3, preparing cathode slurry:
taking a graphite material as a raw material, deionized water as a solvent, sodium carboxymethylcellulose (CMC)/Styrene Butadiene Rubber (SBR) as a binder and acetylene black as a conductive agent, preparing a negative electrode slurry, and coating the negative electrode slurry on a copper aluminum foil with the coating mass of 3mg cm-2Left and right;
the diaphragm adopts a PP/PE/PP composite film;
step 4, assembling and testing the battery:
and (3) assembling the battery by adopting the electrolyte in the step (1) and the battery material in the step (2) in sequence according to the sequence of the positive electrode shell, the positive electrode, the diaphragm, the negative electrode and the negative electrode shell. Standing for 6h after the battery is assembled, and keeping the battery stand at 100mA g-1And (3) performing constant current charge and discharge test under the current density, wherein the test voltage range is 3-4.6V.
Example 2:
the difference from example 1 is: the mass ratio of the protective layer to the positive electrode is 0.02 wt%;
example 3:
the difference from example 1 is: the mass ratio of the protective layer to the positive electrode is 0.05 wt%;
example 4:
the difference from example 1 is: the mass ratio of the protective layer to the positive electrode is 0.5 wt%;
example 5:
the difference from example 1 is: the mass ratio of the protective layer to the positive electrode is 1 wt%;
example 6:
the difference from example 1 is: the content of selenium in the protective layer is 0.1 wt%;
example 7:
the difference from example 1 is: the content of selenium in the protective layer is 1 wt%;
example 8:
the difference from example 1 is: the content of selenium in the protective layer is 10 wt%;
example 9:
the difference from example 1 is: the content of selenium in the protective layer is 50 wt%;
example 10:
the difference from example 1 is: the content of selenium in the protective layer is 99 wt%;
example 11:
the difference from example 1 is: taking cobaltosic oxide, lithium carbonate, magnesium oxide and aluminum oxide with certain mass as raw materials, wherein the mass ratio of lithium: cobalt: magnesium: the molar ratio of aluminum is 1.05: 0.98: 0.01: 0.01, grinding for 30 minutes; then sintering at 900 ℃ for 20h, and grinding for 30 min; sintering at 750 ℃ for 20h, and grinding for 30 minutes to obtain a magnesium and aluminum element doped lithium cobaltate positive electrode material; and then mixing the correction electrode material with the simple substance of tin selenide, grinding for 30 minutes, and sintering at the temperature of 800 ℃ for 12 hours to obtain the magnesium and aluminum element doped and tin selenide surface modified lithium cobalt oxide anode material.
Example 12:
the difference from example 1 is: taking cobaltosic oxide, lithium carbonate and magnesium oxide with certain mass as raw materials, wherein the mass ratio of lithium: cobalt: the molar ratio of magnesium is 1.05: 0.99: 0.01, grinding for 30 minutes; then sintering at 900 ℃ for 20h, and grinding for 30 min; sintering at 750 ℃ for 20h, and grinding for 30 minutes to obtain a magnesium element-doped lithium cobaltate positive electrode material; and then mixing the correction electrode material with gallium selenide, grinding for 30 minutes, and sintering at 800 ℃ for 12 hours to obtain the magnesium element doped and gallium selenide surface modified lithium cobaltate anode material.
Example 13:
the difference from example 1 is: taking cobaltosic oxide, lithium carbonate and aluminum oxide with certain mass as raw materials, wherein the mass ratio of lithium: cobalt: the molar ratio of aluminum is 1.05: 0.99: 0.01, grinding for 30 minutes; then sintering at 900 ℃ for 20h, and grinding for 30 min; sintering at 750 ℃ for 20h, and grinding for 30 minutes to obtain the aluminum element-doped lithium cobaltate positive electrode material; and then mixing the correction electrode material with a simple substance of cobalt selenide, grinding for 30 minutes, and sintering at 800 ℃ for 12 hours to obtain the aluminum element doped and cobalt selenide surface modified lithium cobaltate anode material.
Example 14:
the difference from example 1 is: taking cobaltosic oxide, lithium carbonate and aluminum oxide with certain mass as raw materials, wherein the mass ratio of lithium: cobalt: the molar ratio of aluminum is 1.05: 0.99: 0.01, grinding for 30 minutes; then sintering at 900 ℃ for 20h, and grinding for 30 min; sintering at 750 ℃ for 20h, and grinding for 30 minutes to obtain the aluminum element-doped lithium cobaltate positive electrode material; and then mixing the modified electrode material with a lithium selenate simple substance, grinding for 30 minutes, and sintering at 800 ℃ for 12 hours to obtain the aluminum element-doped and lithium selenate surface modified lithium cobalt oxide anode material.
Example 15:
the difference from example 1 is: taking cobaltosic oxide, lithium carbonate and aluminum oxide with certain mass as raw materials, wherein the mass ratio of lithium: cobalt: the molar ratio of aluminum is 1.05: 0.99: 0.01, grinding for 30 minutes; then sintering at 900 ℃ for 20h, and grinding for 30 min; sintering at 750 ℃ for 20h, and grinding for 30 minutes to obtain the aluminum element-doped lithium cobaltate positive electrode material; and dispersing the correction electrode material in an ethanol solution dissolved with 1% of selenium dioxide, stirring for 30 minutes, heating at 80 ℃ to dryness, and sintering at 300 ℃ for 12 hours to obtain the aluminum element doped and selenium oxide surface modified lithium cobaltate anode material.
Example 16:
the difference from example 1 is: taking cobaltosic oxide, lithium carbonate and aluminum oxide with certain mass as raw materials, wherein the mass ratio of lithium: cobalt: the molar ratio of aluminum is 1.05: 0.99: 0.01, grinding for 30 minutes; then sintering at 900 ℃ for 20h, and grinding for 30 min; sintering at 750 ℃ for 20h, and grinding for 30 minutes to obtain the aluminum element-doped lithium cobaltate positive electrode material; and then dispersing the correction electrode material in a solution of ammonium fluoride and aluminum nitrate, stirring for 2h, heating at 80 ℃ and evaporating to dryness to obtain an aluminum element-doped and aluminum fluoride-coated lithium cobaltate material, then dispersing the aluminum element-doped and aluminum fluoride-coated lithium cobaltate material in an ethanol solution in which 1% selenium dioxide is dissolved, stirring for 30 min, heating at 80 ℃ and evaporating to dryness, and sintering at 300 ℃ for 12h to obtain an aluminum element-doped and aluminum fluoride surface-coated selenium oxide surface-modified lithium cobaltate positive electrode material.
Examples 17 to 27:
example 17 differs from example 1 in that a commercial nickel cobalt manganese ternary material is used for selenium cladding;
example 18 differs from example 2 in that a commercial nickel cobalt manganese ternary material is used for selenium cladding;
example 19 differs from example 3 in that a commercial nickel cobalt manganese ternary material is used for selenium cladding;
example 20 differs from example 4 in that a commercial nickel cobalt manganese ternary material is used for selenium cladding;
example 21 differs from example 5 in that a commercial nickel cobalt manganese ternary material is used for selenium cladding;
example 22 differs from example 6 in that selenium cladding is performed using a commercial nickel cobalt manganese ternary material;
example 23 differs from example 7 in that selenium cladding is performed using a commercial nickel cobalt manganese ternary material;
example 24 differs from example 1 in that commercial lithium manganate ternary material was used for selenium coating;
example 25 differs from example 1 in that a commercial lithium cobalt phosphate ternary material was used for selenium cladding;
example 26 differs from example 1 in that a commercial nickel cobalt aluminum ternary material is used for selenium cladding;
example 27 differs from example 1 in that commercial lithium nickelate ternary material was used for selenium cladding;
comparative examples 1 to 6:
comparative example 1 differs from example 1 in that the positive electrode material was not coated with selenium;
comparative example 2 differs from example 1 in that the positive electrode material was not coated with selenium;
comparative example 3 differs from example 1 in that the positive electrode material was not coated with selenium;
comparative example 4 differs from example 1 in that the positive electrode material was not selenium-coated;
comparative example 5 differs from example 1 in that the positive electrode material was not selenium-coated;
comparative example 6 differs from example 1 in that the positive electrode material was not selenium-coated;
example 28:
step 1, preparing electrolyte:
the solute of the electrolyte is lithium hexafluorophosphate, and the concentration is 1mol L-1The solvent is EC and DEC, the volume ratio of the solvent is 1:1, and an A1 electrolyte additive is introduced into the solvent, and the addition amount is 0.1 percent;
step 2, preparing the anode material and the slurry:
the method is characterized in that cobaltosic oxide, lithium carbonate, titanium oxide, magnesium oxide and aluminum oxide with certain mass are used as raw materials, and the weight ratio of lithium: cobalt: titanium: magnesium: the molar ratio of aluminum is 1.05: 0.97: 0.01: 0.01: 0.01, grinding for 30 minutes; then sintering at 900 ℃ for 20h, and grinding for 30 min; and sintering at 750 ℃ for 20h, and grinding for 30 minutes to obtain the titanium, magnesium and aluminum doped lithium cobaltate cathode material.
Mixing the above positive electrode material with N-methylpyrrolidone (NMP) as solvent, polyvinylidene fluoride (PVDF) as binder, and acetylene black as conductive agent to obtain positive electrode slurry, and coating on aluminum foil with a coating mass of 5mg cm-2Left and right;
step 3, preparing cathode slurry:
taking a graphite material as a raw material, deionized water as a solvent, sodium carboxymethylcellulose (CMC)/Styrene Butadiene Rubber (SBR) as a binder and acetylene black as a conductive agent, preparing a negative electrode slurry, and coating the negative electrode slurry on a copper aluminum foil with the coating mass of 3mg cm-2Left and right; the diaphragm adopts a PP/PE/PP composite film;
step 4, assembling and testing the battery:
and (3) assembling the battery by adopting the electrolyte in the step (1) and the battery material in the step (2) in sequence according to the sequence of the positive electrode shell, the positive electrode, the diaphragm, the negative electrode and the negative electrode shell. Standing for 6h after the battery is assembled, and keeping the battery stand at 100mA g-1Constant current charge-discharge test under current density, test voltageThe range is 3-4.6V.
Examples 29 to 46:
example 29 differs from example 19 in that a1 electrolyte additive was added in an amount of 0.05%;
example 30 differs from example 19 in that a1 electrolyte additive was added in an amount of 0.2%;
example 31 differs from example 19 in that a1 electrolyte additive was added in an amount of 0.5%;
example 32 differs from example 19 in that a2 electrolyte additive was introduced in an amount of 0.1%;
example 33 differs from example 19 in that a3 electrolyte additive was introduced in an amount of 0.1%;
example 34 differs from example 19 in that a4 electrolyte additive was introduced in an amount of 0.1%;
example 35 differs from example 19 in that a6 electrolyte additive was introduced in an amount of 0.1%;
example 36 differs from example 19 in that a7 electrolyte additive was introduced in an amount of 0.1%;
example 37 differs from example 19 in that a12 electrolyte additive was introduced in an amount of 0.1%;
example 38 differs from example 19 in that a13 electrolyte additive was introduced in an amount of 0.1%;
example 39 differs from example 19 in that B1 electrolyte additive was introduced in an amount of 0.1%;
example 40 differs from example 19 in that B2 electrolyte additive was introduced in an amount of 0.1%;
example 41 is different from example 19 in that B3 electrolyte additive was introduced in an amount of 0.1%;
example 42 differs from example 19 in that B4 electrolyte additive was introduced in an amount of 0.1%;
example 43 differs from example 19 in that C1 electrolyte additive was introduced in an amount of 0.1%;
example 44 differs from example 19 in that C2 electrolyte additive was introduced in an amount of 0.1%;
example 45 differs from example 19 in that C3 electrolyte additive was introduced in an amount of 0.1%;
example 46 differs from example 19 in that lithium metal was used for the negative electrode in an amount of 0.1%;
comparative example 7:
comparative example 7 is different from example 23 in that no selenium-containing additive was introduced into the electrolyte and lithium metal was used for the negative electrode;
the test results can be found in the following table:
Figure BDA0003261607060000101
Figure BDA0003261607060000111
Figure BDA0003261607060000121
it can be seen from the examples and comparative examples that when the battery is assembled by using the selenium-containing element-coated positive electrode material or the selenium-containing in-situ electrolyte additive, the capacity retention rate of the battery after 100 cycles is significantly improved, mainly because the selenium-containing protective layer can improve the structural stability of the positive electrode under high-pressure conditions. To further confirm this, we tested XRD on the positive electrode material after cycling 100 cycles, comparing the ratio of the I (003) peak and the I (104) peak, the larger the ratio, the more stable the structure; in addition, the oxygen release amount of the anode in the first charging process is detected through electrochemical synchronous differential gas mass spectrometry (DEMS), and the structure is more stable when the oxygen release amount is smaller.
Figure BDA0003261607060000131
Specifically, the following description is provided:
the same coating weight was used in the examples and comparative examples, and the test conditions and the like were not changed, and the positive electrode material, doping and coating form and the like were not changed so much. However, it is within the scope of the present patent to adopt a positive electrode material with a surface modified selenium-containing material or to adopt an electrolyte containing selenium so that the surface of the positive electrode material contains selenium after cycling. In addition, the test results are only used for reference, and systematic errors are not eliminated.

Claims (10)

1. An electrochemical device comprising a positive electrode, a negative electrode, an electrolyte and a separator, characterized in that the positive electrode material or the electrode has a protective layer:
the weight ratio of the protective layer to the positive electrode is 0.01-1 wt%;
the protective layer contains 2 or more than 2 elements, and the first element is selenium (Se) element;
the selenium element in the protective layer accounts for 0.01-99.5 wt%;
the second element can be carbon, lithium, boron, nitrogen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, gallium, germanium, arsenic, zirconium, niobium, molybdenum, silver, indium, tin, antimony, tellurium, iodine, tantalum, tungsten, lead, astatine;
the second element in the protective layer accounts for 0.1-50 wt%.
2. The electrochemical device according to claim 1, wherein the protective layer comprises a composition of elemental selenium and other nonmetal/metal compounds, or a composition of elemental selenium and inorganic/organic compounds, or a selenium alloy or a selenium-containing compound:
other non-metals/metals include carbon, lithium, sodium, magnesium, aluminum, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, gallium, germanium, zirconium, niobium, molybdenum, silver, indium, tin, antimony, tantalum, tungsten, lead;
the inorganic/organic compounds include one or more of fluorides, oxides, nitrides, phosphides, sulfides, chlorides, phosphates, fluorophosphates, vanadates, borates, titanates, zirconates, metaaluminates, carbonates, alkyl carbonates, polycarbonates of lithium, boron, nitrogen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, gallium, germanium, arsenic, zirconium, niobium, molybdenum, silver, indium, tin, antimony, tellurium, iodine, tantalum, tungsten, lead, astatine elements;
the selenium alloy or selenium-containing compound comprises lithium selenium alloy, selenium iron alloy, selenium zinc alloy, selenium aluminum alloy, selenium magnesium alloy, selenium cobalt alloy, selenium indium alloy and selenium silver alloy; magnesium selenide, aluminum selenide, potassium selenide, cobalt selenide, copper selenide, cuprous selenide, zinc selenide, tellurium selenide, indium selenide, tin selenide, lithium selenate, sodium selenate, potassium selenate.
3. An electrochemical device is characterized in that a positive electrode material or an electrode protection layer is prepared from an additive containing selenium element in electrolyte, the electrolyte additive participates in-situ film forming in the charge and discharge process of a battery, and an interface protection layer containing selenium is formed on the surface interface of a positive electrode;
the content of the additive containing selenium in the electrolyte is 0.01-10 wt%;
the weight ratio of the protective layer to the positive electrode is 0.01-1 wt%;
the protective layer contains 2 or more than 2 elements, and the first element is selenium (Se) element;
the selenium element in the protective layer accounts for 0.01-99.5 wt%;
the second element can be carbon, lithium, boron, nitrogen, fluorine, silicon and phosphorus;
the second element in the protective layer accounts for 0.1-20 wt%.
4. An electrochemical device according to claim 3, wherein said electrolyte additive is of the formula:
Figure FDA0003261607050000021
the structure can beThe structure of formula 1; or a structure of formula 2; or a structure of formula 3; wherein the content of the first and second substances,
Figure FDA0003261607050000022
represents a binding site to an adjacent atom; the bonded object includes a hydrogen atom, a halogen atom, a functional group containing an oxygen atom, and also includes an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a cycloalkyl group, and also includes an alkyl group, an alkenylene group, an alkynylene group, an arylene group, a cycloalkyl group, which are partially or completely substituted with a halogen atom.
5. The electrochemical device as claimed in claim 4, wherein the electrolyte additive is a substance having a structure represented by formula 1, including A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14:
Figure FDA0003261607050000023
6. the electrochemical device as claimed in claim 4, wherein the electrolyte additive is a substance represented by the following formula 2, and comprises B1, B2, B3, B4, B5, B6, B7, C1, C2, and C3:
Figure FDA0003261607050000031
7. an electrochemical device according to claim 4, wherein the electrolyte additive is a substance represented by the following formula 3,
Figure FDA0003261607050000032
8. the electrochemical device according to claim 1 or 3, wherein said electrolyte comprises a solute, a solvent, and a second additive;
the solute is a lithium salt, including lithium hexafluorophosphate (LiPF)6) Lithium difluorophosphate (LiPF)2O2) Lithium difluorobis (oxalato) phosphate, lithium tetrafluorooxalato phosphate, lithium difluoroxantheimide (LiFSI), lithium bistrifluorosulfonylimide (LiTFSI), lithium trifluoromethanesulfonate, lithium tetrafluoroborate (LiBF)4) One or more of lithium perchlorate, lithium nitrate, lithium oxalate, lithium formate, lithium chloride, lithium bromide and lithium iodide;
the solvent is an ester solvent, an ether solvent or a sulfone solvent, and the ester solvent comprises one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), Ethylene Carbonate (EC), Propylene Carbonate (PC), methyl acetate, ethyl acetate, methyl propionate, methyl butyrate, ethyl propionate, propyl propionate and gamma-butyrolactone; the ether solvent includes but is not limited to one or more of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, 15-5 crown ether, Tetrahydrofuran (THF) and 2-methyl tetrahydrofuran; or the solvent is one or more of 1-methylimidazole, acetonitrile, dimethyl sulfoxide, sulfolane, ethyl vinyl sulfone and methyl isopropyl sulfone;
the second additive is at least one of fluoroethylene carbonate (FEC), ethylene sulfate (DTD), Vinylene Carbonate (VC), 1, 3-Propane Sultone (PS), 1, 4-butane sultone, 2, 4-butane sultone, propane sulfonic anhydride, succinic anhydride, lithium difluorophosphate, succinonitrile, adiponitrile, fumaronitrile, glutaronitrile, 1,3, 6-hexanetrinitrile or 1,2, 3-tris (2-cyanato) propane, lithium bis (oxalato) borate and lithium difluoro (oxalato) borate.
9. Electrochemical device according to claim 1 or 3, characterized in that the positive electrode material comprises LiCoO2、NixCoyMn1-x-y(0＜x＜1，0＜y＜1)、NixCoyAl1-x-y(0＜x＜1，0＜y＜1)、LiMn2O4、LiNiO2、LiCoPO4、LiFePO4(ii) a The positive electrode material may be dopedDoping elements comprise one or more of lithium, boron, nitrogen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, gallium, germanium, arsenic, selenium, zirconium, niobium, molybdenum, silver, indium, tin, antimony, tellurium, iodine, tantalum, tungsten, lead, astatine and the like; the coating material comprises one or more of fluoride, oxide, nitride, phosphide, sulfide, chloride, phosphate, vanadate, borate, titanate, zirconate, metaaluminate and carbonate of elements such as lithium, boron, nitrogen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, gallium, germanium, arsenic, selenium, zirconium, niobium, molybdenum, silver, indium, tin, antimony, tellurium, iodine, tantalum, tungsten, lead, astatine and the like.
10. A battery system comprises an electrolyte, a positive plate, a negative plate and a separation film:
the electrolyte is one or more of the components in claim 8;
the protected electrolyte is one or more of claim 8, and selenium-containing additives comprising one of claims 3 to 7 are added;
the positive electrode is a composite positive electrode formed by one or more of the components in claim 9;
the protected positive electrode is a composite positive electrode formed by one or more of the claims 9; the selenium-containing material for modifying the positive electrode is one or more of claims 1 or 2;
the protected electrolyte may be used during battery assembly, the protected positive electrode may be used, or both may be used.
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