WO2022198662A1

WO2022198662A1 - Positive electrode lithium supplementing material, positive electrode plate containing same, and electrochemical device

Info

Publication number: WO2022198662A1
Application number: PCT/CN2021/083392
Authority: WO
Inventors: 周墨林
Original assignee: 宁德新能源科技有限公司
Priority date: 2021-03-26
Filing date: 2021-03-26
Publication date: 2022-09-29
Also published as: CN114097112A

Abstract

The present application provides a positive electrode lithium supplementing material, a positive electrode plate containing same, and an electrochemical device. The chemical component of the positive electrode lithium supplementing material is xLi₂OyLiFzM, wherein x>0, y>0, 0.4x+0.2y≤z≤2x+y, M comprises at least one of Mn, Fe, Co, Ni, Cu, Cr, or V. The positive electrode lithium supplementing material is high in chemical stability, and the particle aggregation phenomenon of the positive electrode lithium supplementing material in a slurry preparation process can be effectively improved. The positive electrode lithium supplementing material is applied to a positive electrode plate, such that active lithium can be supplemented, and the energy density of an electrochemical device is effectively improved.

Description

A kind of positive electrode lithium supplement material, positive electrode plate and electrochemical device comprising the material

technical field

The present application relates to the field of electrochemistry, and in particular, to a positive electrode lithium supplement material, a positive electrode pole piece comprising the material, and an electrochemical device.

Background technique

Lithium-ion secondary batteries have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, and good safety. They are widely used in various fields such as electrical energy storage, mobile electronic equipment, electric vehicles, and aerospace equipment. With the rapid development of mobile electronic devices and electric vehicles, the market has put forward higher and higher requirements for the energy density, cycle performance and kinetic performance of lithium-ion secondary batteries.

During the first charge and discharge process of the lithium-ion secondary battery, a large amount of solid electrolyte interface film (Solid Electrolyte Interphase, SEI) will be produced on the surface of the negative electrode, which consumes the limited lithium ions and electrolyte in the lithium-ion secondary battery, resulting in irreversible capacity loss. , reducing the energy density of lithium-ion secondary batteries. In batteries using graphite anodes, about 10% of the active lithium source is consumed in the first cycle; when using anode materials with high specific capacity, such as alloys (silicon, tin, etc.), oxides (silicon oxide, tin oxide, etc.) and amorphous carbon anode, the consumption of active lithium source will be further exacerbated. Therefore, a suitable lithium replenishment method is particularly important to improve the energy density of lithium ion secondary batteries.

SUMMARY OF THE INVENTION

The purpose of the present application is to provide a positive electrode lithium supplement material, a positive electrode electrode sheet and an electrochemical device comprising the material, so as to improve the energy density of the electrochemical device.

It should be noted that, in the content of the present application, the present application is explained by taking a lithium ion secondary battery as an example of the electrochemical device, but the electrochemical device of the present application is not limited to the lithium ion secondary battery. The specific technical solutions are as follows:

A first aspect of the present application provides a positive electrode lithium supplement material, the chemical composition of which is xLi ₂ O·yLiF·zM; wherein, x>0, y>0, 0.4x+0.2y≤z≤2x+y, M At least one of Mn, Fe, Co, Ni, Cu, Cr or V is included.

The chemical composition of the positive electrode lithium supplement material of the present application is xLi ₂ O·yLiF·zM, wherein: x>0, preferably 1≤x≤25, y>0, preferably 1≤y≤5, 0.4x+0.2y≤z ≤2x+y. M may include at least one of Mn, Fe, Co, Ni, Cu, Cr, V, etc., and M may preferably include at least one of Mn, Fe, Co, Ni, and the like. Among them, the valence state of M can be 0. Those skilled in the art can select x, y, z and M according to actual needs to obtain a positive electrode lithium supplement material that can achieve the purpose of the present application, such as but not limited to Li ₂ O·LiF·Fe, 2Li ₂ O·2LiF 5/3Fe, Li ₂ O 2LiF 4/3Fe, Li ₂ O 3LiF 2Fe, 4Li ₂ O 2LiF 3Co Fe, 2Li ₂ O 2LiF Co Fe, 25Li2O 5LiF 11V, Li Any one of ₂ O·LiF·Mn, Li ₂ O·2LiF·2Ni, and the like. By limiting the above range, the positive electrode lithium supplement material of the present application is obtained. The positive electrode lithium supplement material can release a large amount of lithium ions during the first charging process, has a high specific capacity, and can greatly improve the energy of the lithium ion secondary battery. density.

The inventor unexpectedly found that the positive electrode lithium supplement material with the chemical composition xLi ₂ O yLiF zM of the present application can ensure that the positive electrode lithium supplement material has a high specific capacity, and at the same time effectively enhance the chemical stability of the positive electrode lithium supplement material, which is more difficult. The agglomeration facilitates the preparation and storage of the positive electrode slurry and its coating on the positive electrode sheet, thereby improving the processing performance of the positive electrode slurry and improving the energy density of the lithium ion secondary battery. This may be due to the poor chemical stability of Li ₂ O, which is extremely sensitive to moisture and CO ₂ in the air, and is prone to the reaction of Li ₂ O+H ₂ O=LiOH and Li ₂ O+CO ₂ =Li ₂ CO ₃ The surface "residual alkali" LiOH and Li ₂ CO ₃ , and the positive electrode lithium supplement material with the chemical composition xLi ₂ O yLiF zM of the present application inhibits the generation of LiOH and Li ₂ CO ₃ , so that the lithium ion secondary battery has better performance.

The positive electrode lithium-supplementing material of the present application undergoes a delithiation reaction of xLi ₂ O+yLiF+2M–(2x+y)e ⁻ =MO _x +MFy+(2x+y)Li ⁺ during the first charge, which plays the role of supplementing lithium . At the same time, since the positive electrode lithium supplement material is at the positive electrode, it is difficult for the positive electrode potential to be low enough to generate MO _x +MF _y +(2x+y)Li ⁺ +(2x+y)e ^- =xLi ₂ O during the subsequent discharge process. +yLiF+2M reacts from 0V to 2V, so the active lithium is not consumed during subsequent discharge, thus achieving a net replenishment of active lithium.

On the whole, the chemical composition of the positive electrode lithium supplement material of the present application is xLi ₂ O yLiF zM, and the positive electrode lithium supplement material not only has high specific capacity, no gas is generated during the lithium supplement process, but also contains high specific capacity and is resistant to air. The moisture-insensitive component LiF can effectively enhance the chemical stability of the cathode lithium-supplement material while ensuring a very high specific capacity, and inhibit the generation of "residual alkali" LiOH and Li ₂ CO ₃ on its surface, which can effectively improve the The phenomenon of particle agglomeration during the slurry mixing process of the positive electrode slurry improves the processing performance of the positive electrode slurry. Adding the positive electrode lithium supplement material to the positive electrode plate can supplement the loss of active lithium caused by the generation of SEI, thereby further improving the energy density of the lithium ion secondary battery.

In an embodiment of the present application, the first charging specific capacity of the positive electrode lithium supplement material is ≥450 mAh/g. It shows that the specific capacity of the positive electrode lithium supplementary material is high, and a large amount of lithium ions can be released during the first charge to make up for the loss of active lithium caused by the formation of SEI, and enough lithium ions are inserted back into the positive electrode active material during the first discharge, which effectively improves the lithium ion The discharge specific capacity of the ion secondary battery improves the energy density of the lithium ion secondary battery.

A second aspect of the present application provides a method for preparing the positive electrode lithium supplement material of the present application, comprising the following steps:

(1) dispersing naphthalene in a solvent, slowly adding lithium metal fragments or powder, and uniformly reacting to obtain a lithium naphthalene solution;

(2 ₎ Compounds _MaOb and _McFd _, or _MeOfFg _are slowly added to the lithium naphthalene solution, and the reaction _is uniformly stirred and then filtered and dried to obtain a positive electrode lithium supplement material; wherein, the naphthalene The molar ratio to the lithium metal is 1:(0.6 to 1 ₎ , and the molar ratio of the naphthalene, the compounds _MaOb and _McFd is 1: ₍ 0.05 to 0.2):(0.05 to 0.2) , or the molar ratio of the naphthalene to the compound _MeO _f F _g is 1:(0.2 to 0.4).

It should be noted that the above-mentioned preparation method provided in this application is a preferred method for preparing the positive electrode lithium supplementary material of the present application, and those skilled in the art can also prepare the positive electrode lithium supplementary material of the present application according to other methods. There is no special method for this application. Restrictions, as long as the purpose of the application can be achieved.

The method for preparing the positive electrode lithium supplementary material provided by the present application is a homogeneous reaction at room temperature, and compared with the conventional solid-phase sintering method, the method has higher safety, lower production cost, and more uniform and sufficient reaction. The preparation method is simple in principle, convenient in operation, excellent in effect, and easy to realize large-scale production.

In one embodiment of the present application, the type of solvent is not particularly limited, as long as the purpose of the present application can be achieved. For example, it may be an aprotic solvent, including at least one of tetrahydrofuran, ethylene glycol dimethyl ether, and the like.

In one embodiment of the present application, there is no particular limitation on the type of compound M _a O _b , as long as the purpose of the present application can be achieved. For example, the _compound _MaOb may include _MnO , _Mn2O3 , _MnO2 , _FeO , _Fe2O3 , _CoO , _Co2O3 , _Co3O4 , _NiO , _Ni2O3 , _Cu2O , _CuO At least one of , CrO, Cr ₂ O ₃ , CrO ₃ , VO, V ₂ O ₃ , VO ₂ or V ₂ O ₅ and the like. The type of compound _McFd is not particularly limited as long as the object of the present application can be achieved _. For example, the compound _McFd may include _MnF2 , _MnF3 , _FeF2 , _FeF3 , _CoF2 , _CoF3 , _NiF2 , _NiF3 , _CuF , _CuF2 , _CrF3 , _VF3 , _VF4 , or _VF5 , etc. at least one of them. The type of _compound _MeOfFg _is not particularly limited as long as the object of the present application can be achieved. For example, the _compound _MeOfFg may include _Mn2OF2 , _MnOF , _Fe2OF2 , _FeOF , _Co2OF2 , _CoOF , _Ni2OF2 , _NiOF , _Cu3OF _, _Cu2OF2 , _CrOF , At least one of VOF, VOF ₂ , VOF ₃ or VO ₂ F and the like.

A third aspect of the present application provides a positive electrode sheet, including a positive electrode lithium supplement material, and the positive electrode lithium supplement material is the positive electrode lithium supplement material described in any one of the above embodiments. The application of the positive electrode lithium supplement material of the present application to the positive electrode plate can realize the effective supplement of active lithium and improve the energy density of the lithium ion secondary battery.

The positive electrode sheet in the present application is not particularly limited, as long as the purpose of the present application can be achieved. For example, a positive electrode sheet typically includes a positive electrode current collector and a positive electrode active material layer. Among them, the positive electrode current collector is not particularly limited, as long as the purpose of the present application can be achieved, for example, it may include aluminum foil, aluminum alloy foil, or composite current collector. The positive electrode active material layer includes a positive electrode active material and a positive electrode lithium supplement material. The type of positive active material is not particularly limited, as long as it can achieve the purpose of the present application, for example, it can include nickel cobalt lithium manganate (811, 622, 523, 111), nickel cobalt lithium aluminate, lithium iron phosphate, lithium rich manganese At least one of base material, lithium cobaltate, lithium manganate, lithium iron manganese phosphate or lithium titanate. The positive electrode lithium supplement material is at least one of the positive electrode lithium supplement materials provided in this application. In the present application, the thicknesses of the positive electrode current collector and the positive electrode active material layer are not particularly limited as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm, and more preferably 8 μm to 16 μm. The thickness of the positive electrode active material layer is 30 μm to 120 μm. In the present application, the positive electrode active material layer may be provided on one surface (the first surface) of the positive electrode current collector in the thickness direction, or may be provided on both surfaces (the first surface and the second surface) in the thickness direction of the positive electrode current collector )superior. It should be noted that the “surface” here can be the entire area of the positive electrode current collector, or a partial area of the positive electrode current collector, which is not particularly limited in this application, as long as the purpose of the application can be achieved. Optionally, the positive electrode sheet may further comprise a conductive layer, and the conductive layer is located between the positive electrode current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder.

In an embodiment of the present application, based on the total mass of the positive electrode active material layer, the mass percentage content of the positive electrode lithium supplement material is 1% to 10%, preferably 4% to 10%. For example, the mass percentage of the positive electrode lithium supplement material may include: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and the like. By controlling the content of the positive electrode lithium supplement material in the positive electrode active material layer within the above-mentioned range, the positive electrode pole piece has good structural stability, and the capacity loss and volume change caused by the delithiation of the positive electrode lithium supplement material can be reduced. Controlling the mass percentage content of the positive electrode lithium supplement material within the above-mentioned preferred range can make the positive electrode pole piece have better structural stability, and can also maximize the capacity of the battery.

There is no particular limitation on the method of adding the positive electrode lithium supplement material in the present application, and those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved. For example, the positive electrode lithium supplement material may be directly added to the slurry during the positive electrode material slurry mixing process to form a positive electrode slurry containing the positive electrode lithium supplement material of the present application, which is coated on the surface of the positive electrode current collector. It is also possible to pre-deposit a positive electrode lithium supplement material film on the surface of the positive electrode current collector. It is also possible to deposit a positive electrode lithium supplement material film on the surface of the positive electrode active material after the positive electrode active material of the positive electrode sheet is coated. The lithium ion secondary battery is assembled after the positive electrode lithium supplement material is added. During the first charging process, the positive electrode lithium supplement material is delithiated and the lithium supplement effect can be exerted. It should be noted that the above-mentioned "surface" may be the entire area of the positive electrode current collector/positive electrode active material, or may be a partial area of the positive electrode current collector/positive electrode active material, which is not particularly limited in this application, as long as the purpose of the application can be achieved. Can.

The negative electrode sheet of the present application may be a negative electrode active material layer including a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The present application does not specifically limit the negative electrode current collector as long as it can achieve the purpose of the present application. For example, it may contain copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, foam copper or composite current collector. The anode active material layer in the present application includes an anode active material, a conductive agent, and a thickener. The negative electrode active material of the present application may include natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO _x (0<x<2), Li-Sn At least one of alloys, Li-Sn-O alloys, Sn, SnO, SnO ₂ , spinel-structured lithium titanate Li ₄ Ti ₅ O ₁₂ , Li-Al alloys, metallic lithium, and the like. In this application, the thickness of the negative electrode current collector and the negative electrode active material layer is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode current collector is 6 μm to 10 μm, and the thickness of the negative electrode active material layer is 30 μm to 10 μm. 120μm. In the present application, the thickness of the negative electrode sheet is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode sheet is 50 μm to 150 μm. Optionally, the negative electrode sheet may further comprise a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode material layer. The composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder.

The above-mentioned conductive agent is not particularly limited as long as the object of the present application can be achieved. For example, the conductive agent may include conductive carbon black (Super P), carbon nanotubes (CNTs), carbon nanofibers, flake graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, or graphene, among others. at least one. The above-mentioned binder is not particularly limited, and any binder known in the art can be used as long as the purpose of the present application can be achieved. For example, the binder may include polyacryl alcohol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyimide, polyamideimide, styrene butadiene rubber (SBR), polyvinyl alcohol ( PVA), polyvinylidene fluoride, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, carboxymethyl cellulose (CMC) or carboxymethyl At least one of sodium cellulose (CMC-Na) and the like.

The separator in the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, polyethylene (PE), polypropylene (PP)-based polyolefin (PO) separators, polyester films (such as polyethylene terephthalate (PET) films), cellulose films, polyimide Amine film (PI), polyamide film (PA), spandex or aramid film, woven film, non-woven film (non-woven fabric), microporous film, composite film, diaphragm paper, rolled film, spinning film, etc. at least one of. For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer can be a non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, etc. kind. Optionally, polypropylene porous membranes, polyethylene porous membranes, polypropylene non-woven fabrics, polyethylene non-woven fabrics, or polypropylene-polyethylene-polypropylene porous composite membranes may be used. Optionally, at least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. For example, the inorganic substance layer includes inorganic particles and a binder, the inorganic particles are not particularly limited, for example, can be selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide , at least one of zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is not particularly limited, for example, it can be selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyethylene One or a combination of rolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly( At least one of vinylidene fluoride-hexafluoropropylene) and the like.

The lithium ion secondary battery of the present application further includes an electrolyte, and the electrolyte may be at least one of a gel electrolyte, a solid electrolyte, and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent. In some embodiments of the present application, the lithium salt may include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB(C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN(SO ₂ CF ₃ ) _2. At least one of LiC(SO ₂ CF ₃ ) ₃ , LiSiF ₆ , LiBOB or lithium difluoroborate. For example, LiPF ₆ may be chosen as the lithium salt because it gives high ionic conductivity and improves cycling characteristics. The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof. The above-mentioned carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof. Examples of the above-mentioned chain carbonate compound are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), carbonic acid Methyl ethyl ester (MEC) and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), and combinations thereof. Examples of fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Ethyl carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-dicarbonate Fluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof. Examples of the above-mentioned carboxylate compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone , caprolactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof. Examples of the above ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethyl ether Oxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof. Examples of the above-mentioned other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, Formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof. A fourth aspect of the present application provides an electrochemical device including the positive electrode plate provided by the present application, and the electrochemical device has good energy density.

The electrochemical device of the present application is not particularly limited, and it may include any device in which an electrochemical reaction occurs. In some embodiments, the electrochemical device may include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery, and the like.

The present application also provides an electronic device comprising the electrochemical device described in the embodiments of the present application, the electronic device having good energy density. The electronic device of the present application is not particularly limited, and it may be used for any electronic device known in the prior art. In some embodiments, electronic devices may include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, bicycles, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large-scale household storage batteries and lithium-ion capacitors, etc.

The preparation process of the electrochemical device is well known to those skilled in the art, and the present application is not particularly limited. For example, an electrochemical device can be manufactured by the following process: overlapping the positive electrode and the negative electrode through a separator, wrapping them, folding them, etc., and putting them into the casing as needed, injecting the electrolyte into the casing and sealing it, wherein The separator used is the aforementioned separator provided in this application. In addition, if necessary, an overcurrent preventing element, a guide plate, etc. may be placed in the case to prevent pressure rise and overcharge and discharge inside the electrochemical device.

The present application provides a positive electrode lithium supplement material, a positive electrode plate comprising the material, and an electrochemical device. The chemical composition of the positive electrode lithium supplement material is xLi ₂ O·yLiF·zM; wherein, x>0, y>0, 0.4x+0.2y≤z≤2x+y, M includes at least one of Mn, Fe, Co, Ni, Cu, Cr or V. The positive electrode lithium supplement material has strong chemical stability and can effectively improve the particle agglomeration phenomenon during the slurry mixing process. Applying the positive electrode lithium supplement material in the positive electrode plate can realize the supplement of active lithium and effectively improve the energy density of the electrochemical device.

Description of drawings

In order to illustrate the technical solutions of the present application and the prior art more clearly, the following briefly introduces the drawings required in the embodiments and the prior art. Obviously, the drawings in the following description are only for the present application. some examples.

Fig. 1 is the XRD (X-ray diffraction) pattern of the positive electrode lithium supplement material of Example 1 of the application;

Fig. 2 is the SEM (scanning electron microscope) image of the positive electrode lithium supplement material of Example 1 of the application;

Fig. 3 is the iron element EDS (X-ray energy dispersive analysis) spectrum in the positive electrode lithium supplement material of the embodiment 1 of the application;

Fig. 4 is the oxygen element EDS spectrum in the positive electrode lithium supplement material of Example 1 of the application;

FIG. 5 is an EDS spectrum of fluorine element in the positive electrode lithium supplement material of Example 1 of the present application.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the present application more clear, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. All other technical solutions obtained by those of ordinary skill in the art based on the embodiments in this application fall within the protection scope of this application.

It should be noted that, in the specific embodiment of the present application, the present application is explained by taking a lithium ion secondary battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion secondary battery.

FIG. 1 shows the XRD pattern of the positive electrode lithium supplement material of Example 1 of the present application. Among them, (a) in Figure 1 is the spectrum of the positive electrode lithium supplement material, (b) in Figure 1 is the Fe standard diffraction card, (c) in Figure 1 is the Li ₂ O standard diffraction card, ( d) is a LiF standard diffraction card. As shown in Figure 1, it can be seen in the spectrum (a): diffraction peaks with 2θ of 45.1° and 65.7° appeared, corresponding to the diffraction peaks of Fe; diffraction peaks with 2θ of 38.7°, 45.0° and 65.5° appeared, The diffraction peaks corresponding to LiF; and the diffraction peaks with 2θ of 33.1°, 38.4°, 55.4°, 66.0° and 69.4° appear, corresponding to the diffraction peaks of Li ₂ O, indicating that there is a positive electrode lithium supplement material in Example 1 of the present application. Fe, LiF and _Li2O .

FIG. 2 shows a SEM image of the positive electrode lithium supplement material of Example 1 of the present application. As shown in FIG. 2 , the particle size distribution of the positive electrode lithium supplement material is uniform. 3 shows the EDS spectrum of iron element in the positive electrode lithium supplement material of Example 1 of the present application, indicating that the positive electrode lithium supplement material of the present application contains iron element and is uniformly distributed in the positive electrode lithium supplement material. FIG. 4 shows the EDS spectrum of oxygen element in the positive electrode lithium supplement material of Example 1 of the present application, indicating that the positive electrode lithium supplement material of the present application contains oxygen element and is uniformly distributed in the positive electrode lithium supplement material. FIG. 5 shows the EDS spectrum of fluorine element in the positive electrode lithium supplement material of Example 1 of the present application, indicating that the positive electrode lithium supplement material of the present application contains fluorine element and is uniformly distributed in the positive electrode lithium supplement material.

Example

Hereinafter, the embodiment of the present application will be described more specifically with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

Test methods and equipment:

First charge specific capacity test:

The positive electrode lithium supplement material to be tested, the conductive agent conductive carbon black (Super P) and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 80:10:10, and N-methylpyrrolidone (NMP) was added as The solvent was mixed and prepared into a slurry with a solid content of 40%, and a coating of 100 μm thickness was applied on the current collector aluminum foil with a scraper. A 1cm-diameter disk was formed, a metal lithium sheet was used as a counter electrode in a glove box, a ceglard composite membrane was selected as the separator, and an electrolyte solution was added to assemble to obtain a button battery. The electrolyte is ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of 30:50:20 to obtain an organic solution, and then add lithium salt lithium hexafluorophosphate to the organic solvent to dissolve and mix uniform, and an electrolyte solution with a lithium salt concentration of 1.15 mol/L was obtained.

In this application, Wuhan Blue Electric CT2001A system is used to test the specific charging capacity. The button-type battery to be tested containing the positive electrode lithium supplementary material is allowed to stand for 30min in the environment of 25±3℃, and the rate of 0.1C (the theoretical gram of the positive electrode lithium supplementary material) The capacity was calculated at 600mAh/g) with constant current charging to a voltage of 4.45V, followed by constant voltage charging to a current of 0.025C, and the first charging capacity was recorded.

The charging specific capacity of the button battery of the positive electrode lithium supplement material = the first charging capacity/the quality of the positive electrode lithium supplement material.

First discharge capacity test:

The lithium ion secondary battery to be tested containing the positive electrode lithium supplement material was left standing for 30min in the environment of 25±3℃, charged with a constant current of 600mA (rated capacity in 2000mAh) to a voltage of 4.4V, and then charged with a constant voltage to 4.4V. The current was 50mA, and it was allowed to stand for 5min, and the discharge capacity was recorded for the first time by constant current discharge at a current of 600mA to a termination voltage of 3.0V.

Example 1

Disperse 128.17g of naphthalene in 1L of tetrahydrofuran solvent, slowly add 6.25g of lithium metal fragments, and react uniformly to obtain a lithium naphthalene solution; weigh 15.97g of compound Fe ₂ O ₃ and 11.28g of compound FeF ₃ , slowly add the above lithium naphthalene solution , the reaction is uniformly stirred and then filtered and dried to obtain Li ₂ O·LiF·Fe, a positive electrode lithium supplement material.

The positive electrode active material lithium cobalt oxide (LiCoO ₂ ), the positive electrode lithium supplement material prepared above, the conductive agent Super P, and the binder PVDF are mixed according to the mass ratio of 95:2:1.5:1.5, and NMP is added as a solvent. A slurry with a solid content of 75%, and stir well. The slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm, and dried at 130° C. to obtain a positive electrode sheet with a coating thickness of 110 μm. After the above steps are completed, the single-side coating of the positive electrode sheet is completed. After that, the above steps are repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet coated with positive active material on both sides. After the coating is completed, the positive pole piece is cut into a size of 74mm×867mm, and the tabs are welded for use.

The graphite, the negative electrode active material SiO, the conductive agent nano-conductive carbon black, and the binder polyacryl alcohol (PAA) were mixed according to the mass ratio of 78:15:3:4, and deionized water was added as a solvent to prepare a solid content of 60 % slurry, and stir evenly, then add an appropriate amount of deionized water, adjust the viscosity of the slurry to 5000 Pa·s, and prepare a negative electrode slurry. The slurry was uniformly coated on the negative current collector copper foil with a thickness of 8 μm, dried at 110°C, and cold pressed to obtain a negative electrode sheet with an active material layer coated on one side with a thickness of 100 μm. After the above steps are completed, these steps are also completed on the back side of the negative electrode pole piece by the same method, that is, the negative pole piece with double-sided coating is obtained. After the coating is completed, the negative pole piece is cut into a size of 76mm×851mm, and the tabs are welded for use.

In a dry argon atmosphere, organic solvents EC, EMC and DEC were mixed in a mass ratio of 30:50:20 to obtain an organic solution, and then a lithium salt lithium hexafluorophosphate was added to the organic solvent to dissolve and mix evenly to obtain a lithium salt concentration of 1.15mol /L of electrolyte.

A polypropylene (PP) film (supplied by Celgard) with a thickness of 14 μm was used.

The positive electrode, the separator and the negative electrode prepared above are stacked in sequence, so that the separator is placed between the positive and negative electrodes to play a role of isolation, and the electrode assembly is obtained by winding. The electrode assembly is put into an aluminum-plastic film packaging bag, and the moisture is removed at 80°C, and the prepared electrolyte is injected.

Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8, Example 9, Example 10, Example 11, Example 12, Example 13, and Example In 14, <preparation of positive electrode lithium supplement material>, <preparation of positive electrode pole piece>, <preparation of negative electrode pole piece>, <preparation of electrolyte solution>, <preparation of separator> and <preparation of lithium ion secondary battery The preparation steps of > are all the same as in Example 1, and the changes of relevant preparation parameters are shown in Table 1:

Table 1

Example 15

The negative electrode active material graphite, nano-conductive carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed according to the mass ratio of 95:2:2:1, and deionized water is added as a solvent to prepare a slurry with a solid content of 70%. ingredients and mix well. The slurry was uniformly coated on the current collector copper foil, dried at 110° C., and cold-pressed to obtain a single-sided active material layer-coated negative pole piece with an active material layer thickness of 150 μm. After the above steps are completed, these steps are also completed on the back side of the negative electrode pole piece by the same method, that is, the negative pole piece with double-sided coating is obtained. After the coating is completed, the negative pole piece is cut into a size of 76mm×851mm, and the tabs are welded for use.

<Preparation of Lithium Supplement Material for Positive Electrode>, <Preparation of Positive Electrode Sheet>, <Preparation of Electrolyte Solution>, <Preparation of Separator Film>, and <Preparation of Lithium Ion Secondary Battery> are the same as in Example 1.

In Comparative Example 1 and Comparative Example 2, the preparation of <preparation of positive electrode sheet>, <preparation of negative electrode sheet>, <preparation of electrolyte solution>, <preparation of separator> and <preparation of lithium ion secondary battery> The steps are the same as in Example 1. In Comparative Example 2, <Preparation of positive electrode lithium supplement material> is the same as in Example 1, and the changes in relevant preparation parameters are shown in Table 2:

Table 2

Note: "/" in Table 2 indicates that the corresponding preparation parameter does not exist.

Comparative Example 3

The metal lithium fragments and the oxide Co ₃ O ₄ are mixed according to a molar ratio of 8:1 to obtain a first mixture; the first mixture is sintered at 180° C. for 4 h under an argon protective atmosphere to obtain a second mixture; the second mixture is obtained The mixture is mixed and reacted with a mixed gas with a volume ratio of Ar, O ₂ and HF=3:0.05:96.95 to obtain a positive electrode lithium supplement material 2.1Li ₂ O·Co·0.5CoO _0.05 F _0.1 .

<Preparation of Positive Electrode Sheet>, <Preparation of Negative Electrode Sheet>, <Preparation of Electrolyte Solution>, <Preparation of Separator Film>, and <Preparation of Lithium Ion Secondary Battery> are the same as in Example 1.

Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8,

The preparation parameters of Example 9, Example 10, Example 11, Example 12, Example 13, Example 14, Example 15, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in Table 3:

table 3

Note: "/" in Table 3 indicates that the corresponding preparation parameter does not exist.

From Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8, Example 9, Example 10 and Comparative Example 1, Comparative Example 3 It can be seen that the positive electrode slurry made of the positive electrode lithium supplement material of the present application does not agglomerate, indicating that the positive electrode lithium supplement material of the present application has excellent chemical stability; when the positive electrode lithium supplement material does not contain the positive electrode lithium supplement material of the present application When the composition of LiF is high (for example, Comparative Example 3), Li ₂ O in this kind of material can easily react with moisture and CO ₂ in the air to form LiOH and Li ₂ CO ₃ , and the phenomenon of positive electrode slurry agglomeration will occur. The application of the above-mentioned positive electrode lithium supplement material in the positive electrode plate can realize the effective supplement of active lithium, improve the first charge specific capacity of the positive electrode lithium supplement material, and at the same time effectively improve the energy density of the lithium ion secondary battery.

From Example 1, Example 11, Example 12, Example 13, Example 14 and Comparative Example 2, it can be seen that the positive electrode sheet with the positive electrode lithium supplement material in the content range of the present application can effectively improve the secondary lithium ion The energy density of the battery. In particular, when the mass percentage of the positive electrode lithium supplement material is preferably 4% to 10% (eg Example 12, Example 13 and Example 14), the energy density of the lithium ion secondary battery can be more effectively improved.

Based on the above analysis, it can be seen that the chemical composition of the positive electrode lithium supplement material provided by the present application is xLi ₂ O·yLiF·zM. The positive electrode lithium supplement material has strong chemical stability, and can effectively improve the particle agglomeration phenomenon in the slurry mixing process. Applying the cathode lithium supplement material to an electrochemical device can effectively supplement active lithium and effectively improve the energy density of the electrochemical device.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection of the present application. within the range.

Claims

A positive electrode lithium supplement material, comprising xLi 2 O·yLiF·zM; wherein, x>0, y>0, 0.4x+0.2y≤z≤2x+y, M includes Mn, Fe, Co, Ni, Cu, At least one of Cr or V.
The positive electrode lithium supplement material according to claim 1, wherein the M comprises at least one of Mn, Fe, Co or Ni; and the valence state of the M is zero.
The positive electrode lithium supplement material according to claim 1, wherein the first charge specific capacity of the positive electrode lithium supplement material is greater than or equal to 450mAh/g.
A method for preparing the positive electrode lithium supplement material according to any one of claims 1 to 3, comprising the following steps:

(1) dispersing naphthalene in a solvent, slowly adding lithium metal fragments or powder, and uniformly reacting to obtain a lithium naphthalene solution;

( 2 ) slowly adding the compounds MaOb and McFd or MeOfFg to the lithium naphthalene solution, stirring and reacting evenly, filtering and drying to obtain the positive electrode lithium-supplementing material;

Wherein, the molar ratio of the naphthalene to the lithium metal is 1:(0.6 to 1), and the molar ratio of the naphthalene, the compound M a O b and the M c F d is 1: (0.05 to 0.2): (0.05 to 0.2), or the molar ratio of the naphthalene to the compound MeOfFg is 1 :(0.2 to 0.4).
The method of claim 4, wherein the solvent comprises at least one of tetrahydrofuran or ethylene glycol dimethyl ether.
The method of claim 4, wherein the compound M a O b comprises MnO, Mn 2 O 3 , MnO 2 , FeO, Fe 2 O 3 , CoO, Co 2 O 3 , Co 3 O 4 , NiO, At least one of Ni 2 O 3 , Cu 2 O, CuO, CrO, Cr 2 O 3 , CrO 3 , VO, V 2 O 3 , VO 2 or V 2 O 5 , the compound McF d includes MnF 2 , at least one of MnF 3 , FeF 2 , FeF 3 , CoF 2 , CoF 3 , NiF 2 , NiF 3 , CuF, CuF 2 , CrF 3 , VF 3 , VF 4 or VF 5 , the compound Me OfFg includes Mn2OF2 , MnOF , Fe2OF2 , FeOF , Co2OF2 , CoOF , Ni2OF2 , NiOF , Cu3OF , Cu2OF2 , CrOF , VOF , VOF2 , VOF 3 or at least one of VO 2 F.
A positive electrode plate, comprising the positive electrode lithium supplement material according to any one of claims 1 to 3.
The positive electrode sheet according to claim 7, wherein, based on the total mass of the positive electrode active material layer, the mass percentage content of the positive electrode lithium supplementing material is 1% to 10%.
An electrochemical device comprising the positive electrode plate of claim 7 or 8.
An electronic device comprising the electrochemical device of claim 9 .