CN114843590A - Preparation and application of ultrathin organic-inorganic composite solid electrolyte membrane - Google Patents

Abstract

A preparation and application of an ultrathin organic-inorganic composite solid electrolyte membrane belong to the technical field of lithium ion battery electrolytes. Firstly, selecting high molecular polymer and highly dispersed inorganic nano particles, preparing an ultrathin composite electrolyte self-supporting base membrane with controllable thickness by a casting method, then selecting a carbonate-based polymer electrolyte with high ionic conductivity, and preparing an ultrathin organic-inorganic composite electrolyte membrane by a solution casting method. The thickness of the ultrathin organic-inorganic composite electrolyte membrane prepared by the invention can be reduced to below 10 mu m, and the ultrathin organic-inorganic composite electrolyte membrane has high ionic conductivity, wide electrochemical stability window and excellent mechanical properties. The preparation method is simple in preparation process, convenient for large-scale production and suitable for commercial lithium ion solid-state batteries.

Description

Preparation and application of an ultrathin organic-inorganic composite solid electrolyte membrane

technical field

The invention relates to a lithium ion battery solid electrolyte, in particular to the preparation and application of an ultra-thin organic-inorganic composite solid electrolyte membrane, and belongs to the technical field of lithium ion battery electrolytes.

Background technique

As a new type of electrochemical energy storage device, lithium-ion batteries have been widely used in mobile electronic devices, electric vehicles, and emergency power supplies, and have been gradually promoted and used in energy storage power stations, rail transit, and aerospace. So far, commercial lithium-ion batteries mostly use conventional organic liquid electrolytes, such as ethylene carbonate and propylene carbonate. However, lithium-ion batteries using organic liquid electrolytes have huge safety problems, which seriously hinder the further popularization and wider application of lithium-ion batteries. The main reason is that organic electrolytes usually have high chemical activity, volatility, easy ignition , explosion and other safety defects. Therefore, the use of solid-state electrolytes instead of traditional organic electrolytes is one of the effective ways to solve the above-mentioned safety problems of lithium-ion batteries. At the same time, solid electrolytes also have the advantages of high ionic conductivity, wide electrochemical window, wide operating temperature, and can be arbitrarily tailored or changed.

For solid electrolytes, the diffusion time of Li ⁺ is closely related to the thickness of the solid electrolyte. According to the equation τ=l ² /D, where τ is the diffusion time, l is the thickness of the solid electrolyte, and D is the diffusion constant, it can be seen that reducing the thickness l of the solid electrolyte membrane can effectively shorten the transport distance and transport time of lithium ions. In addition, reducing the thickness of the solid-state electrolyte also helps to improve the energy density and power density of solid-state batteries. In addition, reducing the thickness of the solid-state electrolyte can reduce the manufacturing cost of solid-state batteries, which is of great significance for promoting the commercialization of batteries. It should be noted that in addition to reducing the thickness of the solid electrolyte membrane, the structure of the electrolyte also needs to be designed to achieve interface matching with the anode and cathode materials. For example, on the positive side, the anti-oxidation ability of the solid electrolyte membrane needs to be considered; on the negative side, especially if the lithium metal negative electrode is used, it needs to have the effect of inhibiting the growth of lithium dendrites. The Chinese patent (CN202111078836.X) discloses that the cellulose aerogel is used as the skeleton and the gelatinous guar gum electrolyte is used as the filler. Step 1, prepare cellulose aerogel; Step 2, prepare colloidal guar gum electrolyte; Step 3, prepare solid electrolyte film: dope the colloidal guar gum electrolyte into the cellulose aerogel In the glue, the solid electrolyte is prepared. In thin-film all-solid-state batteries, limited by the low ionic conductivity of solid-state electrolytes, narrow electrochemical windows, and serious interface problems between electrolytes and electrode materials, all-solid-state batteries cannot match high-voltage cathode materials, and the cycle performance is relatively poor. The battery has low power density, and its application is limited to a certain extent.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the present invention provides an ultra-thin organic-inorganic composite solid-state electrolyte membrane prepared by a casting method combined with a solution casting method, and a lithium-ion secondary all-solid-state battery is constructed with the thin-film electrolyte.

The technical scheme of the present invention is:

First, disperse high molecular polymer (20wt%-80wt%) and highly dispersed inorganic nanoparticles (20wt%-80wt%, add up to high molecular polymer to 100%) in organic solvent, prepare thickness by casting method A controllable ultra-thin composite electrolyte self-supporting base film with a large number of pores inside, and then a carbonate-based polymer electrolyte precursor solution with high ionic conductivity is selected and poured into the base film by solution casting to reach a saturated state, and the high temperature (60 -120°C) to obtain an ultrathin organic-inorganic composite electrolyte membrane after polymerization.

The selected high molecular polymers include but are not limited to polyethylene oxide (PEO) and its derivatives, polyvinylidene fluoride (PVDF) and its derivatives, polyacrylonitrile (PAN) and its derivatives, polysiloxane and its derivatives. Derivatives, one or more of such polymers. The selected organic solvent is one or more of the following: N-methylpyrrolidone (NMP), ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate , γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, acetonitrile, 1,2-dimethoxyethane, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether , dimethyl sulfoxide;

Highly dispersed inorganic nanoparticles include, but are not limited to, garnet-type Li ₇ La ₃ Zr ₂ O ₁₂ and doped-modified solid-state electrolyte nanoparticles, perovskite-type LiLaTiO ₃ and doped-modified solid-state electrolyte nanoparticles, NASICON-type Li _1+x Al _x Ti _2-x (PO ₄ ) ₃ and doped modified solid electrolyte nanoparticles, LISICON type Li ₁₄ Zn(GeO ₄ ) ₄ and doped modified solid electrolyte nanoparticles, crumb type LiTaSiO ₅ and Doping modified solid electrolyte nanoparticles, sulfide Li ₁₀ GeP ₂ S ₁₂ solid electrolyte nanoparticles, halide Li ₃ InCl ₆ solid electrolyte nanoparticles, montmorillonite nanoparticles, silica nanoparticles, zirconia nanoparticles , barium titanate nanoparticles, calcium carbonate nanoparticles, aluminum oxide nanoparticles, titanium dioxide nanoparticles, silicon carbide nanoparticles, Li ₁₄ Zn(GeO ₄ ) ₄ nanoparticles, LiZr ₂ (PO ₄ ) ₃ nanoparticles, LiPON nanoparticles , etc. One or more kinds of nanoparticles.

Carbonate-based polymer electrolyte precursors are precursors capable of forming carbonate-based polymer electrolytes, including but not limited to polycarbonate precursor solutions (including carbonate + lithium salt + initiator), polyvinyl carbonate Precursor solution (carbonate + lithium salt + initiator), polyethylene ethylene carbonate precursor solution (ethylene ethylene carbonate + lithium salt + initiator), polyallyl methyl carbonate precursor solution (alkene propyl methyl carbonate + lithium salt + initiator), polyvinylene carbonate precursor solution (vinylene carbonate + lithium salt + initiator), polyfluoroethylene carbonate precursor solution (fluoroethylene carbonate +lithium salt+initiator), one or more of such polymers.

The thickness of the prepared ultrathin organic-inorganic composite electrolyte membrane can be reduced to less than 10 μm and has good mechanical properties.

The prepared ultrathin organic-inorganic composite electrolyte membrane has high room temperature ionic conductivity (>1.0×10 ^-3 S/cm), wide electrochemical stability window (>5.5V (vs. Li ⁺ / Li)) and high ion mobility number (>0.65) and good stability with Li metal electrodes.

A lithium-ion secondary all-solid-state battery is constructed by using the solid-state electrolyte film of the present invention:

The positive active materials of lithium ion batteries are lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium ion fluorophosphate, lithium manganate, lithium-rich manganese based oxide, lithium manganese iron phosphate, nickel cobalt aluminate One or more of lithium (NCA), lithium nickel cobalt manganate, lithium iron phosphate (LiFeO ₄ ), and lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ); the negative electrode active material is lithium metal, lithium alloy , graphite, hard carbon, lithium metal nitride, antimony oxide, carbon germanium composite material, carbon silicon composite material, lithium titanate, lithium titanium oxide, one or more. The initiator or catalyst is one of the following: dibutyltin dilaurate, bis(acetylacetonate) dibutyltin, azobisisoheptonitrile (ABVN), azobisisobutyronitrile (AIBN), azobisisobutyronitrile (AIBN), Dimethyl azodiisobutyrate (AIBME), benzoyl peroxide (BPO), platinum water (Pt);

The preparation of the positive electrode material for the lithium ion battery includes the following steps: grinding and mixing the positive electrode active material with a mass fraction of 50-90% and a conductive agent acetylene black with a mass fraction of 5-30%; adding a mass fraction of 1-15% Polyvinylidene fluoride (PVDF), 1-15% polycarbonate-based organic-inorganic composite solid electrolyte (the above substances add up to 100%) and 1-methyl-2-pyrrolidone (NMP) are ground and mixed; coated on the surface of aluminum foil, baked Dry; metal lithium and metal lithium alloy can be directly used as the corresponding negative electrode material; the preparation of other negative electrode materials includes the following steps: the negative electrode active material with a mass fraction of 50-90%, the conductive agent acetylene with a mass fraction of 5-30% Black grinding and mixing, adding 5-25% mass fraction of polyvinylidene fluoride (PVDF) (the above substances add up to 100%), 1-methyl-2-pyrrolidone (NMP) grinding and mixing; coating on the surface of copper foil, baking Dry;

The lithium-ion battery assembly includes a button battery and a soft pack battery, and the internal stacking sequence of the solid-state battery is positive electrode-the ultra-thin organic-inorganic composite solid-state electrolyte membrane of the present invention-negative electrode.

The innovation and practicability of the present invention lie in:

1. The thickness of the ultra-thin organic-inorganic composite solid electrolyte membrane prepared by the present invention can be reduced to less than 10 μm, and at the same time, it has good flexibility and machining performance.

2. The ultrathin organic-inorganic composite solid-state electrolyte membrane prepared by the present invention has good electrochemical performance, high room temperature ionic conductivity (>1.0×10 ^-3 S/cm), wide electrochemical stability window (>5.5V) (vs. Li ⁺ /Li)) and high ion mobility number (>0.65), and good stability with Li metal electrodes.

3. The ultra-thin organic-inorganic composite solid-state electrolyte membrane prepared by the present invention has a simple preparation process and can be produced quantitatively.

Description of drawings

FIG. 1 is a picture of the optical topography of the base film in Example 2 of the ultra-thin organic-inorganic composite solid-state electrolyte membrane.

Fig. 2 The charge-discharge curve of the lithium cobalt oxide positive solid-state battery assembled with the ultra-thin organic-inorganic composite solid-state electrolyte membrane obtained in Example 2 according to Example 6.

Detailed ways

The present invention will be described below through specific examples, which are provided for a better understanding of the present invention and are by no means intended to limit the scope of the present invention.

Preparation of electrolyte:

Example 1

First, 1 g of polyvinylidene fluoride (PVDF) was dispersed and dissolved in NMP organic solvent, fully stirred to dissolve completely, and the same amount of garnet-type Li _6.6 La _2.9 Ca _0.1 Zr _1.75 W _0.25 O ₁₂ solid electrolyte nanoparticles was added as PVDF and stirred vigorously 12h and ultrasonication for 2h to obtain a slurry with uniformly dispersed particles, and an ultra-thin composite electrolyte base membrane was prepared by a casting method to obtain a thin film electrolyte base membrane; Ethylene ethylene ester (76%) + LiTFSI (23.99%) + azobisisobutyronitrile (0.01%)), poured into the thin film electrolyte base membrane by solution casting method, and cured at 80 °C to obtain excellent performance ultrathin organic-inorganic composite electrolyte membrane.

Example 2

First, 1 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) was dispersed and dissolved in NMP organic solvent, fully stirred and completely dissolved, and the same amount of garnet-type Li _6.6 La _2.9 Ca _0.1 Zr _1.75 W _0.25 as PVDF-HFP was added. O ₁₂ solid electrolyte nanoparticles were vigorously stirred for 12 h and ultrasonicated for 2 h to obtain a slurry with uniform particle dispersion. An ultra-thin composite electrolyte base film was prepared by a casting method to obtain a thin film electrolyte base film; then high-ion polyethylene carbonate electrolyte precursor was selected. The bulk solution (ethylene ethylene carbonate (76%) + LiTFSI (23.99%) + azobisisobutyronitrile (0.01%)) was poured into the thin film electrolyte base membrane by solution casting, and cured at 80°C An ultrathin organic-inorganic composite electrolyte membrane with excellent properties is obtained.

Example 3

First, 1 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) was dispersed and dissolved in NMP organic solvent, fully stirred and completely dissolved, and the same amount of silica nanoparticles as PVDF-HFP was added, stirred vigorously for 12 hours, and ultrasonicated for 2 hours to obtain particles The uniformly dispersed slurry was prepared by casting method to obtain an ultra-thin composite electrolyte base film to obtain a thin film electrolyte base film; Polyethylene carbonate electrolyte precursor solution (ethylene ethylene carbonate (76%) + LiTFSI (23.99%) + azobisisobutyronitrile (0.01%)), poured into the thin-film electrolyte base membrane by solution casting method, and cured at high temperature to obtain an ultra-thin organic-inorganic composite electrolyte membrane with excellent performance.

Example 4

First, 1 g of polyacrylonitrile (PAN) was dispersed and dissolved in NMP organic solvent, fully stirred and completely dissolved, and the same amount of silica nanoparticles as PAN was added, stirred vigorously for 12 hours, and ultrasonicated for 2 hours to obtain a slurry with uniform particle dispersion. The ultra-thin composite electrolyte base membrane was prepared by the method to obtain a thin-film electrolyte base membrane; Polyethylene carbonate electrolyte precursor solution (ethylene ethylene carbonate (76%) + LiTFSI (23.99%) + azobisisobutyronitrile (0.01%) %)), poured into the thin-film electrolyte base membrane by solution casting method, and cured at 80°C to obtain an ultra-thin organic-inorganic composite electrolyte membrane with excellent performance.

Example 5

First, 1 g of polyethylene oxide (PEO) was dispersed and dissolved in NMP organic solvent, fully stirred to dissolve completely, and the same amount of garnet-type Li _6.6 La _2.9 Ca _0.1 Zr _1.75 W _0.25 O ₁₂ solid electrolyte nanoparticles was added as PEO and stirred vigorously for 12h And ultrasonic for 2 hours to obtain a slurry with uniform particle dispersion, and an ultra-thin composite electrolyte base film was prepared by a casting method to obtain a thin film electrolyte base film; Polyethylene carbonate electrolyte precursor solution (ethylene ethylene carbonate (76%) + LiTFSI (23.99%) + azobisisobutyronitrile (0.01%)) was poured into the thin-film electrolyte base membrane by solution casting method, and then cured at 80°C to obtain an ultra-thin organic-inorganic composite electrolyte membrane with excellent performance.

Electrolyte thickness: use a micrometer (accuracy 0.01 mm) to measure the thickness of the ultra-thin organic-inorganic composite electrolyte membrane, and measure at 3 points on the membrane arbitrarily, and calculate the average value.

其中，L为聚合物电解质的厚度，S为不锈钢垫片面积，R为测量得到的阻抗值。Ionic conductivity: Using two stainless steel spacers to sandwich the polymer electrolyte, assemble the R2032 coin cell to measure the impedance, according to the formula

Among them, L is the thickness of the polymer electrolyte, S is the area of the stainless steel gasket, and R is the measured impedance value.

Electrochemical window: Use stainless steel and lithium sheet to clamp the polymer electrolyte, assemble the R2032 button cell, and perform linear voltammetry (LSV) measurement. The initial voltage is 2.8V, the highest potential is 6.5V, and the scanning speed is 1mV/S.

Example 6

240 mg of lithium cobalt oxide positive electrode and 45 mg of conductive agent acetylene black were uniformly ground for 40 minutes; 15 mg of binder polyvinylidene fluoride, 15 mg of electrolyte mixture and 150 μL of 1-methyl-2-pyrrolidone were added for uniform grinding for 40 minutes; coated on the surface of aluminum foil, Dry at 80°C for 8h under vacuum conditions; cut the pole pieces into discs with R=12mm, use the ultra-thin organic-inorganic composite electrolyte membrane of Example 2 above, and metal lithium as the negative electrode to assemble a solid-state lithium-ion battery. The assembled solid-state battery can be charged to 4.6V, and can be stably cycled for 200 cycles at room temperature with a charge cut-off voltage of 4.5V, with a capacity retention rate of over 74%.

Table 1

Claims (10)

1. The preparation method of the ultrathin organic-inorganic composite solid electrolyte membrane is characterized by comprising the following steps of: firstly, dispersing high molecular polymer and highly dispersed inorganic nano particles in an organic solvent, preparing an ultrathin composite electrolyte self-supporting base membrane with controllable thickness and a large number of pores in the interior by a casting method, then selecting a carbonate-based polymer electrolyte precursor solution with high ionic conductivity, pouring the solution into the base membrane by a solution casting method to reach a saturated state, and polymerizing at a high temperature of 60-120 ℃ to obtain an ultrathin organic-inorganic composite electrolyte membrane; 20-80 wt% of high molecular polymer, 20-80 wt% of highly dispersed inorganic nano particles, and 100% of inorganic nano particles and high molecular polymer.

2. The method for preparing an ultra-thin organic-inorganic composite solid electrolyte membrane according to claim 1, wherein the selected high molecular polymer is one or more selected from the group consisting of polyethylene oxide (PEO) and its derivatives, polyvinylidene fluoride (PVDF) and its derivatives, Polyacrylonitrile (PAN) and its derivatives, and polysiloxane and its derivatives.

3. The method for preparing an ultrathin organic-inorganic composite solid electrolyte membrane according to claim 1, wherein the organic solvent is one or more of the following: n-methylpyrrolidone (NMP), ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylene carbonate, methyl ethyl carbonate, gamma-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, acetonitrile, 1, 2-dimethoxyethane, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethyl sulfoxide.

4. The method for preparing an ultra-thin organic-inorganic composite solid electrolyte membrane according to claim 1, wherein the highly dispersed inorganic nanoparticles are selected from garnet-type Li ₇ La ₃ Zr ₂ O ₁₂ And doping modified solid electrolyteRice particle, perovskite type LiLaTiO ₃ And doped modified solid electrolyte nanoparticles, NASICON type Li _1+x Al _x Ti _2-x (PO ₄ ) ₃ And doping modified solid electrolyte nano-particles, LISICON type Li ₁₄ Zn(GeO ₄ ) ₄ And doping modified solid electrolyte nano-particles and debris LiTaSiO ₅ And doping modified solid electrolyte nano-particles and sulfide Li ₁₀ GeP ₂ S ₁₂ Solid electrolyte nanoparticles, halide Li ₃ InCl ₆ Solid electrolyte nanoparticles, montmorillonite nanoparticles, silica nanoparticles, zirconia nanoparticles, barium titanate nanoparticles, calcium carbonate nanoparticles, alumina nanoparticles, titania nanoparticles, silicon carbide nanoparticles, Li ₁₄ Zn(GeO ₄ ) ₄ Nanoparticles, LiZr ₂ (PO ₄ ) ₃ One or more of nanoparticles and LiPON nanoparticles.

5. The method for preparing an ultra-thin organic-inorganic composite solid electrolyte membrane according to claim 1, the preparation method is characterized in that a carbonate-based polymer electrolyte precursor is a precursor capable of forming a carbonate-based polymer electrolyte, and is selected from one or more of a polycarbonate precursor solution (comprising carbonate + lithium salt + initiator), a polyethylene carbonate precursor solution (comprising carbonate + lithium salt + initiator), a polyethylene ethylene carbonate precursor solution (comprising ethylene carbonate + lithium salt + initiator), a polyallyl methyl carbonate precursor solution (comprising allyl methyl carbonate + lithium salt + initiator), a polyethylene carbonate precursor solution (comprising ethylene carbonate + lithium salt + initiator), and a polyvinyl fluoride carbonate precursor solution (comprising fluoroethylene carbonate + lithium salt + initiator).

6. A method for manufacturing an ultra-thin organic-inorganic composite solid electrolyte membrane according to claim 1, wherein the ultra-thin organic-inorganic composite electrolyte membrane is manufactured to have a thickness of 10 μm or less.

7. An ultrathin organic-inorganic composite solid electrolyte membrane prepared by the method according to any one of claims 1 to 6.

8. An ultrathin organic-inorganic composite solid electrolyte membrane having room-temperature ionic conductivity, prepared by the method according to any one of claims 1 to 6>1.0×10 ^-3 S/cm, electrochemical stability window > 5.5V (vs. Li) ⁺ Per Li), ion transport number>0.65。

9. A lithium ion secondary all-solid battery comprising an ultrathin organic-inorganic composite solid electrolyte membrane prepared by the method of any one of claims 1 to 6.

10. The lithium ion secondary all-solid-state battery according to claim 9, wherein the positive active material of the lithium ion battery is lithium cobaltate (LiCoO) ₂ ) Lithium nickelate (LiNiO) ₂ ) Lithium ion fluorophosphate, lithium manganate, lithium-rich manganese-based layered oxide, lithium manganese iron phosphate, lithium Nickel Cobalt Aluminate (NCA), lithium nickel cobalt manganese oxide, lithium iron phosphate (LiFeO) ₄ ) Lithium vanadium phosphate (Li) ₃ V ₂ (PO ₄ ) ₃ ) One or more of the above; the negative active material is one or more of metallic lithium, lithium alloy, graphite, hard carbon, lithium metal nitride, antimony oxide, carbon-germanium composite material, carbon-silicon composite material, lithium titanate and lithium-titanium oxide; the initiator or catalyst is one of the following: dibutyl tin dilaurate, dibutyl tin bis (acetylacetonate), Azobisisoheptonitrile (ABVN), Azobisisobutyronitrile (AIBN), dimethyl Azobisisobutyrate (AIBME), Benzoyl Peroxide (BPO), platinum water (Pt);

the preparation method of the lithium ion battery anode material comprises the following steps: grinding and mixing 50-90% of positive electrode active material and 5-30% of conductive agent acetylene black; adding polyvinylidene fluoride (PVDF) accounting for 1-15% of the mass fraction, polycarbonate-based organic-inorganic composite solid electrolyte accounting for 1-15% of the mass fraction and 1-methyl-2-pyrrolidone (NMP) for grinding and mixing; coating on the surface of the aluminum foil, and drying; the metal lithium and the metal lithium alloy are directly used as corresponding negative electrode materials; or other negative electrode materials are prepared by the following steps: grinding and mixing a negative electrode active material accounting for 50-90% by mass and a conductive agent acetylene black accounting for 5-30% by mass, adding polyvinylidene fluoride (PVDF) accounting for 5-25% by mass and 1-methyl-2-pyrrolidone (NMP), grinding and mixing; coating the copper foil on the surface of the copper foil, and drying;

the lithium ion battery assembly comprises a button cell and a soft package cell, and the stacking sequence in the solid-state cell is positive electrode-ultrathin organic-inorganic composite solid-state electrolyte membrane-negative electrode.

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