Solid electrolyte membrane, preparation method of solid electrolyte membrane, and lithium ion battery

A solid electrolyte membrane and electrolyte technology, applied in the manufacture of solid electrolytes, non-aqueous electrolyte batteries, electrolyte batteries, etc., can solve the problems of brittle and hard mechanical properties, difficult processing, no elasticity, etc., and achieve high ion conductivity, good The effect of processability

Inactive Publication Date: 2017-11-28

上海纳晓能源科技有限公司

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Problems solved by technology

[0004] The purpose of the present invention is to provide a solid electrolyte membrane and its preparation method, lithium ion battery, to overcome the e...

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Abstract

The invention discloses a solid electrolyte membrane, a preparation method of the solid electrolyte membrane, and a lithium ion battery. The solid electrolyte membrane is a material of a composite structure, wherein the material is formed by compounding lithium inorganic solid electrolyte and a polymer; a polymer with a continuous three-dimensional sponge network structure is filled with the lithium inorganic solid electrolyte; the primary particle size of the lithium inorganic solid electrolyte is 0.01-3 microns; the polymer has the continuous three-dimensional sponge network structure; the diameter of the polymer in the network structure is 0.002-0.5 micron; a weight ratio of the lithium inorganic solid electrolyte to the polymer is 70:30 to 95:5; the composite structure has pores; the size of each pore is 0.01-3 microns; a ratio of the pore volume to the volume of the whole composite material is 1-15%; the overall thickness of the composite material is 1-50 microns; and the tensile strength is higher than 10MPa. According to the solid electrolyte membrane disclosed by the invention, high ionic conductivity of the lithium inorganic solid electrolyte can be maintained, and excellent processability, mechanical property, corrosion resistance and oxidation resistance can be provided.

Application Domain

Solid electrolytesFinal product manufacture +1

Technology Topic

ChemistryCorrosion +10

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Examples

Experimental program(7)

Example Embodiment

[0029] The embodiment of the present application also discloses a method for preparing a solid electrolyte membrane, comprising the steps of:

[0030] (1) The polymer matrix of the three-dimensional network structure is prepared by the phase separation method;

[0031] (2) The lithium inorganic solid electrolyte powder is mixed with the binder, and ball-milled to form a uniformly dispersed mixed slurry;

[0032] (3), soaking the porous polymer matrix into the mixed slurry, pulling out and drying to obtain a solid electrolyte membrane.

[0033] Preferably, the step (1) includes: blending the polymer resin with a diluent, melting at high temperature into a homogeneous solution → extrusion, casting film → cooling in a cooling bath, phase separation occurs → high temperature evaporation of solvent → high temperature bidirectional Stretch into a film → extract and remove the diluent under the condition that a certain tension is provided to ensure that the film will not shrink → the film after stretching and extraction is further slightly stretched and heat-set to obtain a volume ratio of pore volume to polymer material of 60-90% polymer matrix.

[0034] The polymer described in step (1) can be polyethylene (PE) with a molecular weight of not less than 50,000, polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polymethyl fluoride One or more of polymers such as methyl acrylate (PMMA), polyethylene oxide (PEO), polyacrylonitrile (PAN), polystyrene, polyvinyl alcohol and polyvinyl acetate.

[0035] Preferably, the polymer has a molecular weight of at least 0.5×10 5 the polymer polyolefin resin; the polymer concentration in the polymer melt is 5-50wt%; the coolant in the cooling bath described in step (1) is a poor solvent for the polymer, preferably water, coolant The temperature is controlled at 5 ~ 30 ℃. In the coolant, the polymer film containing the solvent undergoes phase separation to obtain a porous gel film with sufficient strength and stable structure; the temperature of the high-temperature heating to evaporate the solvent in step (1) is controlled by the temperature of the polymer in the solvent. Above the dissolution temperature, in order to suppress the shrinkage of the polyolefin film after the solvent volatilizes at high temperature, the polyolefin gel film is bidirectionally fixed during the solvent volatilization process; the temperature of the high temperature biaxial stretching described in step (1) is the melting point of the polymer resin At 10°C or lower, the stretching ratio is 10 to 80 times.

[0036]In order to ensure that the inorganic solid electrolyte can be evenly distributed on the polymer porous membrane, and the phenomenon of powder falling does not occur, the lithium inorganic solid electrolyte and the binder are ball-milled and dispersed in a ball-milling aid according to a certain mass ratio. In the preparation method of the present invention, the binder described in step 2 is polyvinyl alcohol, polyvinyl acetate, polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyethylene oxide (PEO) ), polyacrylonitrile (PAN), polystyrene and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and other polymers; the mass ratio of the binder to the inorganic solid electrolyte is 0.5 : 9.5 to 2: 8; the ball milling aid is a good solvent for the binder, preferably one or more of the following solvents: acetone, ethanol, N-methylpyrrolidone, N,N-dimethylformamide Wait.

[0037] The present application also discloses a lithium ion battery, comprising a positive electrode, a negative electrode and the solid electrolyte membrane.

[0038] The present invention is further illustrated by the following examples: According to the following examples, the present invention can be better understood. However, those skilled in the art can easily understand that the specific material ratios, process conditions and results described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0039] Examples 1-6 The solid electrolyte membrane of the novel composite structure was prepared according to the following process, and the specific process parameters are shown in Table 1.

[0040] (1) Preparation of polymer microporous membrane by thermally induced phase separation method:

[0041] The polymer resin is blended with the diluent and melted at a high temperature of 150 °C into a polyolefin homogeneous solution with a certain concentration → extruded through a die head of a certain thickness through a twin-screw extruder, cast into a film → cooled in a water bath at 20 °C, the occurrence of Phase separation → evaporation of solvent at high temperature → biaxially stretched film at a certain stretching ratio at high temperature → extraction and removal of diluent under the condition that a certain tension is provided to ensure that the film will not shrink → the film after stretching and extraction is further slightly stretched and heat-set to make A polymer microporous membrane with a certain thickness and porosity is formed.

[0042] (2), soaking the polymer microporous membrane with high porosity in the slurry containing the solid electrolyte powder, pulling it out and drying, to obtain a solid electrolyte layer with a new structure of certain thickness and porosity.

[0043] Table 1 Process parameters of solid electrolyte layer preparation

[0044]

Example Embodiment

[0046] Example 1

[0047] The ultra-high molecular weight polyethylene (UHMWPE, 1×10 6 , the melting point is 128 °C, and the glass transition temperature is -78 °C) into the twin-screw extruder, and 95% (accounting for the percentage of the total feed mass) solid paraffin is added through the side feeding port. Under the condition of 160 rpm, the resin is melted and mixed. The mixed polyolefin melt was extruded through a die into a polyolefin film with a thickness of 0.2 mm, and the polyolefin film was directly cooled in a 20° C. water bath to obtain a porous polyolefin gel film. The porous polyolefin gel film was fixed in two directions, placed in an oven at 120 °C for 12 hours, and after the solvent was completely volatilized, longitudinally stretched and transversely stretched at 130 °C in turn, stretching ratio = vertical × horizontal = 10 × 8, to obtain The thickness is 1 μm, the wire diameter is 0.002-0.5 μm, the pore size is 0.01-3 μm, the porosity is 90%,

[0048] A three-dimensional sponge-like structure polyolefin porous membrane with a tensile strength greater than 10 MPa.

[0049] Li7La with a particle size of 3 μm 3 Zr 2 O 12 (LLZO) powder and polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) solvent in a mass ratio of 95:5, and ball-milled in a planetary ball mill at a speed of 450 rpm for 12 hours to obtain a mixed solution. slurry. The polyolefin porous membrane was immersed in the mixed slurry, pulled out, dried in an oven at 80 °C for 24 hours to completely volatilize NMP, and finally obtained a thickness of 2 μm, a pore size of 0.01-3 μm, a porosity of 85%, and a tensile strength greater than 10MPa, conductivity is 10 -7 S/cm LLZO-polyethylene composite structure solid electrolyte membrane.

Example Embodiment

[0050] Example 2

[0051] The ultra-high molecular weight polyethylene (UHMWPE, 1×10 6 , the melting point is 128 °C, and the glass transition temperature is -78 °C) into the twin-screw extruder, and 95% (accounting for the percentage of the total feed mass) solid paraffin is added through the side feeding port. Under the condition of 160 rpm, the resin is melted and mixed. The mixed polyolefin melt was extruded through a die into a polyolefin film with a thickness of 0.2 mm, and the polyolefin film was directly cooled in a 20° C. water bath to obtain a porous polyolefin gel film. The porous polyolefin gel film was fixed in two directions, placed in an oven at 120 °C for 12 hours, and after the solvent was completely volatilized, longitudinal stretching and transverse stretching were carried out at 130 °C in turn, stretching ratio = vertical × horizontal = 5 × 2, to obtain A polyolefin porous membrane with a three-dimensional sponge-like structure with a thickness of 10 μm, a wire diameter of 0.002 to 0.5 μm, a pore size of 0.01 to 3 μm, a porosity of 90%, and a tensile strength of more than 10 MPa.

[0052] Li with a particle size of 3 μm 7 La 3 Zr 2 O 12 (LLZO) powder and polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) solvent in a mass ratio of 95:5, and ball-milled in a planetary ball mill at a speed of 450 rpm for 12 hours to obtain a mixed solution. slurry. The polyolefin porous membrane was soaked in the mixed slurry, pulled out, and the NMP was completely volatilized in an oven at 80 °C for 24 hours. Finally, a thickness of 15 μm, a pore size of 0.01 to 3 μm, a porosity of 15%, and a tensile strength greater than 10 MPa were obtained. , with a conductivity of 10 -3 S/cm LLZO-polyethylene composite solid electrolyte membrane.

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PUM

Property	Measurement	Unit
Particle size	0.01 ~ 3.0	µm
Diameter	0.002 ~ 0.5	µm
Size	0.01 ~ 3.0	µm
tensile		MPa
Particle size		Pa
strength	10

Description & Claims & Application Information

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Improve ionic conductivity
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ActiveCN102263257AImprove electronic conductivityImprove ionic conductivityCell electrodesSolventAnodic oxidation

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Abstract

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Description & Claims & Application Information

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