LG New Energy Patent Disclosure: Diaphragm MOF Layer

technical problem:

When manufacturing separators, coating using already grown crystals is conventionally employed, rather than utilizing Langmuir-Blodgett coating. In the case of coating using already grown crystals, the uniformity of coating formation is determined by the spacing between the crystals (a few hundred nanometers to a few microns), but this has the effect of the pore size of the crystals in which the coating is formed (a few microns). Angstrom) influence is difficult to obtain. In addition, the conventional coating method may have the following problem: when the separator is formed, an uneven coating may be formed and the thickness may become thick, which acts as a resistance during operation of the battery.

Technical means:

The present invention provides a separator for lithium secondary batteries, including a porous substrate and a MOF (metal organic framework) layer formed on one or both surfaces of the porous substrate, wherein the MOF layer includes more than one MOF molecular film and Has an amorphous structure.

The present invention also provides a method for manufacturing a separator for lithium secondary batteries, which includes the following steps: (S1) forming a MOF molecular film by mixing an aqueous solution containing a zinc precursor and an organic solution containing an organic ligand precursor; and ( S2) Deposit the MOF molecular film on the surface of the porous substrate, wherein the deposition is performed by the Langmuir-Burget method.

Example 1:

(1) Manufacturing of separator: (1-1) Formation of MOF molecular membrane: Dissolve terephthalic acid as an organic ligand precursor in a chloroform solvent to prepare a saturated solution of the organic ligand precursor. Zinc acetate as a zinc precursor was dissolved in water to prepare a zinc precursor aqueous solution with a concentration of 0.002M. The organic ligand precursor solution is added dropwise into the zinc precursor aqueous solution to form a MOF-5 molecular film.

(1-2) Deposition of MOF layer on porous substrate: As a porous substrate, a porous substrate made of polypropylene (PP) and with a porosity of 50% was prepared as a separator. Using a Langmuir-Budget device (KSV NIMA Company, KN2002), the PP separator was passed through the MOF-5 molecular film in the vertical direction to deposit the MOF-molecule film. This deposition process was performed five times to prepare a separator in which MOF-5 molecular films were formed on both surfaces of the PP separator.

(2) Manufacturing of lithium-sulfur secondary batteries: The separator is placed between the positive and negative electrodes, thereby positioned inside the case, and then the electrolyte is injected inside the case to prepare a lithium-sulfur secondary battery in the form of a CR-2032 coin battery . At this time, the positive electrode was prepared by coating an Al foil with a slurry for a positive electrode by combining a positive electrode active material, a conductive material (Super P) and a binder (Super P) and drying and rolling them. Styrene-butadiene rubber (SBR) is mixed with a weight ratio of 80:10:10. The positive active material is an S/MOF-5 composite obtained by mixing sulfur (a product from Sigma-Aldrich) with carbonized MOF-5 using a ball mill and then heat-treating them at 155°C. Lithium foil was used as the negative electrode, and the electrolyte was prepared by dissolving 0.3M LiNO3 and 1M LiTFSi in DOL and DME (DOL:DME=1:1 (volume/volume)) (DOL: dioxolane, DME : dimethoxyethane) in a mixed solvent.

Technical effect:

The separator for lithium secondary batteries according to the present invention can prevent the shuttling phenomenon caused by polysulfides that may occur in batteries containing sulfur-containing materials as positive electrode active materials, thereby improving the cycle performance of the battery.