Lithium secondary battery polymer material and manufacturing method therefor
A polymer material for a lithium secondary battery having ionic conductivity and electronic conductivity at the same time, and a method for preparing the same. The polymer material includes a polythiophene-based polymer and a conductive polymer, and the polymer material may be formed by forming a polythiophene-based polymer, forming a conductive polymer, and heat-treating the polythiophene-based polymer and the conductive polymer.
1. An all-solid-state lithium secondary battery comprising an electrode assembly consisting of:
a positive electrode, a solid electrolyte, and a negative electrode, which are sequentially stacked;
wherein the solid electrolyte comprises:
a blend-type polymer formed by blending of:
(i) a polythiophene-based polymer represented by the following Formula 1:
wherein n is 70 to 280, PEG is polyethylene glycol, and when a number of ethylene oxide units of PEG is m, m is 4 to 15; and
(ii) a conductive polymer,
wherein the conductive polymer comprises poly-(3,4-ethylenedioxythiophene): poly(styrenesulfonate)(PEDOT: PSS),
wherein the polythiophene-based polymer and the conductive polymer are contained in a weight ratio of 95:5 to 80:20,
wherein the blend-type polymer has an electron conductivity of 10 −8 S/cm to 10 −2 S/cm, and
wherein the solid electrolyte is a film comprising the blend-type polymer.
2. The all-solid-state lithium secondary battery according to claim 1 , wherein the blend-type polymer has an ionic conductivity of 10 −6 S/cm to 10 −4 S/cm.
3. A method for preparing the all-solid-state lithium secondary battery according to claim 1 , comprising:
(a) forming a polythiophene-based polymer represented by the following Formula 1;
(b) forming a conductive polymer;
(c) heat treating the polythiophene-based polymer and the conductive polymer to form a blend-type polymer:
wherein n is 70 to 280, PEG is polyethylene glycol, and when a number of ethylene oxide units of PEG is m, m is 4 to 15; and
(d) sequentially stacking the positive electrode, the solid electrolyte, and the negative electrode, wherein the solid electrolyte comprises the blend-type polymer.
4. The method for preparing the all-solid-state lithium secondary battery according to claim 3 , wherein the step (a) comprises,
(a1) adding methanol and sulfuric acid to thiophene acetic acid to form thiophene methyl acetate;
(a2) adding iron chloride to thiophene methyl acetate to form polythiophene methyl acetate;
(a3) adding sodium hydroxide to the polythiophene methyl acetate to form polythiophene sodium acetate;
(a4) adding hydrogen chloride to the polythiophene sodium acetate to form polythiophene acetic acid; and
(a5) adding polyethylene glycol to the polythiophene acetic acid to form poly (3-polyethylene glycol thiophene).
5. The method for preparing the all-solid-state lithium secondary battery according to claim 3 , wherein in the step (c), the heat treatment is performed at 120° C. to 250° C.