Packaging material for flat electrochemical cell

Abstract

In a packaging material for electrochemical cell, a thermally adhesive resin layer is configured of a resin having a propylene based elastomer resin in a propylene based resin. This propylene based elastomer resin is a copolymer composed of a constitutional unit derived from propylene and a constitutional unit derived from an alpha-olefin having from 2 to 20 carbon atoms; when the total sum of the constitutional unit derived from propylene and the constitutional unit derived from an alpha-olefin is defined as 100% by mole, contains 50% by mole or more of the constitutional unit derived from propylene; and is satisfied with (a) a Shore A hardness (ASTM D2240) of from 65 to 90, (b) a melting point of from 130 DEG C to 170 DEG C, (c) a density (ASTM D1505) of from 860 to 875 kg / m3 and (d) a glass transition temperature as measured by DSC of from -25 DEG C to -35 DEG C.

Description

technical field [0001] The present invention relates to a packaging material for flat electrochemical cells having stable sealing properties, insulating properties, and formability. Background technique [0002] Lithium-ion batteries, also called lithium secondary batteries, have liquid, gel or polymer electrolytes, and contain positive and negative active materials made of polymers. In this lithium ion battery, lithium atoms (Li) in the positive electrode active material, that is, lithium transition metal oxides, become lithium ions (Li) during charging. + ) into the carbon layer of the negative electrode (intercalation), lithium ions (Li + ) from the carbon layer (deintercalation) and move to the positive electrode, and become the original lithium compound for charge and discharge reactions. Compared with nickel-cadmium batteries and nickel-hydrogen batteries, the battery has a higher output voltage and lower energy density. High, and there will be no apparent discharge ...

AI Technical Summary

Problems solved by technology

[0010] However, on the inner fold line of the peripheral sealing portion 10b, that is, the curved portion 10c, since the innermost layer of the outer package 10, that is, the hot-melt adhesive resin layer, has been melted once and crystallized during heat sealing, it is easy to bend. break

Moreover, when this fracture occurs, the electrolyte inside the outer package 10 will come into contact with the metal foil constituting the outer package 10, causing the metal foil to be energized, resulting in a significant drop in the output of the lithium ion battery and loss of battery function.

[0011] In addition, in the embossing process of forming the outer packaging body 10 by press molding, when a metal having excellent ductility such as aluminum is used on the metal foil constituting the outer packaging body 10, the innermost layer of the outer packaging body 10 The extension of the hot-melt adhesive resin layer cannot catch up with the extension of the aluminum, and the aluminum and the hot-melt adhesive resin layer may peel off, resulting in cracks on the hot-melt adhesive resin layer

Moreover, the battery packaging material shown in JP-A-2005-56729 does not completely solve the above-mentioned problems.

[0012] In addition, in addition to housing the lithium ion battery main body 2 in the outer packaging body 10, the same problem also occurs when a capacitor or an electric double layer capacitor is sealed.

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