Polyimide-based binder for power storage device, electrode mixture paste, negative electrode active material layer, negative electrode sheet for power storage device, and power storage device

1. A polyimide-based binder for power storage device having a repeated breaking energy retention ratio of 70% or more, wherein

the polyimide-based binder is obtained by imidizing a polyamic acid solution comprising a repeating unit represented by the following general formula (I):

wherein, A is one or more tetravalent groups selected from groups having aromatic ring(s), open-chain aliphatic groups or groups having an alicyclic structure, which may be substituted with halogen and may be the same or two or more types; and B is one or more divalent groups selected from groups having aromatic ring(s), open-chain aliphatic groups or groups having an alicyclic structure, which may be substituted with halogen, and may be the same or two or more types; and

wherein in the general formula (I), 50 mol % or more of one of the groups A and B is an open-chain aliphatic group.

2. The polyimide-based binder for power storage device according to claim 1 , wherein the binder does not melt at a temperature of 300° C. or less.

3. The polyimide-based binder for power storage device according to claim 1 , wherein in the general formula (I), 50 mol % or more of A is a group represented by the following general formula (II):

wherein, X is a single bond or an oxygen atom, n is an integer from 0 to 2, and if n is 1 or 2, X may be the same or different.

4. A resin composition for a binder, comprising a polyamic acid having a repeating unit represented by the following general formula (I) and a solvent, and capable of forming the polyimide-based binder for power storage device according to claim 1 by an imidization reaction:

wherein A is one or more tetravalent groups selected from groups having aromatic ring(s), open-chain aliphatic groups or groups having an alicyclic structure, which may be substituted with halogen and may be the same or two or more types; and B is one or more divalent groups selected from groups having aromatic ring(s), open-chain aliphatic groups or groups having an alicyclic structure, which may be substituted with halogen, and may be the same or two or more types.

5. An electrode mixture paste containing the resin composition for binder according to claim 4 and an electrode active material.

6. A negative electrode active material layer comprising the binder for power storage device according to claim 1 and an electrode active material.

7. A negative electrode sheet for power storage device, comprising the negative electrode active material layer according to claim 6 formed on a surface of a current collector.

8. A power storage device comprising the negative electrode sheet for the power storage device according to claim 7 .