Power storage device including power storage cells having a positive electrode, a negative electrode, a separator, and an accommodation chamber for a liquid electrolyte
A power storage device includes power storage cells that includes a positive electrode, a negative electrode, a separator, and an accommodation chamber accommodating a liquid electrolyte in a liquid-tight manner. The power storage device includes a cell stack in which the power storage cells are stacked in series. A side surface of the cell stack is covered with a seal portion made of a plastic. A terminal positive electrode current collector and a terminal negative electrode current collector located in the outermost layer of the cell stack are made of a high thermal conductivity material having a thermal conductivity greater than or equal to 100 W/(m·K). The power storage device includes a positive electrode cooling unit, which cools the terminal positive electrode current collector, and a negative electrode cooling unit, which cools the terminal negative electrode current collector. The liquid electrolyte contains an ester compound.
1 . A power storage device, comprising a cell stack in which power storage cells are stacked in series, wherein
each power storage cell includes:
a positive electrode, in which a positive electrode active material layer is bonded to a first surface of a positive electrode current collector;
a negative electrode, in which a negative electrode active material layer is bonded to a first surface of a negative electrode current collector, the negative electrode active material layer being disposed to face the positive electrode active material layer of the positive electrode;
a separator disposed between the positive electrode active material layer and the negative electrode active material layer;
a seal portion disposed between a first surface of the positive electrode current collector of the positive electrode and a first surface of the negative electrode current collector of the negative electrode, and on an outer side of the positive electrode active material layer and the negative electrode active material layer, and bonded to both the positive electrode current collector and the negative electrode current collector; and
an accommodation chamber defined by the seal portion, the positive electrode and the negative electrode and accommodates a liquid electrolyte in a liquid-tight manner,
wherein
the liquid electrolyte is a liquid electrolyte containing an ester compound and a nonaqueous solvent,
the ester compound is at least one of methyl acetate, ethyl acetate, or methyl propionate,
the positive electrode current collector and the negative electrode current collector located as outermost layers of the cell stack are terminal current collectors,
at least one of the terminal current collectors is made of a high thermal conductivity material having a thermal conductivity greater than or equal to 100 W/(m·K), and
the power storage device comprises a cooling unit that cools the at least one terminal current collector made of the high thermal conductivity material.
2 . The power storage device according to claim 1 , wherein at least one of the following conditions is met: a weight per unit area of the positive electrode active material layer is greater than or equal to 55 mg/cm 2 , and a weight per unit area of the negative electrode active material layer is greater than or equal to 25 mg/cm 2 .
3 . The power storage device according to claim 1 , wherein the separator is bonded to the positive electrode active material layer and the negative electrode active material layer.
4 . The power storage device according to claim 1 , further comprising a conductive layer disposed between the cooling unit and the at least one terminal current collector.
5 . The power storage device according to claim 1 , wherein the ester compound is contained in an amount of 30 to 95% by volume based on the total volume of the nonaqueous solvent in the liquid electrolyte.
6 . The power storage device according to claim 1 , wherein a second surface of the positive electrode current collector and a second surface of the negative electrode current collector, which are contact portions of the power storage cells adjacent to each other in a stacking direction, are bonded via an adhesive having conductivity.
7 . The power storage device according to claim 1 , wherein each separator has an adhesive layer on at least one surface.
8 . The power storage device according to claim 1 , wherein the seal portion includes an outer peripheral portion, which extends outward beyond each edge portion of the positive electrode current collector and the negative electrode current collector,
the outer peripheral portion protrudes in a direction orthogonal to a stacking direction from each edge portion of the positive electrode current collector and the negative electrode current collector, and
the power storage cells adjacent to each other in the stacking direction are integrated by bonding the outer peripheral portions of the seal portions to each other.
9 . The power storage device according to claim 1 , wherein the liquid electrolyte is in free liquid form.
10 . The power storage device according to claim 1 , wherein the liquid electrolyte has a viscosity at 25° C. is 7 mPa·s or less.