Lithium secondary battery
View Patent ↗A lithium secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte having lithium ion conductivity. Lithium metal is deposited on the negative electrode during charging, and dissolves from the negative electrode during discharging. A spacer is provided between the separator and at least one of the positive electrode and the negative electrode. A first length of the separator in a first direction D 1 is shorter than a second length of the separator in a second direction D 2 intersecting the first direction D 1 . In a cross section of the spacer taken along a thickness direction of the separator and the first direction D 1 , at least one of a spacer-side angle between the separator and the spacer and a spacer-side angle between the spacer and the electrode in contact with the spacer is greater than 90°.
1 . A lithium secondary battery comprising:
a positive electrode;
a negative electrode;
a separator disposed between the positive electrode and the negative electrode; and
a non-aqueous electrolyte having lithium ion conductivity, wherein
lithium metal is deposited on the negative electrode during charging, and dissolves from the negative electrode during discharging,
a spacer is provided between the separator and at least one of the positive electrode and the negative electrode, the spacer including a plurality of protrusions formed on a surface of the separator,
a first length of the separator in a first direction D 1 is shorter than a second length of the separator in a second direction D 2 intersecting the first direction D 1 ,
in a cross section of the spacer taken along a thickness direction of the separator and the first direction D 1 , a spacer-side angle between the protrusion spacer and the electrode in contact with the protrusion spacer is greater than 90°, and
configured such that a straight line SL extending along the first direction D 1 and crossing the spacer three or more times can be drawn when viewed in a normal direction of a main surface of the separator.
2 . The lithium secondary battery according to claim 1 , wherein the cross section of the spacer includes a curved line that is in contact with at least one of the separator and the electrode.
3 . The lithium secondary battery according to claim 2 , wherein a radius of curvature of the curved line at an intersection between the curved line and the separator or the electrode is greater than or equal to half a longer contact length out of a contact length between the electrode and the spacer and a contact length between the separator and the spacer.
4 . The lithium secondary battery according to claim 1 , wherein, in the cross section of the spacer, a contact length between the separator and the spacer and a contact length between the electrode and the spacer are 500 μm or more and 2000 μm or less.
5 . The lithium secondary battery according to claim 1 , wherein, in the cross section of the spacer, a contact length between the electrode and the spacer is different from a contact length between the separator and the spacer.
6 . The lithium secondary battery according to claim 5 , wherein, when one of the contact lengths is referred to as a length L 1 and the other contact length that is longer than the length L 1 is referred to as a length L 2 , a ratio L 1 /L 2 between the length L 1 and the length L 2 is 0.5 or more and 0.95 or less.
7 . The lithium secondary battery according to claim 5 , wherein the contact length between the separator and the spacer is longer than the contact length between the electrode and the spacer.
8 . The lithium secondary battery according to claim 1 , wherein a cross-sectional shape of the spacer in the cross section is a rectangle including a curved line forming at least one corner, a trapezoid, an ellipse, or a portion of an ellipse.
9 . The lithium secondary battery according to claim 8 , wherein
the cross-sectional shape of the spacer is a portion of an ellipse, and
a relationship of θ≥2×θe is satisfied,
where, among the positive electrode, the negative electrode, and the separator, a first member is in contact with an arc of the cross-sectional shape of the spacer and a second member is in contact with a chord of the cross-sectional shape of the spacer,
a contact angle θ is a spacer-side angle between the second member and a tangent of the arc at an intersection between the arc and the second member, and
an elevation angle θe is a spacer-side angle between the second member and a straight line connecting the intersection between the arc and the second member and a middle point in a contact portion between the first member and the spacer.
10 . The lithium secondary battery according to claim 8 , wherein
the cross-sectional shape of the spacer is a portion of an ellipse, and
a maximum diameter L 3 of the cross section in a direction extending along a surface of the separator is 500 μm or more and 2000 μm or less.
11 . The lithium secondary battery according to claim 8 , wherein
the cross-sectional shape of the spacer is a portion of an ellipse, and
a maximum diameter L 3 of the cross section in a direction extending along a surface of the separator is greater than a contact length between the separator and the spacer and a contact length between the electrode and the spacer.
12 . The lithium secondary battery according to claim 8 , wherein
the cross-sectional shape of the spacer is the rectangle, and
a radius of curvature of the curved line is greater than or equal to three times a longer contact length out of a contact length between the electrode and the spacer and a contact length between the separator and the spacer.
13 . The lithium secondary battery according to claim 1 , wherein the spacer has a height of 15 μm or more and 60 μm or less.
14 . The lithium secondary battery according to claim 1 , wherein
the non-aqueous electrolyte includes lithium ions and anions, and
the anions include at least oxalate complex anions.
15 . The lithium secondary battery according to claim 1 , wherein, when viewed in a normal direction of the main surface of the separator, a ratio s/S between an area S of a region of the positive electrode overlapping the negative electrode and an area s of the spacer arranged between the positive electrode and the negative electrode is 0.05 or more and 0.2 or less.
16 . The lithium secondary battery according to claim 1 , wherein, when viewed in a normal direction of the main surface of the separator, a ratio d/h between the minimum distance d (μm) between adjacent portions of the spacer along the straight line SL and the height h (μm) of the spacer in a normal direction of a main surface of the separator is 10 or more and 800 or less.
17 . The lithium secondary battery according to claim 1 , wherein, when viewed in a normal direction of the main surface of the separator, a ratio 1 /L of a length 1 of portions of the straight line SL occupied by the spacer to the first length of the separator in the first direction D 1 is 0.05 or more and 0.2 or less.
18 . The lithium secondary battery according to claim 1 , wherein plurality of protrusions are spot-shaped.