NEGATIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERY AND LITHIUM ION SECONDARY BATTERY
A negative electrode including a negative electrode current collector, first protrusions on a surface of the negative electrode current collector, a separation-stopping area on at least a part of a surface of each first protrusion, and a negative electrode active material layer including a negative electrode active material and formed on at least a top face of the first protrusion. This structure suppresses the separation of the negative electrode active material layer from the negative electrode current collector, the degradation of the current collecting ability, and the deformation of the negative electrode itself. A lithium ion secondary battery including this negative electrode has a high battery capacity, a high energy density, and an excellent charge/discharge cycle characteristic, and is capable of stably maintaining a high power over an extended period of time.
1 . A negative electrode for a lithium ion secondary battery, comprising:
a negative electrode current collector made of metal and shaped like a plate;
first protrusions extending outwardly from a surface of said negative electrode current collector;
a columnar structure formed on at least a top face of each of said first protrusions, said columnar structure including a negative electrode active material; and
a separation-stopping area provided on at least a part of a surface of each of said first protrusions for stopping said columnar structure from becoming separated from the surface of said first protrusion due to expansion or contraction of said negative electrode active material.
2 . The negative electrode for a lithium ion secondary battery in accordance with claim 1 , wherein said separation-stopping area is provided on at least a part of a side face of each of said first protrusions.
3 . The negative electrode for a lithium ion secondary battery in accordance with claim 2 , wherein said separation-stopping area includes one or more steps formed on the side face of each of said first protrusions.
4 . The negative electrode for a lithium ion secondary battery in accordance with claim 3 , wherein at least one of said one or more steps is shaped like stairs.
5 . The negative electrode for a lithium ion secondary battery in accordance with claim 2 , wherein said separation-stopping area includes one or both of:
1) a depression in said side face of said first protrusion; and
2) a second protrusion extending outwardly from said side face of said first protrusion,
in the circumferential direction of the side face of said first protrusion.
6 . The negative electrode for a lithium ion secondary battery in accordance with claim 5 , wherein said depression is formed in the side face of said first protrusion near the surface of said negative electrode current collector.
7 . A lithium ion secondary battery comprising:
a positive electrode including a positive electrode active material capable of reversibly absorbing and desorbing lithium ions;
the negative electrode for a lithium ion secondary battery in accordance with claim 1 ;
a separator; and
a lithium-ion conductive electrolyte.