| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a secondary battery capable of improving capacity and cycle characteristics. <P>SOLUTION: The secondary battery includes a wound electrode 20 formed by winding a positive electrode 21 and a negative electrode 22 through a separator 23 and a battery can 11 in which the electrode 20 is housed. A negative active material layer 22B is formed in the negative electrode 22, and the negative active material layer 22B contains first graphite particles and second graphite particles. The first graphite particles have a breaking strength of 40-70 MPa, and a median diameter D<SB>50</SB>of 18-26 μm. The second graphite particles have a breaking strength of 20-90 MPa, and a median diameter D<SB>50</SB>of 8-15 μm, and the mass ratio of the first graphite particles to the second graphite particles is 2/3 to 3/2. <P>COPYRIGHT: (C)2009,JPO&INPIT |
