{
  "$type": "site.standard.document",
  "description": "A purpose of one embodiment of the present invention is to provide a lithium ion secondary battery which has improved cycle characteristics and comprises a Si material in the negative electrode. The lithium ion secondary battery according to the present invention comprises a negative electrode…",
  "path": "/patents/1290872",
  "publishedAt": "2021-05-20T00:00:00.000Z",
  "site": "at://did:plc:oql6ds5vnff4ugar6rruliwd/site.standard.publication/3mn3ohu7oxx5w",
  "tags": [
    "H01M4/386",
    "NEC CORPORATION"
  ],
  "textContent": "A purpose of one embodiment of the present invention is to provide a lithium ion secondary battery which has improved cycle characteristics and comprises a Si material in the negative electrode. The lithium ion secondary battery according to the present invention comprises a negative electrode comprising a negative electrode active material, a positive electrode comprising a positive electrode active material and an electrolyte solution, wherein the negative electrode active material comprises a Si material, and a ratio (Ia/Ib) of a peak intensity (Ia) at 290 eV to a peak intensity (Ib) at 285 eV is 0.7 or more in a C1s spectrum obtained by surface analysis of the negative electrode by X-ray photoelectron spectroscopy.",
  "title": "LITHIUM ION SECONDARY BATTERY"
}