SECONDARY BATTERY-USE ACTIVE MATERIAL, SECONDARY BATTERY, AND ELECTRONIC APPARATUS
A secondary battery capable of obtaining superior battery characteristics is provided. The secondary battery of the present technology includes a cathode, an anode including an active material, and an electrolytic solution. The active material includes a core section and covering section, the core section being capable of inserting and extracting lithium ions, and the covering section being provided in at least part of a surface of the core section and being a low-crystalline or a noncrystalline. The core section includes Si and O as constituent elements, and an atom ratio x (O/Si) of O with respect to Si satisfies O≦x<0.5. The covering section includes Si and O as constituent elements, and an atom ratio y (O/Si) of O with respect to Si satisfies 0.5≦y≦1.8. The covering section has voids, and a carbon-containing material is provided in at least part of the voids.
1 . A secondary battery comprising:
a cathode;
an anode including an active material; and
an electrolytic solution, wherein
the active material includes a core section and a covering section, the core section being capable of inserting and extracting lithium ions, and the covering section being provided in at least part of a surface of the core section and being a low-crystalline or a noncrystalline,
the core section includes Si and O as constituent elements, and an atom ratio x (O/Si) of O with respect to Si satisfies 0≦x<0.5,
the covering section includes Si and O as constituent elements, and an atom ratio y (O/Si) of O with respect to Si satisfies 0.5≦y≦1.8, and
the covering section has voids, and a carbon-containing material is provided in at least part of the voids.
2 . The secondary battery according to claim 1 , wherein a ratio IG/ID between a G band peak intensity IG and a D band peak intensity ID of the carbon-containing material measured by Raman spectrum method is from 0.3 to 3 both inclusive.
3 . The secondary battery according to claim 1 , wherein a void diameter of a maximum peak in a void distribution of the covering section that is measured by a nitrogen absorption method and a mercury intrusion method is equal to or less than 500 nanometers.
4 . The secondary battery according to claim 1 , wherein the covering section has a multilayer structure.
5 . The secondary battery according to claim 1 , wherein
a carbon-containing layer is provided in at least part of a surface of the active material,
an average thickness of the carbon-containing layer is equal to or less than 500 nanometers, and
an average coverage ratio of the carbon-containing layer with respect to the active material is equal to or larger than 30 percents.
6 . The secondary battery according to claim 1 , wherein
a median diameter (D50) of the core section is from 0.1 micrometers to 20 micrometers both inclusive,
an average thickness of the covering section is from 1 nanometer to 3000 nanometers both inclusive, and
an average coverage ratio of the covering section with respect to the core section is equal to or larger than 30 percents.
7 . The secondary battery according to claim 1 , wherein crystallinity of the covering section is lower than crystallinity of the core section.
8 . The secondary battery according to claim 1 , wherein the covering section has a low-crystalline state including a noncrystalline region and a crystal region (crystal grains), and the crystal grains are scattered in the noncrystalline region.
9 . The secondary battery according to claim 8 , wherein
an average area occupancy of the crystal grains attributable to a (111) plane and a (220) plane of Si is equal to or less than 35 percents, and an average grain diameter of the crystal grains is equal to or less than 50 nanometers,
when the covering section is divided into two equal parts in a thickness direction, an average area occupancy and an average grain diameter in an inner section of the crystal grains attributable to the (111) plane and the (220) plane of Si are the same as or larger than an average area occupancy and an average grain diameter in an outer section of the crystal grains attributable to the (111) plane and the (220) plane of Si.
10 . The secondary battery according to claim 1 , wherein the covering section is noncrystalline.
11 . The secondary battery according to claim 1 , wherein
the core section includes Fe as a constituent element, and
a ratio (Fe/(Si+O)) of Fe with respect to Si and O is from 0.01 weight percent to 7.5 weight percent both inclusive.
12 . The secondary battery according to claim 1 , wherein
the core section includes at least one of Fe, Al, Ca, Mn, Cr, Mg, and Ni as constituent elements, and
the covering section includes at least one of Fe, Al, and Ca as constituent elements.
13 . The secondary battery according to claim 1 , wherein
the anode has an active material layer on a current collector, and the active material layer includes the active material, and
the current collector includes C and S as constituent elements, and a content of C and S is equal to or less than 100 parts per million.
14 . A secondary battery-use active material comprising:
a core section capable of inserting and extracting lithium ions; and
a covering section provided in at least part of a surface of the core section and being a low-crystalline or a noncrystalline, wherein
the core section includes Si and O as constituent elements, and an atom ratio x (O/Si) of O with respect to Si satisfies 0≦x<0.5,
the covering section includes Si and O as constituent elements, and an atom ratio y (O/Si) of O with respect to Si satisfies 0.5≦y≦1.8, and
the covering section has voids, and a carbon-containing material is provided in at least part of the voids.
15 . An electronic apparatus comprising a secondary battery as an electric power supply source, wherein
the secondary battery includes a cathode, an anode including an active material, and an electrolytic solution,
the active material includes a core section and a covering section, the core section being capable of inserting and extracting lithium ions, and the covering section being provided in at least part of a surface of the core section and being a low-crystalline or a noncrystalline,
the core section includes Si and O as constituent elements, and an atom ratio x (O/Si) of O with respect to Si satisfies 0≦x<0.5,
the covering section includes Si and O as constituent elements, and an atom ratio y (O/Si) of O with respect to Si satisfies 0.5≦y≦1.8, and
the covering section has voids, and a carbon-containing material is provided in at least part of the voids.