Power storage device

1. A power storage device comprising:

a positive electrode including a positive electrode current collector and a positive electrode active material layer;

a negative electrode including a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer including at least a carbon material with an R value of 1.1 or more; and

an electrolyte solution containing a lithium ion and an ionic liquid composed of an organic cation and an anion,

wherein a melting point of the ionic liquid is −10° C. or lower,

wherein a content percentage of the carbon material with the R value of 1.1 or more is less than 2 wt % in the negative electrode active material layer, and

wherein the R value is a ratio of a peak intensity I 1360 to a peak intensity I 1580 (I 1360 /I 1580 ), the peak intensity I 1360 and the peak intensity I 1580 are observed by Raman spectrometry at a Raman shift of 1360 cm −1 and a Raman shift of 1580 cm −1 , respectively.

2. The power storage device according to claim 1 ,

wherein the melting point of the ionic liquid is −30° C. or lower.

3. The power storage device according to claim 1 ,

wherein a discharge capacity of the power storage device until discharge voltage 2.0 V is greater than 100 mAh/g.

4. The power storage device according to claim 1 ,

wherein the organic cation is a quaternary ammonium cation, a tertiary sulfonium cation, a quaternary phosphonium cation, an imidazolium cation, or a pyridinium cation.

5. The power storage device according to claim 1 ,

wherein a maximum current density of the ionic liquid measured by a cyclic voltammetry method at a scan rate of 0.1 mV/sec is lower than or equal to 2 mA/g at a voltage within a range of 1.0 V to 1.5 V (vs. Li/Li + ).

6. The power storage device according to claim 1 ,

wherein the ionic liquid is represented by a General Formula (G1),

wherein R 1 to R 6 separately represent an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom, and

wherein A − represents a monovalent amide anion, a monovalent methide anion, a fluorosulfonate anion, a perfluoroalkylsulfonate anion, tetrafluoroborate, perfluoroalkylborate, hexafluorophosphate, or perfluoroalkylphosphate.

7. The power storage device according to claim 1 ,

wherein the ionic liquid is represented by a General Formula (G2),

wherein R 7 to R 13 separately represent an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom, and

wherein A − represents a monovalent amide anion, a monovalent methide anion, a fluorosulfonate anion, a perfluoroalkylsulfonate anion, tetrafluoroborate, perfluoroalkylborate, hexafluorophosphate, or perfluoroalkylphosphate.

8. The power storage device according to claim 1 ,

wherein the ionic liquid includes two aliphatic rings and is represented by a General Formula (G3),

wherein n and m are greater than or equal to 1 and less than or equal to 3,

wherein α is greater than or equal to 0 and less than or equal to 4 when n is 1, α is greater than or equal to 0 and less than or equal to 5 when n is 2, and α is greater than or equal to 0 and less than or equal to 6 when n is 3,

wherein β is greater than or equal to 0 and less than or equal to 4 when m is 1, β is greater than or equal to 0 and less than or equal to 5 when m is 2, and β is greater than or equal to 0 and less than or equal to 6 when m is 3,

wherein “α or β is 0” means that at least one of the two aliphatic rings is unsubstituted, and a case where both α and β are 0 is excluded,

wherein X or Y is a substituent which is a straight chain or lateral chain alkyl group having 1 to 4 carbon atoms, a straight chain or lateral chain alkoxy group having 1 to 4 car bon atoms, or a straight chain or lateral chain alkoxyalkyl group having 1 to 4 carbon atoms, and

wherein A − represents a monovalent amide anion, a monovalent methide anion, a perfluoroalkylsulfonate anion, tetrafluoroborate, perfluoroalkylborate, hexafluorophosphate, or perfluoroalkylphosphate.

9. An electric appliance comprising the power storage device according to claim 1 .

10. A power storage device comprising:

a positive electrode including a positive electrode current collector and a positive electrode active material layer;

a negative electrode including a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer including at least a carbon material with an R value of 1.1 or more; and

an electrolyte solution containing a lithium ion and an ionic liquid composed of an organic cation and an anion,

wherein a content percentage of the carbon material with the R value of 1.1 or more is less than 2 wt % in the negative electrode active material layer,

wherein a discharge capacity of the power storage device until discharge voltage 2.0 V is greater than 100 mAh/g, and

wherein the R value is a ratio of a peak intensity I 1360 to a peak intensity I 1580 (I 1360 /I 1580 ), the peak intensity I 1360 and the peak intensity I 1580 are observed by Raman spectrometry at a Raman shift of 1360 cm −1 and a Raman shift of 1580 cm −1 , respectively.

11. The power storage device according to claim 10 ,

wherein the melting point of the ionic liquid is −30° C. or lower.

12. The power storage device according to claim 10 ,

wherein the organic cation is a quaternary ammonium cation, a tertiary sulfonium cation, a quaternary phosphonium cation, an imidazolium cation, or a pyridinium cation.

13. The power storage device according to claim 10 ,

wherein a maximum current density of the ionic liquid measured by a cyclic voltammetry method at a scan rate of 0.1 mV/sec is lower than or equal to 2 mA/g at a voltage within a range of 1.0 V to 1.5 V (vs. Li/Li + ).

14. The power storage device according to claim 10 ,

wherein the ionic liquid is represented by a General Formula (G1),

wherein R 1 to R 6 separately represent an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom, and

wherein A − represents a monovalent amide anion, a monovalent methide anion, a fluorosulfonate anion, a perfluoroalkylsulfonate anion, tetrafluoroborate, perfluoroalkylborate, hexafluorophosphate, or perfluoroalkylphosphate.

15. The power storage device according to claim 10 ,

wherein the ionic liquid is represented by a General Formula (G2),

wherein R 7 to R 13 separately represent an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom, and

wherein A − represents a monovalent amide anion, a monovalent methide anion, a fluorosulfonate anion, a perfluoroalkylsulfonate anion, tetrafluoroborate, perfluoroalkylborate, hexafluorophosphate, or perfluoroalkylphosphate.

16. The power storage device according to claim 10 ,

wherein the ionic liquid includes two aliphatic rings and is represented by a General Formula (G3),

wherein n and m are greater than or equal to 1 and less than or equal to 3,

wherein α is greater than or equal to 0 and less than or equal to 4 when n is 1, α is greater than or equal to 0 and less than or equal to 5 when n is 2, and α is greater than or equal to 0 and less than or equal to 6 when n is 3,

wherein β is greater than or equal to 0 and less than or equal to 4 when m is 1, β is greater than or equal to 0 and less than or equal to 5 when m is 2, and β is greater than or equal to 0 and less than or equal to 6 when m is 3,

wherein “α or β is 0” means that at least one of the two aliphatic rings is unsubstituted, and a case where both α and β are 0 is excluded,

wherein X or Y is a substituent which is a straight chain or lateral chain alkyl group having 1 to 4 carbon atoms, a straight chain or lateral chain alkoxy group having 1 to 4 carbon atoms, or a straight chain or lateral chain alkoxyalkyl group having 1 to 4 carbon atoms, and

wherein A − represents a monovalent amide anion, a monovalent methide anion, a perfluoroalkylsulfonate anion, tetrafluoroborate, perfluoroalkylborate, hexafluorophosphate, or perfluoroalkylphosphate.

17. An electric appliance comprising the power storage device according to claim 10 .