ELECTROLYTE OF ENERGY STORAGE DEVICE, ENERGY STORAGE DEVICE, AND MANUFACTURING METHOD OF ENERGY STORAGE DEVICE
An electrolyte of an energy storage device includes a non-aqueous solvent, an electrolyte salt including LiPF 6 , and at least two compounds selected from among a phosphite ester compound represented by a formula 1, a compound configured to form lithium and a complex and including a formation constant equal to or greater than 10 2 , difluorophosphate represented by a formula 2, and a phosphate ester compound represented by a formula 3, the at least two compounds including at least the phosphite ester compound represented by the formula 1: where each of R11, R12, and R13 is independently one of a monovalent hydrocarbon group and a monovalent fluorinated hydrocarbon group, where M21 + is one of lithium ion (Li + ) and sodium ion (Na + ), where each of R31, R32, and R33 is independently one of a monovalent hydrocarbon group and a monovalent fluorinated hydrocarbon group.
1 . An electrolyte of an energy storage device, the electrolyte comprising:
a non-aqueous solvent;
an electrolyte salt including LiPF 6 ; and
at least two compounds selected from among a phosphite ester compound represented by a formula 1, a compound configured to form lithium and a complex and including a formation constant equal to or greater than 10 2 for forming a lithium complex, difluorophosphate represented by a formula 2, and a phosphate ester compound represented by a formula 3, the at least two compounds including at least the phosphite ester compound represented by the formula 1:
where each of R11, R12, and R13 is independently one of a monovalent hydrocarbon group and a monovalent fluorinated hydrocarbon group,
where M21 + is one of lithium ion (Li + ) and sodium ion (Na + ),
where each of R31, R32, and R33 is independently one of a monovalent hydrocarbon group and a monovalent fluorinated hydrocarbon group.
2 . The electrolyte according to claim 1 , wherein a content of the phosphite ester compound is in a range from 0.1 wt % to 20 wt %, inclusive, relative to a content of the non-aqueous solvent and the electrolyte salt in the electrolyte.
3 . The electrolyte according to claim 1 , wherein a content of the compound configured to form lithium and a complex and including a formation constant equal to or greater than 10 2 is in a range from 1 wt % to 5 wt %, inclusive, relative to a content of the non-aqueous solvent and the electrolyte salt in the electrolyte.
4 . The electrolyte according to claim 1 , wherein a content of the difluorophosphate is equal to or greater than 0.1 wt % relative to a content of the non-aqueous solvent and the electrolyte salt in the electrolyte.
5 . The electrolyte according to claim 1 , wherein a content of the phosphate ester compound is in a range from 1 wt % to 5 wt %, inclusive, relative to a content of the non-aqueous solvent and the electrolyte salt in the electrolyte.
6 . An energy storage device comprising:
a positive electrode including a carbon material;
a negative electrode including a negative electrode material that is configured to adsorb and desorb lithium ion; and
an electrolyte,
the electrolyte including:
a non-aqueous solvent;
an electrolyte salt including LiPF 6 ; and
at least one compound selected from among a phosphite ester compound represented by a formula 4, a compound configured to form lithium and a complex and including a formation constant equal to or greater than 10 2 for forming a lithium complex, difluorophosphate represented by a formula 5, and a phosphate ester compound represented by a formula 6, the at least two compounds including at least the phosphite ester compound represented by the formula 4,
the carbon material at which functional groups exist, the functional groups at least including a lactone group arranged at a surface of the carbon material,
an amount of the phosphite ester compound contained in the electrolyte and represented by the formula 4 and a sum of amounts of a phenolic hydroxyl group and a carboxyl group existing at the carbon material and included in the functional groups satisfying a relational expression 1,
[An amount (mol) of the phosphite ester compound contained in the electrolyte and represented by the formula 4]= a 1×[a sum of amounts (mol) of a phenolic hydroxyl group and a carboxyl group existing at the carbon material and included in the functional groups] (Relational expression 1)
where a coefficient a1 is equal to or greater than 1.67,
where each of R41, R42, and R43 is independently one of a monovalent hydrocarbon group and a monovalent fluorinated hydrocarbon group,
where M51 + is one of lithium ion (Li + ) and sodium ion (Na + ),
where each of R61, R62, and R63 is independently one of a monovalent hydrocarbon group and a monovalent fluorinated hydrocarbon group.
7 . The energy storage device according to claim 6 , wherein a mole percentage of an amount of the lactone group relative to a total amount of the functional groups is equal to or greater than 8 mol %.
8 . The energy storage device according to claim 6 , wherein the energy storage device is a lithium ion capacitor.
9 . The energy storage device according to claim 6 , wherein a content of the phosphite ester compound is in a range from 0.1 wt % to 20 wt %, inclusive, relative to a content of the non-aqueous solvent and the electrolyte salt in the electrolyte.
10 . The energy storage device according to claim 6 , wherein a content of the compound configured to form lithium and a complex and including a formation constant equal to or greater than 10 2 is in a range from 1 wt % to 5 wt %, inclusive, relative to a content of the non-aqueous solvent and the electrolyte salt in the electrolyte.
11 . The energy storage device according to claim 6 , wherein a content of the difluorophosphate is equal to or greater than 0.1 wt % relative to a content of the non-aqueous solvent and the electrolyte salt in the electrolyte.
12 . The energy storage device according to claim 6 , wherein a content of the phosphate ester compound is in a range from 1 wt % to 5 wt %, inclusive, relative to a content of the non-aqueous solvent and the electrolyte salt in the electrolyte.
13 . A method of manufacturing an energy storage device, comprising:
assembling an energy storage device including a positive electrode, a negative electrode including a negative electrode material that is configured to adsorb and desorb lithium ion, and an electrolyte, the electrolyte including a non-aqueous solvent, an electrolyte salt including LiPF 6 , and at least one compound selected from among a phosphite ester compound represented by a formula 7, a compound configured to form lithium and a complex and including a formation constant equal to or greater than 10 2 for forming a lithium complex, difluorophosphate represented by a formula 8, and a phosphate ester compound represented by a formula 9, the at least two compounds including at least the phosphite ester compound represented by the formula 7; and
performing an aging process where the assembled energy storage device is applied with a voltage and is left for a predetermined time period depending on a magnitude and a state of the applied voltage under temperature environment ranging from 80° C. to 120° C., inclusive,
where each of R71, R72, and R73 is independently one of a monovalent hydrocarbon group and a monovalent fluorinated hydrocarbon group,
where M81 + is one of lithium ion (Li + ) and sodium ion (Na + ),
where each of R91, R92, and R93 is independently one of a monovalent hydrocarbon group and a monovalent fluorinated hydrocarbon group.
14 . The manufacturing method according to claim 13 , further comprising:
applying a voltage to the assembled energy storage device while the assembled energy storage device is being left in a manner that charging and discharging are repeatedly performed between a first SOC range where a state of charge of the assembled energy storage device is specified from 50% to 100%, inclusive, and a second SOC range where the state of charge of the assembled energy storage device is specified from 0% to 20%, inclusive.
15 . The manufacturing method according to claim 14 , wherein the predetermined time of the aging process is in a range from 5 hours to 17 hours, inclusive.
16 . The manufacturing method according to claim 13 , further comprising:
applying a voltage to the assembled energy storage device while the assembled energy storage device is being left in a manner that the applied voltage is retained at a voltage level selected from among voltages corresponding to a first SOC range where a state of charge of the assembled energy storage device is specified from 50% to 100%, inclusive.
17 . The manufacturing method according to claim 16 , wherein the predetermined time of the aging process is in a range from 50 hours to 153 hours, inclusive.