Lithium secondary battery

A lithium secondary battery comprising a nonaqueous electrolytic solution containing a compound which is oxidized at a voltage higher than a charge end voltage of the lithium secondary battery and a compound which inhibits reactions at voltages lower than said charge end voltage wherein said nonaqueous electrolytic solution is composed of a fluorinated solvent represented by the chemical formula (1) and an aromatic compound represented by the chemical formula (2) below.

• Rf1-X-Rf2 (1)
• (where Rf1 denotes an entirely or partly fluorinated C2-10 alkyl group, Rf2 denotes an entirely or partly fluorinated C1-5 alkyl group, and X denotes an ether or ester.)
• 7
• (where R1, R2, R3, and R4 each denotes hydrogen, fluorine, chlorine, bromine, a C1-3 alkyl group or alkoxyl group, a phenyl group, a phenoxy group, an alkyl-substituted phenyl group or phenoxy group, a C1-4 carboxyl group, a benzyl group, or an alkyl-substituted or alkoxyl-substituted silyl group;
• and R5 and R6 each denotes hydrogen, fluorine, chlorine, bromine, or a C1-3 alkyl group.)

A lithium secondary battery having a nonaqueous electrolytic solution characterized in that the lithium secondary battery has a charge capacity of C1 when it (in discharged state) is charged with constant current until a voltage V1 of 1.2V is reached and the lithium secondary battery has a charge capacity of C2 when it is charged further (at a voltage higher than V1) until it cannot be charged any longer, with the ratio (ξ) of C1/C2 being lower than 0.7 and wherein said nonaqueous electrolytic solution is composed of a fluorinated solvent represented by the chemical formula (1) and an aromatic compound represented by the chemical formula (2) below.

• Rf1-X-Rf2 (1)
• (where Rf1 denotes an entirely or partly fluorinated C2-10 alkyl group, Rf2 denotes an entirely or partly fluorinated C1-5 alkyl group, and X denotes an ether or ester.)
• 9
• (where R1, R2, R3, and R4 each denotes hydrogen, fluorine, chlorine, bromine, a C1-3 alkyl group or alkoxyl group, a phenyl group, a phenoxy group, an alkyl-substituted phenyl group or phenoxy group, a C1-4 carboxyl group, a benzyl group, or an alkyl-substituted or alkoxyl-substituted silyl group;
• and R5 and R6 each denotes hydrogen, fluorine, chlorine, bromine, or a C1-3 alkyl group.)

An electrical appliance using a lithium secondary battery as a power source which comprises a means for protecting the lithium secondary batteries from overcharging and overdischarging being free from temperature and pressure detection of the batteries, a means for detecting voltages or current of the batteries and a means for controlling to turn on or off the batteries said lithium secondary battery comprising a nonaqueous electrolytic solution containing a compound which is oxidized at a voltage higher than a charge end voltage of the lithium secondary battery and a compound which inhibits reactions at voltages lower than said charge end voltage wherein said nonaqueous electrolytic solution is composed of a fluorinated solvent represented by the chemical formula (1) and an aromatic compound represented by the chemical formula (2) below.

• Rf1-X-Rf2 (1)
• (where Rf1 denotes an entirely or partly fluorinated C2-10 alkyl group, Rf2 denotes an entirely or partly fluorinated C1-5 alkyl group, and X denotes an ether or ester.)
• 15
• (where R1, R2, R3, and R4 each denotes hydrogen, fluorine, chlorine, bromine, a C1-3 alkyl group or alkoxyl group, a phenyl group, a phenoxy group, an alkyl-substituted phenyl group or phenoxy group, a C1-4 carboxyl group, a benzyl group, or an alkyl-substituted or alkoxyl-substituted silyl group;
• and R5 and R6 each denotes hydrogen, fluorine, chlorine, bromine, or a C1-3 alkyl group.)

An electrical appliance using a lithium secondary battery as a power source which comprises a means for protecting the lithium secondary batteries from overcharging and overdischarging being free from temperature and pressure detection of the batteries, a means for detecting voltages or current of the batteries and a means for controlling to turn on or off the batteries said lithium secondary battery comprising a nonaqueous electrolytic solution characterized in that the lithium secondary battery has a charge capacity of C1 when it (in discharged state) is charged with constant current until a voltage V1 of 1.2V is reached and the lithium secondary battery has a charge capacity of C2 when it is charged further (at a voltage higher than V1) until it cannot be charged any longer, with the ratio (ξ) of C1/C2 being lower than 0.7 and wherein said nonaqueous electrolytic solution is composed of a fluorinated solvent represented by the chemical formula (1) and an aromatic compound represented by the chemical formula (2) below.

• Rf1-X-Rf2 (1)
• (where Rf1 denotes an entirely or partly fluorinated C2-10 alkyl group, Rf2 denotes an entirely or partly fluorinated C1-5 alkyl group, and X denotes an ether or ester.)
• 17
• (where R1, R2, R3, and R4 each denotes hydrogen, fluorine, chlorine, bromine, a C1-3 alkyl group or alkoxyl group, a phenyl group, a phenoxy group, an alkyl-substituted phenyl group or phenoxy group, a C1-4 carboxyl group, a benzyl group, or an alkyl-substituted or alkoxyl-substituted silyl group;
• and R5 and R6 each denotes hydrogen, fluorine, chlorine, bromine, or a C1-3 alkyl group.)

A method of fabricating a lithium secondary battery comprising the steps of:

• providing an anode;
• providing a cathode;
• providing a separator;
• and
• providing a nonaqueous electrolytic solution containing a compound which is oxidized at a voltage higher than a charge end voltage of the lithium secondary battery and a compound which inhibits reactions at voltages lower than said charge end voltage.

A method of fabricating a lithium secondary battery comprising the steps of:

• providing an anode;
• providing a cathode;
• providing a separator;
• and
• providing a nonaqueous electrolytic solution characterized in that the lithium secondary battery has a charge capacity of C1 when it (in discharged state) is charged with constant current until a voltage V1 of 1.2V is reached and the lithium secondary battery has a charge capacity of C2 when it is charged further (at a voltage higher than V1) until it cannot be charged any longer, with the ratio (ξ) of C1/C2 being lower than 0.7.

A method of fabricating a lithium secondary battery comprising the steps of:

• providing an anode;
• providing a cathode;
• providing a separator;
• and
• providing a nonaqueous electrolytic solution containing a compound which is oxidized at a voltage higher than a charge end voltage of the lithium secondary battery and a compound which inhibits reactions at voltages lower than said charge end voltage wherein said nonaqueous electrolytic solution is composed of a fluorinated solvent represented by the chemical formula (1) and an aromatic compound represented by the chemical formula (2) below.
• Rf1-X-Rf2 (1)
• (where Rf1 denotes an entirely or partly fluorinated C2-10 alkyl group, Rf2 denotes an entirely or partly fluorinated C1-5 alkyl group, and X denotes an ether or ester.)
• 23
• (where R1, R2, R3, and R4 each denotes hydrogen, fluorine, chlorine, bromine, a C1-3 alkyl group or alkoxyl group, a phenyl group, a phenoxy group, an alkyl-substituted phenyl group or phenoxy group, a C1-4 carboxyl group, a benzyl group, or an alkyl-substituted or alkoxy-substituted silyl group;
• and R5 and R6 each denotes hydrogen, fluorine, chlorine, bromine, or a C1-3 alkyl group.)

A method of fabricating a lithium secondary battery comprising the steps of:

• providing an anode;
• providing a cathode;
• providing a separator;
• and
• providing a nonaqueous electrolytic solution characterized in that the lithium secondary battery has a charge capacity of C1 when it (in discharged state) is charged with constant current until a voltage V1 of 1.2V is reached and the lithium secondary battery has a charge capacity of C2 when it is charged further (at a voltage higher than V1) until it cannot be charged any longer, with the ratio (ξ) of C1/C2 being lower than 0.7 and wherein said nonaqueous electrolytic solution is composed of a fluorinated solvent represented by the chemical formula (1) and an aromatic compound represented by the chemical formula (2) below.
• Rf1-X-Rf2 (1)
• (where Rf1 denotes an entirely or partly fluorinated C2-10 alkyl group, Rf2 denotes an entirely or partly fluorinated C1-5 alkyl group, and X denotes an ether or ester.)
• 25
• (where R1, R2, R3, and R4 each denotes hydrogen, fluorine, chlorine, bromine, a C1-3 alkyl group or alkoxyl group, a phenyl group, a phenoxy group, an alkyl-substituted phenyl group or phenoxy group, a C1-4 carboxyl group, a benzyl group, or an alkyl-substituted or alkoxy-substituted silyl group;
• and R5 and R6 each denotes hydrogen, fluorine, chlorine, bromine, or a C1-3 alkyl group.)