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US 6,746,804 B2Granted
Nonaqueous organic electrolytes for low temperature discharge of rechargeable electrochemical cells
AssigneeWilson Greatbatch Technologies, Inc.
InventorsHong Gan, Esther S. Takeuchi, Robert Rubino
Life of this patent
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Abstract
An alkali metal secondary electrochemical cell, and preferably a lithium ion cell, activated with an equilibrated quaternary solvent system, is described. The solvent system comprises a mixture of dialkyl carbonates and cyclic carbonates, and preferably a quaternary mixture of dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate and ethylene carbonate with dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate in an equilibrated molar mixture. Lithium ion cells activated with this electrolyte have good room temperature cycling characteristics and excellent low temperature discharge behavior.
Claims29
An electrochemical cell, which comprises:
- a) a negative electrode of a negative electrode active material which intercalates and deintercalates with an alkali metal;
- b) a positive electrode comprising an alkali metal intercalated electrode active material which intercalates and deintercalates with the alkali metal;
- c) an electrolyte solution activating the negative and positive electrodes, the electrolyte (including an alkali metal salt dissolved in a mixture comprising dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein from a beginning molar mixture of DMC and DEC solvents in a ratio of a% of DMC and 1−a% of DEC and with the negative electrode deintercalated with the alkali metal and the positive electrode intercalated with the alkali metal before being activated with the electrolyte, the DMC, EMC and DEC are in an essentially equilibrated mixture, by molar percent, as determined by the formula:
- [EMC]2/([DMC][DEC]) equal to about 4.0±0.15 and wherein in the equilibrated molar mixture, the rate at which ethyl methyl carbonate is producible from dimethyl carbonate and diethyl carbonate by an ester exchange reaction is essentially equal to the rate at which ethyl methyl carbonate is disproportionable into dimethyl carbonate and diethyl carbonate such that the equilibrated molar mixture of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate essentially does not change as the cell discharges.
1 more element
An electrochemical cell, which comprises:
- a) a negative electrode of a negative electrode active material which intercalates and deintercalates with lithium;
- b) a positive electrode comprising a lithiated electrode active material which intercalates and deintercalates with lithium;
- and
- c) an electrolyte solution activating the negative and positive electrodes, the electrolyte including an alkali metal salt dissolved in a mixture comprising dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein with the negative electrode deintercalated with lithium and the positive electrode intercalated with lithium before being activated with the electrolyte, the dimethyl carbonate, the ethyl methyl carbonate and the diethyl carbonate are in an essentially equilibrated molar mixture as determined by the graph of:
- d) wherein from a beginning molar mixture of DMC and DEC solvents in a ratio of a% of DMC and 1−a% of DEC entered on the abscissa of the graph and then from the a(DMC)% point moving up the y-intersect to determine the equilibrated molar mixture by intersecting curve 10 to get the equilibrated molar percentage of DMC, intersecting curve 12 to get the equilibrated molar percentage of ENG and intersecting curve 14 to get the equilibrated molar percentage of DEC;
- and
- e) wherein in the equilibrated molar mixture, the rate at which ethyl methyl carbonate is producible from dimethyl carbonate and diethyl carbonate by an ester exchange reaction is essentially equal to the rate at which ethyl methyl carbonate is disproportionable into dimethyl carbonate and diethyl carbonate such that the equilibrated molar mixture of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate essentially does not change as the cell discharges.
4 more elements
An electrochemical cell, which comprises:
- a) a negative electrode of a carbonaceous material which intercalates and deintercalates with lithium;
- b) a positive electrode comprising lithium cobalt oxide which intercalates and deintercalates with lithium;
- and
- c) an electrolyte solution activating the negative electrode and the positive electrode, the electrolyte including a lithium salt dissolved in a mixture comprising dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein with the negative electrode deintercalated with lithium and the positive electrode intercalated with lithium before being activated with the electrolyte, the dimethyl carbonate, the ethyl methyl carbonate and the diethyl carbonate are in an essentially equilibrated molar mixture as determined by the graph of:
- wherein from a beginning molar mixture of DMC and DEC solvents in a ratio of a% of DMC and 1−a% of DEC entered on the abscissa of the graph and then from the a(DMC)% point moving up the y-intersect to determine the equilibrated molar mixture by intersecting curve 10 to get the equilibrated molar percentage of DMC, intersecting curve 12 to get the equilibrated molar percentage of EMC and intersecting curve 14 to get the equilibrated molar percentage of DEC;
- and
- d) wherein in the equilibrated molar mixture, the rate at which ethyl methyl carbonate is producible from dimethyl carbonate and diethyl carbonate by an ester exchange reaction is essentially equal to the rate at which ethyl methyl carbonate is disproportionable into dimethyl carbonate and diethyl carbonate such that the equilibrated molar mixture of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate essentially does not change as the cell discharges.
4 more elements
A method for converting chemical energy to electrical energy from an electrochemical cell, comprising the steps of:
- a) providing a negative electrode comprising a carbonaceous negative electrode active material which intercalates and deintercalates with an alkali metal;
- b) providing a positive electrode comprising an alkali metal intercalated electrode active material which intercalates and deintercalates with the alkali metal;
- c) providing an electrolyte including an alkali metal salt dissolved in a mixture comprising dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC);
- d) assembling the negative electrode deintercalated with the alkali metal and the positive electrode intercalated with the alkali metal before activating the negative electrode and the positive electrode with the electrolyte, the electrolyte having from a beginning molar mixture of DMC and DEC solvents in a ratio of a% of DMC and 1−a% of DEC, the DMC, EMC and DEC in an essentially equilibrated mixture, by molar percent, as determined by the formula:
- [EMC]2/([DMC][DEC]) equal to about 4.0±0.15;
- and
- e) re-charging the cell a first time with the negative electrode intercalating the alkali metal and the positive electrode deintercalating the alkali metal, wherein in the equilibrated molar mixture, the rate at which ethyl methyl carbonate is producible from dimethyl carbonate and diethyl C carbonate by an ester exchange reaction is essentially equal to the rate at which ethyl methyl carbonate is disproportionable into dimethyl carbonate and diethyl carbonate such that the equilibrated molar mixture of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate essentially does not change as the cell discharges.
4 more elements
A method for providing an electrochemical cell, comprising the steps of:
- a) providing a negative electrode comprising a negative electrode active material which intercalates and deintercalates with lithium;
- b) providing a positive electrode comprising a lithiated electrode active material which intercalates and deintercalates with lithium;
- and
- c) providing an electrolyte including an alkali metal salt dissolved in a mixture comprising dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC);
- d) assembling the cell having the negative electrode deintercalated with the lithium and the positive electrode intercalated with lithium before activating the negative electrode and the positive electrode with the electrolyte having the dimethyl carbonate, the ethyl methyl carbonate and the diethyl carbonate in an essentially equilibrated molar mixture as determined by the graph of:
- wherein from a beginning molar mixture of DMC and DEC solvents in a ratio of a% of DMC and 1−a% of DEC entered on the abscissa of the graph and then from the a(DMC)% point moving up the y-intersect to determine the equilibrated molar mixture by intersecting curve 10 to get the equilibrated molar percentage of DMC, intersecting curve 12 to get the equilibrated molar percentage of EMC and intersecting curve 14 to get the equilibrated molar percentage of DEC;
- and
- e) re-charging the cell a first time with the negative electrode intercalating the alkali metal and the positive electrode deintercalating the alkali metal such that the rate at which EMC is producible from DMC and DEC by an ester exchange reaction is essentially equal to the rate at which EMC is disproportionable into DMC and DEC such that the equilibrated molar mixture of DMC, DEC and ENG essentially does not change upon further charging and discharging of the cell.
5 more elements
An electrolyte for activating an electrochemical cell, the electrolyte comprising:
- a) dimethyl carbonate (DMC);
- b) ethyl methyl carbonate (EMC);
- and
- c) diethyl carbonate (DEC), wherein the DMC, EMC and DEC are in an essentially equilibrated molar
- mixture as determined by the graph of:
- d) wherein from a beginning molar mixture of DMC and DEC solvents in a ratio of a% of DMC and 1−a% of DEC entered on the abscissa of the graph and then from the a(DMC)% point moving up the y-intersect to determine the equilibrated molar mixture by intersecting curve 10 to get the equilibrated molar percentage of DMC, intersecting curve 12 to get the equilibrated molar percentage of EMC and intersecting curve 14 to get the equilibrated molar percentage of DEC.
3 more elements
A method for providing an electrolyte, comprising the steps of:
- a) providing a beginning molar mixture of dimethyl carbonate (DMC) and diethyl carbonate (DEC);
- and
- b) determining an essentially equilibrated molar mixture of DMC, DEC and ethyl methyl carbonate (EMC) by the graph of:
- wherein from a beginning molar mixture of DMC and DEC solvents in a ratio of a% of DMC and 1−a% of DEC entered on the abscissa of the graph and then from the a(DMC)% point moving up the y-intersect to determine the equilibrated molar mixture by intersecting curve 10 to get the equilibrated molar percentage of DMC, intersecting curve 12 to get the equilibrated molar percentage of EMC and intersecting curve 14 to get the equilibrated molar percentage of DEC.
1 more element
An electrochemical cell, which comprises:
- a) a negative electrode of a negative electrode active material which intercalates and deintercalates with lithium;
- b) a positive electrode comprising a lithiated electrode active material which intercalates and deintercalates with lithium;
- and
- c) an electrolyte solution activating the negative and positive electrodes, the electrolyte including an alkali metal salt dissolved in a mixture comprising dimethyl carbonate (DMC), ethyl methyl carbonate (ENG) and diethyl carbonate (DEC), wherein with the negative electrode deintercalated with lithium and the positive electrode intercalated with lithium before being activated with the electrolyte, the dimethyl carbonate, the ethyl methyl carbonate and the diethyl carbonate are in an essentially equilibrated molar mixture as determined by the graph of:
- d) wherein the equilibrated molar mixture is determined by intersecting curves 10, 12 and 14 with a line projecting from the abscissa of the graph and aligned parallel to the ordinate, and wherein the intersection of the line with curve 10 is the equilibrated molar percentage of DMC, the intersection of the line with curve 12 is the equilibrated molar percentage of EMC and the intersection of the line with curve 14 is the equilibrated molar percentage of DEC;
- and
- e) wherein in the equilibrated molar mixture, the rate at which ethyl methyl carbonate is producible from dimethyl carbonate and diethyl carbonate by an ester exchange reaction is essentially equal to the rate at which ethyl methyl carbonate is disproportionable into dimethyl carbonate and diethyl carbonate such that the equilibrated molar mixture of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate essentially does not change as the cell discharges.
4 more elements
A method for providing an electrochemical cell, comprising the steps of:
- a) providing a negative electrode comprising a negative electrode active material which intercalates and deintercalates with lithium;
- b) providing a positive electrode comprising a lithiated electrode active material which intercalates and deintercalates with lithium;
- and
- c) providing an electrolyte including an alkali metal salt dissolved in a mixture comprising dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC);
- d) assembling the cell having the negative electrode deintercalated with the lithium and the positive electrode intercalated with lithium before activating the negative electrode and the positive electrode with the electrolyte having the dimethyl carbonate, the ethyl methyl carbonate and the diethyl carbonate in an essentially equilibrated molar mixture as determined by the graph of:
- wherein the equilibrated molar mixture is determined by intersecting curves 10, 12 and 14 with a line projecting from the abscissa of the graph and aligned parallel to the ordinate, and wherein the intersection of the line with curve 10 is the equilibrated molar percentage of DMC, the intersection of the line with curve 12 is the equilibrated molar percentage of EMC and the intersection of the line with curve 14 is the equilibrated molar percentage of DEC;
- and
- f) re-charging the cell a first time with the negative electrode intercalating the alkali metal and the positive electrode deintercalating the alkali metal such that the rate at which EMC is producible from DMC and DEC by an ester exchange reaction is essentially equal to the rate at which EMC is disproportionable into DMC and DEC such that the equilibrated molar mixture of DMC, DEC and EMC essentially does not change upon further charging and discharging of the cell.
5 more elements
An electrolyte for activating an electrochemical cell, the electrolyte comprising:
- a) dimethyl carbonate (DMC);
- b) ethyl methyl carbonate (EMC);
- and
- c) diethyl carbonate (DEC), wherein the DMC, EMC and DEC are in an essentially equilibrated molar mixture as determined by the graph of:
- d) wherein the equilibrated molar mixture is determined by intersecting curves 10, 12 and 12 with a line projecting from the abscissa of the graph and aligned parallel to the ordinate, and wherein the intersection of the line with curve 10 is the equilibrated molar percentage of DMC, the intersection of the line with curve 12 is the equilibrated molar percentage of ENG and the intersection of the line with curve 14 is the equilibrated molar percentage of DEC.
2 more elements
A method for providing an electrolyte, comprising the steps of:
- a) determining an essentially equilibrated molar mixture of DMC, DEC and ethyl methyl carbonate (EMC) by the graph of:
- wherein the equilibrated molar mixture is determined by intersecting curves 10, 12 and 14 with a line projecting from the abscissa of the graph and aligned parallel to the ordinate, and wherein the intersection of the line with curve 10 is the equilibrated molar percentage of DMC, the intersection of the line with curve 12 is the equilibrated molar percentage of EMC and the intersection of the line with curve 14 is the equilibrated molar percentage of DEC.
Dependencies are inferred from the claim text.