Iron, fluorine, sulfur compounds for battery cell cathodes
Provided herein are energy storage device cathodes with high capacity electrochemically active material including compounds that include iron, fluorine, sulfur, and optionally oxygen. Batteries with active materials including a compound of the formula FeF a S b O c exhibit high capacity, high specific energy, high average discharge voltage, and low hysteresis, even when discharged at high rates. Iron, fluorine, and sulfur-containing compounds may be ionically and electronically conductive.
1. A cathode for a battery, comprising:
(i) particles of FeF a S b O c ; and
(ii) particles of a combination of iron metal, and lithium fluoride, lithium oxide, and/or lithium sulfide,
wherein the atomic ratio of the iron to fluorine, sulfur, and oxygen in (i) and (ii) is 1:a:b:c, and
wherein 1≦a≦9, 0<b≦3, and 0≦c≦2;
wherein the particles have a median characteristic dimension of between about 10 nm and 10000 nm; wherein the particles are approximately spherical.
2. The cathode of claim 1 , wherein 1≦a≦5, 0<b≦2, and 0≦c≦1.5.
3. The cathode of claim 1 , wherein the compound of the formula FeF a S b O c has a discharge capacity of at least about 400 mAh/g when discharged from 4.5 volts versus a lithium metal electrode to 1 volt versus the lithium metal electrode, and when discharged at a rate of at least 100 mA/g and at a temperature of 40-120° C.
4. The cathode of claim 1 , wherein the compound of the formula FeF a S b O c has an average discharge voltage of at least about 2 volts when discharged from 4.5 volts versus a lithium metal electrode to 1 volt versus the lithium metal electrode, and when discharged at a rate of at least 100 mA/g and at a temperature of 40-120° C.
5. The cathode of claim 1 , wherein the compound of the formula FeF a S b O c has an average hysteresis of at most about 2 volts when discharged from 4.5 volts versus a lithium metal electrode to 1 volt versus the lithium metal electrode, and when discharged at a rate of at least 100 mA/g and at a temperature of 40-120° C.
6. The cathode of claim 1 , wherein the electrochemically active material or combination of electrochemically active materials has a specific capacity of at least about 300 mAh/g above a voltage of at least about 2.5 volts relative to lithium, when charged to a voltage of 3.9 volts relative to lithium and discharged at a rate of at least 100 mA/g and at a temperature of 40-120° C.
7. The cathode of claim 1 , wherein the electrochemically active material or combination of electrochemically active materials has a specific capacity of at least about 500 mAh/g above a voltage of at least about 1 volt relative to lithium, when charged to a voltage of 3.9 volts relative to lithium and discharged at a rate of at least 100 mA/g and at a temperature of 40-120° C.
8. The cathode of claim 1 , wherein the electrochemically active material or combination of electrochemically active materials has a specific energy of at least about 600 mWh/g above a voltage of at least about 2.9 volts relative to lithium, when charged to a voltage of 3.9 volts relative to lithium and discharged at a rate of at least 100 mA/g and at a temperature of 40-120° C.
9. The cathode of claim 1 , wherein the electrochemically active material or combination of electrochemically active materials has a specific energy of at least about 1000 mWh/g above a voltage of at least about 1 volt relative to lithium, when charged to a voltage of 3.9 volts relative to lithium and discharged at a rate of at least 100 mA/g and at a temperature of 40-120° C.
10. The cathode of claim 1 , further comprising a current collector in electrical communication with the material or combination of materials.
11. The cathode of claim 10 , wherein the current collector comprises copper, a copper alloy, nickel, steel, stainless steel, aluminum, carbon-coated aluminum or an aluminum alloy.
12. An energy storage device comprising:
an anode;
an electrolyte; and
a cathode of claim 1 .
13. The device of claim 12 , wherein the device has a specific energy of at least about 200 Wh/kg when measured at 60° C. and a current of at least 100 mA/g of active cathode material.
14. The device of claim 12 , wherein the anode, electrolyte, and cathode, together comprise a stack of about 1 μm to 500 μm thickness.