Battery cell engineering and design to reach high energy
Improved high energy capacity designs for lithium ion batteries are described that take advantage of the properties of high specific capacity anode active compositions and high specific capacity cathode active compositions. In particular, specific electrode designs provide for achieving very high energy densities. Furthermore, the complex behavior of the active materials is used advantageously in a radical electrode balancing design that significantly reduced wasted electrode capacity in either electrode when cycling under realistic conditions of moderate to high discharge rates and/or over a reduced depth of discharge.
1. A lithium ion secondary battery comprising a positive electrode, a negative electrode, a separator between the positive electrode comprising a lithium metal oxide and the negative electrode comprising a lithium intercalation/alloying composition, a polymer binder, and distinct electrically conductive carbon particles blended into the binder with the lithium intercalation/alloying composition, supplemental lithium in an amount with an oxidation capacity corresponding to 20% to 110% of the irreversible capacity loss of the negative electrode and an electrolyte comprising lithium ions,
wherein the negative electrode lithium intercalation/alloying composition comprises a silicon based active material,
wherein the silicon based active material comprises a composite comprising silicon oxide and carbon,
wherein during an initial activation charge the battery has a negative electrode charge capacity of about 75% to about 99.5% at a rate of C/20 from an open circuit voltage to 4.6V relative to the sum of the first activation cycle positive electrode charge capacity at a rate of C/20 from an open circuit voltage to 4.6V plus the oxidation capacity of any supplemental lithium,
wherein following activation of the battery in the initial activation charge and an initial discharge at a C/20 rate, the negative electrode has a capacity greater than the positive electrode at a discharge rate of C/3 or greater discharged from 4.5V to 1.5V, the positive electrode has a specific discharge capacity of at least 200 mAh/g based on the weight of the positive electrode active material at a rate of C/3 discharged from 4.5V to 1.5V, the negative electrode has a specific discharge capacity of at least about 700 mAh/g based on the weight of the negative electrode active material at a rate of C/3 discharged from 4.5V to 1.5V, and
wherein the battery has a discharge energy density at the 50th cycle of at least about 250 Wh/kg at C/3 when discharged from 4.5V to 1.5V.
2. The battery of claim 1 wherein the battery is a pouch cell battery having a ceramic separator.
3. The battery of claim 1 wherein the positive electrode comprises about 90 wt % to about 96 wt % positive electrode active material, about 2 wt % to about 6 wt % polymeric binder, and about 0.5 wt % to about 8 wt % conductive additive.
4. The battery of claim 3 wherein the conductive additive comprises carbon fibers, carbon nanotubes, graphene, graphite, carbon black, or a combination thereof.
5. The battery of claim 1 wherein the positive electrode has a loading level of positive electrode active material on a current collector that is between about 10 mg/cm 2 to about 30 mg/cm 2 and wherein the positive electrode has a density in the range of about 2.2 g/mL to about 3.3 g/mL.
6. The battery of claim 1 wherein the supplemental lithium is in an amount with an oxidation capacity corresponding to about 20% to about 100% of the irreversible capacity loss of the negative electrode.
7. The battery of claim 1 wherein the positive electrode comprises a positive electrode active material that is approximately represented by the formula Li 1+b Ni α Mn β Co γ A δ O 2-z F z , where b ranges from about 0.01 to about 0.3, α ranges from about 0 to about 0.4, β range from about 0.2 to about 0.65, γ ranges from 0 to about 0.46, δ ranges from 0 to about 0.15 and z ranges from 0 to about 0.2 with the proviso that both α and γ are not zero, and where A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li or combinations thereof.
8. The battery of claim 1 wherein the negative electrode comprises about 60 weight % (wt %) to about 90 wt % of a silicon based negative electrode active material, about 8 wt % to about 30 wt % a polymeric binder, and about 1 wt % to about 15 wt % of distinct conductive carbon.
9. The battery of claim 8 wherein the distinct conductive carbon comprises carbon fibers, carbon nanotubes, graphene, graphite, carbon black, or a combination thereof.
10. The battery of claim 1 wherein the negative electrode comprises a silicon based material when measured against a lithium metal counter electrode having a first cycle C/10 intercalation/alloying capacity from 1.5V to 5 mV in the range of about 2000 mAh/g to about 3900 mAh/g and first cycle C/10 deintercalation/dealloying capacity from 5 mV to 1.5V in the range of about 1300 mAh/g to about 2500 mAh/g, a C/3 deintercalation/dealloying capacity from 5 mV to 1.5V in the range of about 1000-2400 mAh/g, and an irreversible capacity loss of less than about 35%.
11. The battery of claim 1 wherein the negative electrode has a loading level of negative electrode active material that is at least 1.5 mg/cm 2 , wherein the negative electrode has a density in the range of about 0.4 g/mL to about 1.3 g/mL, and wherein the negative electrode comprises nanostructured silicon, silicon oxide or composites of silicon oxide and silicon.
12. The battery of claim 1 wherein the battery has a discharge energy density of at least about 350 Wh/kg at C/3 when discharged from 4.5V to 1.5V.
13. The battery of claim 1 wherein during an initial activation charge the battery has a negative electrode charge capacity of about 80% to about 97.5% at a rate of C/20 from the open circuit voltage to 4.6V relative to the sum of the first cycle initial positive electrode charge capacity at a rate of C/20 from the open circuit voltage to 4.6V plus the oxidation capacity of any supplemental lithium.
14. The battery of claim 1 wherein the battery has a discharge volumetric energy density of at least about 600 Wh/l (watt hours per liter) at a rate of C/20 from 4.6V to 1.5V.
15. The battery of claim 1 wherein the negative electrode comprises a germanium based active material or a tin based active material.
16. The battery of claim 1 wherein the battery has a discharge energy density at the 500th cycle of at least about 200 Wh/kg when discharged at a rate of C/3 from 4.3V to 1.5V.
17. The battery of claim 1 , wherein the silicon based active material has a a C/3 deintercalation/dealloying capacity from 5mV to 1.5V in the range of about 1000-2400mAh/g when measured against a lithium metal counter electrode.