Replenished negative electrodes for secondary batteries
A method is provided for activating a secondary battery having a negative electrode, a positive electrode, and a microporous separator between the negative and positive electrodes permeated with carrier-ion containing electrolyte, the negative electrode having anodically active silicon or an alloy thereof. The method includes transferring carrier ions from the positive electrode to the negative electrode to at least partially charge the secondary battery, and transferring carrier ions from an auxiliary electrode to the positive electrode, to provide the secondary battery with a positive electrode end of discharge voltage V pos,eod and a negative electrode end of discharge voltage V neg,eod when the cell is at a predefined V cell,eod value, the value of V pos,eod corresponding to a voltage at which the state of charge of the positive electrode is at least 95% of its coulombic capacity and V neg,eod is at least 0.4 V (vs Li) but less than 0.9 V (vs Li).
1. A secondary battery comprising a negative electrode, a positive electrode, a microporous separator between the negative and positive electrodes permeated with a carrier ion-containing electrolyte in ionic contact with the negative and positive electrodes, and a control unit, wherein
the positive electrode comprises a cathodically active material and has a coulombic capacity for the carrier ions,
the negative electrode comprises anodically active silicon or an alloy thereof and has a coulombic capacity for the carrier ions that exceeds the positive electrode coulombic capacity,
the control unit comprises a sensor and a controller electrically coupled to the sensor,
the sensor is configured to measure a cell voltage of the secondary battery during operation of the secondary battery,
the controller is programmed with a predefined cell end of charge voltage V cell,eoc value and a predefined cell end of discharge voltage V cell,eod value, and
the positive electrode has an end of discharge voltage V pos,eod and the negative electrode has an end of discharge voltage V neg,eod when the cell is at the predefined V cell,eod , the value of V pos,eod corresponding to a voltage at which the state of charge of the positive electrode is at least 95% of its coulombic capacity and V neg,eod is at least 0.4 V (vs Li) but less than 0.9 V (vs Li).
2. The secondary battery of claim 1 wherein the carrier ions are lithium, sodium, potassium, magnesium or aluminum ions.
3. The secondary battery of claim 1 wherein the carrier ions are lithium, magnesium or aluminum ions.
4. The secondary battery of claim 1 wherein the carrier ions are lithium ions.
5. The secondary battery of claim 1 wherein a ratio of the reversible coulombic capacity of the negative electrode to the reversible coulombic capacity of the positive electrode is at least 1.2:1, respectively, when cycled against a counter-electrode.
6. The secondary battery of claim 1 wherein a ratio of the reversible coulombic capacity of the negative electrode to the reversible coulombic capacity of the positive electrode is at least 1.5:1, respectively, when cycled against a counter-electrode.
7. The secondary battery of claim 1 wherein a ratio of the reversible coulombic capacity of the negative electrode to the reversible coulombic capacity of the positive electrode is at least 2:1, respectively, when cycled against a counter-electrode.
8. The secondary battery of claim 1 wherein a ratio of the reversible coulombic capacity of the negative electrode to the reversible coulombic capacity of the positive electrode is at least 4:1, respectively, when cycled against a counter-electrode.
9. The secondary battery of claim 1 wherein a ratio of the reversible coulombic capacity of the negative electrode to the reversible coulombic capacity of the positive electrode is at least 5:1, respectively, when cycled against a counter-electrode.
10. The secondary battery of claim 1 wherein the negative electrode comprises a microstructured silicon-containing active material that contains a significant void volume fraction to accommodate volume expansion and contraction as carrier ions are incorporated into or leave the negative electrode during charging and discharging cycles.
11. The secondary battery of claim 10 wherein the void volume fraction of the microstructured silicon-containing active material is about 0.2 to about 0.7.
12. The secondary battery of claim 10 wherein the void volume fraction of the microstructured silicon-containing active material is about 0.25 to about 0.6.
13. The secondary battery of claim 5 wherein the carrier ions are lithium ions.
14. The secondary battery of claim 6 wherein the carrier ions are lithium ions.
15. The secondary battery of claim 7 wherein the carrier ions are lithium ions.
16. The secondary battery of claim 8 wherein the carrier ions are lithium ions.
17. The secondary battery of claim 9 wherein the carrier ions are lithium ions.
18. The secondary battery of claim 10 wherein the carrier ions are lithium ions.
19. The secondary battery of claim 11 wherein the carrier ions are lithium ions.
20. The secondary battery of claim 12 wherein the carrier ions are lithium ions.