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 method for activating a secondary battery, the 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 programmed with a predefined cell end of discharge voltage V cell,eod value, the negative electrode comprising anodically active silicon or an alloy thereof and having a coulombic capacity for the carrier ions, the positive electrode comprising a cathodically active material and having a coulombic capacity for the carrier ions, the negative electrode coulombic capacity exceeding the positive electrode coulombic capacity, the method comprising:
(i) transferring carrier ions from the positive electrode to the negative electrode to at least partially charge the secondary battery wherein a solid electrolyte interphase is formed on a surface of the negative electrode during the transfer, and
(ii) 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 the predefined V cell,eod value, wherein the value of V pos,eod corresponds 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 method of claim 1 , wherein step (ii) is performed after or simultaneously with step (i).
3. The method of claim 2 , wherein in a case where step (ii) is performed after step (i), the process further comprises step (iii) of transferring, after step (ii), carrier ions from the positive electrode to the negative electrode to charge the secondary battery.
4. The method of claim 2 , wherein step (ii) is performed simultaneously with step (i), and wherein step (ii) comprises transferring carrier ions from the auxiliary electrode to the positive electrode at a first rate, and step (i) comprises transferring carrier ions from the positive electrode to the negative electrode at a second rate, the second rate being higher that the first rate.
5. The method of claim 1 wherein the value of V pos,eod corresponds 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) when the cell is at V cell,eod .
6. The method of claim 1 wherein the value of V pos,eod corresponds to a voltage at which the state of charge of the positive electrode is at least 99% of its coulombic capacity and V neg,eod is at least 0.4 V (vs Li) but less than 0.9 V (vs Li) when the cell is at V cell,eod .
7. The method of claim 1 wherein V neg,eod is at least 0.4 V (vs Li) but less than 0.8 V (vs Li) when the cell is at V cell,eod .
8. The method of claim 1 wherein V neg,eod is at least 0.5 V (vs Li) but less than 0.7 V (vs Li) when the cell is at V cell,eod .
9. The method of claim 1 wherein the carrier ions are lithium, sodium, potassium, magnesium or aluminum ions.
10. The method of claim 1 wherein the carrier ions are lithium ions.
11. The method 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.
12. The method 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.
13. The method 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.
14. The method 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.
15. The method of claim 1 wherein a ratio of the coulombic capacity of the auxiliary electrode to the reversible coulombic capacity of the positive electrode is at least 1.2:1, respectively, when cycled against a counter-electrode.
16. The method of claim 1 wherein a ratio of the coulombic capacity of the auxiliary electrode to the reversible coulombic capacity of the positive electrode is at least 1.5:1, respectively, when cycled against a counter-electrode.
17. The method of claim 1 wherein a ratio of the coulombic capacity of the auxiliary electrode to the reversible coulombic capacity of the positive electrode is at least 2:1, respectively, when cycled against a counter-electrode.
18. The method of claim 1 wherein a ratio of the coulombic capacity of the auxiliary electrode to the reversible coulombic capacity of the positive electrode is at least 5:1, respectively, when cycled against a counter-electrode.
19. The method of claim 1 wherein the negative electrode comprises a 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.
20. The method of claim 19 wherein the void volume fraction of the anodically active material is at least 0.1.
21. The method of claim 19 wherein the void volume fraction of the anodically active material is not greater than 0.8.
22. The method of claim 19 wherein the void volume fraction of the anodically active material is about 0.15 to about 0.75.
23. The method of claim 19 wherein the void volume fraction of the anodically active material is about 0.25 to about 0.6.
24. The method of claim 19 wherein the anodically active material comprises macroporous, microporous or mesoporous material layers or a combination thereof.
25. 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, an auxiliary electrode, 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 controller and a sensor electrically coupled to the sensor,
the sensor is configured to measure a cell voltage of the secondary battery during operation of the secondary battery and to measure the voltage of the positive or negative electrode relative to the auxiliary electrode,
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).
26. The secondary battery of claim 25 wherein controller is programmed to transfer carrier ions from the auxiliary electrode to the positive or negative electrode when the value of V neg,eod is in excess of 0.9 V (vs Li) and when the secondary battery is at the predefined V cell,eod value at the end of a discharge cycle of the secondary battery.
27. The secondary battery of claim 25 wherein controller is programmed to transfer carrier ions from the auxiliary electrode to the positive or negative electrode when the value of V neg,eod is in excess of 0.5 V (vs Li) and when the secondary battery is at the predefined V cell,eod value at the end of a discharge cycle of the secondary battery.
28. The secondary battery of claim 25 wherein the carrier ions are lithium, sodium, potassium, magnesium or aluminum ions.
29. The secondary battery of claim 25 wherein the carrier ions are lithium ions.
30. The secondary battery of claim 25 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.
31. The secondary battery of claim 25 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.
32. The secondary battery of claim 25 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.
33. The secondary battery of claim 25 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.
34. The secondary battery of claim 25 wherein a ratio of the coulombic capacity of the auxiliary electrode to the reversible coulombic capacity of the positive electrode is at least 1.2:1, respectively, when cycled against a counter-electrode.
35. The secondary battery of claim 25 wherein a ratio of the coulombic capacity of the auxiliary electrode to the reversible coulombic capacity of the positive electrode is at least 1.5:1, respectively, when cycled against a counter-electrode.
36. The secondary battery of claim 25 wherein a ratio of the coulombic capacity of the auxiliary electrode to the reversible coulombic capacity of the positive electrode is at least 2:1, respectively, when cycled against a counter-electrode.
37. The secondary battery of claim 25 wherein a ratio of the coulombic capacity of the auxiliary electrode to the reversible coulombic capacity of the positive electrode is at least 5:1, respectively, when cycled against a counter-electrode.
38. The secondary battery of claim 25 wherein the negative electrode comprises a 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.
39. The secondary battery of claim 38 wherein the void volume fraction of the anodically active material is at least 0.1.
40. The secondary battery of claim 38 wherein the void volume fraction of the anodically active material is not greater than 0.8.
41. The secondary battery of claim 38 wherein the void volume fraction of the anodically active material is about 0.15 to about 0.75.
42. The secondary battery of claim 38 wherein the void volume fraction of the anodically active material is about 0.25 to about 0.6.
43. The secondary battery of claim 38 wherein the anodically active material comprises macroporous, microporous or mesoporous material layers or a combination thereof.