State of health of partially discharged cells
A method may determine a remaining capacity of a cell that includes a lithium-alloying material in an electrode using a controller. The method includes receiving a temperature signal representing a temperature of a partially discharged cell and receiving a voltage signal representing a voltage of the partially discharged cell. The method further includes determining a time-dependent fade component and a cycle-dependent fade component of the cell. The time-dependent fade component of the cell is determined based on the temperature, the voltage, and an operating time of the cell. The cycle-dependent fade component of the cell is determined based on a depth of discharge of the partially discharged cell and cycle count data representing cycle-dependent fade from previous cycles of the cell. The method further includes determining a remaining capacity of the cell based on the time-dependent fade component, the cycle-dependent fade component, and a reference capacity of the cell.
1. A method, comprising:
receiving, by a controller, a temperature signal representing a temperature of a partially discharged cell, wherein the cell includes a lithium-alloying material in an electrode;
receiving, by the controller, a voltage signal representing a voltage of the partially discharged cell;
determining, by the controller, a time-dependent fade component of the cell based on the temperature, the voltage, and an operating time of the cell;
determining, by the controller, a cycle-dependent fade component of the cell based on a depth of discharge of the partially discharged cell and cycle count data representing cycle-dependent fade from previous cycles of the cell; and
determining, by the controller, a remaining capacity of the cell based on the time-dependent fade component, the cycle-dependent fade component, and a reference capacity of the cell.
2. The method of claim 1 , further comprising determining, by the controller, the depth of discharge based on the voltage.
3. The method of claim 1 , further comprising:
receiving, by the controller, a current signal representing a current of the partially discharged cell; and
determining, by the controller, the depth of discharge based on the current.
4. The method of claim 1 , wherein determining the time-based fade component further comprises:
determining a time-dependent fade parameter based on the temperature and the voltage, wherein the time-dependent fade parameter is derived from a reference cell corresponding to the cell; and
determining the time-dependent fade component based on the time-dependent fade parameter and the operating time of the cell.
5. The method of claim 1 , wherein determining the cycle-based fade further comprises:
determining a cycle-dependent fade parameter based on the depth of discharge, wherein the cycle-dependent fade parameter is derived from a reference cell corresponding to the cell; and
determining the cycle-based fade component based on the cycle-dependent fade parameter and the cycle count data, wherein the cycle count data includes cycle-dependent fade parameters from previous cycles.
6. The method of claim 5 , wherein the cycle-dependent fade parameter depends on the depth of discharge for a depth of discharge greater than a depth of discharge at which the lithium-alloying material contributes substantially to a capacity of the cell.
7. The method of claim 6 , wherein the cycle-dependent fade parameter depends on the depth of discharge in a monotonically increasing way for a depth of discharge greater than a depth of discharge at which the lithium-alloying material contributes substantially to a capacity of the cell.
8. The method of claim 6 , wherein the cycle-dependent fade parameter depends linearly on the depth of discharge for a depth of discharge greater than a depth of discharge at which the lithium-alloying material contributes substantially to a capacity of the cell.
9. The method of claim 5 , wherein the cycle-dependent fade parameter is constant for a depth of discharge less than or equal to a depth of discharge at which the lithium-alloying material contributes substantially to the capacity of the cell.
10. The method of claim 9 , wherein the cycle-dependent fade parameter is 0 for a depth of discharge less than or equal to the depth of discharge at which the lithium-alloying material contributes substantially to the capacity of the cell.
11. The method of claim 1 , wherein determining the cycle-dependent fade is further based on the temperature.
12. The method of claim 1 , wherein the lithium-alloying material is a silicon-based material.
13. The method of claim 12 , wherein the silicon-based material is a silicon-based alloy and the electrode includes graphite.
14. The method of claim 12 , wherein the silicon-based material is a silicon-based alloy comprising silicon, a transition metal, and carbon.
15. The method of claim 1 , wherein the cell includes an electrolyte containing at least one of fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, propylene carbonate, and carbon dioxide.
16. The method of claim 1 , wherein the time-dependent fade component is a time-dependent electrolyte consumption component, the cycle-dependent fade is a cycle-dependent electrolyte consumption component, the remaining capacity is a remaining amount of electrolyte mass, and the initial capacity of the cell is an initial amount of electrolyte mass.
17. A system, comprising:
a controller configured to:
receive a temperature signal representing a temperature of a partially discharged cell, wherein the cell includes a lithium-alloying material in an electrode;
receive a voltage signal representing a voltage of the partially discharged cell;
determine a time-dependent fade component of the cell based on the temperature, the voltage, and an operating time of the cell;
determine a cycle-dependent fade component of the cell based on a depth of discharge of the partially discharged cell and cycle count data representing cycle-dependent fade from previous cycles of the cell; and
determine a remaining capacity of the cell based on the time-dependent fade component, the cycle-dependent fade component, and a reference capacity of the cell.
18. The system of claim 17 , wherein the controller is further configured to:
determine a time-dependent fade parameter based on the temperature and the voltage, wherein the time-dependent fade parameter is derived from a reference cell corresponding to the cell;
determine the time-dependent fade component based on the time-dependent fade parameter and the operating time of the cell
determine a cycle-dependent fade parameter based on the depth of discharge, wherein the cycle-dependent fade parameter is derived from a reference cell corresponding to the cell; and
determine the cycle-based fade component based on the cycle-dependent fade parameter and the cycle count data, wherein the cycle count data includes cycle-dependent fade parameters from previous cycles.
19. The system of claim 17 , further comprising:
a temperature sensor coupled to the controller and configured to measure the temperature and send the temperature signal; and
a voltage sensor coupled to the controller and configured to measure the voltage and send the voltage signal.
20. A computer-readable storage medium storing instructions that, when executed, cause a controller to:
receive a temperature signal representing a temperature of a partially discharged cell, wherein the cell includes a lithium-alloying material in an electrode;
receive a voltage signal representing a voltage of the partially discharged cell;
determine a time-dependent fade component of the cell based on the temperature, the voltage, and an operating time of the cell;
determine a cycle-dependent fade component of the cell based on a depth of discharge of the partially discharged cell and cycle count data representing cycle-dependent fade from previous cycles of the cell; and
determine a remaining capacity of the cell based on the time-dependent fade component, the cycle-dependent fade component, and a reference capacity of the cell.