Lithium rechargable cell with reference electrode for state of health monitoring

Abstract

A battery management system includes one or more lithium ion cells in electrical connection, each said cell comprising: first and second working electrodes and one or more reference electrodes, each reference electrode electronically isolated from the working electrodes and having a separate tab or current collector exiting the cell and providing an additional terminal for electrical measurement; and a battery management system comprising a battery state-of-charge monitor, said monitor being operable for receiving information relating to the potential difference of the working electrodes and the potential of one or more of the working electrodes versus the reference electrode.

1 . A lithium ion battery, comprising:
 first and second working electrodes separated by at least one separator, the first working electrode in electrical connection with a first terminal, the second working electrode in electrical connection with a second terminal, and the first and second working electrodes comprising electroactive materials capable lithium uptake and release;   one or more reference electrodes; and   a can housing the working electrodes and the one or more reference electrodes, wherein the can is electrically isolated from the first and second terminals and is electrically connected to the one or more reference electrodes to provide terminals for the one or more reference electrodes.   
     
     
         2 . A method of supplying power, the method comprising:
 installing the lithium ion battery of  claim 1 .   
     
     
         3 . The method of  claim 2 , further comprising: interfacing the one or more reference electrodes with a battery management system;
 charging the battery;   and monitoring the state of charge.   
     
     
         4 . The method of  claim 2 , further comprising:
 maintaining the one or more reference electrodes within their two-phase stoichiometry over the course of repeated voltage measurements,   wherein the maintaining occurs by compensating for the current passed during voltage measurement.   
     
     
         5 . The method of  claim 4 , wherein the compensation occurs by alternating measurement between the reference-to-negative electrode and positive-to-reference electrode. 
     
     
         6 . The method of  claim 4 , wherein the compensation occurs by periodically switching the connection of the voltage leads between the one or more reference electrodes and one or more working electrodes. 
     
     
         7 . The method of  claim 4 , wherein the compensation occurs by periodically passing current between the one or more reference electrodes and either the positive or negative electrode, with the direction and amount of current determined by the amount of current passed during voltage measurement. 
     
     
         8 . A method of avoiding lithium plating in a lithium ion battery comprising:
 measuring the potential of the negative electrode relative to a reference electrode during charging of a lithium ion battery;   comparing the measured potential to a critical potential associated with the plating of lithium metal; and   adjusting the charging conditions of the lithium ion battery to reduce the risk or prevent plating of lithium at the negative electrode.   
     
     
         9 . The method of  claim 8 , wherein adjusting charging comprises terminating charging. 
     
     
         10 . The method of  claim 8 , wherein adjusting charging comprises altering the charge rate. 
     
     
         11 . A method of minimizing charge time of a lithium-ion battery by maximizing the charge current that is applied at any particular SOC during a charging event, comprising:
 measuring the potential of the negative electrode relative to a reference electrode during charging of the battery, said charging having a charge rate;   determining the state of charge of the battery;   comparing the measured state of charge to a state of charge profile; and   adjusting the charge rate upwards or downwards to maintain the actual charge rate within a predetermined range that provides one or more of optimal safety operation and optimal charge rate to minimize charge time.   
     
     
         12 . A method of detecting whether there is an electrical connection between a can and either terminal of a cell, comprising:
 applying a material to the inside of the can, said material having a redox potential that differs from that of either terminals, where the potential difference is greater than  0 . 2  V; and   measuring the voltage between at least one terminal and the can.   
     
     
         13 . A method of supplying power, the method comprising implementing a lithium ion battery system comprising:
 (a) one or more lithium ion cells in electrical connection, each said cell comprising:
 first and second working electrodes separated by separator membranes, the working electrodes capable of lithium ion uptake and release, the first working electrode comprising a first electroactive layer on a first current collector, and the second working electrode comprising a second electroactive layer on a second current collector; and 
 one or more reference electrodes, each reference electrode electronically isolated from the working electrodes and having a separate tab or current collector exiting the cell and providing an additional terminal for electrical measurement; and 
   (b) a battery management system comprising:
 a battery state-of-charge monitor, said monitor being operable for receiving information relating to the potential difference of the working electrodes and the potential of one or more of the working electrodes vs. the one or more reference electrodes. 
   
     
     
         14 . The method of  claim 13 , further comprising monitoring one or more parameters selected from the group comprising overcharge, overdischarge, excessive charge current, and excessive discharge current. 
     
     
         15 . The method of  claim 13 , further comprising estimating the state-of-charge. 
     
     
         16 . The method of  claim 13 , wherein the lithium ion battery system further comprises a balancing module. 
     
     
         17 . The method of  claim 16 , further comprising:
 evaluating the relative voltage levels of adjacent cell pairs; and   redistributing charge between adjacent cells to mitigate differences in the cell voltages of the pairs.   
     
     
         18 . The method of  claim 13 , wherein the lithium ion battery system further comprises a controller. 
     
     
         19 . The method of  claim 18 , further comprising raising and/or lowering the charge rate of one or more cells. 
     
     
         20 . The method of  claim 13 , wherein the one or more reference electrodes can allow substantially instantaneous feedback of the state-of-charge of each individual cell to the battery management system. 
     
     
         21 . The method of  claim 20 , further comprising adjusting the charging protocol of at least one cell in substantially real-time.