Method for determining state of charge in lithium batteries through use of a novel electrode

A battery cell comprising:

• a cathode comprising:
• first cathode active material particles, wherein the first cathode active material is LFP;
• second cathode active material particles, wherein the second cathode active material has an open circuit voltage change of at least 10 mV as SOC changes from 100% to 15%;
• optional carbon particles
• optional binder;
• and
• a first electrolyte;
• wherein the first cathode active material particles, the second cathode active material particles, optional carbon particles, optional binder and the first electrolyte are all mixed together to form the cathode;
• an anode comprising lithium metal or alloy;
• and
• a separator between the cathode and the anode, the separator comprising a second electrolyte.

A method of determining SOC for a lithium battery that has a LFP-based cathode, comprising:

• providing a cathode comprising LFP particles and particles made from a material that has an open circuit voltage change of at least 100 mV as SOC changes from 100% to 15%;
• forming a lithium battery cell comprising the cathode, a Li metal anode and a second electrolyte;
• measuring an OCV for the cell;
• and
• comparing the OCV to a previously-obtained correlation between OCV and SOC to determine the SOC.