Batteries produce energy from electrochemical reactions. Batteries typically include a positive electrode and a negative electrode; an ionic electrolyte solution that supports the movement of ions back and forth between the two electrodes; and a porous separator that ensures the two electrodes do not touch but allows ions to travel back and forth between the electrodes.
Contemporary portable electronic appliances rely almost exclusively on rechargeable lithium (Li)-ion batteries as the source of power. This has spurred a continuing effort to increase their energy storage capability, power capabilities, cycle life and safety characteristics, and decrease their cost. Lithium-ion battery or lithium ion cell refers to a rechargeable battery having a negative electrode capable of storing a substantial amount of lithium at a lithium chemical potential above that of lithium metal. When a lithium-ion battery is charged, lithium ions travel from the positive electrode to the negative electrode. On discharge, these ions return to the positive electrode releasing energy in the process.
In a typical Li-ion battery, the cell includes metal oxides for the positive electrode (or cathode), carbon/graphite for the negative electrode (or anode), and a lithium salt in an organic solvent for the electrolyte. More recently, lithium metal phosphates have been used as a cathode electroactive material.
These Li-ion batteries using lithium iron phosphate (LFP)-based cathode materials are useful in a variety of different application. In certain applications, such as hybrid electric vehicles that charge the batteries through energies collected while the vehicle is braking, batteries that exhibit high specific capacity (or specific power) is desirable as fast recharge and discharge rates of these batteries are important. In other applications, such as plug-in electric vehicles where the distance the vehicle can travel is dependent on the total amount of electrical energy that can be stored in the battery, high energy density (or specific energy) is desirable. Accordingly, materials for Li-ion batteries are optimized for the envisioned particular applications.