The adoption rate of lithium polymer technology in the marketplace since the early 1990s has been delayed by the instability of the supply chain as researchers struggled with manufacturing processes that combined plastics process technology with electrochemical engineering concepts, the need to manufacture the technology within reasonable economic limits and business models, and the requirement to keep pace with the rapidly growing performance of standard lithium ion chemistry.
Polymer Lithium ion batteries consist of a cathode of lithiated metal oxide or phosphate, and a graphite anode separated by a polyethylene or polypropylene separator material in a non-aqueous electrolyte. When the battery is charged, lithium ions leave the cathode and are intercalated into the layered structure of the graphite. As the battery discharges, lithium ions leave the anode and return to the cathode, while electrons travel in the opposite direction, completing the circuit.
Lithium polymer lifepo4 batteries have the same common electrochemistry as conventional lithium ion batteries, they have a lithiated oxide cathode and a graphite anode held together in a binder matrix of polyvinlydiene fluoride and coated and/or laminated to a current collector grid. However, they contain a highly porous separator, which converts to a gel when a minimum amount of electrolyte is added to operate the cell. Lithium polymer technology uses stacked plate cell architecture, as opposed to a wound found in conventional lithium ion cells, which means that they consist of die-cut anode and cathode plates that are about the size of the battery and are stacked on top of each other like a deck of cards, with the plates connected in parallel.
Lithium polymer 18650 batteries have comparable energy density to lithium ion batteries and are achieving cost parity. The cells are sealed in a plastic aluminum laminate, so if the battery sees an overcharge condition, the seal ruptures and vents any gases due to electrolyte oxidation and the cell shuts down rather than having steel or aluminum casings fragment, as in the case of lithium ion batteries that may result in metal shards.