This layer interferes with the charge/discharge cycle and both the difference of potential (voltage) and the number of charged ions that can be attracted changes.
These particles are made from lithium oxide (lithium bonded with oxygen) atoms and lithium carbonate (lithium bonded with carbon) atoms, neither of which has the same chemical or electrical properties as graphite. When every positively charged ion is stripped away from the anode in a battery a microscopic layer of particles is left behind and has been chemically bonded to the graphite anode. The same way water and air can cause iron to rust (which is where the word oxidization comes from), lithium, graphite and electrolyte salts will cause an electrode to oxidize. But that doesn't mean the negative electrode is clean and exactly the same as it was before you started.Įlectrodes oxidize. The opposite is true while discharging a battery and the difference of potential decreases until it reaches zero because no more positively charged ions are present at the negative electrode. Once it reaches a specific reading the battery is considered fully charged. That's how you measure voltage - the difference of potential energy between two electrodes. As more and more charged ions are attracted, the difference of potential between the negative electrode and positive electrode increases. We know that charging a battery positively charges lithium ions which are then magnetically (electricity is magnetism) attracted to the negative electrode. Plugging it into a charger resets this cycle. The longer you pull the stored energy away from a charged battery, the number of lithium ions that are no longer charged increases until there just aren't enough of them left to produce any output and the battery is dead. When you pull a charge away from the battery these lithium ions lose their positive charge and are no longer attracted to the negative electrode. When you apply a charge to the electrodes (from your charger) lithium ions are positively charged and are attracted to the negative electrode. The chemistry between these three things is simple at its base and is why they can be used to store energy. Inside a phone battery, you'll find three components that are important for what we're talking about: a negative electrode (called an anode and typically made of graphite), a positive electrode (called a cathode and made from a mix of lithium and other metals), and an electrolyte solution. The estimated life of a phone battery is just that - an estimate.