Battery Basics

• All batteries work by creating electric current using the movement of charged particles between the cathode and anode. The differences between battery designs is in the electrochemistry of the design. This includes what the cathode, anode and the electrolyte between them are made of; and what charged particle is migrating in the battery.
  
  

Lithium Ion Electrochemistry

• Most lithium ion battery designs use graphite for the anode. The cathode is made from either lithium manganese oxide, lithium iron phosphate,or lithium cobalt oxide. Lithium ions are the charged particle moving between them. The electrolyte is often solid lithium salts plus an organic solvent. Which lithium compound is used used for a compound depends the desired balance between voltage, storage capacity and the rate of charge deterioration in the battery.
  
  

The Recharging Process

• Lithium ion batteries are a rechargeable design. When a lithium ion battery is recharged, which happens when an electrical current is applied to the battery instead of flowing out of it, the movement of the lithium ions reverses. In other words, lithium ions migrate from the cathode back into the anode.
  
  

Gradual Degradation

• A major qualitative difference between lithium ion batteries and other designs is that they are steadily decaying, whether in use or not. From the time a lithium ion battery is assembled, it immediately starts a slow, continuous degradation. Keeping a high charge and continuing to apply electricity after reaching a high charge actually accelerate the degradation, which is the constant blunder of many cell phone and laptop computer owners who leave their devices charging past maximum overnight. It is useful to imagine the electrochemistry of these batteries as being like steel springs, which are sturdy, but still wear out if kept regularly and/or constantly under maximum tension.