Three major components of Li-Ion battery are anode,cathode,and electrolyte. Every of them has a range of choice of materials. Different configuraion can lead to different capacity, life and safety.
The anode make with Lithium Cobalt oxide, the cathode is generally one of three material: a layered oxide (such as cobalt oxide), one based on a polyanion (such as iron phosphate), or a spinel (such as manganese). Inside the battery there is electrolyte which is a lithium salt in an organic solvent.
The battery pack is not a simple configuration of cells. They equipped with a variety of safety measures and protective electronics and fuses to prevent reverse polarity, over voltage and over heating , or shorted. It can explode when shorted, this is really dangerous, make sure you know what you are doing when deal with Li-Ion battery.
The main components of a battery pack include the cells, which are the primary energy source; the PCB, which provides system intelligence, the plastic enclosure, external contacts, and insulation.
Lithium batteries are de facto for Bosch Cordless Drill nowadays because of its high performance weight ratio, longer run time, without 'memory effect' and other advantages.
They also widely used on all kinds of portable devices like cell phone, laptop computers and cordless power tools.
But like all other kind of batteries, the chemical reactions inside the battery tend to attenuate as time, which makes the Lithium battery perform poorly as time.
If you recently notice poor performance of your Bosch Cordless Drill batteries like last short time, can not hold charge. There are must be some problem inside the battery.
Seems you have to find a replacement battery, but you will find out that the battery cost almost 1/2, or 1/3 or even more than the Drill itself at the time you need to replace the battery. If you dont want to spend so much money on the new battery , you can consider rebuild it on your own, replacing each individual cell inside the pack.
Before you do this, better know something about lithium battery.
Reaction principle
When charged Lithium in positive electrode is ionized and moves to the negative electrode, when dischared , Li ions move to positive electrode and return to the original compound.