A bio-battery is an energy storing device that is powered by organic compounds, usually being glucose, such as the glucose in human blood. When enzymes in human bodies break down glucose, several electrons and protons are released. Therefore, by using enzymes to break down glucose, bio-batteries directly receive energy from glucose. These batteries then store this energy for later use. This concept is almost identical to how both plants and many animals obtain energy. 

WORKING OF BIOBATTERY

Bio-batteries consist of an anode, cathode, separator and electrolyte with each component layered on top of another. Anodes and cathodes are the positive and negative areas on a battery that allow electrons to flow in and out. The anode is located at the top of the battery and the cathode is located at the bottom of the battery. Anodes allow current to flow in from outside the battery, whereas cathodes allow current to flow out from the battery.Between the anode and the cathode lies the electrolyte which contains a separator. The main function of the separator is to keep the cathode and anode separated, to avoid electrical short circuits. This system as a whole, allows for a flow of protons ({\displaystyle {\ce {H+}}}) and electrons ({\displaystyle {\ce {e-}}}) which ultimately generates electricity. In the anode the sugar is broken down, producing both electrons and protons.

Glucose → Gluconolactone + 2H⁺ + 2e⁻

These electrons and protons produced now play an important role in creating energy. They travel through the electrolyte, where the separator redirects electrons to go through the mediator to get to the cathode. On the other hand, protons are redirected to go through the separator to get to the cathode side of the battery.The cathode then consists of an oxidation reduction reaction. This reaction uses the protons and electrons, with the addition of oxygen gas, to produce water.

O₂ + 4H⁺ + 4e⁻ → 2H₂O

ADVANTAGES

A constant supply of sugar, or glucose, bio batteries are able to continuously keep themselves charged without an external power supply. Bio batteries are also a source of non-flammable, and non-toxic fuel. This provides a clean alternative renewable power source.

DISADVANTAGES

Compared to conventional batteries, such as lithium batteries, bio-batteries are less likely to retain most of their energy.This causes a problem when it comes to long term usage and storage of energy for these batteries. However, researchers are continuing to develop the battery in order to make it a more practical replacement for current batteries and sources of energy.