Introduction:
A battery cell is a device that converts chemical energy into electrical energy. It consists of two electrodes, an electrolyte, and a separator. When the battery is connected to a circuit, a chemical reaction occurs within the cell, producing a flow of electrons from the negative electrode to the positive electrode, creating an electric current.

Explanation:
The energy stored in a battery cell is in the form of chemical energy. Let's understand why this is the correct answer:

1. Chemical Reactions:
Inside a battery cell, chemical reactions take place between the electrodes and the electrolyte. These reactions involve the transfer of electrons between different chemical species. The reactants are converted into products, and this conversion releases or absorbs energy. This energy is stored in the chemical bonds of the reactants and products.

2. Electrodes and Electrolyte:
A battery cell consists of two electrodes: a negative electrode (anode) and a positive electrode (cathode). These electrodes are made of different materials that can undergo chemical reactions. The electrodes are immersed in an electrolyte, which is a solution or a paste that allows the flow of ions between the electrodes.

3. Oxidation and Reduction:
During the discharge of a battery, the chemical reaction at the anode involves oxidation, where the anode material loses electrons. At the cathode, reduction occurs, where the cathode material gains electrons. The overall reaction is a redox reaction (oxidation-reduction).

4. Flow of Electrons:
As the chemical reactions occur, electrons are released at the anode and flow through the external circuit to the cathode. This flow of electrons constitutes an electric current that can perform useful work in the circuit, such as powering a device.

5. Conversion of Chemical Energy to Electrical Energy:
The chemical energy stored in the reactants of the battery cell is converted into electrical energy by the movement of electrons. This conversion allows the battery to provide a continuous supply of electrical energy until the reactants are consumed or the chemical reactions reach equilibrium.

Conclusion:
In conclusion, energy is stored in the form of chemical energy in a battery cell. The chemical reactions between the electrodes and electrolyte allow for the conversion of this chemical energy into electrical energy, which can be used to power various devices.