Lithium-ion batteries (Li-ion) are a type of rechargeable battery technology widely used for various applications, including smartphones, laptops, electric vehicles, and solar energy storage. These batteries work based on the movement of lithium ions between electrodes during charging and discharging cycles. Here’s a step-by-step explanation of how lithium-ion batteries work:

1. Basic Structure: A typical lithium-ion battery consists of several components, including two electrodes (cathode and anode), an electrolyte, and a separator that prevents direct contact between the electrodes.

2. Charging Process: When a lithium-ion battery is connected to a charging source, such as a charger or a solar panel, the following reactions occur at the electrodes:

Positive Electrode (Cathode): Lithium Cobalt Oxide (LiCoO2)

• During charging, lithium ions are extracted from the cathode material (usually lithium cobalt oxide) and move through the electrolyte towards the anode.
• The chemical reaction at the cathode is: LiCoO2 ↔ Li1-xCoO2 + xLi+ + xe-
• Lithium ions are removed from the cathode material, leading to a reduction in the concentration of lithium cobalt oxide.

Negative Electrode (Anode): Graphite

• At the anode, lithium ions are inserted into the graphite anode material.
• The chemical reaction at the anode is: Li1-xC6 + xLi+ + xe- ↔ LiC6
• Lithium ions are intercalated (inserted) into the graphite structure, forming lithium-intercalated graphite.

3. Charging Stage: As the battery charges, lithium ions move from the cathode to the anode through the electrolyte, storing energy in the form of electrochemical potential energy.

4. Discharging Process: When the battery is connected to a load, such as an electronic device or an electric vehicle, the reactions reverse, and stored energy is released as electrical energy:

Positive Electrode (Cathode): Lithium Cobalt Oxide (LiCoO2)

• During discharge, lithium ions migrate back from the anode to the cathode through the electrolyte.
• The chemical reaction at the cathode is reversed: Li1-xCoO2 + xLi+ + xe- ↔ LiCoO2
• Lithium ions are reinserted into the cathode material, reversing the reduction reaction from the charging stage.

Negative Electrode (Anode): Graphite

• At the anode, lithium ions move out of the graphite structure and travel through the electrolyte back to the cathode.
• The chemical reaction at the anode is reversed: LiC6 ↔ Li1-xC6 + xLi+ + xe-
• Lithium ions are extracted from the graphite, reversing the intercalation process from the charging stage.

5. Discharging Stage: As the battery discharges, the lithium ions move back from the anode to the cathode, releasing stored electrical energy.

This cyclic movement of lithium ions between the cathode and anode during charge and discharge cycles is the basis of how lithium-ion batteries work. The voltage produced by a single lithium-ion cell is typically around 3.7-3.8 volts. Multiple cells are connected in series and sometimes in parallel to achieve the desired battery voltage and capacity for various applications. Proper management systems, thermal controls, and safety measures are crucial to maximize the performance, lifespan, and safety of lithium-ion batteries.

Rechargeable lithium-ion batteries are made up of power-generating cells. Each of these cells have 3 components: a negative electrode, a positive electrode and a chemical named an electrolyte between the positive and negative electrodes. The positive electrode consists of a chemical known as lithium-cobalt oxide. New lithium-ion batteries consist of lithium iron as a chemical compound for the positive electrode. Carbon (graphite) is the chemical compound which makes up the negative electrode. However, this varies depending on the battery and manufacturer of the battery.  

Lithium-ion batteries works similarly as standard batteries in a basic way. When the battery receives a charge, lithium-cobalt oxide, positive electrode loses some of its lithium ions. These lithium ions move to the negative electrode and stays there.  During this process, the lithium-ion battery absorbs and stores power. On the other hand, when the battery is being discharged, the lithium ions move the other direction to through the electrolyte to the positive electrode. Therefore, generating the energy which will be used to power the lithium-ion battery.

In both scenarios, lithium ions move in the opposite direction towards the ions around the outer circuit. However, electrons do not flow through the electrolyte. The electrolyte acts more like an insulating barrier to electrons. The flow of ions and electrons are interconnected processes, which means, if one should stop flowing, the other one will also stop. If the battery discharged completely, the ions stops moving through the electrolyte, therefore, the electrons won’t be able to flow through the outer circuit. On the other hand, if you disconnect any device that receives power from the battery, electrons will stop to flow and also the ions. The battery will keep discharging even if no device is pulling power from it. However, the rate of discharge is very slow. Lithium-ion batteries consist of electronic controllers that can be used to regulate the charge and discharge of the battery. These lithium-ion electronic controllers, also prevent the battery from overcharging, too fast charging and overheating. These factors can be dangerous as it can cause lithium-ion batteries to explode.