Operating Principles of Lithium-ion Batteries

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GeePower® Lithium-ion Battery Knowledge Column

A lithium-ion battery is a rechargeable battery. It works by the intercalating and deintercalating of Li+ between two electrodes. For lithium-ion batteries, you need to be familiar with the following knowledge:

lithium-ion battery

lithium-ion battery

  • Positive electrode structure: LiCoO2 + conductive agent+ binding agent (PVDF) + current collector (aluminum foil).
  • Negative electrode structure: graphite + conductive agent + thickening agent (CMC) + binding agent (SBR) + current collector (copper foil).
  • When charging lithium-ion battery, the electrons on the positive electrode run to the negative electrode through the external circuit. While the Li+ “jumps” into the electrolyte from the positive electrode, and then it “crawls” through the curved holes on the diaphragm, and “swims” to the negative electrode. Finally it is combined with the electrons already here.

Positive electrode reaction:

LiCoO2Li1-xCoO2 +xLi+ + xe

Negative electrode reaction:

6C+ xLi+ +xeLix C6

  • Discharging process: The discharging can be divided into a constant-current discharging and a constant-resistance discharging. Constant-current discharge refers to the installation of a resistor that can change with voltage in the external circuit. And the constant resistance-discharge refers to add a resistor to both the positive and negative terminals of the battery to allow electrons to pass.

Therefore, it can be seen that the battery will not discharge as long as the electrons on the negative electrode cannot reach the positive electrode from the negative electrode. Actually, electrons and Li+ move simultaneously, in the same direction but in different ways.

During discharging, electrons travel from the negative electrode through the electron conductor to the positive electrode. And then lithium-ion Li+ “jumps” into the electrolyte from the negative electrode, “crawls” into the diaphragm through the curved hole, “swims” to the positive pole, and finally combined with the electrons.

lithium-ion battery

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