Lithium-ion batteries are known as the “engine of the modern energy revolution”, from cell phones, drones, home energy storage batteries to electric vehicles, its technology supports the global intelligent process. By 2023, the global lithium-ion battery market size has exceeded $100 billion, with an annual growth rate of more than 15%.
1. Cathode: the “source factory” of energy.
Material selection: lithium cobalt oxide (LiCoO₂), ternary materials (NCM/NCA), lithium iron phosphate (LiFePO₄) as the mainstream, directly affecting the battery energy density and cost.
Function: Release lithium ions when discharging and recycle lithium ions when charging.
2. Negative electrode (Anode): the “temporary warehouse” for lithium ions.
Graphite dominates the market: the layered structure can efficiently embed/de-embed lithium ions.
Direction of innovation: silicon-based anode (10 times higher theoretical capacity) is the future trend, but need to solve the expansion problem.
3. Electrolyte: the “highway” for ions.
Composition: lithium hexafluorophosphate (LiPF₆) dissolved in carbonate organic solvent.
Key role: Allows lithium ions to travel freely while isolating electron flow.
4. Diaphragm (Separator): the “gatekeeper” of safety.
Material: polyethylene (PE) or polypropylene (PP) porous membrane.
Dual mission: to prevent positive and negative short-circuit, to ensure that the ion channel is open.
5. Shell and collector: the structure of the “skeleton”
Metal casing: steel shell or aluminum-plastic film (soft pack batteries) to provide physical protection.
Copper/aluminum foil: acts as a current collector for the negative and positive electrodes respectively.
The essence of charging and discharging is the reversible conversion of chemical and electrical energy through the synergy of external circuits and ionic circuits.
Discharge process (output energy)
Lithium ions detach from the graphite negative electrode and migrate through the electrolyte toward the positive electrode; electrons flow to the positive electrode through the external circuit to drive the device; lithium ions and electrons combine in the positive electrode material.
Charging process (energy storage)
The power supply forces lithium ions to detach from the positive electrode and return to the negative electrode; electrons flow back from the positive electrode to the negative electrode via an external circuit; lithium ions are re-embedded in the graphite interlayer, waiting for the next discharge.
The structure and working principle of lithium-ion batteries are inextricably linked, with the positive and negative materials, electrolyte and diaphragm forming the “highway” for lithium-ion migration, while the casing and collector provide a stable operating environment for the battery. Understanding this synergistic mechanism will help us to better utilize lithium-ion battery technology and promote the innovative development of future energy storage.
