Lithium-ion capacitors represent a groundbreaking amalgamation of technologies, marrying the longevity of electric double-layer capacitors with the high energy density of lithium-ion secondary batteries. These capacitors operate efficiently at a relatively lower voltage of 3.8V, a feat achieved by the pre-doping of lithium ions into the negative electrode. A key environmental benefit of these capacitors is their eco-friendly manufacturing process, which notably excludes the use of environmentally detrimental heavy metals.
The essence of lithium-ion capacitors lies in their dual nature. They not only embrace the operational principles of traditional electric double-layer capacitors but also incorporate carbon-based materials in the negative electrode. These materials are adept at absorbing lithium ions, significantly amplifying the energy density of the capacitors. Structurally, lithium-ion capacitors are asymmetric, combining the positive electrode of an electric double-layer capacitor with the negative electrode of a lithium-ion secondary battery. The charging and discharging of the positive electrode occur through physical effects, while the negative electrode undergoes an oxidation-reduction reaction involving lithium. This unique combination grants them a higher energy density compared to conventional capacitors, largely attributable to the high capacity of the negative electrode, and their exceptional reliability and safety at high temperatures.
In high-temperature conditions, lithium-ion capacitors excel, outperforming electric double-layer capacitors in terms of high-temperature load characteristics. This superiority stems primarily from the pre-doped lithium ions in the negative electrode, which considerably boost their electrostatic capacity. Safety-wise, the materials used in lithium-ion capacitors are inherently less flammable. When compared to lithium-ion secondary batteries, they exhibit a reduced likelihood of thermal runaway, thereby markedly elevating their safety profile. Another notable aspect is their low self-discharge rate, positioning them as optimal choices for standby power sources in various machines.
A distinct feature of lithium-ion capacitors is the absence of oxygen (oxide) in their constituent elements. This omission means that even if Joule heat is generated from the accumulated charge, it does not trigger a chemical reaction, thus averting the risk of thermal runaway. Consequently, there is no danger of energy loss or fire hazard upon charge release, further solidifying the safety and practicality of lithium-ion capacitors in a wide array of applications.