Lithium battery basic technical terms(二）

Cathode: Electrode in an electrochemical cell in which reduction takes place by absorbing electrons. During discharge, the cathode is positive; reverse on charge.

Cell mismatch: Cells in a battery pack that have unequal capacities, voltages or resistive values.

Cell reversal: Cell polarity reverses on a deep discharge at high load. Damages affected cell.

Charge: Replenishing electrical charge to a cell or battery.

Chemical battery: Behavior of the actual battery as opposed to monitoring peripheral activities.

Cobalt (Co): Hard, lustrous, gray metal; used in batteries, magnets, and high-strength alloys.

Coulomb: Unit of electric charge. One coulomb (1C) equals one ampere-second (1As).

Coulombic efficiency: also called faradaic efficiency or current efficiency describes the charge efficiency by which electrons are transferred in a batteries.

C rate: Unit by which charge and discharge times are scaled. At 1C, the battery charges and discharges at a current that is at par with the marked Ah

Cycle: Charge/discharge/charge. No standard exists as to what constitutes a cycle.

Cycle life: Number of cycles a battery can deliver. (End of-battery-life for portable devices is commonly set to 80%.)

Cylindrical cell: Positive and negative plates are rolled up and placed into a cylindrical container.

DC: Direct current: current flows in one direction. A battery delivers a DC current.

DC-to-DC converter: Converts DC to a higher or lower voltage potential.

DoD: Depth of discharge; 100% is full discharge; 80% is commonly used for specification.

Double-layer capacitor: Electrostatic storage device utilizing the electrical double layer effect that is formed near the surface of the carbon electrode; also called super capacitors or ultracapacitors.

Driving range: EVs display the allowable driving rang range rather than capacity. As the capacity fades, battery gets charged more and discharged deeper. The full capacity is hidden.

Electrochemical impedance spectroscopy (EIS): also known as impedance spectroscopy; method to test electrochemical characteristics of a battery; EIS injects AC signals at different frequencies and analyzes the response.

Electrode: Conductor or plate in a cell in which an electrochemical reaction occurs.

Electrolyte: Non-metallic conductor of electricity (typically liquid) placed between positive and negative electrodes of a battery. Ion movement enables current flow.

Electrolyte oxidation (EO): Formation of a restrictive film on the Li-ion cathode if the voltage is kept above 4.10V/cell. The longer the battery stays in a high voltage, the more pronounced the degradation will be.

Energy: Work measures over time. Multiplying voltage x current x time = Watt-hours (Wh). Energy is also given in joules (J); 1,000 joules are 0.277Wh.

Energy Cell: Battery cell designed for maximum capacity. Power density may be compromised.

Energy density: Also known as volumetric energy density; specifies the amount of energy a cell can hold in volume (Wh/l). Energy density is synonymous with the runtime of a battery.