Lithium-ion batteries are a type of rechargeable battery commonly used in portable electronic devices and electric vehicles and are increasingly popular in military and aerospace applications.
In the battery, lithium ions move from the negative electrode through the electrolyte to the positive electrode during discharge, and back during charging. Lithium-ion batteries use embedded lithium compounds as the positive electrode material, with graphite typically used as the negative electrode material. The battery has high energy density, no memory effect (except for LFP batteries), and low self-discharge.
Handheld electronic products mostly use lithium polymer batteries (with a polymer gel as the electrolyte), LiCoO2 cathode material and graphite anode, providing high energy density. Lithium iron phosphate, lithium manganese oxide, and lithium nickel manganese cobalt oxide may provide longer life and better rate capability. Such batteries are widely used in power tools, medical devices, and other roles.
Research on lithium-ion batteries includes extending life, increasing energy density, improving safety, reducing costs, and increasing charging speed. Research in the field of non-flammable electrolytes is underway based on the flammability and volatility of organic solvents typically used in electrolytes as a means of improving safety. Strategies include aqueous lithium-ion batteries, ceramic solid electrolytes, polymer electrolytes, ionic liquids, and perfluorinated systems.
The three primary functional components of a lithium-ion battery are the positive electrode, the negative electrode, and the electrolyte. Typically, the negative electrode of a conventional lithium-ion battery is made of carbon. The positive electrode is typically a metal oxide. The electrolyte is a lithium salt in an organic solvent. The electrochemical action of the electrode is reversed between the anode and cathode depending on the direction of current flow through the battery.
The most commonly used commercial anode (negative electrode) is graphite, which has a capacity of xxx mAh/g in its fully lithiated LiC6 state. The positive electrode is generally one of three materials: layered oxide (such as LiCoO2), polyanion (such as lithium iron phosphate), or spinel (such as lithium manganese oxide). Recently, graphene electrodes have also been used as components of lithium-ion battery electrodes.
The electrolyte is typically a mixture of organic carbonate esters, such as lithium ion complexes of ethylene carbonate or diethylene carbonate. These non-aqueous electrolytes typically use non-coordinating anion salts, such as lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate monohydrate, lithium perchlorate, lithium tetrafluoroborate, and lithium trifluoromethanesulfonate.
The charging temperature limit for bulk lithium batteries is more stringent than the operating limit. Lithium-ion chemistry performs well at high temperatures, but extended exposure to high temperatures will shorten battery life.
Lithium-ion batteries provide good charging performance at cooler temperatures and can even charge rapidly within the temperature range of 5-45°C. Charging should be done within this temperature range. Charging at temperatures between 0-5°C is possible, but the charging current should be reduced. High temperatures may be beneficial during low-temperature charging due to internal battery resistance. Charging at too high a temperature may cause battery degradation, and charging at temperatures above 45°C will reduce battery performance, while at lower temperatures the internal resistance of the battery may increase, leading to a slower charging rate and longer charging time.
Consumer-grade lithium-ion batteries should not be charged at temperatures below 0°C. Although the battery pack may appear to be charging normally, the negative electrode may experience metallic lithium plating during low-temperature charging, which may not be removable even with repeated cycles. For safety reasons, most devices equipped with lithium-ion batteries do not allow charging outside the range of 0-45°C, except mobile phones which may allow a certain amount of charging when detecting an emergency call in progress.