Lithium, being the lightest metal and the one with the highest electrochemical potential, has become a common choice for battery manufacturing. However, use of lithium metal as an electrode in rechargeable batteries poses a risk of explosion. In a lithium ion battery, an electrode made out of lithium compound is used as a positive electrode and graphite as the negative. These batteries are the ones with the highest energy density and a single cell provides 3.7V to 4.2V (i.e., 3 times that of an Ni-Cd cell).
Apart from light weight and high energy density, lithium provides other advantages as well:
• Low maintenance
: These batteries are hassle free because they don’t need regular maintenance like maintaining the water level in lead acid cell or complete discharging before being charged again in case of Ni-Cd batteries (memory effect).
• Low Self Discharge rate
: The self discharge rate of Lithium ion battery is approx. 5-10 percent per month which is on the order of 3 times lower than NiMH batteries.
Lithium ion batteries have some significant disadvantages:
• Cell Life
: An Li-ion battery requires more frequent recharging after one or two years of initial usage. This is because the charging process forms deposits inside the electrolyte which in turn increases the internal resistance and results in loss of capacity.
• Over charging and temperature
: If the Li-ion battery is over charged or operated at elevated temperatures, then it loses capacity.
: As these batteries are supposed to be used at a particular voltage and temperature range, a monitoring circuit is required that shuts down the system if the voltage or temperature goes out of the range. This additional circuit increases the cost of the complete lithium ion battery charger.
Despite these disadvantages, Li-ion batteries are finding their way into more and more mobile applications because of their high energy density and light weight.
Below is table providing a summary of the different types of batteries discussed.
Editor’s note: Part 2 will discuss how to implement a battery charger using Li-Ion technology as the example.
About the authors:
is currently working with Cypress Semiconductor India Pvt. Ltd. as a Senior Application Engineer. His interests lie in designing Embedded system applications in C and assembly languages, working with analog and digital circuits, developing GUIs in C# and, above all, enjoying adventure sports. Pushek can be reached at email@example.com
is an applications engineer on the PSoC 1 Applications team at Cypress Semiconductor. He can be reached at firstname.lastname@example.org
If you found this article to be of interest, visit SmartEnergy Designline
where you will find the latest and greatest design, technology,
product, and news articles with regard to all aspects of clean
technologies. And, to register to our weekly newsletter, click here.