Monday, 29 April 2013

Volumetric and Gravimetric energy density comparison of various battery technologies

The following graph shows a high level view of Volumetric and Gravimetric energy density comparison of various battery technologies.  

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Comparison of different cathode and anode materials for lithium ion batteries

Chemical formula
Lithium Cobalt
High Power Applications, High working voltage, high rate capability, Reasonably good cycle life.

Capacity > 140mAh/g.
High cost, lower safety
Lithium Nickel Cobalt Aluminum Oxide (NCA)

High Energy Density use, Reasonably good cycle life, Slightly better safety than lithium cobalt oxide.

Capacity >185mAh/g.
Hard to process, Higher cost, swells at high temperatures.
Lithium Nickel Manganese Cobalt  Oxide (NCM)

High energy density applications, Reasonably good cycle life, Less expensive, Safer than Lithium Cobalt Oxide.

Capacity > 144mAh/g.
Low working Voltage
Lithium Manganese Oxide
High power applications. Long cycle life, high safety and low cost. 

Capacity > 95mAh/g.
High temperature performance, low energy density.
Lithium iron phosphate (LFP)
High power applications. Long cycle life, High safety,

Capacity > 125mAh/g.
Poor energy density, Low operating voltage, low temperature performance.
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Friday, 26 April 2013

Potential and Capacity of various cathode materials used in lithium ion batteries

The following picture was authored by John B. Goodenough and Youngsik Kim and published at Chem. Mater.201022 (3), pp 587–603.  Thanks to them for compiling these data to the battery community around the world.

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Monday, 22 April 2013

Cylindrical Lithium ion battery manufacturing steps

The following is an outline of various steps used in Lithium ion battery manufacturing process.


In cylindrical cell manufacturing process cathode, separator and anode are fed into a winder where it uniformly winded into a cylinder.  The radius of the cylinder varies depending on the cell design.  After the specified length of the electrode assembly is wound then it is cut and taped.


In this step the anode and cathode electrode tabs are connected separately using clamping process to avoid accidental shorting.


The wound electrode roll is inserted into the appropriate metal casing.  

Sub Assembly:

During this process terminals, vents, safety devices, O-rings, washers and other connections are done.


During this process the anode tabs are welded to the case at the bottom and the cathode tabs are welded to the top cover.

The next three steps vacuum drying, electrolyte filling and sealing process are done in a dry room where the humidity is controlled.

Vacuum Heating:

This process will remove any moisture absorbed by the electrodes during the proceeding processes.  

Electrolyte Filling:

After the moisture is removed appropriate amount of electrolyte is filled.  I general there are two types of filling process is used.  1.  Fill with particular amount of electrolyte 2. Overfill with the electrolyte,, followed by soaking and dumping the excess electrolyte.


Once the electrolyte filling process is done then the cell is sealed.


All the cells will then go through formation process where they will be go through predetermined charge, discharge, procedures.


The formed cells are stored for several days.  Number of days may vary depending upon the manufacturer and their quality process.


At the end of the above storage process the cells will be tested for Open Circuit Voltage and capacity.


Based on the capacity the cells will be sorted and labeled accordingly.

Packaging and shipping:

The cells will then be packaged and shipped or stored.

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Wednesday, 3 April 2013

Electrode manufacturing process for lithium ion batteries

Electrode Manufacturing Process For lithium ion batteries:


This step involves mixing active materials with appropriate particle size with binder and conductive carbon. Mixing is done for different length of time depending upon the starting material, application needs, final viscosity of the slurry etc.,


Slurry obtained from the mixing process slowly poured on the substrate foil (Copper or Aluminum) in a controlled way. The slurry is then spread uniformly on to the substrate and partially dried. Small area on the side of the electrode is not coated usually.  This small area will later be cut into tabs/terminals.


Then it is pressed and dried.  During this process the electrode is pressed and passed through number of rotating cylinders.


The electrode is then dried and may be pressed again.


During this process the electrode is cut according to the required width and rolled.  This finished electrode will be used for manufacturing cells.