Increasing the stiffness of battery cells for portable electronic devices
The disclosed embodiments relate to the manufacture of a battery cell. The battery cell includes a set of layers including a cathode with an active coating, a separator, and an anode with an active coating. The battery cell also includes a pouch enclosing the layers, wherein the pouch is flexible. The layers may be wound to create a jelly roll prior to sealing the layers in the flexible pouch. The stiffness of the battery cell may be increased by applying a pressure of at least 0.13 kilogram-force (kgf) per square millimeter and a temperature of about 85° C. to the layers.
1. A method for manufacturing a battery cell, comprising:
obtaining a set of layers for the battery cell, wherein the set of layers comprises a cathode with an active coating, a separator, and an anode with an active coating;
sealing the layers in a pouch to form the battery cell, wherein the pouch is flexible; and
increasing a stiffness of the battery cell by applying a pressure of at least 0.13 kilogram-force (kgf) per square millimeter and a temperature of about 85° C. to the layers, wherein the pressure and the temperature are applied to the layers for about eight hours.
2. The method of claim 1 , further comprising:
winding the layers to create a jelly roll prior to sealing the layers in the flexible pouch.
3. The method of claim 1 , further comprising:
performing a formation charge on the battery cell prior to applying the pressure and the temperature to the layers; and
degassing the battery cell after applying the pressure and the temperature to the layers.
4. The method of claim 3 , wherein degassing the battery cell involves:
puncturing a portion of the pouch that does not contact the layers to release gas generated during the formation charge by the battery cell; and
resealing the pouch along a line that is closer to the layers than the punctured portion; and
removing extra pouch material associated with the punctured portion from the battery cell.
5. The method of claim 1 , wherein the layers further comprise a binder coating that laminates the layers together upon applying the pressure and the temperature to the layers.
6. The method of claim 5 , wherein the binder coating is approximately 1 micron thick.
7. The method of claim 5 , wherein the binder coating is applied to at least one of the cathode, the anode, and the separator.
8. The method of claim 7 , wherein the binder coating is applied using at least one of a dip-coating technique and a spray-coating technique.
9. The method of claim 3 , further comprising:
prior to performing the formation charge on the battery cell, flattening the battery cell by applying a pressure for about a minute to the layers.