Stack type electrode assembly in which bending phenomenon is alleviated, and manufacturing method therefor
An electrode includes a unit body stack part formed by stacking at least one basic unit having a four-layer structure in which a first electrode, a first separator, a second electrode and a second separator are sequentially stacked. Each surface of the first separator and the second separator is coated with a coating material having adhesiveness, and the basic unit adheres to an adjacent radial unit in the unit body stack part. The electrode assembly of allows a heating and pressing process to be performed prior to a primary formation process so that a separator of one basic unit and a first electrode of the other basic unit to be adhered and fixed by a coating material coated on the separator, and thus a bending phenomenon caused by a difference in electrode expansion rates in a charging/discharging process is prevented.
1. An electrode assembly comprising a unit body stack portion which is generated by stacking at least two basic unit bodies, each basic unit body having at least a four-layer structure in which a first electrode, a first separator, a second electrode and a second separator are sequentially stacked and adhered prior to the at least two basic unit bodies being stacked,
wherein coating materials having adhesive force are applied to respective surfaces of the first and second separators,
wherein one basic unit body of the at least two basic bodies is adhered to an adjacent basic unit body of the at least two basic bodies in the unit body stack portion, and
wherein adhesive force between the one basic unit body and the adjacent basic unit body is greater than adhesive force between the first electrode and the first separator in each basic unit body.
2. The electrode assembly of claim 1 , wherein the second separator is coated with the coating material on one side facing the second electrode and on an opposite side thereof, and the at least two basic unit bodies are adhered to each other by the coating material of the second separator.
3. The electrode assembly of claim 1 , wherein a difference between a thickness of the electrode assembly measured for 2 seconds under a pressure of 30 kgf and a thickness of the electrode assembly measured for 2 seconds under a pressure of 90 kgf is 100 μm or less.
4. The electrode assembly of claim 1 , wherein the first electrode is a positive electrode, and
wherein the second electrode is a negative electrode.
5. The electrode assembly of claim 1 , wherein each basic unit body is formed by repeatedly stacking the four-layer structure.
6. A method for manufacturing a secondary battery including the electrode assembly of claim 1 , the method comprising steps of:
preparing each basic unit body having the four-layer structure in which the first electrode, the first separator, the second electrode and the second separator are sequentially stacked (S 100 );
preparing the unit body stack portion by repeatedly stacking the basic unit bodies (S 200 );
accommodating the electrode assembly including the unit body stack portion in a battery case, then injecting electrolyte and sealing the battery case (S 300 ); and
making the second separator of the one basic unit body be adhered to the first electrode of the adjacent basic unit body in the unit body stack portion by applying heat and pressure (S 400 ).
7. The method of claim 6 , wherein the coating material having the adhesive force includes a binder.
8. The method of claim 7 , wherein a temperature of the applied heat of step S 400 is 45° C. to 85° C.
9. The method of claim 7 , wherein a temperature of the applied heat of step S 400 is 45° C. to 70° C.
10. The method of claim 6 , wherein a pressure of the applied pressure of step S 400 is 1 to 10 kgf/cd, and heating and pressurizing time is 2 to 20 minutes.
11. The method of claim 6 , wherein, after the step S 400 , a primary formation process is performed.
12. The method of claim 11 , wherein a temperature during the primary formation process is 45° C. or less.
13. The method of claim 6 , wherein a solvent of the electrolyte is ethyl methyl carbonate or dimethyl carbonate.
14. A secondary battery including an electrode assembly according to claim 1 .