STACK/FOLDING-TYPED ELECTRODE ASSEMBLY AND METHOD FOR PREPARATION OF THE SAME

• US 20110052964A1
• Filed: 12/12/2008
• Published: 03/03/2011
• Est. Priority Date: 12/14/2007
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: Kim, KiJae, Kim, Min Su
• Granted Patent: US 9,209,491 B2
• Time in Patent Office: Days
• US Class Current: 429/152
• CPC Class Codes: H01M 10/0459 Cells or batteries with folded separator between plate-like electrodes
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/0583 of accumulators with folded construction elements except wound ones, i.e. folded positive or negative electrodes or separators, e.g. with "Z"-shaped electrodes or separators
• CPC Class Codes: H01M 50/417 Polyolefins
• CPC Class Codes: H01M 50/46 Separators, membranes or diaphragms characterised by their combination with electrodes
• CPC Class Codes: H01M 50/463 Separators, membranes or diaphragms characterised by their shape
• CPC Class Codes: H01M 50/489 Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
• CPC Class Codes: H01M 50/491 Porosity
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y10T 29/49108 Electric battery cell making

Abstract

Disclosed herein is an electrode assembly constructed in a structure in which a plurality of electrochemical cells, formed of full cells having a cathode/separator/anode structure, as basic units, are overlapped, and a continuous separator sheet is disposed between the overlapped electrochemical cells, wherein a unit electrode surrounded by the separator sheet is located at a middle of the overlapped electrochemical cells, which is a winding start point, and the full cells disposed above and below the unit electrode are symmetrical to each other about the unit electrode in the direction of electrodes of the full cells. The electrode assembly is manufactured with high productivity while the electrode assembly exhibits performance and safety equal to those of a conventional stack/folding type electrode assembly.

Claims

1. An electrode assembly constructed in a structure in which a plurality of electrochemical cells, formed of full cells having a cathode/separator/anode structure, as basic units, are overlapped, and a continuous separator sheet is disposed between the overlapped electrochemical cells, wherein

a unit electrode surrounded by the separator sheet is located at a middle of the overlapped electrochemical cells, which is a winding start point, and the full cells disposed above and below the unit electrode are symmetrical to each other about the unit electrode in the direction of electrodes of the full cells.

3. The electrode assembly according to claim 1, wherein the separator sheet has unit lengths sufficient to surround the respective electrochemical cells, and the separator sheet is bent inward every unit length to successively surround the unit electrode or the central bi-cell and the full cells from the central unit electrode or the central bi-cell to the outermost full cell.

4. The electrode assembly according to claim 1, wherein the full cells have i) a cathode/separator/anode structure or ii) a cathode/separator/anode/separator/cathode/separator/anode structure.

5. The electrode assembly according to claim 1, wherein the unit electrode or the bi-cell located at the middle of the overlapped electrochemical cells, which is the winding start point, is an anode or a C-type bi-cell.

6. The electrode assembly according to claim 1, wherein the electrode assembly is constructed such that anodes are located at the topmost layer and the bottommost layer of the electrode assembly forming an outer surface of the electrode assembly.

7. The electrode assembly according to claim 6, wherein, when a cathode or an A-type bi-cell is located at the middle of the overlapped electrochemical cells, which is the winding start point, C-type bi-cells are located at the topmost layer and the bottommost layer of the electrode assembly.

8. The electrode assembly according to claim 1, wherein the outermost end of the separator sheet is fixed by thermal welding or a tape.

9. The electrode assembly according to claim 1, wherein the separator or the separator sheet is made of one selected a group consisting of micro porous polyethylene film, polypropylene film, multi-layered film manufactured by a combination of the polyethylene film and the polypropylene film, and polymer film for a polymer electrolyte, such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, and polyvinylidene fluoride hexafluoropropylene copolymer.

10. The electrode assembly according to claim 1, wherein the cathode is an electrode manufactured by coating opposite major surfaces of a cathode current collector with a cathode material, and the anode is an electrode manufactured by coating opposite major surfaces of an anode current collector with an anode material.

11. A secondary battery comprising the electrode assembly according to claim 1.

12. The secondary battery according to claim 11, wherein the secondary battery is a lithium secondary battery.

13. A middle- or large-sized battery module comprising the secondary battery according to claim 12 as a unit cell.

2. An electrode assembly constructed in a structure in which a plurality of electrochemical cells, formed of full cells having a cathode/separator/anode structure, as basic units, are overlapped, and a continuous separator sheet is disposed between the overlapped electrochemical cells, wherein

i) a bi-cell (‘

A-type bi-cell’

), having a cathode/separator/anode/separator/cathode structure, surrounded by the separator sheet, or ii) a bi-cell (‘

C-type bi-cell’

), having an anode/separator/cathode/separator/anode structure, surrounded by the separator sheet, is located at a middle of the overlapped electrochemical cells, which is a winding start point, and the full cells disposed above and below the bi-cell are symmetrical to each other about the bi-cell in the direction of electrodes of the full cells.

14. A method of manufacturing an electrode assembly constructed in a structure in which a plurality of electrochemical cells, formed of full cells having a cathode/separator/anode structure, as basic units, are overlapped, and a separator sheet is disposed between the overlapped electrochemical cells, the method comprising:

1) stacking a long cathode sheet and a long anode sheet, while disposing a separator between the cathode sheet and the anode sheet, and cutting the stack into a predetermined size to manufacture a plurality of full cells;

2) placing a unit electrode, which is a cathode or an anode, at a first stage of a long separator sheet and placing the full cells (the first full cell, the second full cell, the third full cell . . . ) manufactured by step

     1) from a second stage at predetermined intervals in the same electrode orientation; and

3) winding the unit electrode with the separator sheet once and folding the separator sheet from the first full cell toward the outside where the neighboring full cells are located such that the respective full cells are overlapped.

16. The method according to claim 14, further comprising:

attaching the unit electrode or the bi-cell and the full cells placed at step

     2) to the separator sheet before the winding.

17. The method according to claim 14, wherein, at step 2), the full cells are located such that top electrodes of the full cells have a polarity opposite to that of a bottom electrode of the unit cell or the bi-cell located at the first stage of the separator sheet.

18. The method according to claim 14, wherein the full cells are wound such that the first full cell has a bottom electrode opposite in polarity to a top electrode of the third full cell, the second full cell has a bottom electrode opposite in polarity to a top electrode of the fourth full cell, and the third full cell has a bottom electrode opposite in polarity to a top electrode of the fifth full cell.

19. The method according to claim 14, wherein, at step 2), the unit electrode or the bi-cell located at the first stage of the separator sheet is spaced from the end of the separator sheet where the winding starts by at least a distance equivalent to the sum of a width and thickness of the unit electrode, and the second and following full cells are located at intervals equivalent to the sum of a thickness of each full cell and a thickness of the separator sheet increased by winding.

20. The method according to claim 14, wherein, at step 2), the first full cell is spaced from the unit electrode or the bi-cell located at the first stage of the separator sheet by at least a distance equivalent to the sum of a width and thickness of the unit electrode or the bi-cell, and the second and following full cells are located at intervals equivalent to the sum of a thickness of each full cell and a thickness of the separator sheet increased by winding.

21. The method according to claim 14, wherein a unit cell (n^th cell) located at the last stage of the separator sheet at step 2) and an n−

1^th cell adjacent to the n^th cell are constructed such that bottom electrodes of the n^th and n−

1^th cells become anodes.

22. The method according to claim 21, wherein, when a cathode or an A-type bi-cell is located at the first stage of the separator sheet, the n^th and n−

1^th cells are C-type bi-cells.

15. A method of manufacturing an electrode assembly constructed in a structure in which a plurality of electrochemical cells, formed of full cells having a cathode/separator/anode structure, as basic units, are overlapped, and a separator sheet is disposed between the overlapped electrochemical cells, the method comprising:

1) stacking a long cathode sheet and a long anode sheet, while disposing a separator between the cathode sheet and the anode sheet, and cutting the stack into a predetermined size to manufacture a plurality of full cells;

2) placing an A-type bi-cell or a C-type bi-cell at a first stage of a long separator sheet and placing the full cells (the first full cell, the second full cell, the third full cell . . . ) manufactured by step

     1) from a second stage at predetermined intervals in the same electrode orientation; and

3) winding the bi-cell with the separator sheet once and folding the separator sheet from the first full cell toward the outside where the neighboring full cells are located such that the respective full cells are overlapped.