Making a pouch format cell and attaching a tab to an electrode
To make a pouch format cell, an outermost stack (including a negative electrode and separators positioned on opposed surfaces thereof) is formed. An inner stack is formed, including a positive electrode and a sub-stack (i.e., another negative electrode with separators positioned on opposed surfaces thereof and another positive electrode). The inner stack is positioned on the outermost stack to form a core stack, such that i) one inner stack end substantially aligns with one outermost stack end, ii) another end and a portion of the outermost stack remain exposed, and iii) the inner stack positive electrode is adjacent to one of the outermost stack separators. The outermost stack exposed portion is folded around another inner stack end and to cover a portion of an outer layer of the inner stack. This forms an initial overlay. The core stack is folded around at least a portion of the initial overlay.
1. A method for making a pouch format cell, comprising:
forming an outermost stack including a negative electrode and separators positioned on opposed surfaces of the negative electrode;
forming an inner stack including:
a positive electrode; and
at least one sub-stack of another negative electrode, another positive electrode, and other separators positioned on opposed surfaces of the other negative electrode;
positioning the inner stack on the outermost stack such that i) a first end of the inner stack substantially aligns with one end of the outermost stack, ii) a second end of the inner stack and a portion of the outermost stack remain exposed, and iii) the positive electrode of the inner stack is adjacent to one of the separators of the outermost stack, thereby forming a core stack;
folding the exposed portion of the outermost stack around the second end of the inner stack so as to cover a portion of an outer layer of the inner stack, thereby forming an initial overlay; and
folding the core stack a predetermined number of times around at least a portion of the initial overlay.
2. The method as defined in claim 1 wherein the inner stack includes a plurality of sub-stacks.
3. The method as defined in claim 1 wherein the negative electrodes are lithium metal and wherein the pouch format cell excludes a negative-side current collector.
4. The method as defined in claim 1 wherein the negative electrodes are carbon and wherein the pouch format cell excludes a negative-side current collector.
5. The method as defined in claim 1 wherein the positive electrodes are sulfur-carbon composite electrodes and wherein the pouch format cell excludes a positive-side current collector.
6. The method as defined in claim 5 wherein the positive electrodes include a binder and a conductive filler.
7. The method as defined in claim 1 wherein prior to forming the outermost stack and the inner stack, the method further comprises attaching a tab to each of the negative electrodes by:
forming a sandwich structure including a first piece of foil, the negative electrode, the tab, and a second piece of foil; and
welding the sandwich structure.
8. The method as defined in claim 7 wherein after the folding of the core stack, the method further comprises welding the tabs attached to each of the negative electrodes together to form a single negative electrode tab.
9. The method as defined in claim 1 wherein prior to forming the outermost stack and the inner stack, the method further comprises attaching a tab to each of the positive electrodes by:
forming a sandwich structure including a first piece of foil, the positive electrode, the tab, and a second piece of foil; and
welding the sandwich structure.
10. The method as defined in claim 9 wherein after the folding of the core stack, the method further comprises welding the tabs attached to each of the positive electrodes together to form a single positive electrode tab.
11. The method as defined in claim 1 , further comprising trimming an edge of the core stack such that the positive electrodes, the negative electrodes, and the separators are substantially aligned with one another at the edge of the core stack.
12. The method as defined in a claim 1 wherein the core stack includes:
n number of negative electrodes including the negative electrode and the other electrode;
n number of positive electrodes including the positive electrode and the other positive electrode; and
2n number of separators including the separators and the other separators;
wherein a single separator of the 2 n number of separators is positioned between adjacent electrodes of the n number of negative electrodes and the n number of positive electrodes.
13. The method as defined in claim 1 wherein the predetermined number of times is one time.
14. The method as defined in claim 1 wherein the predetermined number of times is at least two times.
15. The method as defined in claim 1 , further comprising:
placing the pouch format cell into a pouch;
adding an electrolyte to the pouch; and
sealing the pouch.