High-capacity and high-reliability lithium iron disulfide cell designs and methods for making the same
View Patent ↗The invention relates to primary electrochemical cells, in addition to methods for manufacturing and discharging the same, having a jellyroll electrode assembly that includes a positive electrode with a coating comprising iron disulfide deposited on a current collector situated on the outermost circumference of the jellyroll, a lithium-based negative electrode and a polymeric separator. More particularly, the invention relates to a cell design which optimizes cell capacity and substantially eliminates premature voltage drop-off on intermittent service testing by eliminating the edge effect through, for example, deliberately relieving stack pressure and/or extending the distance lithium ions proximate to the terminal end of the positive electrode must travel to undergo an electrochemical reaction in that region.
1. An electrochemical cell comprising:
a container;
an organic, non-aqueous electrolyte;
an electrode assembly having an anode consisting essentially of lithium or a lithium alloy strip, a cathode comprising iron disulfide at least partially coated onto both sides of a solid, metallic foil current collector and a separator disposed between the anode and the cathode;
wherein the cell possesses an interfacial anode under-balance and the anode and the cathode are spirally wound so that less than 50% of an outermost surface of the electrode assembly, excluding the separator and optional non-active components, is covered by the anode; and
means for eliminating an edge effect positioned proximate to the cathode in the outermost surface of the electrode assembly that comprises a pore-blocking substance disposed within the cathode coating along an axial strip at a terminal edge of the cathode.
2. An electrochemical cell comprising:
a container;
an organic, non-aqueous electrolyte;
an spirally wound electrode assembly having a separator, an anode consisting essentially of lithium or a lithium alloy strip and a cathode having active material comprising iron disulfide at least partially coated onto both sides of a current collector having a terminal edge oriented on an outermost surface of the spirally wound electrode assembly;
a spacer situated proximate to the terminal edge having a thickness that is: i) at least twice the thickness of the cathode, inclusive of the coating on both sides and the current collector, or ii) greater than a combined thickness of the anode, the cathode and the separator; and
wherein the cell possesses an interfacial anode under-balance and the anode and the cathode are spirally wound so as to have a cathode-outer wrap.
3. The electrochemical cell according to claim 2 , wherein the spacer comprises a plurality of members.
4. The electrochemical cell according to claim 3 , wherein the members are stacked on top of one another.
5. The electrochemical cell according to claim 3 , wherein the members are aligned along an axis that coincides with the terminal edge of the cathode.
6. The electrochemical cell according to claim 2 , wherein the spacer comprises an elastomeric material.