Battery with enhanced resistance to dendrite formation
A battery includes a case having a feedthrough port, a feedthrough assembly disposed in the feedthrough port, and a cell stack disposed within the case. The feedthrough port includes an inner conductor and an insulator core separating the inner conductor from the case. The cell stack includes an anode, a cathode, and a separator insulating the anode from the cathode, wherein the anode and cathode are offset from one another. An insulating boot surrounding the cell stack insulates the cell stack from the case. The insulating boot has an opening configured to receive therein the feedthrough assembly, which may include overmolded insulation. The interior surfaces and interior walls of the battery case may be thermal spray-coated with a dielectric material to prevent lithium dendrite formation between cathode and anode surfaces.
1. A battery, comprising:
a case having an inner surface and a feedthrough port;
a layer of a dielectric material disposed over at least a portion of the inner surface of the case, the layer of dielectric material being operable to prevent short circuits;
a feedthrough assembly disposed in the feedthrough port, the feedthrough assembly including:
a ferrule having a lumen;
an inner conductor disposed within the lumen of the ferrule;
an insulating core disposed within the lumen of the ferrule and separating the inner conductor from the ferrule; and
feedthrough insulation disposed circumferentially around a portion of the ferrule positioned in the case;
a cell stack disposed within the case, the cell stack including
an anode having a main anode body and an anode tab projecting from the main anode body, the main anode body having an anode outer edge, the anode outer edge having a first peripheral portion distant from the anode tab, and a second peripheral portion that is a remainder of the anode outer edge, surfaces of the main anode body including an anode active material;
a cathode having a main cathode body and a cathode tab projecting from the main cathode body, the main cathode body having a cathode outer edge, the cathode outer edge having a first peripheral portion adjacent the cathode tab, and a second peripheral portion that is a remainder of the cathode outer edge, surfaces of the main cathode body including a cathode active material; and
one or more separator layers electrically insulating the anode from the cathode, the anode, the cathode and the one or more separator layers being stacked together with the main anode body offset from the main cathode body such that the first peripheral portion of the main anode body is recessed from the first peripheral portion of the main cathode body by a first offset distance, and such that the anode active material at the first peripheral portion of the main anode body is recessed from the cathode active material at the first peripheral portion of the main cathode body; and
an insulating boot surrounding the cell stack to electrically insulate the cell stack from the case, the insulating boot having an opening, the feedthrough insulation being positioned in the opening and sealed to the insulating boot.
2. The battery as claimed in claim 1 , wherein the insulating boot includes a lip around the opening that overlaps at least a part of the feedthrough insulation and is sealed to the feedthrough insulation.
3. The battery as claimed in claim 2 , wherein the insulating boot forms a liquid-tight seal with the feedthrough insulation, the liquid-tight seal being formed by heat-sealing, a compression joint, an adhesive, or a combination thereof.
4. The battery as claimed in claim 3 , wherein the insulating boot is heat-sealed to the feedthrough insulation by a laser weld, an RF weld, a resistance weld, a friction weld, or combinations thereof.
5. The battery as claimed in claim 1 , wherein the insulating boot comprises a material selected from the group consisting of polyethylene (PE), ethyltetrafluoroethylene (ETFE), polyether ether ketone (PEEK), polypropylene (PP), and mixtures thereof.
6. The battery as claimed in claim 5 , wherein the material of the insulating boot has an average pore diameter of up to 0.05 μm.
7. The battery as claimed in claim 5 , wherein the feedthrough insulation comprises a material selected from the group consisting of polyethylene (PE), ethylenetetrafluoroethylene (ETFE), polyether ether ketone (PEEK), polypropylene (PP), polyurethane (PU), polycarbonate (PC), silicones, and mixtures thereof.
8. The battery as claimed in claim 1 , wherein the separator layers and the insulating boot are formed from the same material.
9. The battery as claimed in claim 1 , further comprising an electrolyte, wherein a weight ratio of the electrolyte to the cathode active material is between 0.25 and 0.4.
10. The battery as claimed in claim 1 , wherein the cathode active material comprises silver vanadium oxide (SVO) or a mixture of SVO and carbon monofluoride (CFx).
11. The battery as claimed in claim 1 , wherein the first offset distance is between 0.001 inches and 0.03 inches.
12. The battery as claimed in claim 11 , wherein the first offset distance is between 0.01 inches and 0.02 inches.