Cell structure for electrochemical devices and method of making same
An electrochemical device comprising alternating layers of positive and negative electrodes separated from each other by separator layers. The electrode layers extend beyond the periphery of the separator layers providing superior contact between the electrodes and battery terminals, eliminating the need for welding the electrode to the terminal. Electrical resistance within the battery is decreased and thermal conductivity of the cell is increased allowing for superior heat removal from the battery and increased efficiency. Increased internal pressure within the battery can be alleviated without damaging or removing the battery from service while keeping the contents of the battery sealed off from the atmosphere by a pressure release system. Nonoperative cells within a battery assembly can also be removed from service by shorting the nonoperative cell thus decreasing battery life.
1. An electrochemical device, comprising:
an electrode assembly comprising: an elongated positive electrode;
an elongated negative electrode; and
a plurality of separation layers engagable with each other to form a continuous separation barrier between each of the positive electrode and the negative electrode; the plurality of separation layers positioned such that the positive electrodes, separation layers, and negative electrode are wound around a central axis thereby forming a coil of alternating electrode and separation layers such that the separation layer prevents direct contact between successive electrode layers;
a first longitudinal edge of the positive electrode extending beyond a first longitudinal edge of the separation layer, and a first longitudinal edge of the negative electrode extending beyond a second longitudinal edge of the separation layer such that the plurality of separation layers is tensioned across the electrode assembly and defines a cell width with the width of the electrodes extending beyond the width of the plurality of separator layers; and
a housing having a positive plate electrically coupled to the first longitudinal edge of the positive electrode and a negative plate electrically coupled to the first longitudinal edge of the negative electrode, wherein the electrode assembly is enclosed by the housing.
2. The device of claim 1 , wherein the separation layer comprises a central portion having a first end and second end and a first protruding portion and second protruding portion with the central portion being longer than the first and second protruding portions, the first and second protruding portions extending from substantially the first and second ends respectively with the negative electrode partially disposed between the central portion and the first protruding portion and the positive electrode partially disposed between the central portion and the second protruding portion.
3. The device of claim 2 , wherein each of the protruding portions of each of the plurality of separation layers overlaps the protruding portion of another separation layer.
4. The device of claim 3 , wherein the separation layers are indexed such that position of the overlap of the separation layers varies substantially evenly across the cell width.