ELECTROCHEMICAL SEPARATORS WITH INSERTED CONDUCTIVE LAYERS
Disclosed are electrochemical cells including a composite separator capable of changing the performance of the cell by a) changing the internal electric field of the cell, b) activating lost active material, c) providing an auxiliary current collector for an electrode and/or d) limiting or preventing hot spots and/or thermal runaway upon formation of an electronic short in the system. An exemplary composite separator includes at least one electronically conducting layer and at least one electronically insulating layer. Another exemplary composite separator includes an electronically conducting layer and a solid ionic conductor. Also disclosed are methods for detecting and managing the onset of a short in an electrochemical cell and for charging an electrochemical cell.
1 . An electrochemical cell comprising:
a positive electrode;
a negative electrode;
one or more ionically conductive electrolytes positioned between said positive electrode and said negative electrode; and
a composite separator comprising at least one electronically insulating layer and at least one electronically conductive layer; said composite separator being positioned between said positive electrode and said negative electrode and being permeable to ionic charge carriers, but not electronically conductive across the composite separator;
wherein said electronically conductive layer undergoes deposition or electroplating of ionic charge carriers or chemical reaction with a dendrite structure or an internal defect upon formation of an internal short between the negative or the positive electrode and said electronically conductive layer, the short formed by contact of the dendrite structure or the internal defect with said electronically conductive layer.
2 . The electrochemical cell of claim 1 , wherein the electronically conductive layer is chemically reactive with the dendrite structure.
3 . The electrochemical call of claim 2 , wherein the chemical reaction is an alloying reaction.
4 . The electrochemical cell of claim 1 , wherein the dendrite structure is a lithium or zinc dendrite.
5 .- 7 . (canceled)
8 . The electrochemical cell of claim 1 , wherein said positive electrode comprises a positive electrode active material, said negative electrode comprises a negative electrode active material and said electronically conductive layer is provided between said insulating layer and said positive electrode or said negative electrode, thereby providing an additional electronic path for the positive electrode active material or the negative electrode active material.
9 . The electrochemical cell of claim 1 further comprising a second insulating layer, wherein said electronically conductive layer is provided between the two insulating layers.
10 .- 14 . (canceled)
15 . The electrochemical cell of claim 1 , wherein said electronically conductive layer is a perforated or porous layer having a porosity greater than or equal to 30% and less than or equal to 90%.
16 .- 17 . (canceled)
18 . An electrochemical cell comprising:
a positive electrode comprising a positive electrode active material and a first current collector in electronic communication with the positive electrode active material, the first current collection further comprising a first external connection tab;
a negative electrode comprising a negative electrode active material and a second current collector in electronic communication with the negative electrode active material, the second current collector further comprising a second external connection tab;
one or more ionically conductive electrolytes positioned between said positive electrode and said negative electrode; and
a composite separator comprising at least one electronically insulating layer and at least one electronically conductive layer; said composite separator being positioned between said positive electrode and said negative electrode and being permeable to ionic charge carriers, but not electronically conductive across the composite separator;
wherein said electronically conductive layer further comprises a third external connection tab and is not provided in electrical contact with said positive electrode or said negative electrode in the absence of said electrical short.
19 . The electrochemical cell of claim 18 , further comprising a voltage or current monitoring circuit or voltage or current applying circuit connected between said electronically conductive layer and the negative or positive electrode.
20 .- 21 . (canceled)
22 . The electrochemical cell of claim 18 , wherein said positive electrode comprises a positive electrode active material, said negative electrode comprises a negative electrode active material and said electronically conductive layer is provided between said insulating layer and said positive electrode or said negative electrode, thereby providing an additional electronic path for the positive electrode active material or the negative electrode active material.
23 . The electrochemical cell of claim 18 , further comprising a second insulating layer, wherein said electronically conductive layer is provided between the two insulating layers.
24 .- 29 . (canceled)
30 . The electrochemical cell of claim 18 , further comprising a solid electrolyte, wherein said electronically conductive layer is provided between the solid electrolyte and the insulating layer.
31 . The electrochemical cell of claim 18 , further comprising a solid electrolyte, wherein the electronically conducting layer is porous and the solid electrolyte is provided in the pores of the electronically conducting layer.
32 .- 57 . (canceled)
58 . An electrochemical system comprising the electrochemical cell of claim 18 and further comprising a device for assessing state of charge or state of health of the electrochemical cell, thereby allowing application of voltage or current through voltage or current applying circuit as a function of state of charge and state of health of the cell, during each cycle.
59 . A method of detecting the onset of a short in an electrochemical cell;
said method comprising the steps of:
providing said electrochemical cell comprising:
a positive electrode;
a negative electrode;
one or more ionically conducting electrolytes positioned between said positive electrode and said negative electrode; and
a composite separator comprising an electronically insulating and an electronically conductive layer; said separator positioned between said positive electrode and said negative electrode such that said charge carriers are able to be transported between said positive electrode and said negative electrode; and
monitoring the voltage, current, capacity or a combination thereof of said electrochemical cell, wherein said electrochemical cell undergoes an observable change in voltage, current, capacity or a combination thereof between any two of the positive electrode, the negative electrode and the electronically conductive layer upon formation of an electrical short between the electronically conductive layer and said positive electrode or said negative electrode.
60 . The method of claim 59 , wherein the positive electrode comprises a positive electrode active material and a first current collector in electronic communication with the positive electrode active material, the first current collection further comprising a first external connection tab, the negative electrode comprises a positive electrode active material and a second current collector in electronic communication with the negative electrode active material, the second current collection further comprising a second external connection tab, said electronically conductive layer further comprises a third external connection tab, and the voltage monitored is the voltage between the electronically conductive layer and the positive electrode or the negative electrode.
61 . The method of claim 59 , further comprising the step of changing at least one operating condition of said electrochemical cell in the event of detection of said observable change in voltage, current, capacity or a combination thereof, wherein said operating condition is selected from the group consisting of a discharge rate, a load on said electrochemical cell, an voltage between the positive electrode and the negative electrode, and a temperature of said electrochemical cell.
62 . A method of reducing dendrite growth in an electrochemical cell; said method comprising the steps of:
a) providing said electrochemical cell comprising:
a positive electrode;
a negative electrode;
one or more electrolytes positioned between said positive electrode and said negative electrode; said one or more ionically conductive electrolytes; and
a composite separator comprising an electronically insulating and an electronically conductive layer; said separator positioned between said positive electrode and said negative electrode such that said charge carriers are able to be transported between said positive electrode and said negative electrode; and
charging said electrochemical cell, wherein said electronically conductive layer undergoes deposition, electrochemical plating or alloy reaction with a dendrite structure formed during charge between the electronically conductive layer and said positive electrode, negative electrode or both.
63 . The method of claim 62 , wherein said deposition, electrochemical plating or alloy reaction stops or decrease the rate of growth of said dendrite structure or internal defect.
64 . A method of operating an electrochemical cell, the method comprising the steps of:
providing said electrochemical cell comprising:
a positive electrode;
a negative electrode;
one or more ionically conductive electrolytes positioned between said positive electrode and said negative electrode; and
a composite separator comprising at least one electronically insulating layer and at least one electronically conductive layer; said composite separator being positioned between said positive electrode and said negative electrode and being permeable to ionic charge carriers, but not electronically conductive across the composite separator;
charging, discharging or charging and discharging the electrochemical cell, thereby inducing a surface charge on the surface of the electronically conductive layer.
65 . The method of claim 64 , wherein said electronically conductive layer provides an electric field adjacent to and within said positive electrode, said negative electrode or both, thereby providing uniform ion deposition into said positive electrode, said negative electrode or both during charging or discharging of said electrochemical cell.
66 . (canceled)
67 . The method of claim 64 , further comprising changing at least one operating condition of said electrochemical cell in the event of detection of said observable change in voltage.
68 .- 70 . (canceled)
71 . The electrochemical call of claim 18 , further comprising a voltage or current applying circuit connected between each of said electrochemically conductive layers and one of the positive or the negative electrode, thereby allowing modification of the electric field and the performance of the electrochemical cell.
72 . The method of claim 64 , wherein
the positive electrode comprises a positive electrode active material and a first current collector in electronic communication with the positive electrode active material, the first current collection further comprising a first external connection tab;
the negative electrode comprises a negative electrode active material and a second current collector in electronic communication with the negative electrode active material, the second current collector further comprising a second external connection tab;
electronically conductive layer further comprises a third external connection tab and is not provided in electrical contact with said positive electrode or said negative electrode;
and the method further comprises the step of applying a voltage or current between the third external connection tab and one of the first or the second external connection tab, thereby redistributing active material in the cell.
73 . The method of claim 64 , wherein
the positive electrode comprises a positive electrode active material and a first current collector in electronic communication with the positive electrode active material, the first current collection further comprising a first external connection tab;
a negative electrode comprises a negative electrode active material and a second current collector in electronic communication with the negative electrode active material, the second current collector further comprising a second external connection tab;
the cell further comprises a layer of electrolyte additive attached to said electronically conductive layer; and
the method further comprises the step of applying a voltage or current between the third external connection tab and one of the first or the second external connection tabs, thereby releasing electrolyte additive into the electrolyte of the cell.