Pulse plating of lithium matertal in electrochemical devices
The present invention is directed to battery system and operation thereof. In an embodiment, lithium material is plated onto the anode region of a lithium secondary battery cell by a pulsed current. The pulse current may have both positive and negative polarity. One of the polarities causes lithium material to plate onto the anode region, and the opposite polarity causes lithium dendrites to be removed. There are other embodiments as well.
1. A method for forming a lithium metal anode in an electrochemical device,
the method comprising:
providing a cathode, the cathode having a positive current collector;
providing a lithium conducting electrolyte region having a top surface and a bottom surface, the top surface interfacing a lithiated cathode;
providing a negative current collector interfacing the bottom surface of the electrolyte region, wherein the negative current collector includes a layer of a metal that enhances plating uniformity; and
supplying a plurality of current pulses,
the plurality of current pulses comprising a first pulse and a second pulse,
the first pulse causing a formation of a layer of lithium metal anode positioned between the negative current collector and the bottom surface,
the first pulse being characterized by a first amount of charge and first polarity during a first duration,
the second pulse being characterized by a second amount of charge and second polarity during a second duration,
the first amount of charge being greater than the second amount of charge.
2. The method of claim 1 , wherein:
the layer of lithium metal anode comprises a non-uniform region;
the first polarity is opposite from the second polarity;
the second pulse causes a removal of a portion of the non-uniform region during the second duration.
3. The method of claim 1 , wherein the layer of lithium metal anode is formed in-situ.
4. The method of claim 1 , wherein the magnitude of the second amount of charge is substantially zero.
5. The method of claim 1 , wherein the first polarity and the second polarity are opposite.
6. The method of claim 1 , wherein the electrolyte region is characterized by a thickness of less than 10 microns.
7. The method of claim 1 , wherein the electrolyte region is characterized by a thickness of less than 50 microns.
8. The method of claim 1 , wherein the plurality of current pulses is characterized by an average net current density of 0.1 mA/cm 2 to 50 mA/cm 2 .
9. The method of claim 1 , wherein the plurality of current pulses comprises a pulse of the first polarity to charge the device interspersed by rest periods.
10. The method of claim 1 , wherein the plurality of current pulses comprises a first plurality of pulses in the first polarity to charge the device interspersed by second plurality of pulses in a second polarity, the second polarity being a reverse polarity relative to the first polarity.
11. The method of claim 1 , wherein the lithium conducting electrolyte region interfaces the lithium metal anode at the bottom surface, the lithium metal anode is characterized by a permittivity ε and a conductivity σ, and the majority of current pulses are of a duration longer than εε 0 /σ, wherein εε 0 is the permittivity of free space.
12. The method of claim 11 , wherein the electrolyte comprises a polymer.
13. The method of claim 1 , wherein the electrolyte comprises a solid ceramic.
14. The method of claim 1 , wherein the layer of a metal that enhances plating uniformity comprises a metal selected from indium, aluminum, or magnesium.
15. A method for operating a lithium metal anode electrochemical device, wherein the electrochemical device comprises a cathode current collector, an anode current collector, wherein the anode current collector includes a layer of a metal that enhances plating uniformity, a solid electrolyte region positioned between the cathode current collector and the anode current collector, and an anode region defined between the anode current collector and the solid electrolyte region, the method comprising:
applying a plurality of current pulses between the cathode current collector and the anode current collector;
causing lithium material within the electrochemical device to plate onto the anode region in response to the first pulse of current; further comprising removing a dendrite layer formed near the anode region.
16. The method of claim 15 , wherein a net charge transfer of the plurality of current pulses is greater than zero.
17. The method of claim 15 , wherein the plurality of current pulses comprises pulses of current in a polarity to charge the device interspersed by rest periods.
18. The method of claim 15 , wherein a majority of the plurality of current pulses is of a duration longer than a characteristic relaxation time of a double-layer at the interface of the lithium metal anode.
19. The method of claim 15 , wherein the layer of a metal that enhances plating uniformity comprises a metal selected from indium, aluminum, or magnesium.