Battery anode with preloaded metals

Abstract

A method is presented for fabricating an anode preloaded with consumable metals. The method provides a material (X), which may be one of the following materials: carbon, metals able to be electrochemically alloyed with a metal (Me), intercalation oxides, electrochemically active organic compounds, and combinations of the above-listed materials. The method loads the metal (Me) into the material (X). Typically, Me is an alkali metal, alkaline earth metal, or a combination of the two. As a result, the method forms a preloaded anode comprising Me/X for use in a battery comprising a M1.sub.YM2.sub.Z(CN).sub.N.MH.sub.2O cathode, where M1 and M2 are transition metals. The method loads the metal (Me) into the material (X) using physical (mechanical) mixing, a chemical reaction, or an electrochemical reaction. Also provided is preloaded anode, preloaded with consumable metals.

Claims

1. A method for fabricating an anode preloaded with consumable metals, the method comprising: providing a material (X) selected from the group consisting of carbon, metals able to be electrochemically alloyed with a metal (Me), intercalation oxides, electrochemically active organic compounds, and combinations of the above-listed materials; loading the metal (Me) into the material (X), where Me is selected from the group consisting of alkali metals, alkaline earth metals, terbium (Tb), silver (Ag), aluminum (Al) and combinations thereof; forming a preloaded anode comprising Me/X for use in a battery comprising a M1.sub.YM2.sub.Z(CN).sub.N.MH.sub.2O cathode; where M1 and M2 are independently selected from the group consisting of transition metals, calcium (Ca) and magnesium (Mg); where Y is less than or equal to 1; where Z is less than or equal to 1; where N is less than or equal to 6; where M is less than or equal to 20; wherein loading the metal (Me) into the material (X) includes using an electrochemical reaction as follows: forming an electrode of X and a counter electrode of Me, both inserted into an electrolyte; performing a plurality of charge and discharge operations, where the charge operation uses an external current source to create a positive voltage potential from the electrode to the counter electrode, and where the discharge operation connects an external load between the electrode and counter electrode; in response to the charge and discharge operations, inserting Me particles into the material (X); and, wherein forming the preloaded anode includes forming a Me/X compound, where Me is chemically reacted with X.

2. The method of claim 1 further comprising: consuming the metal (Me) in the preloaded anode; and, forming a stabilized anode comprising the material (X).

3. The method of claim 1 wherein forming the electrode of X includes X being selected from the group of hard carbon, tin, antimony, Na.sub.2Ti.sub.3O.sub.7, Li.sub.4Ti.sub.5O.sub.12, and Fe.sub.3O.sub.4; and, wherein forming the counter electrode of Me includes Me being selected from the group consisting of lithium and sodium.

4. The method of claim 1 wherein Me is selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), calcium (Ca), strontium (Sr), barium (Ba), and magnesium (Mg).

5. The method of claim 1 wherein M1 and M2 are each independently selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn).

6. A preloaded battery with an anode preloaded with consumable metals, the preloaded battery comprising: a non-aqueous electrolyte; a preloaded anode comprising: a conductive current collector; Me/X overlying the current collector, where X is a material selected from the group consisting of carbon, metals able to be electrochemically alloy with metal (Me), intercalation oxides, electrochemically active organic compounds, and combinations of the above-listed materials, and Me is a metal is selected from the group consisting of alkali metals, alkaline earth metals, terbium (Tb), silver (Ag), aluminum (Al) and combinations thereof; a cathode comprising: a conductive current collector; M1.sub.YM2.sub.Z(CN).sub.N.MH.sub.2O overlying the current collector; where M1 and M2 are independently selected from the group consisting of transition metals, calcium (Ca) and magnesium (Mg); where X is less than or equal to 2; where Y is less than or equal to 1; where Z is less than or equal to 1; where N is less than or equal to 6; where M is less than or equal to 20; and, an ion-permeable membrane immersed in the non-aqueous electrolyte, interposed between the anode and the cathode.

7. The preloaded battery of claim 6 wherein Me is selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), calcium (Ca), strontium (Sr), barium (Ba), and magnesium (Mg).

8. The preloaded battery of claim 6 wherein Me/X is selected from the group consisting of: Li.sub.RVO.sub.2, where 0<R<1; Na.sub.sMnO.sub.2, where 0<s<1; a NaSn alloy; a mixture of lithium powder and tin particles; a mixture of sodium particles and hard carbon powder; a compound of hard carbon and lithium; a compound of hard carbon and sodium; a LiSn alloy; a LiSb alloy; a NaSb alloy; a compound of Fe.sub.3O.sub.4 and Li; and, a compound of Fe.sub.3O.sub.4 and Na.

9. The preloaded battery of claim 6 wherein M1 and M2 are each independently derived, as selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn).

10. A method for fabricating an anode preloaded with consumable metals, the method comprising: providing a material (X) selected from the group consisting of carbon, metals able to be electrochemically alloyed with a metal (Me), intercalation oxides, electrochemically active organic compounds, and combinations of the above-listed materials; loading the metal (Me) into the material (X), where Me is selected from the group consisting of alkali metals, alkaline earth metals, and a combination of alkali and alkaline earth metals; forming a preloaded anode comprising Me/X for use in a battery comprising a M1.sub.YM2.sub.Z(CN).sub.N.MH.sub.2O cathode; where M1 and M2 are independently selected from the group consisting of transition metals, calcium, and magnesium; where Y is less than or equal to 1; where Z is less than or equal to 1; where N is less than or equal to 6; where M is less than or equal to 20; wherein loading the metal (Me) into the material (X) includes using a chemical reaction that reduces X with Me-containing reductive agents; and, wherein forming the preloaded anode includes forming a Me/X compound where Me is chemically reacted with X.

11. The method of claim 10 wherein reducing X with Me-containing reductive agents includes a process selected from the group consisting of: reducing VO.sub.2 with n-butyl lithium to form Li.sub.RVO.sub.2, where 0<R<1; reducing MnO.sub.2 with tert-butyl alkoxide-activated NaH in tetrahydrofuran to form Na.sub.sMnO.sub.2, where 0<s<1; reducing TiO.sub.2 with NaH to form NaTiO.sub.2; and, mixing Sn particles in melted Na to form a NaSn alloy.

12. A method for fabricating an anode preloaded with consumable metals, the method comprising: providing a material (X) selected from the group consisting of carbon, metals able to be electrochemically alloyed with a metal (Me), intercalation oxides, electrochemically active organic compounds, and combinations of the above-listed materials; loading the metal (Me) into the material (X), where Me is selected from the group consisting of alkali metals, alkaline earth metals, and a combination of alkali and alkaline earth metals; forming a preloaded anode comprising Me/X for use in a battery comprising a M1.sub.YM2.sub.Z(CN).sub.N.MH.sub.2O cathode; where M1 and M2 are independently selected from the group consisting of transition metals, calcium, and magnesium; where Y is less than or equal to 1: where Z is less than or equal to 1; where N is less than or equal to 6; where M is less than or equal to 20; wherein loading the metal (Me) into the material (X) includes mechanically mixing Me and X particles in an inert atmosphere, without creating a chemical reaction between the Me and X particles.

13. The method of claim 12 wherein mechanically mixing Me and X particles includes a process selected from the group consisting of mixing a lithium powder with tin particles in an atmosphere of Ar by ball-milling, and mixing sodium particles with hard carbon powders in an industrial blender at a temperature above 100 degrees C. and subsequently cooling to room temperature.

14. A method for fabricating an anode preloaded with consumable metals, the method comprising: providing a material (X) selected from the group consisting of carbon, metals able to be electrochemically alloyed with a metal (Me), intercalation oxides, electrochemically active organic compounds, and combinations of the above-listed materials; loading the metal (Me) into the material (X), where Me is selected from the group consisting of alkali metals, alkaline earth metals, and a combination of alkali and alkaline earth metals; forming a preloaded anode comprising Me/X for use in a battery comprising a M1.sub.YM2.sub.Z(CN).sub.N.MH.sub.2O cathode; where M1 and M2 are independently selected from the group consisting of transition metals, calcium, and magnesium; where Y is less than or equal to 1; where Z is less than or equal to 1: where N is less than or equal to 6; where M is less than or equal to 20; wherein loading the metal (Me) into the material (X) includes using an electrochemical reaction that directly contacts Me and X in a Me-ion conductive solution; and, wherein forming the preloaded anode includes forming a Me/X compound, where Me is chemically reacted with X.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram depicting the crystal structure of a metal hexacyanometallate (MHCM) (prior art).

(2) FIG. 2 is a partial cross-sectional view of a preloaded anode, which is preloaded with consumable metals.

(3) FIG. 3 is a partial cross-sectional view of a preloaded battery, with an anode preloaded with consumable metals.

(4) FIG. 4 is a partial cross-sectional view depicting the preloading of Me metal in the form of integrated particles.

(5) FIG. 5 is a partial cross-sectional view depicting the preloading of Me metal in the form of a metal film layer.

(6) FIG. 6 is a graph depicting voltage vs. capacity for a sodium-ion battery comprising a hard carbon anode mixed with sodium metal and a Berlin green cathode (FeFe(CN).sub.6).

(7) FIG. 7 is a graph depicting voltage vs. capacity for a half-cell using a sodium anode and an antimony cathode.

(8) FIG. 8 is a flowchart illustrating a method for fabricating an anode preloaded with consumable metals.

DETAILED DESCRIPTION

(9) FIG. 2 is a partial cross-sectional view of a preloaded anode, which is preloaded with consumable metals. The preloaded anode 200 comprises a conductive current collector 202 and Me/X 204 overlying the current collector 202. X is a material such as carbon, metals able to be electrochemically alloyed with a metal (Me), intercalation oxides, electrochemically active organic compounds, and combinations of the above-listed materials. Me is a metal, typically an alkali metal, alkaline earth metal, or a combination of the two. More explicitly, Me may be lithium (Li), sodium (Na), potassium (K), rubidium (Rh), cesium (Cs), calcium (Ca), terbium (Tb), strontium (Sr), barium (Ba), silver (Ag), aluminum (Al), magnesium (Mg), or combinations of these metals.

(10) Some explicit examples of Me/X materials include Li.sub.RVO.sub.2, where 0<R<1; Na.sub.sMnO.sub.2, where 0<s<1; a NaSn alloy; a mixture of lithium powder and tin particles; a mixture of sodium particles and hard carbon powder; a compound of hard carbon and lithium; a compound of hard carbon and sodium; a LiSn alloy; a LiSb alloy; a NaSb alloy; a compound of Fe.sub.3O.sub.4 and Li; and, a compound of Fe.sub.3O.sub.4 and Na. However, it should be understood that this is just a small list of possible materials.

(11) FIG. 3 is a partial cross-sectional view of a preloaded battery, with an anode preloaded with consumable metals. The preloaded battery 300 comprises an electrolyte 302 and a preloaded anode 200, as described above in the explanation of FIG. 2. Details of the preloaded anode are not repeated here in the interest of brevity. The preloaded battery 300 further comprises a cathode 304 made from a conductive current collector 306 and M1.sub.YM2.sub.Z(CN).sub.N.MH.sub.2O 308 overlying the current collector; where M1 and M2 are transition metals; where X is less than or equal to 2; where Y is less than or equal to 1; where z is less than or equal to 1; where N is less than or equal to 6; and, where M is less than or equal to 20.

(12) An ion-permeable membrane 310 is immersed in the electrolyte 302, interposed between the anode 200 and the cathode 304. As explained above, M1 and M2 are each independently derived, and may be Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ca, or Mg.

(13) A polymeric binder (not shown), such as polytetrafluoroethylene (PTFE) or poly-vinylidene difluoride (PVDF), may be used to provide adhesion between electrode materials and the current collectors to improve the overall physical stability.

(14) The electrolyte 302 may be non-aqueous, such as an organic liquid electrolyte, or alternatively, gel electrolyte, polymer electrolyte, solid (inorganic) electrolyte, etc. Common examples of non-aqueous (liquid) electrolytes include organic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), etc., although many other organic carbonates and alternatives to organic carbonates exist. Typically, gel electrolytes consist of polymeric materials which have been swelled in the presence of liquid electrolytes. Examples of polymers employed as gel electrolytes include, but are not limited to, poly(ethylene)oxide (PEO) and fluorinated polymers such as poly(vinylidene) fluoride (PVDF)-based polymers and copolymers, etc. in contrast, (solid) polymer electrolytes may be prepared using the same classes of polymers for forming gel electrolytes although swelling of the polymer in liquid electrolytes is excluded. Finally, solid inorganic (or ceramic) materials may be considered as electrolytes, which may be employed in combination with liquid electrolytes. Overall, the appropriate electrolyte system may consist of combinations (hybrid) of the above classes of materials in a variety of configurations. In some instances not shown, the ion-permeable membrane 310 and the electrolyte 302 can be the same material, as may be the case for polymer gel, polymer, and solid electrolytes.

(15) Generally, the composite anode (negative electrode) material includes preloaded Me and non-Me-metal (X) anode materials for metal-ion batteries (MeIBs), where Me may, for example, be Na, K, Ca, Cs, Mg, or Al. The composite contains preloaded Me that can be extracted from the host non-Me-metal component X during the discharge (deintercalation) process in a MeIB, thus eliminating the initial irreversible capacity introduced by a conventional non-Me-metal anode, and enabling the use of non-Me-containing cathode materials.

(16) Although Me metal anodes have the highest theoretical capacity and provide the highest energy density in a metal-ion battery because of their low anodic potential, as compared to non-metal anode materials, it is impractical to use sodium or potassium metals in a commercial battery due to safety issues such as dendrite growth during cycling and the high chemical reactivity. Therefore, non-metal materials are considered to be the best choice for anodes in metal-ion batteries. However, as in sodium-ion batteries, all conventional non-metal anodes, as mentioned above in the Background Section, have large irreversible capacities as a result of their initial charge/discharge process. Briefly, this problem is solved by preloading electrochemically active Me into a non-Me-metal (X) anode material, which can be written as Me/X, where X can be one of the aforementioned non-Me-metal anode materials or their combinations. When the Me metal is preloaded, it is consumed by side reactions like solid electrolyte interface (SEI) formation or integrated with non-Me-metal anodes by intercalation. Therefore, no Me-metal remains permanently present in the anode after some initial charge cycling.

(17) FIG. 4 is a partial cross-sectional view depicting the preloading of Me metal in the form of integrated particles. Non-Me-metal anode material 400 overlies current collector 402 with preloaded Me-containing particles 404. A binder and conductive additives 406 may also be present. After charge cycling, Me/X material 408 is formed, where the Me metal is uniformly integrated into the non-Me-metal anode.

(18) FIG. 5 is a partial cross-sectional view depicting the preloading of Me metal in the form of a metal film layer. A non-Me-metal layer 500 overlies current collector 502. A preloaded Me layer 504 overlies the non-Me-metal layer 500. After charge cycling, Me/X material 506 is formed, where the Me metal is uniformly integrated into the non-Me-metal anode.

(19) Me/X can be prepared by mixing Me with X, by reducing X with Me-containing reductive agents, or by an electrochemical reaction process. For example, a Na/hard carbon composite can be prepared by integrating sodium particles into a hard carbon matrix, or the electrochemical insertion of sodium into hard carbon in a non-aqueous electrolyte contains sodium salt. In one aspect, a Na/Sb) composite can be prepared by mechanically mixing sodium and Sb particles. In another aspect, a Na.sub.xSb alloy is formed at elevated temperature in an inert atmosphere.

(20) Two examples are presented below of battery applications based on sodium-ion batteries that comprise a Na/X anode with different cathodes as a means of illustrating the preloaded anode.

(21) FIG. 6 is a graph depicting voltage vs. capacity for a sodium-ion battery comprising a hard carbon anode mixed with sodium metal and a Berlin green cathode (FeFe(CN).sub.6). The preloaded sodium metal at anode side serves as an anode during the first discharge, and intercalates into Berlin green cathode. In the subsequent charge process, sodium is removed from Berlin green and inserted into hard carbon. After three cycles, the preloaded sodium has been completely consumed and a Berlin green/hard carbon sodium battery with capacity more than 130 mAh/g is obtained based on the cathode mass, as shown in the figure. It is noteworthy that the same battery behavior can be achieved using other sodium loading methods like the electrochemical insertion of sodium into hard carbon.

(22) FIG. 7 is a graph depicting voltage vs. capacity for a half-cell using a sodium anode and an antimony cathode. In the first cycle of the battery, Sb undergoes an alloying reaction during discharge, and Na.sub.3Sb is formed at the end of the discharge. Although a high capacity of more than 800 mAh/g is delivered, the reversible capacity is only 600 mAh/g, corresponding to 75% of the initial discharge capacity. The large irreversible capacity is ascribed to the SEI layer formation, which means that the electrolyte is electrochemically reduced on the surface of anode. To resolve this problem a preloaded anode of Na.sub.3Sb alloy can be obtained by heating sodium and antimony at 850 C. in an Ar atmosphere [11], and the preloaded sodium in Na.sub.3Sb enables SEI layers to form once the electrolyte contacts the Na.sub.3Sb. Therefore, the large irreversible capacity shown in the figure can be eliminated.

(23) Thus, anodes made from preloaded Me and a non-Me-metal active material eliminate the irreversible capacity associated with conventional anode materials and enable the usage of non-Me containing cathode materials. As a result, high capacity and long cycle life can be obtained for safe rechargeable Me-ion batteries.

(24) FIG. 8 is a flowchart illustrating a method for fabricating an anode preloaded with consumable metals. Although the method is depicted as a sequence of numbered steps for clarity, the numbering does not necessarily dictate the order of the steps. It should be understood that some of these steps may be skipped, performed in parallel, or performed without the requirement of maintaining a strict order of sequence. Generally however, the method follows the numeric order of the depicted steps. The method starts at Step 800.

(25) Step 802 provides a material (X) that may be carbon, metals able to be electrochemically alloyed with a metal (Me), otherwise referred to as non-Me-metals, intercalation oxides, electrochemically active organic compounds, or combinations of the above-listed materials. Some explicit examples include metal or alloys that contain at least one of Sb, Sn, Pb, P, S, Si, or Se. Me-ion intercalation compounds such as (but not limited to) Li.sub.4Ti.sub.5O.sub.12, Na.sub.4Ti.sub.5O.sub.12, Na.sub.3Ti.sub.2O.sub.7, Na.sub.x[Li.sub.1-yTi.sub.y]O.sub.2; and organic carboxylate based materials such as (C.sub.8H.sub.4Na.sub.2O.sub.4), (C.sub.8H.sub.6O.sub.4), (C.sub.8H.sub.5NaO.sub.4), (C.sub.8Na.sub.2F.sub.4O.sub.4), (C.sub.10H.sub.2Na.sub.4O.sub.8), (C.sub.14H.sub.4O.sub.6), and (C.sub.14H.sub.4Na.sub.4O.sub.8). Step 804 loads the metal (Me) into the material (X). Generally, Me is an alkali metal, alkaline earth metal, or a combination of the two. More explicitly, Me may be lithium (Li), sodium (Na), potassium (K), rubidium (Rh), cesium (Cs), calcium (Ca), terbium (Tb), strontium (Sr), barium (Ba), silver (Ag), aluminum (Al), or magnesium (Mg).

(26) Step 806 forms a preloaded anode comprising Me/X for use in a battery comprising a M1.sub.YM2.sub.Z(CN).sub.N.MH.sub.2O cathode; where M1 and M2 are transition metals; where Y is less than or equal to 1; where Z is less than or equal to 1; where N is less than or equal to 6; and, where M is less than or equal to 20.

(27) Typically, M1 and M2 are each independently derived, meaning they may be the same or different metals. Some examples of M1 and M2 metals include titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), Ca, and Mg.

(28) In one aspect, Step 808 consumes the metal (Me) in the preloaded anode, and Step 810 forms a stabilized anode comprising the material (X). In one aspect, the active material in the anode is exclusively comprised of the X material.

(29) Step 804 loads the metal (Me) into the material (X) using a physical (mechanical) mixing, chemical reaction, or electrochemical reaction process. Step 804 may load the metal (Me) into the material (X) using a chemical reaction by reducing X with Me-containing reductive agents. Then, forming the preloaded anode in Step 806 includes forming a Me/X (MeX) compound where Me is chemically reacted with X. Some examples of reducing X with Me-containing reductive agents include the following:

(30) reducing VO.sub.2 with n-butyl lithium to form Li.sub.RVO.sub.2, where 0<R<1;

(31) reducing MnO.sub.2 with tert-butyl alkoxide-activated NaH in tetrahydrofuran to form Na.sub.sMnO.sub.2, where 0<s<1;

(32) reducing TiO.sub.2 with NaH to form NaTiO.sub.2; and,

(33) mixing Sn particles in melted Na to form a NaSn alloy.

(34) These examples are not a complete list of reduction processes and materials.

(35) In another aspect, Step 804 loads the metal (Me) into the material (X) using physical mixing by mechanically mixing Me and X particles in an inert atmosphere, without creating a chemical reaction between the Me and X particles. Some examples of mechanically mixing Me and X particles include:

(36) mixing a lithium powder with tin particles in an atmosphere of Ar by ball-milling; and,

(37) mixing sodium particles with hard carbon powders in an industrial blender at a temperature above 100 degrees C., and subsequently cooling to room temperature. The physical mixing process may employ both dry and wet processing techniques such as electrostatic assisted spray, hot spray, mechanical mixing, and various printing methods. Other unnamed mixing processes and materials can also be used.

(38) In one aspect, Step 804 loads the metal (Me) into the material (X) by an electrochemical reaction using the following substeps. Step 804a forms an electrode of X and a counter electrode of Me, both inserted into an electrolyte. For example, X may be hard carbon, tin, antimony, Na.sub.2Ti.sub.3O.sub.7, Li.sub.4Ti.sub.5O.sub.12, or Fe.sub.3O.sub.4, and Me may be lithium or sodium.

(39) Step 804b performs a plurality of charge and discharge operations, where the charge operation uses an external current source to create a positive voltage potential from the electrode to the counter electrode. A discharge operation connects an external load between the electrode and counter electrode. In response to the charge and discharge operations, Step 804c inserts Me particles into the material (X). Then, forming the preloaded anode in Step 806 includes forming a Me/X (MeX) compound, where Me is chemically reacted with X.

(40) In another aspect. Step 804 loads the metal (Me) into the material (X) using an electrochemical reaction by directly contacting Me and X in a Me-ion conductive solution. Again, the preloaded anode formed in Step 806 includes a Me/X (MeX) compound, where Me is chemically reacted with X.

(41) A preloaded battery, preloaded anode, and associated fabrication processes have been provided. Examples of particular materials and process steps have been presented to illustrate the invention. However, the invention is not limited to merely these examples. Other variations and embodiments of the invention, will occur to those skilled in the art.