Mixed nano-filament electrode materials for lithium ion batteries
View Patent ↗This invention provides a mixed nano-filament composition for use as an electrochemical cell electrode. The composition comprises: (a) an aggregate of nanometer-scaled, electrically conductive filaments that are substantially interconnected, intersected, or percolated to form a porous, electrically conductive filament network, wherein the filaments have a length and a diameter or thickness with the diameter/thickness less than 500 nm (preferably <100 nm) and a length-to-diameter or length-to-thickness aspect ratio greater than 10; and (b) Multiple nanometer-scaled, electro-active filaments comprising an electro-active material capable of absorbing and desorbing lithium ions wherein the electro-active filaments have a diameter or thickness less than 500 nm (preferably <100 nm). The electro-active filaments (e.g., nanowires) and the electrically conductive filaments (e.g., carbon nano fibers) are mixed to form a mat-, web-, or porous paper-like structure in which at least an electro-active filament is in electrical contact with at least an electrically conductive filament. Also provided is a lithium ion battery comprising such an electrode as an anode or cathode, or both. The battery exhibits an exceptionally high specific capacity, an excellent reversible capacity, and a long cycle life.
1. An electrochemical cell electrode comprising a mixed nano-filament composition, said composition comprising an aggregate of:
a) nanometer-scaled, electrically conductive filaments that are interconnected, intersected, or percolated to form a porous, electrically conductive filament network, wherein said filaments have a length and a diameter or thickness, and the diameter or thickness is less than 500 nm with a length-to-diameter or length-to-thickness aspect ratio greater than 10 and said conductive filaments are selected from nano-scaled graphene platelets with a length-to-width ratio greater than 3, metal nano wires, metal-coated fibrils, and combinations thereof; and
b) multiple nanometer-scaled, electro-active filaments comprising therein or thereon an electro-active material capable of absorbing and desorbing lithium ions wherein said electro-active filaments have a diameter or thickness less than 500 nm; wherein the electro-active filaments comprise an active material selected from the group consisting of:
a) silicon (Si), germanium (Ge), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), and cadmium (Cd);
b) alloys or intermetallic compounds of Si, Ge, Pb, Sb, Bi, Zn, Al, or Cd with other elements, wherein said alloys or compounds are stoichiometric or non-stoichiometric;
c) oxides, carbides, nitrides, sulfides, phosphides, selenides, and tellurides of Si, Ge, Pb, Sb, Bi, Zn, Al, Fe, or Cd, and their mixtures or composites; and
d) combinations thereof; and
wherein said electro-active filaments and said electrically conductive filaments are intertwined to form a mat, web, or porous paper structure in which at least an electro-active filament is in electrical contact with at least an electrically conductive filament.
2. The mixed nano-filament composition of claim 1 wherein said electrically conductive filaments have a diameter or thickness smaller than 100 nm or said electro-active filaments have a diameter or thickness smaller than 100 nm.
3. The mixed nano-filament composition of claim 1 wherein said electro-active filaments comprise nanowires and at least an electro-active filament is in electrical contact with electrically conductive filaments at multiple contact points.
4. The mixed nano-filament composition of claim 1 wherein said electrically conductive filaments comprise nano-scaled graphene platelets with a thickness less than 10 nm.
5. The mixed nano-filament composition of claim 1 wherein said electro-active filaments comprise a nanowire selected from the group consisting of nanowires of Ge, Si, their oxides, carbides, nitrides, sulfides, phosphides, selenides, and tellurides, and combinations thereof.
6. The mixed nano-filament composition of claim 4 wherein said electro-active filaments comprise Si nanowires.
7. The mixed nano-filament composition of claim 5 wherein said electro-active filaments comprise Si nanowires.
8. The mixed nano-filament composition of claim 1 wherein the electro-active filaments comprise an element selected from Si, Ge, Sb, or a combination thereof.
9. The mixed nano-filament composition of claim 3 wherein the nanowires are amorphous or comprise nano crystallites.
10. A lithium secondary battery comprising a positive electrode (cathode), a negative electrode (anode) comprising a mixed nano-filament composition as defined in claim 1 which is capable of absorbing and desorbing lithium ions, and a non-aqueous electrolyte disposed between said negative electrode and said positive electrode.
11. A lithium secondary battery comprising a positive electrode, a negative electrode comprising a mixed nano-filament composition as defined in claim 2 which is capable of absorbing and desorbing lithium ions, and a non-aqueous electrolyte disposed between said negative electrode and said positive electrode.
12. A lithium secondary battery comprising a positive electrode, a negative electrode comprising a mixed nano-filament composition as defined in claim 3 which is capable of absorbing and desorbing lithium ions, and a non-aqueous electrolyte disposed between said negative electrode and said positive electrode.
13. The lithium secondary battery according to claim 10 , wherein said positive electrode comprises lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, lithium vanadium oxide, lithium vanadium phosphate, or a combination thereof.
14. The lithium secondary battery as defined in claim 10 wherein said mixed nano-filament composition further comprises a binder material selected from a polymer, coal tar pitch, petroleum pitch, meso-phase pitch, coke, or a derivative thereof.
15. The lithium secondary battery as defined in claim 10 , wherein said mixed nano-filament composition provides a specific capacity of no less than 1,000 mAh per gram of anode material weight.
16. The lithium secondary battery as defined in claim 10 , wherein said mixed nano-filament composition provides a specific capacity of no less than 2,000 mAh per gram of anode material weight.
17. The lithium secondary battery as defined in claim 10 , wherein said mixed nano-filament composition provides a specific capacity of no less than 3,000 mAh per gram of anode material weight.
18. The lithium secondary battery as defined in claim 11 , wherein said mixed nano-filament composition provides a specific capacity of no less than 2,000 mAh per gram of anode material weight.
19. The lithium secondary battery as defined in claim 12 , wherein said mixed nano-filament composition provides a specific capacity of no less than 3,000 mAh per gram of anode material weight.
20. A lithium secondary battery comprising a negative electrode, a positive electrode comprising a mixed nano-filament composition as defined in claim 1 which comprises a cathode active filament capable of absorbing and desorbing lithium ions, and a non-aqueous electrolyte disposed between said negative electrode and said positive electrode.
21. A lithium secondary battery comprising a negative electrode, a positive electrode comprising a mixed nano-filament composition as defined in claim 2 which comprises a cathode active filament capable of absorbing and desorbing lithium ions, and a non-aqueous electrolyte disposed between said negative electrode and said positive electrode.
22. A lithium secondary battery comprising a negative electrode, a positive electrode comprising a mixed nano-filament composition as defined in claim 3 which comprises a cathode active filament capable of absorbing and desorbing lithium ions, and a non-aqueous electrolyte disposed between said negative electrode and said positive electrode.
23. A lithium secondary battery of claim 20 wherein said mixed nano-filament composition provides a discharge specific capacity greater than 200 mAh/g, based on per gram of cathode material weight.
24. A lithium secondary battery comprising:
a) a negative electrode comprising a mixed nano-filament composition as defined in claim 1 which comprises an anode active filament capable of absorbing and desorbing lithium ions during charging and recharging of said battery;
b) a positive electrode comprising a mixed nano-filament composition as defined in claim 1 which comprises a cathode active filament capable of desorbing and absorbing lithium ions during charging and recharging of said battery; and
c) a non-aqueous electrolyte disposed between said negative electrode and said positive electrode.