Silicon based materials for and method of making and using same
An electrochemically active material includes silicon and a transition metal. At least 50 mole % of the transition metal is present in its elemental state, based on the total number of moles of transition metal elements present in the electrochemically active material. An electrochemically active material includes silicon and carbon. At least 50 mole % of the carbon is present in its elemental state, based on the total number of moles of carbon present in the electrochemically active material.
1. An electrochemically active material comprising:
an electrochemically active phase comprising:
(i) elemental silicon;
(ii) carbon,
(iii) a transition metal; and
wherein at least 50 mole % of the carbon is present in its elemental state, based on the total number of moles of carbon present in the electrochemically active material; and
an electrochemically inactive phase, such that the electrochemically active phase and the electrochemically inactive phase share at least one common phase boundary, wherein the electrochemically inactive phase is in the form of or includes one or more electrochemically inactive chemical elements selected from the group consisting of transition metals, alkaline earth metals, rare earth metals, or combinations thereof; and
wherein prior to incorporation of the electrochemically active material into an electrochemical cell, the electrochemically active material bears on an exterior surface thereof a coating that comprises an alkali metal decomposition product.
2. The electrochemically active material according to claim 1 , wherein the alkali metal decomposition product comprises lithium carbonate.
3. The electrochemically active material according to claim 1 , wherein carbon is present in the electrochemically active material in an amount of between 10 mole % and 90 mole %, based on the total number of moles of all chemical elements present in the electrochemically active material.
4. The electrochemically active material according to claim 1 , wherein the electrochemically active material comprises a silicon alloy material.
5. An electrode composition comprising:
the electrochemically active material according to claim 1 ; and
a binder.
6. An electrode composition according to claim 5 , further comprising graphite.
7. A negative electrode comprising:
the electrode composition according to claim 5 ; and
a current collector.
8. An electrochemical cell comprising:
the negative electrode of claim 7 ;
a positive electrode comprising a positive electrode composition comprising lithium; and
an electrolyte comprising lithium.
9. An electronic device comprising the electrochemical cell according to claim 8 .
10. A method of making an electrochemical cell, the method comprising:
providing a positive electrode comprising a positive electrode composition comprising lithium;
providing a negative electrode according to claim 7 ;
providing an electrolyte comprising lithium; and
incorporating the positive electrode, negative electrode, and the electrolyte into an electrochemical cell.
11. A method of making an electrochemically active material according to claim 1 , the method comprising:
forming a lithium-silicon alloy with carbon to form a lithium-containing alloy; and
removing lithium from the lithium-containing alloy so as to give rise to an electrochemically active material according to claim 1 .
12. The method according to claim 11 , wherein removing the lithium from the lithium-containing alloy comprises exposing the lithium-containing alloy to an alcohol.