Anode materials for lithium ion batteries and methods of making and using same
An electrochemically active material includes an active phase that includes silicon, and at least one inactive phase having a Scherrer Grain Size of greater than 5 nanometers. Each inactive phase of the material having a Scherrer Grain Size of greater than 5 nanometers has a lattice mismatch to Li 15 Si 4 of greater than 5%.
1. An electrochemically active material comprising:
an active phase comprising silicon; and
at least one inactive phase having a Scherrer Grain Size of greater than 5 nanometers which includes or consists essentially of β-FeSi 2 ;
wherein each inactive phase of the material having a Scherrer Grain Size of greater than 5 nanometers has a lattice mismatch to Li 15 Si 4 of greater than 5%.
2. The electrochemically active material according to claim 1 , wherein (i) the inactive silicide phase(s), and (ii) any inactive phases of the material having a Scherrer Grain Size of less than 5 nanometers, are, together, present in the electrochemically active material in an amount of greater than 17.5 vol. %, based on the total volume of the material.
3. The electrochemically active material according to claim 1 , wherein the active phase is present in an amount of between 35 and 55 volume percent based on the total volume of the electrochemically active material.
4. The electrochemically active material according to claim 1 , wherein the at least one inactive phase further comprises SiC.
5. The electrochemically active material according to claim 4 , wherein the active phase is present in an amount of between 35 and 55 volume percent based on the total volume of the electrochemically active material, the FeSi 2 phase is present in an amount of between 35 and 60 volume percent based on the total volume of the electrochemically active material, and the SiC phase is present in an amount of between 4 and 15 volume percent based on the total volume of the electrochemically active material.
6. The electrochemically active material according to claim 3 , wherein the inactive phases are present in the active material in an amount of between 30 vol. % and 70 vol. %, based on the total volume of the active material.
7. The electrochemically active material according to claim 1 , wherein the phases of the electrochemically active material are distributed substantially homogeneously throughout the electrochemically active material.
8. The electrochemically active material according to claim 1 , wherein the Scherrer grain size of each of the phases of the active material is no greater than 50 nanometers.
9. An electrode composition comprising:
the electrochemically active material according to claim 1 ; and
a binder.
10. An electrode composition according to claim 9 , further comprising graphite.
11. A negative electrode comprising:
the electrode composition according to any one of claims 9 - 10 ; and
a current collector.
12. An electrochemical cell comprising:
the negative electrode of claim 11 ;
a positive electrode comprising a positive electrode composition comprising lithium; and
an electrolyte comprising lithium.
13. An electronic device comprising the electrochemical cell according to claim 12 .
14. 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 11 ;
providing an electrolyte comprising lithium; and
incorporating the positive electrode, negative electrode, and the electrolyte into an electrochemical cell.
15. The electrochemically active material according to claim 4 , wherein the at least one inactive phase further comprises α-FeSi 2 .