Use of silicon with impurities in silicon-dominant anode cells
Systems and methods for use of silicon with impurities in silicon-dominant anode cells may include a cathode, an electrolyte, and an anode including an active material, where the anode active material includes silicon, and where an impurity level of the silicon may be more than 400 ppm. The impurity level of the silicon is more than 600 ppm. The impurity level may be for elements with an atomic number between 2 and 42. The silicon may have a purity of 99.90% or less. A resistance of the silicon when pressed into a 4 mm thick and 15 mm diameter pellet may be 25 kΩ or less. The active material may include silicon, carbon, and a pyrolyzed polymer on a metal current collector. The metal current collector may include a copper or nickel foil in electrical contact with the active material. The active material may include more than 50% silicon.
1 . A battery, comprising:
a cathode;
an electrolyte; and
an anode comprising a pyrolyzed binder material and 50% or more silicon by weight, wherein an impurity level of the silicon is more than 400 ppm; and
wherein the pyrolyzed binder comprises thermally-decomposed carbon precursors.
2 . The battery according to claim 1 , wherein the impurity level of the silicon is more than 600 ppm.
3 . The battery according to claim 1 , wherein:
the impurity level is less than 1200 ppm; and
the impurity level is a ppm sum for all elements with an atomic number between 2 and 42 excluding Ne, Ar, Kr, and Si.
4 . The battery according to claim 1 , wherein the silicon has a purity of 99.88% or greater.
5 . The battery according to claim 1 , wherein a resistance of the silicon when pressed into a 4 mm thick and 15 mm diameter pellet is 25 kΩ or less.
6 . The battery according to claim 1 , wherein:
the anode further comprises a metal current collector; and
the pyrolyzed binder material and the silicon are on a surface of the metal current collector.
7 . The battery according to claim 6 , wherein the anode further comprises conductive carbon.
8 . The battery according to claim 6 , wherein the metal current collector comprises a copper or nickel foil in electrical contact with the pyrolyzed binder material and the silicon.
9 . The battery according to claim 1 , wherein the electrolyte comprises a liquid, solid, or gel.
10 . The battery according to claim 1 , wherein the anode, the electrolyte, and the cathode form a lithium ion battery cell.
11 . A method comprising:
forming a mixture comprising a binder material and silicon particles;
coating a surface with the mixture; and
pyrolyzing the mixture to form an anode active material comprising a pyrolyzed binder material and 50% or more silicon by weight, wherein an impurity level of the silicon is more than 400 ppm, wherein the pyrolyzing the mixture converts carbon precursors of a binder material to carbon.
12 . The method according to claim 11 , wherein coating the surface comprises coating a surface of a metal current collector with the mixture.
13 . The method according to claim 11 , wherein:
coating the surface comprises coating a surface of a substrate; and
the method further comprises drying the mixture on the substrate to form a film of the mixture, and peeling the film from the substrate.
14 . The method according to claim 11 , wherein the anode active material comprises conductive carbon.
15 . The method according to claim 11 , wherein the impurity level of the silicon is more than 600 ppm.
16 . The method according to claim 11 , wherein:
the impurity level is less than 1200 ppm; and
the impurity level is a ppm sum for all elements with an atomic number between 2 and 40 excluding Ne, Ar, Kr, and Si.
17 . The method according to claim 11 , wherein the silicon has a purity of 99.88% or greater.
18 . The method according to claim 11 , wherein a resistance of the silicon when pressed into a 4 mm thick and 15 mm diameter pellet is 25 kΩ or less.
19 . The method according to claim 11 , wherein coating the surface comprises coating a copper or nickel foil.
20 . The method according to claim 11 , further comprising forming a lithium ion battery cell comprising a cathode, an electrolyte, and anode active material.
21 . The battery according to claim 1 , wherein the pyrolyzed binder comprises thermally-decomposed carbon precursors form a carbon framework around particles of the silicon.
22 . The method according to claim 11 , wherein the pyrolyzing comprises heating the mixture to at or above 400° C.
23 . The method according to claim 11 , wherein the pyrolyzing comprises heating the mixture to at least one temperature in a range of 500-800° C.
24 . The battery according to claim 6 , wherein the metal current collector comprises perforations that permit lithiation through the metal current collector.
25 . The method according to claim 12 , comprising perforating the metal current collector to permit lithiation through the metal current collector.
26 . The battery according to claim 1 , wherein the 50% or more silicon by weight is provided by silicon particles having a size greater than 1 μm.