Porous electrochemically active-material structures with dispersed inert elements
Described herein are electrochemically active-material structures comprising silicon and one or more inert elements, such that these inert elements are chemically and/or atomically dispersed. Also described are negative battery electrodes and lithium-ion electrochemical cells comprising such electrochemically active-material structures as well as methods of fabricating such structures, electrodes, and lithium-ion electrochemical cells. Some examples of atomically-dispersed inert elements include, but are not limited to, hydrogen (H), carbon (C), nitrogen (N), and chlorine (Cl). Unlike silicon, inert elements do not interact with lithium at an operating voltage of the negative battery electrode and therefore do not contribute to the overall cell capacity. At the same time, these inert elements help to mitigate silicon swelling by operating as a mechanical buffer, support structure, and/or additional conductive pathways. Such electrochemically active-material structures can be formed by reacting (chemically or electrochemically) one or more precursors that include silicon and corresponding inert elements.
1 . An electrochemically active-material structure for use in lithium-ion batteries, the electrochemically active-material structure comprising
silicon in one or more of an amorphous structure and a polycrystalline structure;
carbon (C);
oxygen (O); and
one or more inert elements selected from the group consisting of an additive element (M) and a halogen (X) such that the electrochemically active-material structure has a composition represented by SiC a M b O c X d with “a” being 0.3-0.7, “b” being 0-2, “c” being 0.3-0.7, and “d” being 0-2, the one or more inert elements are chemically dispersed in the electrochemically active-material structure such that the electrochemically active-material structure is a single-phase structure through an entire volume of the electrochemically active-material structure without forming a separate phase comprising the one or more inert elements.
2 . The electrochemically active-material structure of claim 1 , wherein the single-phase structure is a polycrystalline structure consisting of domains less than 5 nm in size.
3 . The electrochemically active-material structure of claim 1 , wherein the single-phase structure is amorphous.
4 . The electrochemically active-material structure of claim 1 , wherein the electrochemically active-material structure comprises one or more closed pores and atomic vacancies such that the electrochemically active-material structure has a skeletal density of between 0.5 to 2.3 g/cm 3 .
5 . The electrochemically active-material structure of claim 1 , wherein the electrochemically active-material structure has a lithium delithiation capacity between 1300 to 3800 mAh/g when delithiated to 2.0V vs Li + /Li after a full lithiation to 5 mV vs Li + /Li.
6 . The electrochemically active-material structure of claim 1 , wherein a weight percentage of the silicon in the electrochemically active-material structure is between 9% to 95%.
7 . The electrochemically active-material structure of claim 1 , wherein:
“a” is 0.4-0.6, and
“c” being 0.4-0.6.
8 . The electrochemically active-material structure of claim 1 , wherein:
“b” is 0.01-2, and
“d” is 0.01-2.
9 . The electrochemically active-material structure of claim 1 , wherein the additive element (M) in SiC a M b O c X d is one or more metal elements selected from the groups consisting of magnesium (Mg), aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), zirconium (Zr), niobium (Nb), molybdenum (Mo), tantalum (Ta), lanthanum (La), sodium (Na), and potassium (K).
10 . The electrochemically active-material structure of claim 1 , wherein the additive element (M) in SiC a M b O c X d is one or more dopants selected from the group consisting of hydrogen (H), boron (B), nitrogen (N), phosphorus (P), sulfur (S), arsenic (As), and telluride (Te).
11 . The electrochemically active-material structure of claim 1 , wherein 0.01≤b≤0.1 in SiC a M b O c X d .
12 . The electrochemically active-material structure of claim 1 , wherein the halogen (X) is selected from the group consisting of fluorine (F) and chlorine (Cl), bromine (Br), and iodine (I).
13 . The electrochemically active-material structure of claim 1 , wherein “d” is 0.01-0.1.
14 . The electrochemically active-material structure of claim 1 , wherein “b” is 0.1-2.
15 . The electrochemically active-material structure of claim 1 , wherein an atomic percentage of the silicon in the electrochemically active-material structure is between 50% to 95%.
16 . The electrochemically active-material structure of claim 1 , wherein a total atomic percentage of all the inert elements is lower than 91% in any 1 nm by 1 nm by 1 nm portion of the entire volume.
17 . The electrochemically active-material structure of claim 1 , wherein an atomic percentage of the silicon in the electrochemically active-material structure is between 9% to 50%.
18 . The electrochemically active-material structure of claim 1 , wherein an atomic percentage of the silicon is higher than 9% in any 1 nm by 1 nm by 1 nm portion of the entire volume.
19 . The electrochemically active-material structure of claim 1 , wherein the electrochemically active-material structure has at least one Raman shift selected from a group of 450-470 cm −1 and 515-525 cm −1 .