Spherical electrochemically active-material structures comprising high-capacity materials and battery electrodes comprising thereof
Described herein are electrochemically active-material structures comprising high-capacity materials. The mean largest cross-sectional dimension of these structures is kept below the pulverization threshold, which corresponds to the structures' composition. As such, the structure fracturing during battery cycling is reduced thereby preserving the battery capacity. Furthermore, these structures have a sphericity of at least about 0.9. Such high sphericity values translate into a small surface area for a given volume thereby reducing the electrolyte decomposition and solid electrolyte interphase (SEI) formation on the surface of these structures. Furthermore, the small size and high sphericity help to keep swelling substantially isotropic nature. The small structure size also helps with preserving the initially formed SEI layer thereby limiting this SEI formation to initial cycles. Finally, the initial distribution, layer porosity, small size, and sphericity help to reduce the coalescence of these structures during cycling, e.g., typically caused by Li-assisted electrochemical welding.
1 . A negative battery electrode for use in a lithium-ion electrochemical cell, the negative battery electrode comprising:
electrochemically active-material structures comprising a high-capacity material, wherein:
the electrochemically active-material structures have a mean largest cross-sectional dimension (LCD) below a pulverization threshold (PT) (LCD<PT), corresponding to composition of the electrochemically active-material structures,
the electrochemically active-material structures have sphericity (S) of at least about 0.9,
the high-capacity material is silicon,
the high-capacity material represents at least 90% atomic of the electrochemically active-material structures, and
the pulverization threshold is 1 micrometer.
2 . The negative battery electrode of claim 1 , wherein the electrochemically active-material structures have the sphericity of at least about 0.95.
3 . The negative battery electrode of claim 1 , wherein the mean largest cross-sectional dimension is within 50% of the pulverization threshold.
4 . The negative battery electrode of claim 1 , wherein:
the electrochemically active-material structures have a dimension ratio (DR) defined as the mean largest cross-sectional dimension divided by the pulverization threshold (DR=LCD/PT), and
a primary ratio (PR), defined as the dimension ratio divided by the sphericity (PR=DR/S), is less than 0.9.
5 . The negative battery electrode of claim 4 , wherein the primary ratio (PR), defined as the dimension ratio divided by the sphericity (PR=DR/S), is less than 0.8.
6 . The negative battery electrode of claim 4 , wherein the primary ratio (PR) is selected based on an expected depth of charge of the high-capacity material.
7 . The negative battery electrode of claim 1 , wherein the electrochemically active-material structures are predominantly disjoint structures with a disjoint ratio of at least 90%.
8 . The negative battery electrode of claim 1 , wherein the electrochemically active-material structures are uniformly distributed within the negative battery electrode.
9 . The negative battery electrode of claim 1 , further comprising additional structures that are configured to experience substantially no volume change during cycling of the lithium-ion electrochemical cell, wherein relative positions of the electrochemically active-material structures and the additional structures remain same during the cycling of the lithium-ion electrochemical cell.
10 . The negative battery electrode of claim 9 , wherein the additional structures are selected from the group consisting of conductive-additive structures, stabilizing structures, and binder.
11 . The negative battery electrode of claim 10 , wherein the additional structures are the conductive-additive structures formed from a material selected from the group consisting of graphite, acetylene black, metal silicides, metal oxides, and silicates.
12 . The negative battery electrode of claim 9 , wherein the additional structures comprise one or more of graphite and lithium titanate (Li 4 Ti 5 O 12 ).
13 . The negative battery electrode of claim 12 , wherein the additional structures contribute at least 20% of a total lithiation capacity of the negative battery electrode.
14 . The negative battery electrode of claim 12 , wherein:
the additional structures comprise graphite,
the electrochemically active-material structures comprise silicon, and
a weight ratio of the additional structures to the electrochemically active-material structures is one of (a) less than 5, (c) greater than 1, (d) greater than 10, or (e) greater than 90.
15 . The negative battery electrode of claim 1 , wherein:
the electrochemically active-material structures further comprise an additional material, besides the high-capacity material,
the additional material is selected from the group consisting of magnesium, lithium, calcium, aluminum, copper, nickel, and iron.
16 . The negative battery electrode of claim 1 , wherein:
the electrochemically active-material structures form, at least in part, a negative active material layer,
the negative active material layer has a specific porosity defined as a ratio of a volume of all void spaces in the negative active material layer to a volume of the electrochemically active-material structures (SP=V VOIDS /V EAMS ), and
the specific porosity (SP) of the negative active material layer is at least 200%.
17 . The negative battery electrode of claim 16 , wherein the specific porosity (SP) of the negative active material layer is at least 300%.
18 . A negative battery electrode for use in a lithium-ion electrochemical cell, the negative battery electrode comprising:
electrochemically active-material structures comprising a high-capacity material, wherein:
the electrochemically active-material structures have a mean largest cross-sectional dimension (LCD) below a pulverization threshold (PT) (LCD<PT), corresponding to composition of the electrochemically active-material structures,
the electrochemically active-material structures have sphericity (S) of at least about 0.9,
the high-capacity material is silicon,
the high-capacity material represents at least 30% atomic of the electrochemically active-material structures, and
the pulverization threshold is 20 micrometers.
19 . Electrochemically active-material structures for use in a negative battery electrode of a lithium-ion electrochemical cell, the electrochemically active-material structures comprising:
a high-capacity material, wherein:
the electrochemically active-material structures have a mean largest cross-sectional dimension (LCD) below a pulverization threshold (PT) (LCD<PT), corresponding to composition of the electrochemically active-material structures,
the electrochemically active-material structures have sphericity (S) of at least about 0.9,
the high-capacity material is silicon,
the high-capacity material represents at least 90% atomic of the electrochemically active-material structures, and
the pulverization threshold is 1 micrometer.