The present application relates to nickel-rich layered oxide electrodes and, in particular, to such electrodes comprising ionically conductive coatings operable to maintain electrode performance and/or enhance electrode lifetimes.
Currently, transportation is consuming ˜30% of the total energy in the United States, while petroleum supplies over 90% of energy needs of transportation. To deal with the ever-aggravating depletion of fossil fuels and environmental issues, transportation electrification represents a renewable clean solution. To date, however, the market share of battery-powered electric vehicles (BEVs) is still very low, less than 3%. To boost the market share of BEVs, state-of-the-art lithium-ion batteries (LIBs) have become insufficient in multiple aspects and next-generation robust LIBs are urgently needed to meet the following requirements: a high energy density of ≥300 Wh/kg for a driving range of ≥300 miles, affordable cost (≤$125/kWh), reliable safety free of fires and explosions, and long lifetime of ≥15 calendar years.
In pursuing high energy LIBs, cathode materials play a crucial role in the whole battery cell system, including working voltage, specific capacity, energy and power density, cycle life, and safety. Currently, the cathodes available for BEVs are spinel LiMn2O4 (LMO), olivine LiFePO4 (LFP), layered LiCoO2 (LCO), layered LiNi0.8Co0.15Al0.05O2 (NCA), and layered LiNix MnyCozO2 (NMC, x+y+z=1). Among all the available cathode materials, NMC cathodes are among the most promising candidates, as illustrated in
With the increasing Ni content, NMC cathodes enable higher capacities, such as NMC811. However, it becomes more challenging for commercialization, due to their lower capacity retention and lower thermal stability (see
In view of these disadvantages, nickel-rich layered oxide electrodes are described herein having high ionic conductivity coatings which, in some embodiments, mitigate degradative pathways, maintain electrode performance and/or enhance electrode lifetimes. In one aspect, an electrode comprises nickel-rich layered oxide, and a lithium-containing sulfide or oxide coating over the nickel-rich layered oxide, the lithium-containing sulfide (or oxide) coating having an ionic conductivity from 1×10−6 S/cm to 9×10−2 S/cm at room temperature. In some embodiments, the ionic conductivity is tunable within this range. Moreover, the lithium-containing sulfide and/or oxide coatings can be binary or ternary. Ternary sulfides and/or oxides, for example, comprise lithium and another metal, including aluminum, zinc, gallium, and/or zirconium. In another aspect, an electrode described herein comprises nickel-rich layered oxide, and a lithium-containing coating over the nickel-rich layered oxide.
Turning now to specific components, the ternary sulfides of the coatings can be of the formula LipMn(2-p)S, wherein 0<p≤2, 0.25≤n≤0.5, M=Al, Zn, Ga, and Zr. The ternary oxides of the coatings can be of the formula LipMn(2-p)O, wherein 0<p≤2, 0.25≤n≤0.5, M=Al, Zn, Ga, and Zr. The binary sulfide is Li2S. The lithium-containing coatings can have any thickness not inconsistent with the technical objectives described herein relative to enhancing and/or maintaining performance of nickel-rich layered oxide electrodes. In some embodiments, the lithium-containing coatings have thickness of 1 nm to 10 nm. Alternatively, the lithium-containing coating can have thickness less than 1 nm or greater than 10 nm, in some embodiments. Additionally, the lithium-containing coatings can exhibit uniform thickness, in some embodiments. As described further herein, the lithium-containing coatings can be deposited over the nickel-rich layered oxide via atomic layer deposition (ALD).
The nickel-rich layered oxide, in some embodiments, can be of the formula LiNi1-x-yMnxCoyO2, wherein 1−x−y≥0.6. In some embodiments, 1−x−y≥0.7 or 1−x−y≥0.8.
In another aspect, batteries are described herein. A battery comprises an anode, and a cathode, the cathode including nickel-rich layered oxide, and a lithium-containing coating over the nickel-rich layered oxide, the lithium-containing coating having an ionic conductivity ranging from 1×10−6 S/cm to 9×10−2 S/cm at room temperature. The lithium-containing coatings can have any composition and/or properties described herein. Additionally, the nickel-rich layered oxide can have any compositions and/or properties described herein. Moreover, batteries having the foregoing constructions can be employed in electric vehicles.
In a further aspect, methods of making electrodes are described herein. In some embodiments, a method of making an electrode comprises providing an electrode substrate comprising nickel-rich layered oxide, and depositing a lithium-containing coating over the nickel-rich layered oxide. The lithium-containing coatings can have an ionic conductivity greater than 1×10−4 S/cm at room temperature. In some embodiments, the ionic conductivity of the sulfide-based coating is at least 1×10−3 S/cm at room temperature. The lithium-containing coatings and nickel-rich layered oxide can have any composition and/or properties described herein. In some embodiments, the lithium-containing coatings are deposited by atomic layer deposition. As described further herein, the atomic layer deposition can comprise individual sub-cycles of Li—S and M-S (M=Al, Zn, Ga, and Zr) in any sub-cycle ratio. In some embodiments, a ratio of Li—S to M-S sub-cycles ranges from 1:10 to 10:1. For example, the ratio of Li—S to Al—S sub-cycles can be 1:4, in some embodiments.
These and other embodiments are further described in the following detailed description.
Embodiments described herein can be understood more readily by reference to the following detailed description and examples and their previous and following descriptions. Elements, apparatus and methods described herein, however, are not limited to the specific embodiments presented in the detailed description and examples. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.
As set forth in the following data, the lithium-containing coatings comprising Li2S, LixAlyS, LixZnyS, LixGayS, LixZryS, or LixZryO can provide several unique benefits to electrodes constructed of nickel-rich layer oxides, including NMC811. These benefits include, but are not limited to:
Some additional, non-limiting, example embodiments are provided below.
Embodiment 1. An electrode comprising: nickel-rich layered oxide; and
Embodiment 2. The electrode of Embodiment 1, wherein the ionic conductivity is at least 1×10−3 S/cm at room temperature.
Embodiment 3. The electrode of Embodiment 1, wherein the sulfide-based coating comprises a ternary sulfide, the ternary sulfide including lithium and aluminum, lithium and zinc, lithium and gallium, or lithium and zirconium.
Embodiment 4. The electrode of Embodiment 1, wherein the sulfide-based coating has a uniform thickness.
Embodiment 5. The electrode of Embodiment 4, wherein the thickness is from 1 nm to 10 nm.
Embodiment 6. The electrode of Embodiment 1, wherein the nickel-rich layered oxide is of the formula LiNi1-x-yMnxCoyO2, wherein 1−x−y≥0.6.
Embodiment 7. The electrode of Embodiment 6, wherein 1−x−y≥0.7.
Embodiment 8. The electrode of Embodiment 6, wherein 1−x−y≥0.8.
Embodiment 9. The electrode of Embodiment 3, wherein the ternary sulfide is of the formula LipMn(2-p)S, wherein 0<p≤2, 0.25≤n≤0.5.
Embodiment 10. The electrode of Embodiment 1, wherein the sulfide-based coating is deposited by atomic layer deposition.
Embodiment 11. An electrode comprising:
Embodiment 12. The electrode of Embodiment 11, wherein the ternary sulfide-based layer includes lithium and aluminum, lithium and zinc, lithium and gallium, or lithium and zirconium.
Embodiment 13. The electrode of Embodiment 11, wherein the ternary sulfide is of the formula LipMn(2-p)S, wherein 0<p≤2, 0.25≤n≤0.5.
Embodiment 14. The electrode of Embodiment 11, wherein the ternary sulfide based layer has ionic conductivity greater than 1×10−4 S/cm at room temperature.
Embodiment 15. The electrode of Embodiment 14, wherein the ionic conductivity is at least 1×10−3 S/cm at room temperature.
Embodiment 16. The electrode of Embodiment 11, wherein the ternary sulfide-based coating has thickness of 1 nm to 10 nm.
Embodiment 17. The electrode of Embodiment 11, wherein the nickel-rich layered oxide is of the formula LiNi1-x-yMnxCoyO2, wherein 1−x−y≥0.6.
Embodiment 18. The electrode of Embodiment 17, wherein 1−x−y>0.7.
Embodiment 19. The electrode of Embodiment 17, wherein 1−x−y≥0.8.
Embodiment 20. A battery comprising:
Embodiment 21. An electric vehicle comprising:
Embodiment 22. A method of making an electrode comprising:
Embodiment 23. The method of Embodiment 22, wherein the ionic conductivity is at least 1×10−3 S/cm at room temperature.
Embodiment 24. The method of Embodiment 22, wherein the sulfide-based lithium-containing coating comprises a ternary sulfide, the ternary sulfide including lithium and aluminum, lithium and zinc, lithium and gallium, or lithium and zirconium.
Embodiment 25. The method of Embodiment 22, wherein the sulfide-based lithium-containing coating is deposited by atomic layer deposition.
Embodiment 26. The method of Embodiment 25, wherein the atomic layer deposition comprises individual sub-cycles of Li—S and Al—S, individual sub-cycles of Li—S and Zn—S, individual sub-cycles of Li—S and Ga—S, or individual sub-cycles of Li—S and Zr—S.
Embodiment 27. The method of Embodiment 26, wherein a ratio of Li—S to M-S (M=Al, Zn, Ga, and Zr) sub-cycles ranges from 1:10 to 10:1. More particularly, Embodiment 27 describes an implementation wherein the ratio of Li—S to Al—S, Zn—S, Ga—S, or Zr—S used in the individual sub-cycles ranges from 1:10 to 10:1.
Embodiment 28. The method of Embodiment 27, wherein the ratio is 1:4.
Embodiment 29. The method of Embodiment 27, wherein the sulfide-based lithium-containing coating is of the formula LipAl(2-p)/3S and LipGa(2-p)/3S, the formula of LipZn(1-p/2)S and the formula of LipZr(0.5-0.25p)S, wherein 0<p≤2, 0.25≤n≤0.5
Embodiment 30. The method of Embodiment 22, wherein the nickel-rich layered oxide is of the formula LiNi1-x-yMnxCoyO2, wherein 1−x−y≥0.6.
Embodiment 31. The method of Embodiment 30, wherein 1−x−y>0.7.
Embodiment 32. The method of Embodiment 30, wherein 1−x−y≥0.8.
The present examples provide aspects of embodiments of the present disclosure. These examples are not meant to limit embodiments solely to such examples herein, but rather to illustrate some possible implementations.
A comparative study using a 1:1 LixAlyS (which is deposited with a 1:1 sub-cycle ratio of Li—S:Al—S via ALD, named as LAS) of low conductivity (6.7×10−7 S/cm at room temperature) and the 1:4 LixAlyS coating (which is deposited with a 1:4 sub-cycle ratio of Li—S:Al—S via ALD, named as sup-LAS having conductivity of at least 1×10−4 S/cm at room temperature) to modify NMC811 electrodes. NMC811 electrodes were coated by the two coatings with different thicknesses, 20 (˜2 nm), 40 (˜4 nm), and 80 (˜8 nm) ALD cycles. The resultant LAS-coated electrodes were signified as LAS20, LAS40, and LAS80, while the resultant sup-LAS-coated electrodes were named as sup-LAS20, sup-LAS40, and sup-LAS80, respectively. The LAS and sup-LAS coated electrodes were tested for their rate capability at different current densities (0.1, 0.2, 0.5, 1, 2, 5, 7, and 0.5C) and compared to the performance of bare NMC811 electrodes in the voltage range of 3.0-4.5 V at RT. 1C is equal to 200 mA/g.
Experimental results revealed that, as shown in
In contrast, the sup-LAS coating improved the performance of NMC811 electrodes. As shown in
The effects of the sup-LAS coating were further tested on cyclability of NMC811 electrodes at 1C at room temperature and an elevated temperature of 55° C. As illustrated in
Normalizing the data in
All these results of the sup-LAS coating are very encouraging and have not been reported in previous studies. In particular, the sup-LAS-coated NMC811 cathodes showed better performance with thicker sup-LAS coatings in the tested film thicknesses. This confirmed that the sup-LAS coating has excellent ionic conductivity. Furthermore, these results demonstrated that the sup-LAS coating has great potentials to change our traditional choices on coating materials, ascribed to its exceptional ionic conductivity of ˜10−3 S/cm at RT. To this end, it becomes very critical to thoroughly reveal the effects of the sup-LAS coating and fully explore the underlying mechanisms.
Based on these preliminary data, it is believed that, compared to the coatings practiced previously, the ALD sup-LAS coating potentially has several novel benefits not realized previously:
With these benefits, we expect that the sup-LAS coating would provide new solutions to the existing challenges in LIBs and this may pave a new technical venue for researchers to tackle issues associated with NMC811 cathodes. It will also be particularly significant to explore the underlying mechanisms responsible for the beneficial effects of the sup-LAS coating.
In addition to the coatings of LixAlyS, we further investigated the effects of two new ALD coatings Li2S (
Ni-rich NMC electrodes will be fabricated using a commercial micron-sized Ni-rich NMC powder (MSE Supplies LLC). Using a Thinky AR-100 mixer, NMC powders will be mixed with a Super P carbon black (MTI Corporation) and a polyvinylidene fluoride binder (PVDF, Sigma-Aldrich) in a weight ratio of 8:1:1 in N-methyl-2-pyrrolidone (NMP, Sigma-Aldrich) at 2000 rpm for 30 min. The resultant slurry will be cast onto an aluminum foil and made into electrode laminates using a doctor blade with a controlled thickness of 200 m. The received NMC electrodes will be dried in air for 24 hours and then transferred into a vacuum heater to cure the PVDF binder at 100° C. for 10 hours. The fabricated NMC electrodes will have a NMC loading of 8-10 mg/cm2. Subsequently, the fabricated NMC cathodes will be deposited with a conformal layer of a lithium-containing coating with controllable thicknesses using an ALD system (Savannah S200, Ultratech Inc.). Bare NMC electrodes and the ALD-coated NMC electrodes will be comparatively studied for their electrochemical performance in CR2032 coin cells at same conditions. A Celgard 2325 membrane will be used as the separator placed between the cathode and anode. The electrolyte will be 1.2 M LiPF6 in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (3/7, wt/wt) (Panax Etec Co.). All the cells will be assembled in a glovebox with both moisture and oxygen below 1 ppm. The bare and ALD-coated NMC electrodes are thoroughly tested (using two Neware battery cyclers with 144 channels) to explore the beneficial effects of the ALD coatings in different voltage ranges and different temperatures. Additionally, we investigate the evolution of both impedance and cyclic voltammetry (CV) of the bare and ALD-coated cells with charge-discharge cycles using an electrochemical impedance spectroscopy (EIS, BioLogic SP-200). We conducted analyses on voltage drop through normalizing charge-discharge profiles and on the evolutions of differential capacity (i.e., (dQ/dV)−V) profiles in order to obtain the effects of the sup-LAS coating on stabilizing the NMC structures.
The ALD Li2S coating was conducted using lithium tert-butoxide (LTB) and H2S as precursors at 150° C., but the deposition temperature can range from 150° C. to 300° C. The ALD LixAlyS used the precursor pair of LTB and H2S for ALD Li—S and the precursor pair of tris(dimethylamido)aluminum (TDMA-Al, Al2(NMe2)6, where Me=CH3) and H2S for ALD Al—S. The ALD LixZnyS used the precursor pair of LTB and H2S for ALD Li—S and the precursor pair of diethylzinc (DEZ, C2H5) and H2S for ALD Zn—S. The ALD LixGayS used the precursor pair of LTB and H2S for ALD Li—S and the precursor pair of hexakis(dimethylamido)digallium (Ga2(NMe2)6, Me=CH3) and H2S for ALD Ga—S. The ALD LixZryS used the precursor pair of LTB and H2S for ALD Li—S and the precursor pair of tetrakis(dimethylamido)zirconium (TDMA-Zr, Zr(NMe2)4, Me=CH3) and H2S for ALD Zr—S. The ALD LixZryO used the precursor pair of LTB and H2O for ALD Li—O and the precursor pair of tetrakis(dimethylamido)zirconium (TDMA-Zr, Zr(NMe2)4, Me=CH3) and H2O for ALD Zr—O.
Various embodiments of the invention have been described in fulfillment of the various objectives of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.
The present application claims priority to U.S. Provisional Application Ser. No. 63/127,481, filed Dec. 18, 2020, the contents and substance of which are incorporated herein in its entirety by reference.
This invention was made with government support under Federal Grant No. OIA1457888 awarded by the National Science Foundation (NSF). The government has certain rights to this invention.
Filing Document | Filing Date | Country | Kind |
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PCT/US2021/063517 | 12/15/2021 | WO |
Number | Date | Country | |
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63127481 | Dec 2020 | US |