Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/058—Construction or manufacture
  • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
  • H01M4/386—Silicon or alloys based on silicon
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/661—Metal or alloys, e.g. alloy coatings
  • H01M4/662—Alloys
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
• • H—ELECTRICITY
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  • H01M4/00—Electrodes
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  • H01M4/64—Carriers or collectors
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  • H01M4/664—Ceramic materials
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/665—Composites
• • H—ELECTRICITY
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  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/665—Composites
  • H01M4/667—Composites in the form of layers, e.g. coatings
• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/669—Steels
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/60—Other road transportation technologies with climate change mitigation effect
  • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Definitions

• This disclosure relates to lithium ion (Li-ion) electrochemical cells (i.e., batteries), particularly secondary (i.e., rechargeable) Li-ion batteries (LiBs).
• LIBs have been a prominent means of storing electrical energy.
• secondary batteries LIBs offer several notable advantages such as high volume and gravimetric energy density, long shelf life and a boarder temperature range of operation.
• the commercialization of LIBs has enabled the realization of laptop computers and high performance smart phones.
• Li-ion batteries are based on the combination of lithium containing transition metal oxides as positive electrodes or cathodes, and carbonaceous materials (especially graphite) as negative electrodes or anodes. So-constructed, the specific energy of existing LIBs is still insufficient for many applications such as electric vehicles, plug-in hybrid electric vehicles, and smart grid community systems due to the limited specific charge capacity of the electrode materials.
• a silicon anode and L12S cathode chemistry yields a LIB with a theoretical specific energy of 1550 Wh/kg, which is four times that of the theoretical specific energy of existing LIBs. Nevertheless, sulfur cathodes and silicon anodes have shortcomings that have prevented their practical application.
• a major drawback sulfur use is the formation during charge-discharge cycle of highly soluble polysulfides species in liquid electrolytes. The result is in the so-called “shuttle effect” that removes active material from the positive sulfur electrode and also damages or deactivates anode surface area. Moreover, sulfur-based batteries have low electronic conductivity with associated inefficiencies.
• a disadvantage of silicone anode use is the large volume change (>400%) that occurs upon cycling. This issue causes fractures, cracks and disconnection of silicon from current collector, leading to loss of capacity during cycling.
• the volume change also causes the irreversible and continuous formation of a solid electrolyte interface (SEI) film. This surface film passivates the anode surface and prevents further decomposition of the electrolyte solution.
• SEI solid electrolyte interface
• LIBs can present a safety issues. Especially when more and more energy is packed into a cell (as with a silicon anode and sulfur cathode chemistry), safety becomes a priority. Many LIBs currently use organic solvent electrolytes which are volatile and flammable. Thus, if the cell is overheated due to overcharging, internal shorting, physical damage, or other failure mechanisms, it may undergo thermal runaway that can result in serious hazards of fire and explosion. Attempts to improve the safety of these electrolytes have focused on creating solid-state batteries using polymer or ceramic/glass solid electrolytes.
• a first set of embodiments involves a solid polymer electrolyte for three-dimensional (3D) battery architectures.
• the polymer electrolyte is a combination of a functionalized poly(ethylene) oxide or poly(ethylene glycol) as poly(ethylene) oxide is referred to when its molecular weight is below 20,000 g/mol (either way, PEG), a lithium salt, an ionic liquid, and graphene oxide as filler.
• PEG poly(ethylene glycol)
• Li salt lithium salt
• ionic liquid lithium salt
• graphene oxide graphene oxide
• the so-called “3D” batteries may share their architecture with those described in US Patent Publication Number (USPPN) 2015/0010788 which are incorporated herein by reference.
• the polymer electrolyte serves several key roles or functions in the system. Namely, it provides a means for the following, either alone or in combination depending on the embodiment, to provide superior battery performance: (1) Li-ion transport between anode and cathode; (2) a physical barrier between electrodes avoiding anode and cathode contact (otherwise resulting in electrical path shorting); (3) insuring safety of the battery as the polymer electrolyte does not contain volatile and flammable organic solvents; (4) accommodating volume change of electrode by buffering stress and strain of electrodes; (5) preventing polysulfide dissolution and a polysulfide shuttle mechanism; and (6) forming a stable SEI on anode surface with the polymer possibly bonding to and thereby stabilizing Si surface(s).
• a second set of embodiments involves fabrication methods or processes for 3D battery production.
• a microscale polymer structure is fabricated to separate interlaced or interleaved anode and cathode (i.e., negative electrode and positive electrode) current collector structures. Placement of the interposed micro- structure polymer element(s) avoids electrical shorting.
• a dimensionally stable ceramic substrate is produced in order to provide interlaced or interleaved anode and cathodes upon application of a conductive growth substrate (e.g., Nickel) thereon for vertically-aligned carbon nanotube (VACNT) growth.
• a conductive growth substrate e.g., Nickel
• VACNT vertically-aligned carbon nanotube
• a third set of embodiments involves compositions and methods using
• poly(ethylene)oxide bis(azide) (PEO-N3) to form a stable SEI during cycling of the silicon anode.
• PEO-N3 poly(ethylene)oxide bis(azide)
• the polymer layer will protect the silicon while allowing good battery performance.
• the thin layer e.g., from between about 10 nm to about lOOnm
• offers low resistivity e.g., from about 103 to about 104 Q.cm
• battery performance is largely unaffected, while the polymer effectively prevents electrolyte decomposition.
• a fourth set of embodiments involves compositions and methods in which a graphene poly(lactic acid) (PLA) composite covers the cells' cathode and/or anode material. As with the third set of embodiments, these are advantageously employed in connection with a VACNT architecture - whether employed in a 2D or 3D arrangement.
• PLA graphene poly(lactic acid)
• Figs 1A-1C are top, side and perspective views of a 3D battery architecture embodiment.
• Figs. 2 A and 2B are electrolyte for the Fig. 1 A-1C embodiment in paste and as-cured solid form, respectively.
• Fig. 3 is a graph comparing the conductivity of solid polymer electrolyte embodiments.
• Fig. 4 is a detail side cross-section view of electrodes (anode or cathode) construction applicable to various embodiments hereof.
• Fig. 5 is an optical microscope view of electrode elements.
• Fig. 6 is an optical microscope view with an inset detail at higher magnification of a micro- structure insulation element.
• Fig. 7 is an optical microscope view showing an assembly of the elements in Figs. 5 and 6.
• Fig. 8 is a flowchart detailing manufacture methods of an embodiment including components as described in connection with Figs. 5-7.
• Figs 9A and 9B are top views of ceramic substrates before and after nickel current collector deposition thereon, respectively.
• Fig. 10 is a flowchart detailing manufacture methods of an embodiment including components as described in connection with Figs. 9 A and 9B.
• Fig. 11 is a flowchart detailing SEI production or manufacture with PEO-N3 in another embodiment.
• Fig. 12 is a graph of illustrating cycling of performance of a S-VACNT electrode with and without a G/PLA trap.
• Figs. 13 A and 13B are flowcharts detailing polysulfide trap type cathode and anode production, respectively, with a graphene PLA composite.
• a "high performance" polymer electrolyte in described for use in conjunction with a 3D battery architecture that may be based on a Si/S LIB battery chemistry.
• the polymer electrolyte is a combination of a functionalized poly(ethylene glycol) (PEG), a lithium salt, an ionic liquid, and graphene oxide as filler.
• the overall combination exploits the advantageous energy characteristics of silicon and sulfur while also taking lifetime and cost issues into account. Moreover, the polymer electrolyte provides safety due to the absence of toxic and unstable materials, as well as the absence of flammable organic solvents.
• Figs. 1 A-1C illustrate a basic configuration of a 3D Si/S battery 10 using a polymer electrolyte.
• the cathode 12 and anode 14 are patterned in a comb-type configuration with comb "teeth” or alternating “fingers” such that both electrode elements (i.e., anode and cathode) are in the same plane when assembled in an interlaced fashion.
• the polymer electrolyte 16 fills the space between the electrode surfaces (along with any optional micro-structure insulating features as referenced below.)
• Figs 1 A and IB In a full or complete assembly as shown in Figs 1 A and IB, these elements are housed or set within a casing 18 and may further include current collector portions 20 upon which VNCTs are set (in this context, "set” means grown, adhered or otherwise attached thereto).
• the electrodes are interlaced within the same plane. Alternatively, they may be setup opposite to or facing one another.
• the former arrangement places the electrode 12 and 14 surfaces or elements very close to each other when interfit, thus reducing ion diffusion lengths or distances.
• the interposed polymer electrolyte 16 insures Li ion transport in between anode and cathode, and acts a physical barrier between the electrodes elements.
• the electrolyte comprises or (optionally) consists of a combination of a functionalized poly(ethylene glycol) (PEG), a lithium salt, an ionic liquid, and graphene oxide as filler.
• PEG poly(ethylene glycol)
• Electrolyte 16 is prepared as a paste at room temperature as shown in Fig. 2A. It can be introduced in the channels 22 of a 3D architecture in this slurry or paste form. It is then cured or otherwise hardened to a solid state of matter. [0046] After cross-linking, the composition develops its intended mechanical properties converting from a paste to a state capable of performing as a stretchable free-standing film. Outside the channels in a battery, this can be seen in Fig. 2B.
• the process of preparation of the polymer electrolyte and its incorporation to electrodes system may be accomplished without the use of organic solvents. Once the subject electrodes are assembled into a mold, the polymer electrolyte can be incorporated.
• all the compounds are mixed together at about 60°C or more (e.g., up to about 80°C as a maximum at which the azide function of optionally associated components elaborated upon below start to decompose) until the mixture is homogeneous (i.e., utilizing the low melting temperature of poly(ethylene glycol) of less than about 60°C).
• the mixture is then poured on top of electrode system 24 seen in Fig. 1C.
• the polymer electrolyte mixture is able infuse into the electrodes system. This process may be performed under vacuum or inert (e.g., noble gas or N 2 ) atmosphere.
• inert e.g., noble gas or N 2
• the polymer electrolyte is subsequently cured. Curing by ultraviolet (UV) light, furnace or oven heat and/or microwave energy leads to the cross-linking of the polymer and a significant increase of mechanical strength.
• the mechanical properties (e.g., flexibility, elastic and/or deformability) of the polymer electrolyte can be optimized by varying the components ratios.
• BMP-TFSI bis(trifluoromethanesulfonyl)imide
• N-butyl N-propylpyrrolidinium
• BMP-FAP tris(pentafluoroethyl)trifluorophosphate
• BMP-FSI N-butyl, N-propylpyrrolidinium bis(fluorosulfonyl)imide
• GO Graphene oxide
• this particular polymer electrolyte possesses both very good mechanical properties and good ionic conductivity.
• ionic conductivity as a function of temperature of several composition of polymer electrolyte is presented Fig. 3. As shown, ionic conductivity close to 1 mS/cm can be achieved at room temperature which is considered high for a solid electrolyte.
• glass-ceramic electrolytes have ionic conductivity in the range of 10 "5 to 10 "4 S/cm and PEO based electrolytes have conductivity in the range of 10 "5 S/cm.
• the conductivity remains about one order of magnitude lower than typical liquid electrolyte such as conventional 1M lithium hexafluorophosphate in ethylene carbonate/dimethyl carbonate (1M LiPF6 in EC/DMC).
• typical liquid electrolyte such as conventional 1M lithium hexafluorophosphate in ethylene carbonate/dimethyl carbonate (1M LiPF6 in EC/DMC).
• the 3D architecture allows for short ion transport lengths between the active material(s) through the electrolyte. Example distances (per below) result in fast ion transport from anode to cathode and vice versa.
• VACNTs configured in various interlaced electrode "finger" widths with electrolytes of different conductivities (i.e., lmS/cm with the subject polymer electrolyte and lOmS/cm with 1M LiPF6 liquid electrolyte), the following values were modeled: Finger Width ( ⁇ ) Electrolyte Power Density (W/L) Energy Density (Wh/L)
• Electrode arrangement is one of the key considerations in making a battery. Whereas current Li-ion batteries with 2D geometries need large footprint areas to achieve large capacities, 3D battery architectures have the advantage of using the out-of-plane dimension. This can increase the areal capacity by increasing the amount of electrode material within a given footprint area. It may also improve electrochemical properties by allowing for more accessible surfaces with shorter ion diffusion distances.
• Example electrode architectures are illustrated in Fig. 4.
• Silicon 26 and sulfur 28 may provide the active electrode material.
• VACNT structures 30 provide a scaffold and (optional) graphene enclosures 32, respectively. When employed in the configuration shown in Figs. 1 A- 1C, this allows (e.g., silicon and sulfur) battery chemistry to expand and contract freely during the charging and discharging cycles.
• Embodiments hereof include two new 3D battery fabrication processes for production with high aspect ratio electrode elements such as shown in Figs 1 A-1C and 4.
• high aspect ratio what is meant is between 2 and about 25 in which maximum VACNT height may be about 500 ⁇ with width of given fingers from about 25 to about 200 ⁇ .
• the subject processes allow separated and independent preparation of each electrode. This is advantageous because the incorporation of the different anode and cathode active materials into each VACNT arrays involves different approaches.
• cathode and anode structures are patterned in a specific structure allowing the electrodes to be interdigitated with alternating anode and cathode. Examples of this configuration are presented Figs. 1A-1C and 5-7.
• the electrodes When assembled, the electrodes are in the same plane (optionally, along with their substrate support surfaces) but situated without touching each other.
• the electrodes have sufficient channel space or gap 22 between them as shown in Fig. 1C and 4 to accommodate the stress and strain induced by volume change during charge-discharge cycles (i.e., even with a Si/S chemistry) while high power density may be achieved by maintaining short electron and ion transport lengths in the active material (typically, less than 100 ⁇ ) and in the electrolyte (typically, less than 100 ⁇ and preferably down to about 30 ⁇ ).
• the shape of the included current collector dictates the shape of both cathode and anode.
• the fabrication process may start by separating the current collectors, machining them from a single piece of material. Contact-free high speed laser or electric discharge machining (EDM) techniques may be used to make a precise electrodes. Alternatively, individual (vs. paired) pieces may be machined.
• EDM electric discharge machining
• each current collector "finger” element is 1.44 cm length and 335 ⁇ width and configured for a channel 22 between interleaved portions of about 30 ⁇ .
• the Nickel (Ni), if desired for catalytic properties or otherwise, can be deposited on the stainless steel (using well-known microfabrication techniques such as lithography, physical vapor deposition (PVD) or electroplating) before or after cutting.
• VACNT scaffolds (not shown in Fig. 5) are then directly grown on the patterned current collector by CVD deposition technique.
• Si and S (or Li2S) may be incorporated separately into VACNT scaffold on each electrode.
• graphene or graphene and PLA composite
• the use of VACNT scaffolds allow the use of very thick films of silicon and sulfur active materials (e.g., up to several mm), without escalating their internal electrical resistance or affecting power density.
• micro- structure polymer element(s) For electrical insulation between the current collector portions upon assembly, micro- structure polymer element(s) may be used. Photolithography techniques may be used to fabricate a micro- structured "mold" using epoxy -based photoresist (e.g., SU-8/2002/2100 or SU- 8/2002/2150). This element will be used to separate the anode and cathode (e.g., fitting into the example 30 ⁇ channel or gap referenced above).
• the photolithography process, used for photoresist patterning generally includes spin coating, soft bake, near UV exposure,
• the SU-8 microstructure may be formed on a glass or silicon oxide substrate or any type of non-conductive substrate.
• an overall high aspect ratio microstructure e.g. on the order of about 5 to about 25
• SU-8/2002 may be used as a base layer followed by application of SU-8 2100 or 2150.
• Fig. 6 shows a SU-8 micro- structure element 40 on a silicon oxide wafer made by lithography technique.
• the width of each "line" to fit in gap 22 is 10 ⁇ and the overall thickness is about 250 ⁇ . This thickness is coordinated with current collector 20 thickness of about 25 ⁇ to about 250 ⁇ .
• the microstructure element or elements insulate the electrode substrates or current collectors from electrical shorting as typically matching the thickness of the stainless steel current collector.
• the polymer micro- structure or micro-structured element 40 separate the base of the electrode, alone. Above their mutual (planar) surface electrolyte separates the VACNTs 30 and associated active material 26, 28 and/or encasing 32. Electrical resistance of the SU-8 material element 40 example is 2.8x1016 Q.cm.
• Fig. 8 details processes in connection with the above.
• the process 100 begins at 102. Along one line of action, at 104, the mold micro- structure element(s) reference above are made. [0068] Along the other line, the current collector portions are cut at 106, optionally as described above. At 108, VACNTs are grown on the substrate or current collector electrode portions.
• Si may be incorporated in the CNT scaffold at 110.
• L12S may be incorporated in its CNTs at 112.
• the anode and the cathode are assembled together with the micro-structure "mold" element(s).
• this subassembly is filled with polymer electrolyte as described above (or otherwise) and/or be encapsulated therewith.
• a housing and various electrical connections can then be applied (e.g., as illustrated in connection with Figs. 1 A and IB).
• the fabrication process involves cutting a ceramic (e.g., AI2O3) substrate with a defined pattern (e.g., in the aforementioned "comb” or “brush” shape) by laser cutting or otherwise.
• a ceramic e.g., AI2O3
• a defined pattern e.g., in the aforementioned "comb” or “brush” shape
• Fig. 9A shows two pieces of ceramic substrate after nickel current collector 20 material deposition.
• Use of the ceramic or a non- conductive polymer such as polydimethylsiloxane (PDMS) as a substrate offers the following potential advantages including: 1) dimensional stability, 2) resistance to warping from cutting, 3) the ability to achieve finer feature resolution and/or 4) no heat-effected zone.
• PDMS polydimethylsiloxane
• VACNT scaffolds can then be grown on the patterned current collector(s) by CVD deposition technique.
• Si and L12S can also be incorporated separately into VACNT scaffolds on each side of cut electrodes. Then, graphene may be used to wrap or cote the
• the electrodes (cathode and anode) are inserted into each other.
• process 120 begins at 122, it involves cutting the ceramic substrate at 124.
• the substrate is then coated or patterned with metal (e.g., Nickel).
• metal e.g., Nickel
• VACNTs are grown upon the patterned metal that will serve as a current collector over the ceramic substrate.
• Active material is incorporated in the VACNTs at 130 and 132, as above.
• the loaded VACNTs may be enclosed in a graphene film at 336 and 138.
• the anode and cathode are then assembled (without the need for a separating micro- structure mold) at 140 and filled with (optionally) polymer electrolyte at 142.
• the polymer electrolyte may then be cured.
• the electrodes may be encapsulated, as above, and/or other final battery manufacture acts or steps completed such as encasing the structure, etc.
• a third set of embodiments involves producing a stable SEI pre-formed on a silicon anode (e.g., as in coating 32 on anode 14 in Fig. 4) using poly(ethylene)oxide bis(azide) (PEONS) polymer.
• PEONS poly(ethylene)oxide bis(azide)
• a thin (e.g., between about 2 nm and 100 nm) protective layer on the silicon surface 26 so-produced contributes to high performance and good cyclability lithium ion batteries (e.g., a maintaining a capacity of 80% of the theoretical value has been obtained over 10 cycles).
• the azide functional groups of the polymer are converted to highly reactive nitrene radicals, resulting in the crosslinking of the polymer and in a significant increase of its mechanical properties.
• These mechanical properties can be enhanced by incorporating into the polymer matrix a small amount (e.g., about 1 to about 2% by weight of the overall composition) of graphene, ionic liquids, or small organic molecules.
• the polymer layer can help to accommodate volume change of the silicon electrode (i.e., it buffers stress and strain of electrodes).
• azide groups Another important feature of azide groups is their abilities to bond to silicon surfaces when they undergo UV irradiation. This feature protects the silicon surface and prevents further decomposition of the electrolyte each cycle. Together, these features or aspects provide a polymer layer forming a stable SEI during cycling of the silicon anode.
• the subject polymer also provides high lithium ion conductivity (e.g., about lmS/cm).
• high lithium ion conductivity e.g., about lmS/cm.
• poly(ethylene)oxide-based polymers are widely used in solid-state lithium ion batteries because of their well-known high ionic conductivity. Accordingly, while the polymer layer protect the silicon surface, it also allow lithium ion transport to and from the anode material.
• a process 150 for forming the polymer layer may be accomplished as illustrated in Fig. 11 without applying high temperature (e.g., about 80°C or less). Specifically, at 152, PEO-N3 is dissolved in an organic solution. Then, at 154 silicon anode is dip coated into the PEO-N3 solution. At 156, the thin (e.g., between about 10 ⁇ to 100 ⁇ , more preferably 10 ⁇ to 20 ⁇ ) polymer layer is subsequently cured. UV light, convective heat (e.g. at about 250°C) or microwave may be used for curing.
• high temperature e.g., about 80°C or less.
• a so-called "polysulfide trap" is produced for lithium- sulfur batteries.
• An example lithium sulfur cell includes a lithium-containing anode, a cathode and a separator between the lithium-containing anode and the sulfur-containing cathode.
• the sulfur active material 28 electrode (cathode) 12 is (at least partially) covered with a graphene and thermoplastic polymer (e.g., poly(lactic acid) (PLA)) composite layer 32 as in Fig. 4.
• the graphene and PLA composite layer shows effective lithium polysulfide traps to prevent the shuttle mechanism (i.e., dissolution of lithium polysulfides in the electrolyte) that would otherwise occur in the battery.
• a cathode comprising a composite of sulfur and VACNTs coated or covered with the graphene and PLA composite.
• the VACNTs are employed to enhance the conductivity of S-based cathodes whereas the graphene and PLA composite assists or altogether prevents dissolution of polysulfides into the electrolytes and minimizes fracture of sulfur particles within the graphene and PLA enclosures.
• the graphene and PLA is an ideal trap for polysulfide due to flexible structure of graphene sheets.
• the graphene sheets may contribute to PLA chain confinement effects leading to improvement in stiffness and strength.
• the graphene and PLA composite enclosures prevent a direct contact between electrolyte and polysulfides formed in the VACNTs.
• dissolution of polysulfides into the electrolyte can be avoided (as noted above) whilst simultaneously allowing electrochemical reaction to occur.
• This activity ultimately improves the battery cycle life, improves overall capacity and minimizes fading in capacity of the S-VACNT as seen in data with the G/PLA trap 160 versus without at 158 in Fig. 12.
• the graphene enclosures also reduce internal resistance of the VACNTs to ultimately improve the overall battery efficiency.
• Fig. 13 A illustrates a process 162 for such cathode preparation.
• molten sulfur and sulfur containing solutions are prepared. They are used, at 166, to infuse sulfur via melting from above and flowing into the VACNT interstices while allowing some inter-space between the coated CNTs so that electrolyte can pass through).
• sulfur has a very good affinity with carbon, the CNT are easily coated, allowing each individual CNT to be coated.
• a successful sulfur infusion process results in a change of between about 300% to about 350% by weight of the VACNT structure (or a ratio of sulfur to VACNT of about 60%).
• the grapheme and PLA composite encapsulates the VACNTs at 168 (via dipping, spin coating or otherwise).
• Different concentration of graphene and PLA solution are obtained by dissolving the graphene and PLA pellets or wire into chlorinated solvent, typically, with a goal of obtaining a G/PLA coating with 1% to 10% by weight of Si.
• the graphene and PLA solution is deposited on the VACNT/S electrodes by spin coating, drop casting or spraying coating methods.
• the coating 32 for each of the anode 14 and cathode 12 described with respect to Fig. 4 includes the graphene and PLA composite.
• that coating 32 includes only the graphene and PLA composite and no other material. Hybridizing a Si-VACNT anode with graphene and PLA provides a solution for utilizing the high theoretical capacity of Si while avoiding structural damage due to the extremely large volume change.
• Such a coating may be applied over a stable SEI layer formed per above. Except in this case, in process 170 of Fig. 13B, Silicone is incorporated in the anode, at 172, by CVD or another technique. Then the Si-VACNT cathode is encapsulated with the graphene and PLA composite at 174.
• the subject methods may be carried out in any order of the events which is logically possible, as well as any recited order of events.

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