CN106910869A - Energy storing device - Google Patents

Energy storing device Download PDF

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Publication number
CN106910869A
CN106910869A CN201610882352.3A CN201610882352A CN106910869A CN 106910869 A CN106910869 A CN 106910869A CN 201610882352 A CN201610882352 A CN 201610882352A CN 106910869 A CN106910869 A CN 106910869A
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cnf
silicon
fiber
carbon nano
insertion material
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罗纳德·罗杰斯基
史蒂文·科兰考斯基
李钧
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/36—Nanostructures, e.g. nanofibres, nanotubes or fullerenes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/50—Electrodes characterised by their material specially adapted for lithium-ion capacitors, e.g. for lithium-doping or for intercalation
    • 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
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0421—Methods of deposition of the material involving vapour deposition
    • H01M4/0423—Physical vapour deposition
    • H01M4/0426—Sputtering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/70—Carriers or collectors characterised by shape or form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • 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
    • Y02E60/13—Energy storage using capacitors
    • 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

Abstract

The application is related to energy storing device.A kind of new mixing lithium-ion anode material, the mixing lithium-ion anode material is based in the coaxial silicon shell for coating on carbon nano-fiber (CNF) array being vertically arranged.Unique cup-shaped stacking graphite microstructure makes the exposed CNF arrays being vertically arranged turn into effective Li+Insertion medium.The Li of high reversible+It is inserted and removed from being observed under high power speed.More importantly, highly conductive and the CNF cores of mechanically stable selectively support the amorphous silicon shell of coaxial coating, the amorphous silicon shell there is much higher theoretical specific capacity by forming the alloy of abundant lithiumation.Ensure to be electrically connected with the good of silicon shell during charge/discharge process at the broken graphite edge of CNF side-walls.

Description

Energy storing device
It is on December 21st, 2012, Application No. 201280070082.6, entitled " energy the applying date that the application is The divisional application of the application of storage device ".
Cross-Reference to Related Applications
This application claims the rights and interests and priority of following U.S. Provisional Patent Application：
In on December 21st, 2011 submit to 61/578,545,
In on 2 27th, 2012 submit to 61/603,833,
In on March 23rd, 2012 submit to 61/615,179,
61/667 submitted on July 3rd, 2012,876, and
61/677,317 submitted on July 30th, 2012.
The disclosure of the patent application of all of above-mentioned interim and non-provisional is accordingly by being incorporated herein by reference.
Background
Invention field
The present invention is in the field of the energy storing device of including but not limited to battery, capacitor and fuel cell.
Correlation technique
Rechargeable lithium ion battery is for the electronic traffic work in portable electric appts, electric tool and future The crucial electrical energy storage device of supply of electric power in tool.High specific energy capacity, charge/discharge speed and cycle life are put forward to them more It is critical to be widely applied.
In the lithium ion battery of current business, graphite or other carbonaceous materials pass through to be formed the LiC being adequately inserted6Chemical combination Thing and be used as the anode of the theoretical capacity limits with 372mAh/g.On the contrary, silicon is by forming the metal of abundant lithiumation Li4.4Si and there is the theoretical specific capacity of much higher 4,200mAh/g.However, the large volume up to~300% of the silicon of lithiumation Expansion causes the great structural stress for inevitably leading to fracture and mechanical breakdown in the past, and this significantly limits the longevity of silicon anode Life.
General introduction
A kind of energy storage device is included in core-shell structure copolymer NW (nano wire) constructions of the mixing in high-performance lithium ion anode, and this is Carbon nano-fiber (VACNF) array being vertically arranged of amorphous si-layer is coaxially coated with by combining.The CNF bags being vertically arranged The CNT (MWCNT) of many walls is included, the CNT of many walls uses the plasma activated chemical vapour deposition of direct current biasing (PECVD) method selectively grows in Copper base material.The carbon nano-fiber (CNF) grown by the method can have uniqueness External morphology, the form by they be different from common MWCNT and routine solid carbon nano-fiber hollow structure.Difference One of feature is that these CNF are selectively made up of a series of bamboo shape nodes for crossing main hollow center channel.It is this Micro-structural can be attributed to elsewhere herein conical graphite cup stacking discussed further.Under larger length scale, this It is evenly distributed and separated from one another well that the CNF of a little PECVD- growths is typically orthogonal to substrate surface.They may be without any The entanglement of minimum is tangled or has, and therefore formation is referred to as the brush-like structure of VACNF arrays.The diameter of single CNF can be with It is selected as providing desired mechanical strength so that VACNF arrays are firm and can be by siliceous deposits and wet electro-chemical test Keep its integrality.
Multiple embodiments of the invention include a kind of energy storage system, and it includes conductive base；Grown on base material The carbon nano-fiber that is vertically arranged of multiple, the carbon nano-fiber includes the CNT of multiple many walls；And electrolyte, the electricity Solution matter includes one or more charge carrier.
Multiple embodiments of the invention include a kind of energy storage system, and it includes conductive base；Grown on base material The carbon nano-fiber that is vertically arranged of multiple；And insertion material layer, the insertion material layer be disposed in the multiple vertical row On the carbon nano-fiber of row and be configured between every gram of insertion material about 1,500 and 4,000mAh lithium ion storage hold Amount.
Multiple embodiments of the invention include a kind of energy storage system, and it includes conductive base；Grown on base material The carbon nano-fiber that is vertically arranged of multiple；And insertion material layer, the insertion material layer be disposed in the multiple vertical row On the carbon nano-fiber of row and it is configured such that the ion storage capacity of the insertion material under the charge rate of 1C and 3C about It is identical.
In one embodiment, the CNT is arranged such that ion insertion can pass through the carbon Nanowire The side wall of dimension occurs between the wall of the nanotube.
In one embodiment, the carbon nano-fiber includes cone-in-cone structure.
In one embodiment, the system is additionally included in the insertion material layer on the carbon nano-fiber, described to insert Entering material layer has the feathery structure produced by the cone-in-cone structure.
In one embodiment, the system is additionally included in the insertion material layer on the carbon nano-fiber, described to insert Entering material layer includes the feathery structure of the silicon filled with surface electrolyte interphase.
In one embodiment, the system is additionally included in the insertion material layer on the carbon nano-fiber, described to insert Enter material with the nominal thickness between 0.1 and 25 μm.
In one embodiment, the insertion material layer includes nanofiber/insertion material compound, the Nanowire Some in dimension/insertion material compound include in a kind of nanofiber and the nanofiber/insertion material compound Include two kinds of nanofibers a bit.
In one embodiment, the system is additionally included in the insertion material layer on the carbon nano-fiber, the silicon With the nominal thickness between about 1.0 μm and 40 μm.
In one embodiment, the length of the carbon nano-fiber is between 3.0 and 200 μm.
In one embodiment, the lithium ion storage between every gram of insertion material about 1,500 and 4,000mAh is held Measure acquisition under the charge rate between 1C and 10C.
In one embodiment, the lithium ion memory capacity between every gram of insertion material about 750 and 4,000mAh Obtained under charge rate between 1C and 10C.
In one embodiment, the lithium ion storage between every gram of insertion material about 1,500 and 4,000mAh is held Amount is obtained after 100 charge-discharge cycles.
In one embodiment, the lithium ion storage between every gram of insertion material about 1,500 and 4,000mAh is held Under charge rate of the amount between C/2 and 10C between every gram of silicon 2,000 and 4,000mAh.
In one embodiment, the insertion material includes silicon.
In one embodiment, when the charge rate increases to 10C from 3C, the ion storage capacity increases.
In one embodiment, the ion storage capacity changes less than 25% between 0.3C and the charge rate of 3C. Multiple embodiments of the invention include a kind of method of production energy storage device, and the method includes providing base material；In base material Upper growth carbon nano-fiber, the carbon nano-fiber has cone-in-cone (stacked-cone) structure；And be applied to insertion material Carbon nano-fiber, the insertion material is arranged to the insertion of charge carrier.In one embodiment, the insertion material for being applied Material produces feathery structure.
In one embodiment, methods described also includes providing the nucleation site for growing the carbon nano-fiber, The density of the nucleation site is selected as obtaining the average arest neighbors interval of the carbon nano-fiber between 75 and 400nm Distance.
In one embodiment, methods described also includes that the regulation energy storing device causes that the energy stores are filled Put with the lithium ion memory capacity under at least charge rate of 1C between every gram of silicon about 750 and 4,000mAh.
In one embodiment, methods described also include the regulation energy storing device cause the insertion material with Electrolyte phase interaction is forming surface electrolyte interphase, feather of the surface electrolyte interphase in the insertion material Formed between shape structure.
In one embodiment, the insertion material includes silicon.
Brief description
Figure 1A and 1B illustrate the CNF arrays of multiple embodiments of the invention, and the CNF arrays are included on base material Multiple CNF of growth.
What the multiple under different conditions that Fig. 2A -2C illustrate multiple embodiments of the invention was vertically arranged CNF。
Fig. 3 A-3C illustrate the details of the CNF of multiple embodiments of the invention.
Fig. 4 illustrates the schematic diagram of the cone-in-cone structure of the CNF of multiple embodiments of the invention.
Fig. 5 A-5C illustrate multiple embodiments of the invention~electrochemical properties of 3 μm of CNF long.
Fig. 6 A-6C illustrate 3 μm of scanning electron microscope diagrams of CNF long of multiple embodiments of the invention Picture.
Fig. 7 A-7C illustrate the using comprising the silicon as anode of lithium ion battery of multiple embodiments of the invention The result that the CNF of layer is obtained.
How the capacity that Fig. 8 illustrates the CNF arrays of multiple embodiments of the invention changes with charge rate.
Fig. 9 illustrates the Raman spectrum of the CNF arrays of multiple embodiments of the invention.
Figure 10 A-10C show the Li during 15 charge-discharge cycles of multiple embodiments of the invention+Insert Enter-take out the change of capacity and coulombic efficiency.
Figure 11 A-11C show that the scanning electron of the CNF arrays for preparing recently of multiple embodiments of the invention shows Micro mirror image.
Figure 11 D show the cross section of the nanofiber/silicon compound comprising more than one CNF.
Figure 12 illustrates the battle array of the carbon nano-fibers including 10 μm of fibers of length of multiple embodiments of the invention Row.
The method that Figure 13 illustrates the production CNF arrays of multiple embodiments of the invention.
Describe in detail
Figure 1A and 1B illustrate the CNF arrays 100 of multiple embodiments of the invention, and the CNF arrays 100 are included in The multiple CNF 110 grown on conductive base 105.In figure ia, CNF arrays 100 are shown as taking out (electric discharge) state in lithium, and In fig. ib, CNF arrays 100 are shown as inserting (charging) state in lithium.In the embodiment of these and other discussed herein CNF110 be selectively vertically arranged.Using plasma activated chemical vapour deposition (PECVD) method of direct current biasing in copper CNF 110 is grown on base material 105.As discussed above, by the method grow CNF 110 can have include with folded cup or Unique form of cone or the similar conical graphite build stack of conveyor screw.This create and promote the very trickle of lithium insertion Structure.This structure is referred to as " cone-in-cone " structure in elsewhere herein.Under larger length scale, these CNF 110 It is typically orthogonal to substrate surface evenly distributed and separated from one another well.The diameter of single CNF can be selected as providing Desired mechanical strength is so that CNF arrays 100 are firm and by siliceous deposits and the circulation of wet electrochemistry its can be kept complete Property.Crystal seed layer is alternatively used for making CNF 110 be grown on base material 105.In use, CNF arrays 100 are placed in and electricity Solution matter 125 is contacted, and the electrolyte 125 includes one or more charge carrier, such as lithium ion.CNF 110 is configured such that Some electrolyte 125 are arranged between CNF 110 and/or can reach base material 105 by the gap between CNF 110.
The diameter of the single CNF 110 illustrated in Figure 1A and 1B is nominally at 100 between 200nm, but is arrived 75 Between 300nm or the diameter of other scopes is possible.CNF 110 is selectively along its length taper.Using begging for herein The CNF 110 of the technology production of opinion has outstanding conductance (σ=~2.5x10 along axle5S/m) and with base material 105 form firm Ohmic contact.It is gradually thinning same to be formed on each CNF that open space between CNF110 can deposit to silicon layer 115 Shaft housing and most of at sophisticated the 120 of CNF 110.It is this to be designed to make whole silicon layer 115 be electrically connected by CNF 110 Connect and fully activity is kept during charge-discharge cycles.The expansion that lithium occurs with the alloying of silicon layer 115 can be with radial direction side To for example the size long perpendicular to CNF 110 is easily accommodated.Can compare what CNF 110 and silicon without silicon coating were coated The charging and discharging capacity and cyclical stability of CNF 110.The addition of silicon layer 115 provides paramount under C/2 speed 3938mAh/gSiSignificant Li+Insert (charging) capacity and keep 1944mAh/g after being circulated at 110 timesSi.The charge/discharge Speed and corresponding capacity are significantly higher than the former construction using silicon nanowires or mixing Si-C nanostructureds.Figure 1A and 1B are Perspective view.
In multiple embodiments, from 0.01 up to 0.5,1.0,1.5,2.5,3.0,4.0,10,20,25 μm (or more) Nominal silicon thickness can be deposited on 3 μm long of CNF 110 with formed such as Figure 1A and 1B in illustrate the CNF arrays of those 100.Similarly, in multiple embodiments, from 0.01 up to 0.5,1.0,1.5,2.5,3.0,4.0,10,20,25 μm (or more It is many) nominal silicon thickness can be deposited on 10 μm long of CNF 110 to form CNF arrays 100.In some embodiments, Between average distance of the nominal thickness of silicon between 0.01 μm and CNF 110.
Using CNF arrays 100, the lithium ion storage of paramount under C/2 speed~4,000mAh/g specific discharge capacities is obtained .Under equal-wattage speed, the capacity is significantly higher than with single silicon nanowires or other silicon nanostructure carbon mixs Those capacity for obtaining.Improved performance is attributed to because the effective charge by CNF 110 in this mixture structure is collected With short Li+Path length and the silicon shell that fully activates.Good cyclical stability is proved in 110 circulations.Various In embodiment, the memory capacity of the lithium ion of CNF arrays 100 storage be every gram of silicon about 750,1500,2000,2500,3000, In 3500 or 4000mAh, or any scope between these values.As used herein, term " nominal thickness " (such as silicon ) be the silicon flat bed that the thickness is produced on base material 105 silicon amount.For example, the nominal thickness of 1.0 μm of silicon is if silicon The amount of the silicon for causing the silicon layer of 1.0 μ m-thicks is deposited directly on base material 105.Report nominal thickness, because it can easily make Measured by weight with methods known in the art.1.0 μm of nominal thickness will cause in the smaller of CNF110 upper silicon layers 115 Thickness because silicon is distributed in the more large area on the surfaces of CNF 110.
Fig. 2A -2C illustrate CNF gusts with about 3 μm of average fiber length of multiple embodiments of the invention Row 100.Fig. 2A -2C are SEM (SEM) image.Fig. 2A shows that the multiple without silicon layer 115 is vertically arranged CNF 110.Fig. 2 B show the CNF 110 that the multiple including silicon layer 115 is vertically arranged.Fig. 2 C show and are experiencing 100 times The CNF 110 being vertically arranged with the multiple of taking-up (electric discharge) state after lithium charge-discharge cycles.CNF 110 is securely attached to Copper base material 105 is simultaneously essentially homogeneously vertically arranged, and random distribution is on substrate surface.The sample for using in our current research has There is 1.11x109CNF/cm2Averaged areal density (being calculated from SEM image top view), corresponding to~330nm average arest neighbors away from From.The average length of the CNF 110 in Fig. 2 be~3.0 μm and>The length of 90% CNF is in the range of 2.5 to 3.5 μm.Directly Footpath expands to 240nm from~80nm, the average value with~147nm.Inverted tear-drop shaped Raney nickel is present at sophisticated 120 At the tip of each CNF 110, the hollow channel of the center of CNF is covered, this promotes CNF 110 during PECVD processes Tip-growth.The size of Raney nickel nano particle defines the diameter of each CNF 110.At most 10 μm of CNF 110 more long Also it is used in some researchs that will be discussed in part below.
In multiple embodiments, average nearest neighbor distance can in 200-450nm, 275-385nm, 300-360nm or Change between similar distance.Additionally, the average length of CNF 110 can be in about 2-20,20-40,40-60,60-80,80- 100th, it is between 100-120,120-150 (μm) or bigger.Standard carbon nano-fiber such as 1 millimeter long is known in the art. In multiple embodiments, average diameter can be in about 50-125,100-200,125-175 (nm) or the anaplasia of other scopes Change.
Unbodied silicon layer 115 is by magnetron sputter deposition on CNF arrays 100.The CNF arrays 100 of brush and sac like Open architecture make silicon engage deep down into arrival the array in and between CNF 110 produce conformal structure be possible.As a result, exist The silicon coating of thickness is formd at CNF tips, is then presented compared with gradually thinning coaxial silicon shell is formed around lower part in CNF Similar to the interesting taper core shell structure of cotton swab.The amount of siliceous deposits uses quartz crystal microbalance (QCM) during sputtering Characterized by the nominal thickness of silicon fiml in the plane.Li+Insertion/take out capacity be normalized be by nominal thickness obtain it is total Siliceous amount.Under 0.50 μm of nominal thickness, the CNF 110 of silicon coating is separated from one another well, forms open nucleocapsid CNF gusts Array structure (shown in Fig. 2 B).The structure allows electrolyte freely to reach the whole surface of silicon layer 115.In the embodiment party of diagram In case, with before application silicon layer 115~average diameter of the CNF 110 of 147nm compared with, average tip diameter for~ 457nm.The silicon thickness of the average radial at sophisticated 120 is estimated as~155nm.This nominal silicon thickness substantially than 0.50 μm It is much smaller, because most of silicon spread along the total length of CNF.In an alternative embodiment, see 10-1000,20-500, In the range of 50-250,100-200 (nm) or different range other radial directions silicon thickness.As elsewhere herein is discussed, CNF 110 cone-in-cone provides extra fine structure for silicon layer 115.The cone-in-cone structure is selectively the result of spiral growth mode, When being observed with cross section, the spiral growth mode produces cone-in-cone structure.
The structure that perspective electron microscope (TEM) image in Fig. 3 A-3C further illustrates the CNF 110 of silicon coating is thin Section.In the silicon layer 115 of the production~390nm silicon immediately above of tip 120 of the CNF 110 of~210nm diameters.The silicon layer of cotton swab shape A diameter of~the 430nm of 115 largest portion, the largest portion is appeared near the least significant end at tip 120.Around CNF 110 The display of coaxial silicon layer 115 have regulation contrast featheriness quality, it is obvious with uniform silicon deposits on tip Different (see Fig. 3 A).This is likely to the result of the cone-in-cone microstructure of the CNF 110 of PECVD- growths.Knowable to document, this The CNF 110 of sample includes the graphite-structure along the uneven folded cup-shaped of the central shafts of CNF 110.The diameter of CNF 110 this Kind change use be on October 13rd, 2010 submit to jointly owned U.S. Patent Application Serial Number 12/904,113 in It is disclosed in advance.In figure 3b it can clearly be seen that cone-in-cone structure is made up of the graphite linings more than ten layers of cup-shaped, such as by dotted line Point out.Because electron beam needs to penetrate CNF the or Si-CNF mixtures of hundreds of nanometer thickness, the resolution ratio of Fig. 3 B and 3C and contrast Degree is limited, but the architectural feature is consistent with the high-resolution TEM researchs in document using smaller CNF.This uniqueness Structure produces broken graphite edge bank, the broken graphite edge bank to cause change during siliceous deposits along CNF sides wall Nucleation rate and therefore silicon layer 115 density of the regulation on the side walls of CNF 110.The density of regulation causes by (100nm in Fig. 3 A2) frame The silicon structure of 310 ultra-high surface areas pointed out.The penniform silicon structure of silicon layer 115 provides outstanding lithium ion interface, should Lithium ion interface causes lithium capacity very high and electronics is also rapidly transferred to CNF 110.In Fig. 3 A at sophisticated 120 Dark area is the Raney nickel for CNF growths.Other catalyst can also be used.
Fig. 3 B and 3C be lithium insertion/take out circulation before (3B) and lithium insertion/take out circulation after (3C) record image.Fig. 3 C In sample be when it is removed from electrochemical cell take off lithiumation (electric discharge) state.Dotted line in Fig. 3 B is in CNF 110 Interior cone-in-cone graphite linings it is visually oriented.Dotted line long in Fig. 3 C represents the sidewall surfaces of CNF 110.
As elsewhere herein is discussed, the cone-in-cone structure of CNF 110 differ greatly from conventional CNT (CNT) or Graphite.Relative to the CNT or nano wire of standard, the cone-in-cone structure causes improved Li+Insertion, even if being not added with silicon layer 115.For example, the cone-in-cone graphite-structure of CNF 110 allows Li+In being inserted into graphite linings by the side wall of CNF 110 (and not only In end).Through the Li of the wall of each CNF 110+Transfer path be very it is short (in some embodiments with D~ 290nm), the path long of the openend being totally different from from conventional seamless CNT (CNT).Fig. 4 illustrates CNF The schematic diagram of 110 cone-in-cone structure.In this special embodiment, the average value of parameter is：CNF radiuses rCNF=74nm, CNF wall thickness tw=~50nm, graphite coning angle θ=10 °, and graphite cone length D=tw/ sin θ=290nm.
Fig. 5 A-5C illustrate~electrochemical properties of 3 μm long of CNF 110.The characteristic illustrates showing on Fig. 4 descriptions As.Fig. 5 A are displayed under 0.1,0.5 and 1.0mV/s scan rates relative to Li/Li+The following from 1.5V to 0.001V of reference electrode Ring voltammogram (CV).Lithium disk is used as to electrode.Data are obtained from second circulation and are normalized to exposed geometrical surface. Fig. 5 B are displayed in the electrostatic charging-discharge curve under C/0.5, C1, C/2 Power Ratio, correspond respectively to 647,323 and 162mA/ G (being normalized to the carbonaceous amount estimated) or 71.0,35.5 and 17.8 μ A/cm2The current density of (being normalized to geometrical surface). Fig. 5 C are inserted and removed from capacity (to left vertical axis) and coulomb effect under being displayed in C/1 recharge-discharge rates relative to period Rate (to right vertical axis).(C/1 discharge rate=1 hour, C/2 discharge rate=120 minute, 2C=C/0.5=30 minutes, etc. Deng).
The half-cell of new assembling is typically shown compared to Li/Li+Reference electrode, uncoated anodes of CNF 110 are opened Road potential (OCP) is~2.50 to 3.00V.The CV measured between 0.001V and 1.50V show when electrode potential be 1.20V with Li when lower+Insertion starts.First time circulation from OCP to 0.001V includes necessary by being decomposed to form for solvent, salt and impurity Protective layer, i.e. solid-electrolyte interphace (SEI), and big cathode current is therefore presented.Subsequent CV shows smaller but more The electric current of stabilization.When electrode potential extends to negative value, with Li+Insert related cathode current slowly to rise, until at 0.18V There is sharp negative electrode peak.0.001V is reached when electrode potential lower limit is backward on the occasion of reverse, such as by continuous anode current with Pointed out in the broad peak of 1.06V, observe that lithium takes out in the up to gamut of 1.50V.
The CV features of CNF arrays 100 are inserted into graphite and Li with segmentation+It is slowly diffused into those of the hollow channel of CNT The CV features of CNF arrays 100 are slightly different.The lithium ion insertion for entering into CNF 110 is likely due to the uniqueness of CNF 110 Structure, through the insertion the graphite linings from side wall.TEM image in Fig. 3 C shows the cone-in-cone in CNF 110 In graphite be stacked on Li+Somewhat it is destroyed during insertion-taking-up circulation, it is likely that due to Li+The large volume occurred during insertion becomes Change.It is observed in the inside of CNF 110 and in outer surface as some fragments and nano particle of white object.
Electrostatic charging-discharge curve in Fig. 5 B shows that (C/0.5 is also referred to as when Power Ratio increases to C/0.5 from C/2 " 2C ") when, Li+Memory capacity reduction.In order to be easier compa-ratios (especially for those higher than C/1), herein I Replace more commonly used in the literature " 2C " using fraction representation method C/0.5.Li+Capacity is inserted and removed to be normalized to estimate The quality (1.1 × 10 of the CNF 110 of meter4g/cm2), the CNF structures that the quality of the CNF 110 is arranged according to hollow vertical are with Column average parameter is calculated：Length (3.0 μm), density (1.1 × 109CNF is per cm2), external diameter (147nm) and inner hollow diameter (49nm, External diameter~1/3).The density of the solid graphite wall of CNF 110 is assumed to be and graphite (2.2g/cm3) identical.In normal C/2 Under speed, insertion capacity is 430mA h g-1And it is 390mA h g to take out capacity-1, both are slightly higher than the theoretical value of graphite 372mA h g-1, perhaps this be attributed to SEI and formed and Li+Irreversibly it is inserted into the hollow cell in CNF 110.In whole Power Ratio under, find take out capacity more than inserted value 90%, and when Power Ratio increases to C/1 from C/2 insert hold Both amount and taking-up capacity reduce~9%, and capacity is inserted when Power Ratio increases to C/0.5 from C/1 and both capacity are taken out ~20% is reduced, comparable to graphite electrode.
Charged-discharge cycles, after 20 circulations under C/1 speed, find insertion capacity from 410mA h g-1Slight drop To 370mA h g-1, and take out capacity and be maintained at 375mA h g-1With 355mA h g-1Between.Except it is preceding circulate twice due to Outside forming SEI on the surfaces of CNF 110, total coulombic efficiency (that is, taking out the ratio of capacity and insertion capacity) is~94%. Know that SEI films are easily formed during initial circulation on carbon anode, it allows lithium ion to spread, but electric insulation, lead Causing series resistance increases.TEM image (Fig. 3 C) and SEM image (Fig. 6 A) be displayed in charge-discharge cycles during uneven film It is deposited on the surfaces of CNF 110.In some embodiments, SEI serves as sheath to increase the mechanical strength of CNF 110, by such as The cohesion capillary force of the solvent observed in using the research of other polymers coating prevents them from collapsing into microbundle.
Fig. 6 A-6C illustrate the scanning electron microscope diagrams of CNF 110 of 3 μm long of multiple embodiments of the invention Picture.Fig. 6 A are displayed in the CNF 110 of de- lithiumation (electric discharge) state after insertion/taking-up circulation.Fig. 6 B take off after being displayed in 100 circulations The CNF110 including silicon layer 115 of state of lithiation.Fig. 6 C are displayed in the CNF including silicon layer 115 of state of lithiation after 100 circulations 110.These images are 45 degree of perspective views.
Fig. 7 A-7C illustrate the result for using the CNF 110 including the silicon layer 115 as anode of lithium ion battery to obtain. These results are obtained using 0.50 μm of nominal silicon thickness.Fig. 7 A are displayed in 0.10,0.50 and 1.0mV s-1Under sweep speed Relative to Li/Li+1.5V and 0.05V between cyclic voltammogram.Measurement is after sample experiences 150 charge-discharge cycles Carry out, and be displayed in second data of circulation under each sweep speed.Fig. 7 B be displayed in C/0.5, C/1 and C/2 Power Ratio, Electrostatic charging-the discharge curve of the lower sample of 120 circulations.All curves are taken in second circulation under each ratio.Fig. 7 C Show and be inserted and removed from capacity (to a left side as two CNF arrays 100 (being used as electrode) of the function of charge-discharge cycles number Side vertical axes) and coulombic efficiency (to right vertical axis).The C/10 speed that the first CNF array 100 is first utilized in circulates next time, Circulate next time in C/5 speed, the circulation regulation twice under C/2 speed.Then 96 remainders of circulation are inserted in C/2 Ratio and C/5 are tested under taking out ratio.Closed square and hollow square represent insertion capacity and take out capacity respectively.Second electrode Adjusted with the circulation twice under each comfortable C/10, C/5, C/2, C/1, C/0.5, C/0.2 speed first.Then to ensuing 88 It is secondary to circulate in test under C/1 speed.Two coulombic efficiencies of electrode are with solid diamond (first electrode) and open diamonds (the second electricity Pole) represent, major part overlaps 99%.
CV in Fig. 7 A presents the feature closely similar with the feature of silicon nanowires.Compared to uncoated CNF arrays 110, Li+The cathodic wave and Li of insertion+The anode ripple both of which of taking-up shifts to relatively low value (respectively lower than~0.5 and 0.7V). After silicon layer 115, peak current density increases by 10 to 30 times and is directly proportional to sweep speed.It is apparent that the Li that alloy is formed+Insert Enter in silicon more faster in uncoated CNF than being inserted into, uncoated CNF is limited to the Li between graphite linings+Slow expansion Dissipate.In the previous studies of pure silicon nano wire, the negative electrode peak at~0.28V is not observed.Li-Si alloy is represented to be transferred to Three anode peaks in amorphous silicon are similar to those of use silicon nanowires, although move 100 to low potential arriving 200mV。
Electrostatic charging-the discharge curve of the CNF arrays including silicon layer 115 that Fig. 7 B show includes two significant features： (1) after or even being circulated at 120 times under C/2 speed, acquisition~3000mA h (gSi)-1Li high+Insertion (charging) and taking-up (are put Electricity) capacity；And (2) Li under C/2, C/1, C/0.5 Power Ratio+Capacity is almost identical.In other words, when charge rate from C/2 When increasing to C/1 and C/0.5, the capacity of the CNF arrays 100 run as electrode does not decline.On these charge rates, many Capacity is hardly dependent on charge rate in planting embodiment.Total Li of the CNF arrays 100 including silicon layer 115+Memory capacity is than lacking The CNF arrays 100 of few silicon layer 115 are high about 10 times.Even if the low potential limit of charging cycle increases to 0.050V from 0.001V, this Or can occur.Therefore, Li+The amount being inserted into CNF cores appears to be insignificant.Specific capacity by only divided by siliceous amount come Calculate, nominal thickness and 2.33g cm of the siliceous amount from measurement-3Bulk density calculate.This method is selected as comparing The appropriate measurement of the specific capacity of silicon layer 115 and the theoretical value of volume silicon.There is 0.456 μm of silicon layer of nominal thickness for deposition The CNF 110 of 3.0 μm long of 115, the actual mass density of silicon layer 115 is~1.06 × 10-4g cm-2, comparable to CNF's 110 Mass density (~1.1 × 10-4g cm-2).Corresponding coulombic efficiency is more than 99% under all three Power Ratios in Fig. 7 B, It is much higher than the coulombic efficiency of the CNF 110 of not silicon-containing layer 115.
How the capacity that Fig. 8 illustrates the CNF arrays 100 of multiple embodiments of the invention changes with charge rate. The data of the multiple periods of display.Fig. 8 displays reach total capacity (C/h, such as total capacity/hour) as within the hour of setting The Average specific discharge capacity of one group of circulation of the use same current ratio of the function of required charge rate (C ratio).Vertical line Concentrate on C/4,1C, 3C and 8C.CNF arrays 100 are first with each comfortable C/8, C/4, C/2, C/1, C/0.8, C/0.4 and C/0.16 Under speed Cyclic Symmetry twice ground regulation, and then circulate in the symmetrical ratios of C/1 at ensuing 88 times under test.From 101 It is secondary to be recycled to 200 circulating repetition above-mentioned steps.Start in 201 circulations, electrode with C/4, C/3, C/2, C/1, C/0.75, Five Cyclic Symmetries ground under each in C/0.66, C/0.50, C/0.33, C/0.25, C/0.20 and C/0.15 is circulated, and Tested under then circulating in the symmetrical ratios of C/1 at ensuing 45 times.400 circulations are recycled to from 301 times and are followed from 401 times Ring is to 500 circulating repetition above-mentioned steps.When C ratio is changed with 32 times, the change of capacity be it is small (<16%).At 100 times After circulation, when C ratio is changed into 8C from 3C, electrode shows increased capacity.Therefore, charge rate causes improved appearance faster Amount.In height ratio and compared with both low-ratios (C/4 and 8C), obtain high power capacity (>2,700mAh/g).When C ratio increases, in 3C Capacity under ratio above increases.Specific capacity is due to the factor of known recoverable with the decline of period.
Both CV and recharge-discharge measurement point out Li+It is quick and high reversible to be inserted into silicon layer 115, and it is high The desired feature of performance anode of lithium ion battery.This is long to two the two of identical sample under different test conditions Loop test is further proved (see Fig. 7 C)：(1) for insertion into C/2 speed and for the C/5 speed taken out it is slow not Symmetrical test；And (2) are for insertion into the fast symmetrical test with the C/1 speed for taking out both.Two datasets show except In the external long circulating of initial regulation circulation (under different low-ratios, the former 4 times circulate 12 circulations with the latter)>98% Coulombic efficiency.In slow asymmetric test, insertion capacity only declines 8.3%, from the 3643mA h g when the 5th is circulated-1 To the 3341mA h g when circulating for the 100th time-1.Even under C/1 charging-discharging rates, insertion capacity only declines 11%, from 3096mA h g when circulating for the 13rd time-1To the 2752mA h g when circulating for the 100th time-1.Between the two data sets Li+The difference of capacity is mainly ascribable to the change of initial regulation parameter and small sample to sample.This is by fig. 7 c in C/ The similar value of the insertion-taking-up capacity during preceding several regulation circulations under 10 and C/5 speed is pointed out.Ratio (sample # faster C/0.5 and the 11st time and the 12nd time C/0.2 of circulation of the 9th time of 2 and the 10th time circulation) it is found to be harmful and causes The irreversible decline of capacity.However, electrode becomes stabilization after longer circulation.As Fig. 7 B show, used in experience 120 times The charge-discharge curves of the sample #1 measurements after circulation are almost identical under C/2, C/1 and C/0.5 speed.This is on four times Charge rate change.
3000 to 3650mA h g-1In the range of silicon layer 115 specific capacity and document in the amorphous silicon anode summarized Peak it is consistent.It is worth noting that, the whole silicon shell in CNF arrays 110 is to Li+Insertion is active and at 120 times Almost 90% capacity is kept in circulation, as far as we know, except it is flat it is ultra-thin (<50nm) outside silicon fiml, this is never real before It is existing.Specific capacity disclosed herein is significantly higher than use other nanostructured silicon materials reported under similar Power Ratio Specific capacity, including with silicon nanowires under C/2 speed~2500mA h g-1With under C/1 speed~2200mA h g-1, and with the carbon nano-fiber-silicon core-shell structure copolymer nano wire of random orientation under C/1 speed~800mA h g-1.It is apparent that Relative to prior art, such as it is included in same on the CNF 110 for well separate in multiple embodiments of the invention The core-shell structure copolymer nano thread structure of axle provides enhanced charging-discharging rates, the almost complete Li of silicon+Memory capacity and length are followed The ring life-span.
As seen in figure 7 c, insertion capacity (~4500mA h g abnormally high-1) be always observed in initial circulation Arrive, its relatively after circulation 20-30% high.By contrast, taking-up value is stablized relatively in whole circulation.Especially big insertion capacity It is attributable to three combinations of irreversible reaction：(1) (tens nanometers) thin SEI (surface electrode interphase) layer is formed；(2) lithium With the SiO being present on silicon facexReaction (SiOx+2xLi→Si+xLi2O)；And (3) will with theoretical capacity higher (~ 4200mA h g-1) starting crystals silicon coating change into compared with low capacity (<3800mA h g-1) amorphous silicon.TEM schemes After being displayed in charge-discharge cycles as (Fig. 3 C) and SEM image (Fig. 6 B), uneven SEI can be deposited on the table of silicon layer 115 On face.It is this to have when CNF arrays 110 experience the expansion-contraction cycle of the large volume occurred during charge-discharge cycles The SEI films of elasticity can help be fixed on silicon layer 115 on the surfaces of CNF 110.It is aobvious between SEM image in Fig. 6 B and 6C Work difference shows the big expansion of the silicon layer 115 of lithiumation (charging) state relative to non-lithiated state.Although (some expansions can Can be due to the oxidation when electrochemical cell is disassembled to be imaged by air to lithium.) note, followed in initial charge-electric discharge The generation of SEI causes the difference seen in the silicon layer 115 between Fig. 3 A and 3B during ring.In figure 3b, silicon and electrolyte phase To produce SEI, the SEI is filled with the gap between feathery structure for interaction.The interaction can include that mixing, chemistry are anti- Should, Charged Couple, encapsulation and/or be similar to effect.Therefore, silicon layer 115 looks like more uniform in figure 3b.However, silicon Layer 115 includes the silicon layer (feathery structure) for intersecting and SEI layers now.Every layer in these layers for intersecting can be about tens Nanometer.SEI layers can be ion permeability material, and it is the phase between electrolyte and silicon layer 115 (or other electrode materials) The product of interaction.
The crystal and impalpable structure of silicon shell are manifested by Raman spectrum.As shown in figure 9, former CNF gusts including silicon layer 115 Row 100 show corresponding with amorphous silicon 350 to 550cm-1In the range of overlap multiple broadbands and with nanocrystalline silicon pair Answer in 480cm-1The sharp band higher at place.After recharge-discharge test, sharp peak disappears, while broadband is merged into 470cm-1That locates is unimodal.Exposed CNF 110 does not show any feature within this range.Crystalline silicon peak is from monocrystalline silicon (100) The peak of chip measurement moves down~40cm-1And move down~20 to 30cm from other microcrystalline silicon materials-1.This movement be likely to by In much smaller crystalline size and big unordered.Initial silicon layer 115 is likely to by being embedded into the TEM figures with Fig. 3 A mesoptile shapes As the nanocrystal composition in associated [amorphous.After initially circulation, si-nanocrystals change into amorphous silicon, with TEM image after loop test is consistent (see Fig. 3 B and 3C).However, (big compared to the big longitudinal dilatation of pure silicon nano wire To 100%), silicon layer 115 is not substantially slided along CNF.Therefore, silicon layer 115 is firmly adhered to CNF in 120 circulations 110.In Li+Silicon shell volume during insertion changes and passes through to be radially expanded to be controlled, while CNF- silicon interfaces keep complete.
Multiple embodiments of the invention include the CNF 110 with different length and silicon thickness of the shell.As generation CNF 110 When a controllable factor be open space between each CNF 110, for example, the CNF 110 in CNF arrays 100 Between average distance.When charging, the space allows silicon layer 115 to be radially expanded, therefore the space in some embodiments Stability is provided.Because optimal electrode structure depends on both the length of CNF 110 and the thickness of silicon layer 115, sometimes Expect to use CNF 110 and thicker silicon layer 115 more long to obtain total Li higher+Memory capacity.CNF 110 more long Associated with bigger memory capacity.Figure 10 A-10C displays have 0.50,1.5 and 4.0 μm of silicon layers of nominal thickness using deposition respectively Li of the samples of CNF 110 of three 10 μm long of 115 in 15 charge-discharge cycles+Insertion-take out capacity and coulombic efficiency Change.After under for the C/10 speed of first time circulation and for being adjusted under the second C/5 speed of circulation, dissymmetry ratio Rate (C/2 be used for insert and C/5 be used for take out) it is similar to the measurement of the sample #1 in Fig. 7 C with Posterior circle in use.Should Scheme provides the decline of almost 100% coulombic efficiency and minimum during circulating.During sputtering, nominal thickness uses stone English crystal microbalance in site measurement.
Up to 3597mA h g are obtained respectively with the silicon layer 115 of 0.50 and 1.5 μ m-thicks-1With 3416mA h g-1Specific volume Amount, this (see Fig. 7 C) closely similar with the specific capacity of the silicon layer 115 with 0.50 μ m-thick on 3.0 μm long of CNF 110.15 In secondary circulation, capacity is kept approximately constant.However, the electrode for having 4.0 μm of nominal silicon thicknesses shows only 2221mA h g-1It is notable Lower specific capacity.This shows, because expansion, silicon layer 115 are contacting one another since neighbouring CNF 110, to limit them and enter one Diffusion of the expansion and limitation lithium of step between CNF 110.As a result, the only a fraction of of silicon coating is activity in lithium insertion 's.The stability of circulation is correspondingly more worse than the sample for having thinner silicon layer 115.
Same amount of Si (500nm nominal thickness) on the CNF arrays 110 of the CNF 110 long including 10 μm gives and 3 The Li of μm CNF long 110+Memory capacity (3643mA h g-1, see Fig. 7 C) and the Li of nearly identical amounts+Memory capacity (3597mA h g-1, see Fig. 6 a), although carbonaceous amount is more than more than 3 times.This is very strong evidence, and the contribution of CNF 110 is calculating Li+Deposit It is insignificant in storage.Few Li+It is likely in the CNF 110 that ion is inserted into silicon coated sample, this contributes to The stability of the structure during multiple charge-discharge cycles.
Li in three samples that the structure with three samples is associated very well+The change of specific capacity is stored by Figure 11 A- The SEM pictures of 11C diagrams show.Figure 11 A-11C show sweeping for freshly prepd CNF arrays 100 (on~10 μm of CNF long 110) Retouch electron microscope image.The nominal silicon thickness of 4.0 μm of 0.50 μm of (a), 1.5 μm of (b) and (c) is used to generate silicon layer 115, nominally Silicon thickness uses quartz crystal microbalance in site measurement during depositing.All images are 45 ° of perspective views.It is nominal at 0.50 μm At silicon thickness, it is found that the average tip diameter on 10 μm of CNF long is~388nm, much smaller than the CNF 110 at 3.0 μm long On~average diameter of 457nm.Silicon layer 115 is thinner but is more uniformly spread along 10 μm of CNF long 110.
It should be noted that 10 μm of CNF 110 of growth spend 120 minutes, this is when growing 3 μm about the six of CNF110 times Between it is long.Some Raney nickels pass through NH during PECVD long3Slowly it is etched, causes the continuous of nano nickel particles size Reduce and cause cone point 120 (as shown in figure 12).The length change of CNF 110 increases also as CNF 110 long.These Factor reduces the screen effect at tip 120 jointly.As a result, or even under 1.5 μm of nominal silicon thicknesses, it is coated with silicon layer 115 CNF 110 well with it is separated from one another.1.5 μm of SEM images of silicon (Figure 11 B) on 10 μm of CNF arrays 100 with 3.0 μ 0.50 μm of SEM image of silicon (Fig. 2 B) on mCNF arrays 110 is closely similar.But when nominal silicon thickness increases to 4.0 μm, silicon Layer 115 substantially with combine with each other and fill the most of space between CNF 110 (see Figure 10 C).Which reduce receiving silicon layer Free space needed for the volumetric expansion of 115l.As a result, Li+Storage specific capacity is remarkably decreased.
Figure 11 A and 11B each include the CNF 110 of approximately same number, but have in Figure 11 B substantially less Visible cusps 120.Because silicon layer 115 can form receiving including single CNF110 (its cross section shows in figure ia) Rice fiber/silicon compound.Or, silicon layer 115 can form the two, three or more being included under single silicon covering Nanofiber/the silicon compound of CNF 110.This two or more CNF 110 during the deposition process of silicon layer 115 is gathered in one Occur when rising.Nanofiber/silicon compound is the structure for including the continuous silicon layer 115 for encapsulating one or more CNF 110.Including Two cross sections of the nanofiber/silicon compound of CNF 110 illustrate in Figure 11 D.In multiple embodiments, at least 1%, 5% or 10% nanofiber/silicon compound includes more than one CNF 110.
In multiple embodiments, the example with 0.50 and 1.5 μm of CNF array 100 of nominal silicon thickness has respectively 3208 ± 343 and 3212 ± 234mA h g-1Comparable quality-specific capacity.Produced with 4.0 μm of samples of nominal silicon thickness Raw 2072 ± 298mA h g-1Much lower capacity.Thinner silicon coating be fully activation and amorphous silicon is provided can be to The maximum lithium insertion capacity for giving.On the other hand, area-specific capacity with silicon thickness from 0.50 μm the 0.373 of silicon thickness ± 0.040mA h cm-2Proportionally increase to 1.5 μm of 1.12 ± 0.08mA h cm of silicon thickness-2But, from linearity curve Decline to produce with 4.0 μm of 1.93 ± 0.28mA h cm of nominal silicon thickness-2.It is apparent that under this thickness, thick silicon coating In extra silicon only a fraction of play an active part in lithium storage.4.0 μm of thickness is more than the average distance between CNF 110. Electrochemical results with the SEM image in Figure 11 C show structure it is consistent, its show CNF 110 between space substantially by Filling.
In multiple embodiments of the invention, the structure of CNF arrays 100 is included in about 200 to 300nm on CNF 110 The silicon layer of radial thickness, the CNF 110 has about 30-40,40-75,75-125 micron length of (or bigger or their combination) The diameter of degree and about~50nm.In some embodiments, these CNF arrays 100 grow on a conductive foil, conductive foil tool There is the thickness in~10 microns ,~10-20 microns ,~10-50 microns or bigger of scope.In multiple embodiments, silicon (equivalent to 1.5 μm of nominal thickness in the plane) is deposited on 10 μm long of CNF 100 to form CNF arrays 100.This is complete Into the vertical-type core-shell structure copolymer nano thread structure for keeping having with the opening of the single CNF 110 for separating very well each other simultaneously so that The CNF arrays 100 that lithium ion can be permeated between CNF 110.This unique combination construction allows silicon layer 115 in Li+Insertion With during taking-up in radial direction free wxpansion/contraction.Even being obtained under C/1 speed has 3000 to 3650mA h g-1's The high-performance lithium storage of quality-specific capacity.The capacity matches with the desired maximum of amorphous silicon from similar mass, this Show that the silicon layer 115 is fully activated.This 3D it is nano-structured be configured to make substantial amounts of silicon materials effectively electrical connection simultaneously Keep short Li+Insertion-take out path.As a result, in 120 charge-discharge cycles close to theoretical limit high power capacity be can Can.When ratio, (or 2C) increases by 20 times from C/10 to C/0.5, and capacity is varied less.Significantly improved charge rate and power High power capacity under speed and outstanding cyclical stability make this new structure turn into for high performance lithium ion battery can Select anode material.Identical core-shell structure copolymer concept can be by with TiO2、LiCoO2、LiNiO2、LiMn2O4、LiFePO4Or the like Replace silicon shell and be applied to cathode material.
Figure 13 illustrates the method for producing CNF arrays 100 disclosed herein.In base material step 1310 is provided, there is provided suitable Together in the base material 105 of the growths of CNF 110.Base material 105 can include multiple material, such as copper.Base material 105 selectively has The conductive foil of thickness described elsewhere herein.In selectable offer nucleation site step 1320, above carried in base material 105 For the nucleation site of the growth for CNF 110.Various nucleation materials, such as nickel particles are well known in the art.Nucleation Site is selectively with so that the density of the average distance between generation CNF 110, such as density of elsewhere herein teaching To provide.It is the growth that nucleation is not required for CNF 110 or similar structures wherein to provide nucleation site step 1320 It is selectable in embodiment.
In CNF steps 1330 are grown, CNF 110 grows on base material 105.CNF 110 is selectively grown with life Produce the cone-in-cone structure or similar varistructure of elsewhere herein teaching.CNF 110 can grow to elsewhere herein religion Any length led.Growth is selectively using PECVD methods for example in " Ahigh-performance lithium-ion battery anode based on the core-shell heterostructure of silicon-coated The .J.Mater.Chem.A, 2013,1,1055 such as vertically aligned carbon nanofibers " Klankowski Middle teaching or the method quoted are completed.
In silicon layer step 1340 is applied, insertion material such as silicon layer 115 is applied to the CNF110 of growth.The material of applying Material can have any nominal thickness that elsewhere herein is instructed to produce the thickness of silicon layer 115 of tens or hundreds of nanometers. In selectable regulating step 1350, insert what circulation regulation was produced using step 1310-1304 using one or more lithium CNF arrays 100.
Multiple embodiments are especially illustrated and/or described herein.However, it should be understood that modifications and variations form is by upper State teaching covering and within the scope of the appended claims, without deviating from their spiritual and expected scope.For example, when this When the example that text is discussed concentrates on the CNF with cone-in-cone structure, the teaching goes for the other materials with similar structure. Similarly, when Copper base material and lithium charge carrier are discussed herein, other base materials and charge carrier are to ordinary skill Personnel are obvious.Silicon layer 115 is selectively formed by the insertion material of substitute in addition to silicon or as silicon.For example Tin, germanium, carbon, silicon or combinations thereof can be used as insertion material.Additionally, TiO2(titanium oxide) or boron nitride nanometer fiber energy It is enough in and replaces carbon nano-fiber.
Can include what is instructed herein in various energy storing device including capacitor, battery and their mixing Electrode.These energy storing devices will be used for for example, load balancing apparatus, communicator, stand-by power supply, the vehicles and meter Calculate device.
The embodiment explanation present invention being discussed herein.When referenced in schematic describes these embodiments of the invention, institute The various modifications and reorganization of the method and/or concrete structure of description can become obvious to those skilled in the art.Depend on this The teaching of invention simultaneously improves all these modification of this area, adapts or version by these teachings, is considered as In the spirit and scope of the present invention.Therefore these descriptions and accompanying drawing are not considered as in limiting sense, and should be understood that this hair It is bright to be not restricted to shown embodiment.

Claims (10)

1. a kind of energy storage system, including：
Conductive base；
The carbon nano-fiber that the multiple for growing on the substrate is vertically arranged, the carbon nano-fiber each includes multiple many walls CNT；And
Electrolyte, the electrolyte includes one or more charge carrier.
2. a kind of energy storage system, including：
Conductive base；
The carbon nano-fiber that the multiple for growing on the substrate is vertically arranged；And
Insertion material layer, the insertion material layer is disposed on the multiple carbon nano-fiber being vertically arranged and is configured as With the lithium ion memory capacity between every gram of insertion material about 1,500 and 4,000mAh.
3. a kind of energy storage system, including：
Conductive base；
The carbon nano-fiber that the multiple for growing on the substrate is vertically arranged；And
Insertion material layer, the insertion material layer is disposed on the multiple carbon nano-fiber being vertically arranged and is configured as So that the ion storage capacity of the insertion material is about identical under the charge rate of 1C and 3C.
4. the system as described in claim 1,2 or 3, wherein the CNT is arranged such that ion insertion can be passed through The side wall of the carbon nano-fiber occurs between the wall of the nanotube.
5. the system as described in claim 1-3 or 4, wherein the carbon nano-fiber includes cone-in-cone structure.
6. the system as described in claim 1-4 or 5, is additionally included in the insertion material layer on the carbon nano-fiber, described to insert Entering material layer has the feathery structure produced by the cone-in-cone structure.
7. the system as described in claim 1-5 or 6, is additionally included in the insertion material layer on the carbon nano-fiber, described to insert Entering material layer includes the feathery structure of the silicon filled with surface electrolyte interphase.
8. the system as described in claim 1-6 or 7, is additionally included in the insertion material layer on the carbon nano-fiber, described to insert Enter material with the nominal thickness between 0.1 and 25 μm.
9. the system as described in claim 1-7 or 8, wherein insertion material layer includes that nanofiber/insertion material is combined Thing, some in the nanofiber/insertion material compound include a kind of nanofiber and the nanofiber/insertion material Some in compound include two kinds of nanofibers.
10. the system as described in claim 1-8 or 9, is additionally included in the insertion material layer on the carbon nano-fiber, the silicon With the nominal thickness between about 1.0 μm and 40 μm.
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