CN104145355A

CN104145355A - Energy storage devices

Info

Publication number: CN104145355A
Application number: CN201280070082.6A
Authority: CN
Inventors: 罗纳德·罗杰斯基; 史蒂文·科兰考斯基; 李钧
Original assignee: Individual
Current assignee: Peter Lonard Rogers Base; Kansas State University
Priority date: 2011-12-21
Filing date: 2012-12-21
Publication date: 2014-11-12
Anticipated expiration: 2032-12-21
Also published as: GB2512230B; GB201411191D0; KR20140128298A; WO2013096931A1; CN104145355B; CN106910869A; KR102036196B1; GB2512230A

Abstract

A novel hybrid lithium-ion anode material based on coaxially coated Si shells on vertically aligned carbon nanofiber (CNF) arrays. The unique cup-stacking graphitic microstructure makes the bare vertically aligned CNF array an effective Li+ intercalation medium. Highly reversible Li+ intercalation and extraction were observed at high power rates. More importantly, the highly conductive and mechanically stable CNF core optionally supports a coaxially coated amorphous Si shell which has much higher theoretical specific capacity by forming fully lithiated alloy. The broken graphitic edges at the CNF sidewall ensure good electrical connection with the Si shell during charge/discharge processes.

Description

Energy storing device

The cross reference of related application

The application requires rights and interests and the priority of following U.S. Provisional Patent Application:

In on December 21st, 2011 submit to 61/578,545,

In on February 27th, 2012 submit to 61/603,833,

In on March 23rd, 2012 submit to 61/615,179,

In 61/667,876 of submission on July 3rd, 2012, and

In 61/677,317 of submission on July 30th, 2012.

All disclosures above-mentioned interim and non-interim patent application are incorporated to herein accordingly by reference.

Background

Invention field

The present invention is in the field of energy storing device that includes but not limited to battery, capacitor and fuel cell.

Correlation technique

Rechargeable lithium ion battery is for the crucial electrical energy storage device in portable electric appts, electric tool and the electric vehicle supply of electric power in future.It is critical that raising specific energy capacity, charge/discharge speed and cycle life are applied widely to them.

In the lithium ion battery of current business, graphite or other carbonaceous materials are by forming the LiC fully inserting ₆compound and be used as the anode of the theoretical capacity limit with 372mAh/g.On the contrary, silicon is by forming the metal Li of abundant lithiumation _4.4si and have much higher 4, the theoretical specific capacity of 200mAh/g.But the height of the silicon of lithiumation expands and causes the great structural stress that inevitably causes fracture and mechanical breakdown to～300% large volume in the past, this significantly limits the life-span of silicon anode.

General introduction

A kind of energy storage device is included in core-shell NW (nano wire) structure of the mixing in high-performance lithium ion anode, and this is by carbon nano-fiber (VACNF) array in conjunction with being coaxially coated with the vertical arrangement of amorphous si-layer.The CNF vertically arranging comprises the carbon nano-tube (MWCNT) of many walls, and the carbon nano-tube of these many walls is used plasma activated chemical vapour deposition (PECVD) method of direct current biasing selectively on copper base material, to grow.The carbon nano-fiber (CNF) of growing by the method can have unique external morphology, and them are different from the hollow structure of common MWCNT and conventional solid carbon nanofiber by this form.One of distinguishing characteristics is that these CNF are selectively made up of a series of bamboo shape nodes that cross main hollow centre passage.This micro-structural can be owing to other local conical graphite cups of further discussing are stacking herein.Under larger length scale, the CNF of these PECVD-growths is typically evenly distributed and separated from one another well perpendicular to substrate surface.They may or have minimum entanglement without any entanglement, and therefore form the brush-like structure that is called as VACNF array.The diameter of independent CNF can be selected as providing expectation mechanical strength so that VACNF array be firm and can keep its integrality by siliceous deposits and wet electro-chemical test.

Multiple embodiments of the present invention comprises a kind of energy storage system, and it comprises conductive base; The carbon nano-fiber of multiple vertical arrangements of growing on base material, this carbon nano-fiber comprises the carbon nano-tube of multiple many walls; And electrolyte, this electrolyte comprises one or more charge carriers.

Multiple embodiments of the present invention comprises a kind of energy storage system, and it comprises conductive base; The carbon nano-fiber of multiple vertical arrangements of growing on base material; And insertion material layer, this insertion material layer is disposed on the carbon nano-fiber of described multiple vertical arrangements and is configured to have every gram of lithium ion memory capacity of inserting between material approximately 1,500 and 4,000mAh.

Multiple embodiments of the present invention comprises a kind of energy storage system, and it comprises conductive base; The carbon nano-fiber of multiple vertical arrangements of growing on base material; And insertion material layer, this insertion material layer is disposed on the carbon nano-fiber of described multiple vertical arrangements and is configured such that the ion storage capacity of this insertion material under the charge rate of 1C and 3C is approximately identical.

Multiple embodiments of the present invention comprises a kind of method of producing energy storing device, and the method comprises provides base material; The carbon nano-fiber of growing on base material, this carbon nano-fiber has cone-in-cone (stacked-cone) structure; And insertion material is applied to carbon nano-fiber, this insertion material is arranged to the insertion of charge carrier.

Accompanying drawing summary

Figure 1A and 1B illustrate the CNF array according to multiple embodiments of the present invention, and this CNF array is included in the multiple CNF that grow on base material.

Fig. 2 A-2C illustrates according to the CNF of the multiple vertical arrangements under different conditions of multiple embodiments of the present invention.

Fig. 3 A-3C illustrates according to the details of the CNF of multiple embodiments of the present invention.

Fig. 4 illustrates according to the schematic diagram of the cone-in-cone structure of the CNF of multiple embodiments of the present invention.

Fig. 5 A-5C illustrate according to multiple embodiments of the present invention～electrochemical properties of the long CNF of 3 μ m.

Fig. 6 A-6C illustrates the scanning electron microscope image of the CNF long according to 3 μ m of multiple embodiments of the present invention.

Fig. 7 A-7C illustrates according to the use of multiple embodiments of the present invention and comprises the result obtaining as the CNF of the silicon layer of lithium ion battery anode.

Fig. 8 illustrates according to the capacity of the CNF array of multiple embodiments of the present invention and how to change with charge rate.

Fig. 9 A illustrates according to the Raman spectrum of the CNF array of multiple embodiments of the present invention.

Figure 10 A-10C shows according to the Li during 15 charge-discharge cycles of multiple embodiments of the present invention ⁺the variation of insertion-taking-up capacity and coulombic efficiency.

Figure 11 A-11C shows the scanning electron microscope image of the CNF array of preparation recently according to multiple embodiments of the present invention.

Figure 11 D shows the cross section of the nanofiber/silicon compound that comprises more than one CNF.

Figure 12 illustrates according to the carbon nano-fiber array of the fiber that comprises 10 μ m length of multiple embodiments of the present invention.

Figure 13 illustrates according to the method for the production CNF array of multiple embodiments of the present invention.

Describe in detail

Figure 1A and 1B illustrate the CNF array 100 according to multiple embodiments of the present invention, and this CNF array 100 is included in multiple CNF 110 of growth on conductive base 105.In Figure 1A, CNF array 100 is shown as at lithium and takes out (electric discharge) state, and in Figure 1B, CNF array 100 is shown as at lithium and inserts (charging) state.CNF 110 in these and other embodiment discussed herein selectively vertically arranges.Use plasma activated chemical vapour deposition (PECVD) method of the direct current biasing CNF 110 that grows on copper base material 105.As discussed above, the CNF 110 growing by the method can have the unique form that comprises that the conical graphite structure similar to folded cup or cone or helicoid is stacking.This has created and has promoted the very trickle structure that lithium inserts.This structure is called as " cone-in-cone " structure in other places of this paper.Under larger length scale, these CNF 110 are typically evenly distributed and separated from one another well perpendicular to substrate surface.The diameter of independent CNF can be selected as providing expectation mechanical strength so that CNF array 100 be firm and can keep its integrality by siliceous deposits and the circulation of wet electrochemistry.Crystal seed layer is selectively used to make CNF 110 to grow on base material 105.In use, CNF array 100 is placed in electrolyte 125 and contacts, and this electrolyte 125 comprises one or more charge carriers, for example lithium ion.CNF 110 is configured such that some electrolyte 125 are arranged between CNF 110 and/or can arrive base material 105 by the gap between CNF 110.

In Figure 1A and 1B, the diameter of illustrated independent CNF 110 is nominally between 100 to 200nm, but between 75 to 300nm or the diameter of other scopes be possible.CNF 110 is selectively taper along its length.The CNF 110 that uses the technology of discussing to produce herein has outstanding conductance (σ=～2.5x10 along axle ⁵s/m) and with base material 105 form firm ohmic contact.It is upper to form coaxial shell and most of 120 places, tip at CNF 110 of attenuation gradually that open space between CNF 110 can make silicon layer 115 deposit to each CNF.This design can make whole silicon layer 115 be electrically connected by CNF 110 and during charge-discharge cycles, keep fully active.The expansion that the alloying of lithium and silicon layer 115 occurs can with radial direction, for example, easily be adapted to perpendicular to the long size of CNF 110.Charging and discharging capacity and the cyclical stability of the CNF 110 that the CNF 110 that can relatively apply without silicon and silicon apply.The interpolation of silicon layer 115 provides paramount 3938mAh/g under C/2 speed _sisignificant Li ⁺insert (charging) capacity and 110 times circulation after maintenance 1944mAh/g _si.This charge/discharge rates and corresponding capacity are significantly higher than the former structure that uses silicon nanowires or mix Si-C nanostructure.Figure 1A and 1B are perspective view.

In multiple embodiments, from 0.01 until the nominal silicon thickness of 0.5,1.0,1.5,2.5,3.0,4.0,10,20,25 μ m (or more) can be deposited on the long CNF 110 of 3 μ m to form such as illustrated those CNF array 100 in Figure 1A and 1B.Similarly, in multiple embodiments, from 0.01 until the nominal silicon thickness of 0.5,1.0,1.5,2.5,3.0,4.0,10,20,25 μ m (or more) can be deposited on the long CNF 110 of 10 μ m to form CNF array 100.In some embodiments, the nominal thickness of silicon is between the average distance between 0.01 μ m and CNF 110.

Use CNF array 100, paramount under C/2 speed～4, the lithium ion storage of 000mAh/g specific discharge capacity is obtained.Under equal-wattage speed, this capacity is significantly higher than those capacity that obtain with independent silicon nanowires or other silicon nanostructure carbon mixs.Improved performance is owing to because the effective charge by CNF 110 in this mixture structure is collected and short Li ⁺path and the abundant silicon shell of activation.Good cyclical stability is proved to be in 110 circulations.In various embodiments, the memory capacity of the lithium ion storage of CNF array 100 is every gram of silicon approximately 750,1500,2000,2500,3000,3500 or 4000mAh, or these value between arbitrary scope in.As used herein, term " nominal thickness " (for example silicon) is the amount that produces the silicon of the silicon flat bed of described thickness on base material 105.For example, the nominal thickness of the silicon of 1.0 μ m is if silicon Direct precipitation causes the amount of the silicon of the silicon layer that 1.0 μ m are thick on base material 105.Report nominal thickness, because it can easily be measured by weight by methods known in the art.The nominal thickness of 1.0 μ m is by the less thickness causing at CNF 110 upper silicon layers 115, because silicon is distributed in the more large area on CNF 110 surfaces.

Fig. 2 A-2C illustrates according to the CNF array 100 of the average fiber length with approximately 3 μ m of multiple embodiments of the present invention.Fig. 2 A-2C is scanning electron microscopy (SEM) image.Fig. 2 A has shown the CNF 110 of multiple vertical arrangements without silicon layer 115.Fig. 2 B has shown the CNF 110 of the multiple vertical arrangements that comprise silicon layer 115.Fig. 2 C has shown after 100 lithium charge-discharge cycles of experience to take out the CNF 110 of multiple vertical arrangements of (electric discharge) state.CNF 110 is securely attached to copper base material 105 and substantially vertically arranges equably, and be randomly dispersed on substrate surface.The sample using in this research has 1.11x10 ⁹cNF/cm ²centre plane density (calculating from SEM image vertical view), corresponding to the average nearest neighbor distance of～330nm.The average length of CNF 110 in Fig. 2 is that the length of CNF of～3.0 μ m and >90% is in the scope of 2.5 to 3.5 μ m.Diameter expands to 240nm, the mean value of have～147nm from～80nm.Be present in the tip place of each CNF 110 at the most advanced and sophisticated 120 inverted tear-drop shaped Raney nickels in place, cover the hollow channel of the center of CNF, this promotes CNF 110 tip-growth during PECVD process.The size of Raney nickel nano particle defines the diameter of each CNF 110.The longer CNF 110 of 10 μ m is also used in some researchs that part is discussed in the back at the most.

In multiple embodiments, average nearest neighbor distance can or similarly change between distance at 200-450nm, 275-385nm, 300-360nm.In addition, the average length of CNF 110 can about 2-20,20-40,40-60,60-80,80-100,100-120,120-150 (μ m) between or larger.If the standard carbon nano-fiber of 1 millimeters long is known in this area.In multiple embodiments, average diameter can change between about 50-125,100-200,125-175 (nm) or other scopes.

Unbodied silicon layer 115 by magnetron sputter deposition on CNF array 100.The open architecture of the CNF array 100 of brush and sac like deeply arrives silicon downwards and produces conformal structure in this array and between CNF 110 is possible.As a result, form thick silicon coating at the most advanced and sophisticated place of CNF, formed subsequently the coaxial silicon shell of attenuation gradually at CNF around compared with lower part, presented the interesting taper nucleocapsid structure that is similar to cotton swab.The amount of siliceous deposits is used quartz crystal microbalance (QCM) to characterize by the nominal thickness of silicon fiml in the plane during sputter.Li ⁺insertion/taking-up capacity is normalized the total siliceous amount for being obtained by nominal thickness.Under the nominal thickness of 0.50 μ m, the CNF 110 that silicon applies is separated from one another well, forms open nucleocapsid CNF array structure (shown in Fig. 2 B).This structure allows electrolyte freely to arrive the whole surface of silicon layer 115.In illustrated embodiment, with in application before silicon layer 115～average diameter of the CNF 110 of 147nm compares, average tip diameter is～457nm.At the be estimated as～155nm of silicon thickness of the average radial at most advanced and sophisticated 120 places.This is obviously much smaller than the silicon thickness of the nominal of 0.50 μ m, because most of silicon scatters along the total length of CNF.In an alternative embodiment, see in 10-1000,20-500,50-250,100-200 (nm) scope or other silicon thicknesses radially of different range.As other local discussion herein, the cone-in-cone of CNF 110 provides extra fine structure for silicon layer 115.This cone-in-cone structure is selectively the result of spiral growth mode, and when with cross-sectional view, this spiral growth mode produces cone-in-cone structure.

Perspective electron microscope (TEM) image in Fig. 3 A-3C further illustrates the CONSTRUCTED SPECIFICATION of the CNF 110 of silicon coating.The direct silicon layer 115 of production～390nm silicon on the tip 120 of the CNF 110 of～210nm diameter.The diameter of the largest portion of the silicon layer 115 of cotton swab shape is～430nm that this largest portion appears near the least significant end at tip 120.CNF 110 coaxial silicon layer 115 around shows the featheriness quality of the contrast with adjusting, from obviously different (the seeing Fig. 3 A) of uniform siliceous deposits thing on tip.This is likely the result of the cone-in-cone microstructure of the CNF 110 of PECVD-growth.This is different from such CNF 110 and comprises along the document of the graphite-structure of the inhomogeneous folded cup-shaped of CNF 110 central shafts.In the U.S. Patent Application Serial Number of owning together 12/904,113 that the use of this variation of the diameter of CNF 110 is to submit on October 13rd, 2010, be disclosed in advance.In Fig. 3 B, can be clear that cone-in-cone structure is by forming more than the graphite linings of ten layers of cup-shaped, as pointed out by dotted line.Because electron beam need to penetrate CNF or the Si-CNF mixture of hundreds of nanometer thickness, resolution and the contrast of Fig. 3 B and 3C are limited, but this architectural feature with in document, use the high-resolution TEM research of less CNF consistent.The structure of this uniqueness produces broken graphite edge bank along CNF sidewall, and this broken graphite edge bank is causing the nucleation rate of variation and is therefore being adjusted in silicon layer 115 density on CNF 110 sidewalls during siliceous deposits.The density regulating causes by (100nm in Fig. 3 A ²) silicon structure of the ultra-high surface area pointed out of frame 310.The penniform silicon structure of silicon layer 115 provides outstanding lithium ion interface, and this lithium ion interface causes very high lithium capacity and also electronics transferred to CNF 110 rapidly.In Fig. 3 A, are the Raney nickels for CNF growth in the dark area at most advanced and sophisticated 120 places.Other catalyst can also be used.

Fig. 3 B and 3C are that lithium inserts/takes out (3B) and lithium before circulation and inserts/take out the image that (3C) records after circulation.Sample in Fig. 3 C is the state of de-lithiumation (electric discharge) in the time that it is removed from electrochemical cell.Dotted line in Fig. 3 B is the visually oriented of cone-in-cone graphite linings in CNF 110.Long dotted line in Fig. 3 C represents the sidewall surfaces of CNF 110.

As other local discussion herein, the cone-in-cone structure of CNF 110 is different from conventional carbon nano-tube (CNT) or graphite greatly.With respect to carbon nano-tube or the nano wire of standard, this cone-in-cone structure causes improved Li ⁺insert, even if do not add silicon layer 115.For example, the cone-in-cone graphite-structure of CNF 110 allows Li ⁺be inserted into (and not only endways) in graphite linings by the sidewall of CNF 110.Pass the Li of the wall of each CNF 110 ⁺transfer path is very short (having in some embodiments D～290nm), is different from completely from the long path of the openend conventional seamless carbon nano-tube (CNT).Fig. 4 illustrates the schematic diagram of the cone-in-cone structure of CNF 110.In this special embodiment, the mean value of parameter is: CNF radius r _cNF=74nm, CNF wall thickness t _w=～50nm, graphite coning angle θ=10 °, and graphite cone length D=t _w/ sin θ=290nm.

The electrochemical properties of the CNF 110 of illustrate～3 μ m length of Fig. 5 A-5C.This characteristic illustrates the phenomenon of describing about Fig. 4.Fig. 5 A be presented at 0.1,0.5 and 1.0mV/s scan rate under with respect to Li/Li ⁺the cyclic voltammogram from 1.5V to 0.001V (CV) of reference electrode.Lithium dish is used as electrode.Data obtain and are normalized to the geometrical surface of exposure from circulation for the second time.Fig. 5 B is presented at the electrostatic charging-discharge curve under C/0.5, C1, C/2 power speed, corresponds respectively to 647,323 and 162mA/g (being normalized to the carbonaceous amount of estimation) or 71.0,35.5 and 17.8 μ A/cm ²the current density of (being normalized to geometrical surface).Fig. 5 C is presented at insertion and taking-up capacity (to left side vertical axes) and the coulombic efficiency (to the right vertical axes) with respect to period under C/1 charging-discharge rate.(C/1 discharge rate=1 hour, C/2 discharge rate=120 minute, 2C=C/0.5=30 minute, etc.).

The half-cell of new assembling typically shows than Li/Li ⁺reference electrode, the open circuit potential (OCP) of uncoated CNF 110 anodes is～2.50 to 3.00V.Li in the time that the CV measuring between 0.001V and 1.50V shows below electrode potential is 1.20V ⁺insert and start.Circulation for the first time from OCP to 0.001V comprises the protective layer necessary by being decomposed to form of solvent, salt and impurity, i.e. solid-electrolyte interphace (SEI), and therefore present large cathode current.CV subsequently shows less but more stable electric current.When electrode potential extends to negative value, with Li ⁺insert relevant cathode current rising, until there is sharp-pointed negative electrode peak at 0.18V place.The lower limit that arrives 0.001V when electrode potential is backward on the occasion of reverse, points out as the anode current by continuous with at the broad peak of 1.06V, observes lithium taking-up at height to the gamut of 1.50V.

CV feature and the segmentation of CNF array 100 are inserted into graphite and Li ⁺the CV feature of those CNF arrays 100 that is slowly diffused into the hollow channel of CNT is slightly different.The lithium ion that enters into CNF 110 inserts the unique structure being likely due to CNF 110, is passed in from the insertion between the graphite linings of sidewall.TEM image in Fig. 3 C shows that the graphite stack in the cone-in-cone in CNF 110 is stacked in Li ⁺insert-taking-up cycle period is destroyed a little, probably due to Li ⁺the large volume occurring when insertion changes.Inner and be observed at outer surface at CNF 110 as some fragments of white object and nano particle.

Electrostatic charging-discharge curve in Fig. 5 B shows in the time that power speed is increased to C/0.5 (C/0.5 is also referred to as " 2C ") from C/2, Li ⁺memory capacity reduces.For easier compa-ratios (especially for higher than those of C/1), we use fraction representation method C/0.5 to replace " 2C " that more generally use in the literature in this article.Li ⁺insertion and taking-up capacity are normalized to the quality (1.1 × 10 of the CNF 110 of estimation ⁴g/cm ²), the CNF structure that the quality of this CNF 110 is vertically arranged according to hollow and the calculating of following mean parameter: length (3.0 μ m), density (1.1 × 10 ⁹the every cm of CNF ²), 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/cm ³) identical.Under normal C/2 speed, insertion capacity is 430mA h g ^-1and taking-up capacity is 390mA h g ^-1, both are slightly higher than the theoretical value 372mA h g of graphite ^-1, perhaps this form and Li owing to SEI ⁺irreversibly be inserted in the hollow cell in CNF 110.Under whole power speed, find that taking-up capacity is greater than 90% of insertion value, and when power speed is inserted capacity and taking-up capacity reduction～9% in the time that C/2 is increased to C/1, in the time that C/1 is increased to C/0.5, insert capacity and taking-up capacity reduction～20% when power speed, equal to graphite electrode.

Through charge-discharge cycles, under C/1 speed, after 20 circulations, find that insertion capacity is from 410mA h g ^-1slightly be down to 370mA h g ^-1, and take out Capacitance reserve at 375mA h g ^-1with 355mA h g ^-1between.Except in front twice circulation owing to forming SEI on CNF 110 surfaces, total coulombic efficiency (, the ratio of taking-up capacity and the capacity of insertion) is～94%.Known SEI film easily formed in initial cycle period on carbon anode, and it allows lithium ion diffusion, but electric insulation, cause series resistance to increase.During TEM image (Fig. 3 C) and SEM image (Fig. 6 A) are presented at charge-discharge cycles, inhomogeneous thin film deposition is on CNF 110 surfaces.In some embodiments, SEI serves as sheath to increase the mechanical strength of CNF 110, by collapse into microbundle as the cohesion capillary force of the solvent of observing prevents them in the research with other polymer coatings.

Fig. 6 A-6C illustrates CNF 110 scanning electron microscope images long according to 3 μ m of multiple embodiments of the present invention.Fig. 6 A is presented at the CNF 110 of rear de-lithiumation (electric discharge) state of insertion/taking-up circulation.Fig. 6 B is presented at the CNF that comprises silicon layer 115 110 of 100 rear de-lithiumation states of circulation.Fig. 6 C is presented at the CNF that comprises silicon layer 115 110 of 100 rear lithiumation states of circulation.These images are perspective views of 45 degree.

Fig. 7 A-7C illustrates to use and comprises the result obtaining as the CNF 110 of the silicon layer 115 of lithium ion battery anode.These results are used the nominal silicon thickness of 0.50 μ m to obtain.Fig. 7 A is presented at 0.10,0.50 and 1.0mV s ^-1under sweep speed with respect to Li/Li ⁺1.5V and 0.05V between cyclic voltammogram.Measure after 150 charge-discharge cycles of sample experience and carry out, and be presented at the data that circulate for the second time under each sweep speed.Fig. 7 B is presented at C/0.5, C/1 and C/2 power speed, the electrostatic charging-discharge curve of the lower sample that circulates for 120 times.All curves are taken from the circulation for the second time under each ratio.Fig. 7 C shows insertion and the taking-up capacity (to left side vertical axes) and coulombic efficiency (to the right vertical axes) as two CNF arrays 100 of the function of charge-discharge cycles number (as electrode).The C/10 speed that is first used in the first CNF array 100 circulates next time, once circulation in C/5 speed, under C/2 speed, twice circulation regulates.Then the remainder of 96 circulations is inserted under ratio and C/5 taking-up ratio and tested at C/2.Closed square and hollow square represent respectively insertion capacity and taking-up capacity.First the second electrode regulates with twice circulation under each comfortable C/10, C/5, C/2, C/1, C/0.5, C/0.2 speed.Subsequently ensuing 88 times are circulated under C/1 speed and tested.The coulombic efficiency of two electrodes represents with solid diamond (the first electrode) and open diamonds (the second electrode), major part overlapping 99%.

CV in Fig. 7 A has presented the feature closely similar with the feature of silicon nanowires.Than uncoated CNF array 110, Li ⁺the cathodic wave and the Li that insert ⁺both all shift to lower value (respectively lower than～0.5 and 0.7V) the anode ripple taking out.After application silicon layer 115, peak current density increases by 10 to 30 times and be directly proportional to sweep speed.Significantly, the Li that alloy forms ⁺be inserted in silicon and be limited to the Li between graphite linings than being inserted in uncoated CNF faster, uncoated CNF ⁺slow diffusion.In research before pure silicon nano wire, do not observe the negative electrode peak at～0.28V place.Represent that lithium silicon alloy transfers to three anode peaks in amorphous silicon and use those of silicon nanowires similar, although to moved 100 to 200mV compared with low potential.

Electrostatic charging-the discharge curve of the CNF array that comprises silicon layer 115 that Fig. 7 B shows comprises two significant features: (1) even after 120 circulations under C/2 speed, acquisition～3000mA h (g _si) ^-1high Li ⁺insert (charging) and (electric discharge) capacity of taking-up; And (2) Li under C/2, C/1, C/0.5 power speed ⁺capacity is almost identical.In other words,, in the time that charge rate is increased to C/1 and C/0.5 from C/2, the capacity of the CNF array 100 moving as electrode does not decline.About these charge rates, in multiple embodiments, capacity depends on charge rate hardly.Comprise total Li of the CNF array 100 of silicon layer 115 ⁺memory capacity is than high approximately 10 times of the CNF array 100 that lacks silicon layer 115.Even if the low potential limit of charging cycle is increased to 0.050V from 0.001V, this still can occur.Therefore, Li ⁺it is insignificant being inserted into taking temperature in CNF core.Specific capacity is by only calculating divided by siliceous amount, and this siliceous amount is from nominal thickness and the 2.33g cm of measurement ^-3bulk density calculate.This method is selected as the suitable tolerance of the specific capacity of comparison silicon layer 115 and the theoretical value of volume silicon.For the long CNF 110 of 3.0 μ m of silicon layer 115 that deposits 0.456 μ m nominal thickness, the actual mass density of silicon layer 115 is～1.06 × 10 ^-4g cm ^-2, equal to the mass density (～1.1 × 10 of CNF 110 ^-4g cm ^-2).In Fig. 7 B, corresponding coulombic efficiency is greater than 99% under whole three power speed, is much higher than the not coulombic efficiency of the CNF 110 of silicon-containing layer 115.

Fig. 8 illustrates according to the capacity of the CNF array 100 of multiple embodiments of the present invention and how to change with charge rate.Show the data of multiple periods.Fig. 8 show as set hour in reach the average specific discharge capacity of one group of circulation of the use same current ratio of the function of total capacity (C/h, for example total capacity/hour) needed charge rate (C ratio).Vertical line concentrates on C/4,1C, 3C and 8C.CNF array 100 first with twice Cyclic Symmetry under each comfortable C/8, C/4, C/2, C/1, C/0.8, C/0.4 and C/0.16 speed regulate, and test circulating in for ensuing 88 times under the symmetrical ratio of C/1 subsequently.Be recycled to 200 times from 101 times and be cycled to repeat above-mentioned steps.Start 201 circulations, electrode with five Cyclic Symmetries under each in C/4, C/3, C/2, C/1, C/0.75, C/0.66, C/0.50, C/0.33, C/0.25, C/0.20 and C/0.15 be recycled, and circulate under the symmetrical ratio of C/1 and test at ensuing 45 times subsequently.Be recycled to 400 circulations and be recycled to 500 times from 401 times from 301 times and be cycled to repeat above-mentioned steps.In the time that C ratio changes with 32 times, the change of capacity is little (<16%).After 100 circulations, in the time that C ratio becomes 8C from 3C, electrode shows the capacity increasing.Therefore, charge rate causes improved capacity faster.Under both, obtain high power capacity (>2,700mAh/g) at height ratio and lower ratio (C/4 and 8C).When C ratio increases, the capacity under the ratio more than 3C increases.Specific capacity is due to known correctable factor with the decline of period.

CV and charging-discharge measuring are pointed out Li ⁺it is quick and highly reversible being inserted in silicon layer 115, and it is the feature that high performance lithium ion battery anode is expected.This is used under different test conditions two of two identical samples long loop tests is further proved to (seeing Fig. 7 C): (1) is for the C/2 speed inserted with for the slow asymmetric test of the C/5 speed of taking out; And (2) are for inserting and take out both fast symmetrical tests of C/1 speed.Two data sets show except outside initial adjustment circulation (under the low ratio of difference, 12 circulations of the former 4 circulations and the latter) in long circulation the coulombic efficiency of >98%.In slow asymmetric test, insertion capacity only declines 8.3%, from the 3643mA h g at the 5th circulation time ^-1arrive at the 3341mA h of the 100th circulation time g ^-1.Even, under C/1 charging-discharge rate, insertion capacity only declines 11%, from the 3096mA h g at the 13rd circulation time ^-1arrive at the 2752mA h of the 100th circulation time g ^-1.Li between these two data sets ⁺the difference of capacity is mainly attributable to initial adjustment parameter and the variation to sample of little sample.This similar value by the insertion-taking-up capacity of the front several adjusting cycle period under C/10 and C/5 speed in Fig. 7 C is pointed out.Ratio (C/0.5 of the 9th time and the 10th time circulation of sample #2 and the C/0.2 of the 11st time and the 12nd time circulation) is found to be irreversible decline harmful and that cause capacity faster.But, become stable at longer circulation rear electrode.As Fig. 7 B shows, the charging-discharge curve that is used in the sample #1 measurement after 120 circulations of experience is almost identical under C/2, C/1 and C/0.5 speed.This is to change about the charge rate of four times.

3000 to 3650mA h g ^-1the specific capacity of the silicon layer 115 in scope is consistent with the peak of the amorphous silicon anode of summarizing in document.It should be noted that whole silicon shell in CNF array 110 is to Li ⁺insertion be active and in 120 circulations almost 90% capacity of maintenance, as far as we know, except flat ultra-thin (<50nm) silicon fiml, this has never been realized before.Specific capacity disclosed herein is significantly higher than the specific capacity of other nanostructure silicon materials of use of having reported under similar power speed, comprise with silicon nanowires under C/2 speed～2500mA h g ^-1with under C/1 speed～2200mA h g ^-1, and with carbon nano-fiber-silicon core-shell nano wire of random orientation under C/1 speed～800mA h g ^-1.Significantly, with respect to prior art, provide such as the coaxial core-shell nano thread structure on the CNF 110 separating being well included in multiple embodiments of the present invention charging-the discharge rate strengthening, the almost Li completely of silicon ⁺memory capacity and long circulation life.

As shown in Fig. 7 C, high insertion capacity (～4500mA h g abnormally ^-1) always in initial circulation, be observed its high 20-30% of circulation after relatively.By contrast, taking-up value is relatively stable in whole circulation.Especially big insertion capacity is attributable to the combination of three irreversible reactions: (1) forms (tens nanometers) thin SEI (phase in the middle of surface electrode) layer; (2) lithium be present in the SiO on silicon face _xreaction (SiO _x+ 2xLi → Si+xLi ₂o); And (3) will have higher theoretical capacity (～4200mA h g ^-1) initial crystalline silicon coating change into and have compared with low capacity (<3800mA h g ^-1) amorphous silicon.TEM image (Fig. 3 C) and SEM image (Fig. 6 B) are presented at after charge-discharge cycles, and inhomogeneous SEI can be deposited on the surface of silicon layer 115.When CNF array 110 experiences expansion-contraction circulation time of the large volume occurring during charge-discharge cycles, this resilient SEI film can help silicon layer 115 to be fixed on CNF 110 surfaces.Significant difference between SEM image in Fig. 6 B and 6C shows the large expansion with respect to the silicon layer 115 of lithiumation (charging) state of non-lithiumation state.Although (some expansions may be the oxidations to lithium by air when be disassembled with imaging when electrochemical cell.) note, cause the difference seen in the silicon layer 115 between Fig. 3 A and 3B in the generation of SEI during initial charge-discharge cycles.In Fig. 3 B, silicon and electrolyte interact to produce SEI, and this SEI has filled the gap between feathery structure.This interaction can comprise mixing, chemical reaction, electric charge coupling, encapsulation and/or similarly effect.Therefore, silicon layer 115 looks like more uniform in Fig. 3 B.But silicon layer 115 comprises silicon layer (feathery structure) and the SEI layer of intersection now.Every layer in the layer of these intersections can be about tens nanometers.SEI layer can be ion permeability material, and it is the interactional product between electrolyte and silicon layer 115 (or other electrode materials).

Crystal and the impalpable structure of silicon shell manifest by Raman spectrum.As shown in Figure 9, the former CNF array 100 that comprises silicon layer 115 has shown corresponding to amorphous silicon 350 to 550cm ^-1overlapping multiple broadbands and corresponding to nanocrystalline silicon 480cm in scope ^-1the higher sharp-pointed band at place.After charging-discharge test, sharp-pointed peak disappears, and broadband is merged at 470cm simultaneously ^-1that locates is unimodal.Exposed CNF 110 does not show any feature within the scope of this.Peak move down～the 40cm of crystalline silicon peak from measuring with monocrystalline silicon (100) wafer ^-1and from other microcrystal silicon materials move down～20 to 30cm ^-1.This movement is likely due to much smaller crystalline size and large unordered.Initial silicon layer 115 is probably made up of the nanocrystal being embedded in the [amorphous joining with the TEM image correlation of Fig. 3 A mesoptile shape.After initial circulation, si-nanocrystals changes into amorphous silicon, consistent with the TEM image after loop test (seeing Fig. 3 B and 3C).But than the large longitudinal dilatation (greatly to 100%) of pure silicon nano wire, silicon layer 115 does not obviously slide along CNF.Therefore, in 120 circulations, silicon layer 115 is attached to CNF 110 securely.At Li ⁺silicon shell volume during insertion changes to be controlled by radial expansion, and CNF-silicon interface keeps complete simultaneously.

Multiple embodiments of the present invention comprises the CNF 110 with different length and silicon thickness of the shell.A factor can controlling in the time producing CNF 110 is the open space between each CNF 110, for example, and the average distance between the CNF 110 in CNF array 100.In the time of charging, this space allows silicon layer 115 radial expansions, and therefore this space provides stability in some embodiments.Because best electrode structure depends on the length of CNF 110 and the thickness of silicon layer 115, so sometimes expect to use longer CNF 110 and thicker silicon layer 115 to obtain higher total Li ⁺memory capacity.Longer CNF 110 is associated with larger memory capacity.Figure 10 A-10C demonstration is used the Li of long CNF 110 samples of three 10 μ m of the silicon layer 115 that deposits respectively 0.50,1.5 and 4.0 μ m nominal thickness in 15 charge-discharge cycles ⁺the variation of insertion-taking-up capacity and coulombic efficiency.Under the C/10 speed for circulation for the first time and for after regulating under the C/5 speed of circulation for the second time, asymmetric ratio (C/2 for insert and C/5 for taking out) use in the circulation subsequently similar to the measurement of the sample #1 of Fig. 7 C.This scheme provides almost 100% coulombic efficiency and minimum decline in cycle period.During sputter, nominal thickness uses quartz crystal microbalance in site measurement.

Obtain respectively high to 3597mA h g with the thick silicon layer 115 of 0.50 and 1.5 μ m ^-1with 3416mA h g ^-1specific capacity, the specific capacity closely similar (seeing Fig. 7 C) of the silicon layer 115 that 0.50 μ m on this CNF 110 long with being used in 3.0 μ m is thick.In 15 circulations, capacity almost remains unchanged.But, there is the electrode of 4.0 μ m nominal silicon thicknesses to show only 2221mA h g ^-1remarkable lower specific capacity.This shows due to expansion, and silicon layer 115 starts to contact each other from contiguous CNF 110, limits their and further expands and the diffusion between CNF 110 of restriction lithium.As a result, the only sub-fraction of silicon coating is active in lithium inserts.The sample of the stability silicon layer 115 thinner than having of circulation is correspondingly poorer.

The Si (500nm nominal thickness) of the same amount on the CNF array 110 that comprises the long CNF 110 of 10 μ m gives the Li of the CNF 110 long with 3 μ m ⁺memory capacity (3643mA h g ^-1, see Fig. 7 C) and the Li of almost identical amount ⁺memory capacity (3597mA h g ^-1, see Fig. 6 a), although carbonaceous amount is greater than more than 3 times.This is very strong evidence, and Li is being calculated in the contribution of CNF 110 ⁺in storage, be insignificant.Few Li ⁺it is likely that ion is inserted in the CNF 110 in silicon coated sample, and this contributes to the stability of the structure during charge-discharge cycles repeatedly.

With Li in fine three the associated samples of structure of three samples ⁺the variation of storage specific capacity is by the illustrated SEM Image Display of Figure 11 A-11C.Figure 11 A-11C shows the scanning electron microscope image of freshly prepd CNF array 100 (on the long CNF 110 of～10 μ m).The nominal silicon thickness of use (a) 0.50 μ m, (b) 1.5 μ m and (c) 4.0 μ m generates silicon layer 115, and nominal silicon thickness uses quartz crystal microbalance in site measurement between depositional stage.All images are 45 ° of perspective views.At 0.50 μ m nominal silicon thickness place, find that the average tip diameter on the long CNF of 10 μ m be～388nm, much smaller than on the CNF 110 growing at 3.0 μ m～average diameter of 457nm.Silicon layer 115 is thinner but scatter more equably along the long CNF 110 of 10 μ m.

It should be noted, growth 10 μ m CNF 110 spend 120 minutes, this be growth 3 μ m CNF 110 approximately six times of times long.Some Raney nickels pass through NH in long PECVD process ₃slowly etched, cause reducing continuously and causing cone point 120 (as shown in figure 12) of nano nickel particles size.The length variations of CNF 110 is also along with long CNF 110 increases.These factors have reduced most advanced and sophisticated 120 screen effect jointly.As a result, even, under 1.5 μ m nominal silicon thicknesses, be coated with the CNF 110 of silicon layer 115 well with separated from one another.The SEM image (Figure 11 B) of 1.5 μ m silicon on 10 μ m CNF arrays 100 is closely similar with the SEM image (Fig. 2 B) of 0.50 μ m silicon on 3.0 μ mCNF arrays 110.But be increased to 4.0 μ m when nominal silicon thickness, silicon layer 115 obviously with merge each other and filling CNF 110 between most of space (seeing Figure 10 C).This has reduced the required free space of volumetric expansion that holds silicon layer 115l.As a result, Li ⁺storage specific capacity significantly declines.

Figure 11 A and 11B comprise the CNF 110 of roughly the same quantity separately, but in Figure 11 B, have substantially less visible most advanced and sophisticated 120.This is because silicon layer 115 can form and comprise the single CNF 110 nanofiber/silicon compound of (its cross section shows in Figure 1A).Or silicon layer 115 can form the nanofiber/silicon compound that is included in two, three or more CNF 110 under single silicon covering.This occurs when during silicon layer 115 deposition process, two or more CNF 110 flock together.Nanofiber/silicon compound is the structure that comprises the continuous silicon layer 115 of sealing one or more CNF 110.The cross section that comprises nanofiber/silicon compound of two CNF 110 illustrates at Figure 11 D.In multiple embodiments, nanofiber/silicon compound of at least 1%, 5% or 10% comprises more than one CNF 110.

In multiple embodiments, the example with the CNF array 100 of 0.50 and 1.5 μ m nominal silicon thicknesses has respectively 3208 ± 343 and 3212 ± 234mA h g ^-1comparable quality-specific capacity.The sample with 4.0 μ m nominal silicon thicknesses produces 2072 ± 298mA h g ^-1much lower capacity.Thinner silicon coating is maximum lithium insertion capacity fully activation and that provide amorphous silicon to give.On the other hand, area-specific capacity is along with silicon thickness is from the 0.373 ± 0.040mA h cm with 0.50 μ m silicon thickness ^-2be increased to pro rata the 1.12 ± 0.08mA h cm with 1.5 μ m silicon thicknesses ^-2, but decline to produce the 1.93 ± 0.28mA h cm with 4.0 μ m nominal silicon thicknesses from linearity curve ^-2.Significantly, under this thickness, the only sub-fraction of the extra silicon in thick silicon coating plays an active part in lithium storage.The thickness of 4.0 μ m is greater than the average distance between CNF 110.Electrochemical results is consistent with the structure showing in SEM image in Figure 11 C, and it shows that the space between CNF 110 is filled substantially.

In multiple embodiments of the present invention, the structure of CNF array 100 is included on CNF 110 approximately 200 silicon layers to 300nm radial thickness, and this CNF 110 has the length of about 30-40,40-75,75-125 micron (or larger or their combination) and the diameter of approximately～50nm.In some embodiments, these CNF arrays 100 are grown on conductive foil, and this conductive foil has the thickness in～10 microns ,～10-20 micron ,～10-50 micron or larger scope.In multiple embodiments, silicon (being equivalent to 1.5 μ m nominal thickness in the plane) is deposited on the long CNF 100 of 10 μ m to form CNF array 100.This is done simultaneously and keeps having and vertical-type core-shell nano thread structure of the opening of the fine independent CNF 110 separating each other, makes lithium ion can permeate the CNF array 100 between CNF 110.The combination construction of this uniqueness allows silicon layer 115 at Li ⁺insert and take out during in radial direction free wxpansion/contraction.Even under C/1 speed, obtain and have 3000 to 3650mA h g ^-1the high-performance lithium storage of quality-specific capacity.This capacity maximum desired to amorphous silicon from similar quality matches, and this shows that this silicon layer 115 fully activates.The nano-structured structure of this 3D can make the effective electrical connection of a large amount of silicon materials keep short Li simultaneously ⁺insert-take out path.As a result, the high power capacity that approaches theoretical limit in 120 charge-discharge cycles is possible.When ratio from C/10 to C/0.5 (or 2C) increases by 20 times, the variation of capacity is very little.High power capacity under significantly improved charge rate and power speed and outstanding cyclical stability makes this new structure become the optional anode material for high performance lithium ion battery.Identical core-shell concept can be by using TiO ₂, LiCoO ₂, LiNiO ₂, LiMn ₂o ₄, LiFePO ₄or analog is replaced silicon shell and is applied to cathode material.

Figure 13 illustrates the method for producing CNF array 100 disclosed herein.Providing in base material step 1310, provide and be suitable for the base material 105 that CNF 110 grows.Base material 105 can comprise multiple material, for example copper.Base material 105 is selectively to have the conductive foil of other local thickness of describing herein.Provide in the step 1320 of nucleation site selectable, on base material 105, be provided for the nucleation site of the growth of CNF 110.Multiple nucleation material, for example nickel particles is well known in the art.Nucleation site is selectively to make to produce the density of the average distance between CNF 110, and for example the density of other local instructions provides herein.Provide nucleation site step 1320 be therein nucleation not to be required in the embodiment of growth of CNF 110 or analog structure be selectable.

In growth CNF step 1330, CNF 110 grows on base material 105.CNF 110 is selectively grown to produce the cone-in-cone structure of other local instructions herein or similar varistructure.CNF 110 can grow to any length of other local instructions herein.Growth is selectively used PECVD method for example at .J.Mater.Chem.A such as " A high-performance lithium-ion battery anode based on the core-shell heterostructure of silicon-coated vertically aligned carbon nanofibers " Klankowski, 2013, the method of instructing in 1,1055 or quote completes.

Applying in silicon layer step 1340, insert for example silicon layer 115 of material and be applied to the CNF 110 of growth.The material applying can have arbitrary nominal thickness of other local instructions herein so that silicon layer 115 thickness of generation tens or hundreds of nanometer.In selectable regulating step 1350, use one or more lithiums to insert circulation and regulate the CNF array 100 that uses step 1310-1304 to produce.

Multiple embodiments illustrate especially herein and/or describe.However, it should be understood that modifications and variations form is covered by above-mentioned instruction and in the scope of appended claim, and do not depart from their spirit and the scope of expection.For example, in the time that the example of discussing herein concentrates on the CNF with cone-in-cone structure, this instruction goes for having the other materials of analog structure.Similarly, in the time that copper base material and lithium charge carrier are discussed in this article, other base materials and charge carrier are obvious to those of ordinary skill in the art.Silicon layer 115 selectively by except silicon or form as the insertion material of the substitute of silicon.For example tin, germanium, carbon, silicon or their combination can be used as inserting material.In addition TiO, ₂(titanium oxide) or boron nitride nanometer fiber can be used in replacement carbon nano-fiber.

Comprise in various energy storing device of capacitor, battery and their mixing and can comprise the electrode of instruction herein.These energy storing devices for example will be used to, load balancing apparatus, communicator, stand-by power supply, the vehicles and calculation element.

The embodiment explanation the present invention who discusses herein.In the time that referenced in schematic is described these embodiments of the present invention, the various amendments of described method and/or concrete structure and reorganization can become obvious to those skilled in the art.Depend on instruction of the present invention and improved all these amendment, reorganization or the version of this area by these instructions, be considered within the scope and spirit of the invention.Therefore these are described and accompanying drawing should not be considered in limiting sense, and should understand the embodiment of the present invention shown in never only limiting to.

Claims

1. an energy storage system, comprising:

Conductive base;

The carbon nano-fiber of multiple vertical arrangements of growing on described base material, described carbon nano-fiber comprises the carbon nano-tube of multiple many walls separately; And

Electrolyte, described electrolyte comprises one or more charge carriers.

2. an energy storage system, comprising:

Conductive base;

The carbon nano-fiber of multiple vertical arrangements of growing on described base material; And

Insert material layer, described insertion material layer is disposed on the carbon nano-fiber of described multiple vertical arrangements and is configured to have every gram of lithium ion memory capacity of inserting between material approximately 1,500 and 4,000mAh.

3. an energy storage system, comprising:

Conductive base;

Insert material layer, described insertion material layer is disposed on the carbon nano-fiber of described multiple vertical arrangements and is configured such that the ion storage capacity of described insertion material under the charge rate of 1C and 3C is approximately identical.

4. the system as described in claim 1,2 or 3, wherein said carbon nano-tube is arranged such that ion insertion can occur through the sidewall of described carbon nano-fiber the wall of described nanotube.

5. the system as described in claim 1-3 or 4, wherein said carbon nano-fiber comprises cone-in-cone structure.

6. the system as described in claim 1-4 or 5, is also included in the insertion material layer on described carbon nano-fiber, and described insertion material layer has the feathery structure by described cone-in-cone structure generation.

7. the system as described in claim 1-5 or 6, is also included in the insertion material layer on described carbon nano-fiber, and described insertion material layer comprises the feathery structure of the silicon that is filled with the middle phase of surperficial electrolyte.

8. the system as described in claim 1-6 or 7, is also included in the insertion material layer on described carbon nano-fiber, and described insertion material has the nominal thickness between 0.1 and 25 μ m.

9. the system as described in claim 1-7 or 8, wherein said insertion material layer comprises nanofiber/insertion material composite, and some in described nanofiber/insertion material composite comprise that some in a kind of nanofiber and described nanofiber/insertion material composite comprise two kinds of nanofibers.

10. the system as described in claim 1-8 or 9, is also included in the insertion material layer on described carbon nano-fiber, and described silicon has the nominal thickness between approximately 1.0 μ m and 40 μ m.

11. systems as described in claim 1-9 or 10, the length of wherein said carbon nano-fiber is between 3.0 and 200 μ m.

12. systems as described in claim 1-10 or 11, wherein every gram of described lithium ion memory capacity of inserting between material approximately 1,500 and 4,000mAh obtains under the charge rate between 1C and 10C.

13. systems as described in claim 1-11 or 12, wherein every gram of described lithium ion memory capacity of inserting between material approximately 750 and 4,000mAh obtains under the charge rate between 1C and 10C.

14. systems as described in claim 1-12 or 13, wherein every gram of described lithium ion memory capacity of inserting between material approximately 1,500 and 4,000mAh obtains after 100 charge-discharge cycles.

15. systems as described in claim 1-13 or 14, wherein every gram insert described lithium ion memory capacity between material approximately 1,500 and 4,000mAh under the charge rate between C/2 and 10C between every gram of silicon 2,000 and 4,000mAh.

16. systems as described in claim 1-14 or 15, wherein said insertion material comprises silicon.

17. systems as described in claim 1-15 or 16, wherein in the time that described charge rate is increased to 10C from 3C described in ion storage capacity increase.

18. systems as described in claim 1-16 or 17, wherein said ion storage capacity changes and is less than 25% between 0.3C and the charge rate of 3C.

Produce the method for energy storing device for 19. 1 kinds, described method comprises:

Base material is provided;

The carbon nano-fiber of growing on described base material, described carbon nano-fiber has cone-in-cone structure; And

Insertion material is applied to described carbon nano-fiber, and described insertion material is arranged to the insertion of charge carrier.

20. methods as claimed in claim 19, the insertion material production feathery structure that wherein applied.

21. methods as described in claim 19 or 20, also comprise the nucleation site of the described carbon nano-fiber that is provided for growing, the density in described nucleation site be selected as obtaining 75 and 400nm between the average arest neighbors spacing distance of described carbon nano-fiber.

22. methods as described in claim 19,20 or 21, also comprise and regulate described energy storing device to make described energy storing device have under the charge rate of 1C at least the lithium ion memory capacity between every gram of silicon approximately 750 and 4,000mAh.

23. methods as described in claim 19-21 or 22, also comprise and regulate described energy storing device to make described insertion material and electrolyte interact to form the middle phase of surperficial electrolyte, in the middle of described surperficial electrolyte, between the feathery structure of described insertion material, forms.

24. systems as described in claim 19-22 or 23, wherein said insertion material comprises silicon.