CN104748690A - Raman spectrum method for measuring the thickness of non-crystal solid electrolyte interface film - Google Patents

Abstract

The invention relates to a method for measuring the thickness of a non-crystal solid electrolyte interface (SEI) film. Specifically, the invention provides a method for measuring the thickness of an SEI film on the surface of a substrate by a laser Raman spectroscopy. According to the method, the Raman spectrum is measured by measurement laser, an SEI film is burnt by ablation laser, and the thickness H of the SEI film is calculated according to the complete ablation time Tc and the ablation rate V deduced from the obtained laser Raman.

Description

Measure the Raman optical spectrum method of the thickness of Amorphous solids electrolyte interface film

Technical field

The present invention relates to a kind of method measuring the thickness of Amorphous solids electrolyte interface (SEI) film.Particularly, the invention provides a kind of method utilizing laser Raman spectrometer to measure SEI film thickness on matrix surface.

Background technology

SEI film is electrode material and the reaction product of electrolytic solution in battery charge and discharge process, and its formation has vital impact to the performance of electrode material.On the one hand, the formation of SEI film makes first charge-discharge irreversible capacity increase, and reduces the efficiency for charge-discharge of electrode material; On the other hand, it can stop organic electrolyte intercalation electrode inner, contributes to the mechanical stability of maintenance electrode, thus substantially increases cycle performance and the serviceable life of battery.Need in the industry to characterize to the SEI film of lithium ion battery the performance improving battery.Measure a kind of effective ways that SEI film thickness is assessment SEI film.

Generally speaking, the thickness of SEI film, lower than 40nM, due to too thin, its thickness of Measurement accuracy very difficult.Generally adopt atomic force microscope (Atomic Force Microscope, AFM) or X-ray photoelectron spectroscopic analysis (X-Ray Photoelectron Spectrometer, XPS) device to measure film thickness at present in this area.The most advanced and sophisticated resolving power of AFM device can detect film thickness (such as, see, Electrochemistry Communications7 (2005) 107-112) in atomic level.XPS device carrys out etching-film by argon ion sputtering, thus obtains the information (such as, see, CARBON52 (2013) 388-397) of the film vertical depth with etching period.But all there is intrinsic problem in these two kinds of methods.Such as, if film is multilayer, the resolving power at AFM tip is inevitable fuzzy; And the etching energy of XPS is too strong so that can destroy SEI film, and also film thickness can be changed under argon ion sputtering.In addition, AFM can not measure the film thickness on the thick surface of the micron particles used in commercial battery well, and XPS etching typically has a diameter from grade, therefore can not measure micron-sized film thickness.

Because SEI film has very important impact to battery performance, in the urgent need to the method for energy Accurate Determining SEI film thickness in this area, thus improve battery performance by improving SEI film.

Summary of the invention

The present invention proposes a kind of new method being measured SEI film thickness by laser Raman spectrometer, the method can measure nano level SEI film thickness exactly.

That is, the invention provides following content:

1. use laser Raman spectrometer to measure a method for the thickness of Amorphous solids electrolyte interface (SEI) film of matrix surface, it comprises:

I. starting described SEI film to be exposed to the different time point place of at least two of melting laser, the Raman spectrum measuring laser measurement SEI film described in this time point place is used respectively;

Use the spectral line of the Raman spectrum of described measurement laser determination when ii. not forming SEI film according to the Raman spectrum obtained in i and the described matrix that measures in advance, melt laser described in deriving and described SEI film is melted required time Tc completely; And

Iii. according to time Tc and film ablation factor V, the thickness H of described SEI film is calculated, wherein H=V × Tc.

2. the method for 1, wherein, described measurement and the power bracket melting laser are 0.1-10mW.

3. the method any one of 1 to 2, wherein, described measurement and the scope melting the spot diameter of laser on film are 0.1-3.0 micron.

4. the method any one of 1 to 3, wherein, melts laser described in the energy density of described measurement laser is less than.

5. the method for 4, wherein, described measurement laser described some radius is the some radius of described measurement laser on film.

6. the method for 4, wherein, melts laser described some radius melts the some radius of laser on film described in being.

7. the method any one of 1 to 6, wherein, described measurement and melt laser and all derive from He-Ne laser instrument.

8. the method any one of 1 to 7, wherein, described use is measured laser measurement and is comprised described matrix or described SEI film to be exposed to and measure a period of time that laser reaches 10 seconds to 120 seconds.

9. the method any one of 1 to 8, wherein, one of described at least two different time points are that accumulative to be exposed to the time of melting laser be the time point of 0.

10. the method any one of 1 to 9, wherein, described at least two different time points comprise at least two time points before SEI film melts completely.

Method any one of 11. 1 to 10, wherein, uses and measures the Raman spectrum that laser measures described SEI film under the same conditions.

Method any one of 12. 1 to 11, wherein, the described Raman line of measurement comprises the Raman migration in certain limit, and wherein, the high-energy point of this scope is 1700cm ^-1to 1650cm ^-1, low-yield point is 1250cm ^-1to 1200cm ^-1.

The method of 13. 12, wherein, the scope of described Raman migration is selected from lower group: 1650cm ^-1to 1250cm ^-1, 1660cm ^-1to 1240cm ^-1, 1670cm ^-1to 1230cm ^-1, 1680cm ^-1to 1220cm ^-1, 1690cm ^-1to 1210cm ^-1, and 1700cm ^-1to 1200cm ^-1.

Method any one of 14. 1 to 13, wherein, described Raman line comprises G peak and D peak.

Method any one of 15. 1 to 14, wherein, all Raman line standardization first will obtained before step I i.

The method of 16. 15, wherein, uses G peak height angle value to carry out described standardization.

Method any one of 17. 1 to 16, wherein in step I i, melt laser described in being derived by m-difference in height figure during drafting and SEI film is melted required time Tc completely, time described, m-difference in height figure is as follows:

A. its transverse axis represents that described SEI film melts the time t of laser described in adding up to be exposed to, and the longitudinal axis represents Δ h=ht-h, here,

Difference in height between the Raman line that on the Raman line that ht measures when representing time t, wave number σ is corresponding and baseline,

H represents on the Raman line when the described matrix measured in advance does not form SEI film, the difference in height between the Raman line that described wave number σ is corresponding and baseline,

Δh=ht-h>0，

Described wave number σ is the wave number corresponding to point in G peak and the peak-to-peak trough of D; And

B. at least two Raman lines obtained from step I, draw the point (t, ht-h) that it is corresponding on m-difference in height figure when described respectively, and these points are fitted to straight line;

C. melt laser described in the time that the intercept of this straight line and transverse axis represents is and SEI film is melted required time Tc completely.

Method any one of 18. 1 to 16, wherein in step I i, melts laser and SEI film is melted required time Tc completely described in deriving as follows:

B. for any two Raman lines obtained from step I, obtain respectively measure the time point of this Raman line add up to be exposed to described in melt time t and the Δ h=ht-h now of laser, here,

Difference in height between the Raman line that on the Raman line that ht measures when representing time t, wave number σ is corresponding and baseline,

H represents on the Raman line when the described matrix measured in advance does not form SEI film, the difference in height between the Raman line that described wave number σ is corresponding and baseline,

Δh=ht-h>0，

Described wave number σ is the wave number corresponding to point in G peak and the peak-to-peak trough of D; And

B. at least two groups obtained (t, Δ h) are carried out linear fit as the solution of equation y=ax+b to this equation, obtain a and b;

C. in the equation y=ax+b tried to achieve, make y=0, obtain x, be described laser and SEI film is melted required time Tc completely.

Method any one of 19. 1 to 18, wherein, derive described ablation factor V as follows:

$V=\frac{\mathrm{E\ρ}\left(775K\right)}{\frac{p}{{\mathrm{\πr}}^2}\×a}$

Here, E ρ represents the energy density of material with carbon element, melt the power of laser described in p represents, melt the some radius of laser on film described in r represents, a is constant=6.56 × 10 ^-11.

The method of 20. 19, wherein, absolute temperature is 775K, and gas law constant is 8.314J mol ^-1k ^-1, average carbon density is 2 × 10 ^-12g um ^-3, carbon atom quality is 12g mol ^-1.

Above-outlined is only exemplary, and is not intended to limit by any way.Except above-described exemplary aspect, embodiment and feature, other side, embodiment and feature will by accompanying drawing and hereafter describe in detail illustrate.

Accompanying drawing explanation

From hereafter describing and appended claims, in conjunction with institute's accompanying drawing, preceding feature of the present disclosure and further feature will become more apparent.Should be understood these drawings depict only according to several embodiment of the present disclosure and be not intended to be considered as limiting its scope, will partly, via institute's accompanying drawing use particularly and describe the disclosure in detail.

Fig. 1 shows the spectral line of Raman spectrum using and measure laser determination, wherein draws baseline and at wave number 1475cm ^-1point on place's spectral line and the difference in height of baseline.

Fig. 2 draws exemplary time m-height map, and transverse axis is add up to be exposed to the time of melting laser, and the longitudinal axis is rear twice measurement, and the difference in height poor relative to the height of spectral line measured when not forming SEI film changes, and matching gained straight-line extrapolation is obtained x intercept.

Fig. 3 depicts according to time corresponding to x intercept, the schematic diagram of prediction SEI film thickness.

Fig. 4 depicts laser energy density on carbon film surface and the thick carbon film of 1nm and melts associated diagram between required time completely, and wherein melting the required time completely at 500 DEG C of carbon films is 5 seconds.

Fig. 5 melts laser action in the schematic diagram of SEI film.

Detailed Description Of The Invention

Unless the context clearly indicates otherwise, generally use term of the present invention according to implication common in this area, in case of conflict, will be as the criterion with the present invention.

(I) mensuration of Raman spectrum

In one aspect, the invention provides a kind of method utilizing laser Raman spectrometer to measure the thickness of Amorphous solids electrolyte interface (SEI) film of matrix surface, it comprises:

I. starting described SEI film to be exposed to the different time point place of at least two of melting laser, the Raman spectrum measuring laser measurement SEI film described in this time point place is used respectively;

Use the spectral line of the Raman spectrum measuring laser determination when ii. not forming SEI film according to the Raman spectrum obtained in i and the described matrix that measures in advance, melt laser described in deriving and described SEI film is melted required time Tc completely; And

Iii. according to time Tc and film ablation factor V, the thickness H of described SEI film is calculated, wherein H=V × Tc.

Generally speaking, described matrix is that battery is as dry cell, lithium battery etc.In one embodiment of the invention, described matrix is button cell, is preferably the button cell comprising Carbon anode and lithium metal positive-pole.

In method provided by the invention, the power bracket of described excitation laser is 0.1-10mW, and the scope of the spot diameter on film is 0.1-3.0 micron.Excitation laser is divided into measures laser and melt laser, and wherein preferably, the energy density measuring laser is less than and melts laser, specifically, measures the p/r of laser ²be less than 1.15mW/um ², melt the p/r of laser ²be more than or equal to 1.15mW/um ², this value by calculating gets.Ideally, measure laser and any infringement or ablation are not produced to SEI film.In a specific embodiment, the power of described measurement laser is 1.3mW, and the spot diameter on film is 0.6um, and the power melting laser is 3.7mW, and the spot diameter on film is 0.6um.

In one embodiment, described laser source, in He-Ne laser instrument, more specifically, derives from 633nm He-Ne laser instrument.

In the method for the invention, described use is measured laser measurement and is comprised and described matrix (when SEI film is not formed) and SEI film are exposed to measurement laser reach a period of time, this time period is 10 seconds to 120 seconds, such as but not limited to, 0 second, 10 seconds, 15 seconds, 20 seconds, 25 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds, 110 seconds, 120 seconds etc., as long as measure laser to melt SEI film hardly within this time period.In a specific embodiment, the time of measuring laser measurement is used to be 50 seconds.Preferably, the identical measurement lasing condition of each use measures matrix and SEI film, thus is convenient to compare in follow-up data process and reduces error between measurement.

After formation SEI film, start film to be exposed to melt laser, melt laser and can melt SEI film.Such as, SEI film is exposed at every turn the time of melting laser can be 3 seconds to 30 seconds, include but not limited to, 3 seconds, 4 seconds, 7 seconds, 10 seconds, 15 seconds, 20 seconds, 25 seconds, 30 seconds etc.Such as, melting laser after 10 seconds when being exposed to, being switched to and measuring laser and namely use and measure laser spectral measurement is carried out to film, and then switching back to melt laser and be exposed to and melt laser 15 seconds, then be switched to measurement laser again and carry out film spectral measurement, swap operation like this.

Preferably, described in be exposed to the different time points melting laser and comprise the time point being not yet exposed to and melting laser, it is namely accumulative that to be exposed to the time of melting laser be the starting point of 0.Generally speaking, because the thickness of SEI film is no more than 40nm, be therefore exposed to the time of melting laser not long to prevent the time point measured from being time point after film thickness melts completely.In the method for the invention, be accumulatively exposed to the time of melting laser and be generally no more than 200 seconds.

In a specific embodiment, the time point of described measurement is included in the pre-test Raman spectrum not forming SEI film, measure Raman spectrum with being exposed to melt when Laser Time is 0 after formation SEI film, and measure Raman spectrum when to be exposed to the time of melting laser be 60 seconds.

At the laser Raman spectrometer that utilizes of the present invention in the method measuring SEI film thickness, the described Raman line of measurement comprises the Raman migration in certain limit, and wherein, the high-energy point of this scope is 1700cm ^-1to 1650cm ^-1, low-yield point is 1250cm ^-1to 1200cm ^-1.Described Raman migration circle comprises the scope being selected from lower group: 1650cm ^-1to 1250cm ^-1, 1660cm ^-1to 1240cm ^-1, 1670cm ^-1to 1230cm ^-1, 1680cm ^-1to 1220cm ^-1, 1690cm ^-1to 1210cm ^-1, 1700cm ^-1to 1200cm ^-1.In one embodiment, described Raman migration circle is 1700cm ^-1to 1200cm ^-1.Preferably, G peak and D peak is comprised in described Raman migration circle.

(II) to the data processing of Raman spectrum

Melt time Tc completely

The method of measurement SEI film thickness of the present invention is also included in the data processing after recording Raman spectrum and melts laser to derive SEI film is melted required time Tc completely.In one embodiment, during by drawing, m-difference in height figure derives Tc, and time described, m-difference in height figure draws as follows:

A. its transverse axis represents that described SEI film melts the time t of laser described in adding up to be exposed to, and the longitudinal axis represents Δ h=ht-h, here,

Difference in height between the Raman line that on the Raman line that ht measures when representing time t, wave number σ is corresponding and baseline,

H represents on the Raman line when the described matrix measured in advance does not form SEI film, the difference in height between the Raman line that described wave number σ is corresponding and baseline,

Δh=ht-h>0，

Described wave number σ is the wave number corresponding to point in G peak and the peak-to-peak trough of D; And

B. at least two Raman lines obtained from step I, draw the point (t, ht-h) that it is corresponding on m-difference in height figure when described respectively, and these points are fitted to straight line;

C. melt laser described in the time that the intercept of this straight line and transverse axis represents is and SEI film is melted required time Tc completely.

In alternative at one, derive described excitation laser as follows and SEI film melted required time Tc completely:

A. for any two Raman lines obtained from step I, obtain respectively measure the time point of this Raman line add up to be exposed to described in melt time t and the Δ h=ht-h now of laser, here,

Difference in height between the Raman line that on the Raman line that ht measures when representing time t, wave number σ is corresponding and baseline,

H represents on the Raman line when the described matrix measured in advance does not form SEI film, the difference in height between the Raman line that described wave number σ is corresponding and baseline,

Δh=ht-h>0，

Described wave number σ is the wave number corresponding to point in G peak and the peak-to-peak trough of D; And

B. at least two groups obtained (t, Δ h) are carried out linear fit as the solution of equation y=ax+b to this equation, obtain a and b;

C. in the equation y=ax+b tried to achieve, make y=0, obtain x, be described laser and SEI film is melted required time Tc completely.

Before above-mentioned data processing step, first standardization is carried out to all Raman spectrums recorded.In one embodiment, G peak height angle value is used to carry out standardization to all Raman spectrograms recorded.

As used in this article, " baseline " is by connecting 1700cm on spectral line ^-1and 1200cm ^-1the straight line that two points located are formed.

In the method for the invention, the wave number σ of the some correspondence in described trough is at 1550cm ^-1to 1400cm ^-1raman migration circle in.

In one embodiment, the wave number σ of the some correspondence selected in G peak and the peak-to-peak trough of D is 1475cm ^-1, herein, the spectral line when matrix measured in advance does not form SEI film and the difference in height h of baseline are 1.0, and being 2.7 in the difference in height of the Raman line of first time point determining, is 1.5 in the difference in height of the Raman line of second time point determining.So, first time and second time raman spectroscopy measurement are respectively 1.7 and 0.5 relative to the Δ h of raman spectroscopy measurement when not forming SEI film, time m-difference in height figure on corresponding point be respectively (0,1.7) and (60,0.5).Be linked to be straight line by 2, and by straight-line extrapolation to X-axis, gained intercept reflects Δ h and reaches time Tc required for 0 (film thickness of increase melts completely).In this embodiment, the film thickness increased after intercept and discharge and recharge is melted laser, and to melt required time Tc be completely 85 seconds.

In the method for measurement SEI film thickness of the present invention, along with the increase being exposed to the cumulative time t melting laser, the difference in height on corresponding Raman line should reduce gradually, until equal with difference in height when not forming SEI film, namely Δ h is reduced to 0.Δ h reflects the change of film thickness.Those skilled in the art can easily understand, and when Δ h is reduced to 0, mean that the SEI film of formation is melted laser and completely melts.

Ablation factor V

In order to obtain film thickness, also laser ablation speed V must be derived.In the method for measurement SEI film thickness of the present invention, comprise the film ablation factor V deriving as follows and be exposed to when melting laser further:

$V=\frac{\mathrm{E\ρ}\left(775K\right)}{\frac{p}{{\mathrm{\πr}}^2}\×a}$

Here, E ρ (775K) represents the energy density of material with carbon element 500 DEG C time, and P represents the power melting laser, and r represents and melts the some radius of laser on film, a=6.56 × 10 ^-11; Particularly, wherein

Absolute temperature units is K, and gas law constant is 8.314J mol ^-1k ^-1, average carbon density is 2 × 10 ^-12gum ^-3, carbon atom quality is 12g mol ^-1, therefore E ρ (775K)=1.073 × 10 ^-12j um ^-2nm ^-1.

In above-mentioned formula, the derivation of a value relates to Japanese patent application JPY2009-270130.According to this patented claim, the laser of 240W gives 14J mm to base material ^-2energy density (laser machine: EOSCo.EOSINT Model M250Xtended).Therefore, assuming that melt laser penetrating as 1nm s material with carbon element ^-1, so the energy density corresponding to laser of 3.7mW is 2.15x10 ^-13jum ^-2nm ^-1s ^-1.Correspondingly, the E ρ (775K)=1.073 × 10 of the thick carbon film of 1nm ^-12j um ^-2nm ^-1, both compare and are ablation factor V=0.2nm s ^-1.This value substituted in above-mentioned formula, can obtain a is constant 6.56 × 10 ^-11.

In one embodiment, P is in units of mW, and r is in units of um, and absolute temperature is 775K, and gas law constant is with J mol ^-1k ^-1for unit, average carbon density is with g um ^-3for unit, carbon atom quality is with gmol ^-1for unit, the unit of gained V is nm s ^-1.

In a specific embodiment, melt laser power P=3.7mW, the some radius on film is 0.6um.Under the existence of oxygen in an atmosphere, in absolute temperature=773K coal, gas law constant is 8.314J mol ^-1k ^-1, average carbon density is 2 × 10 ^-12g um ^-3, carbon atom quality is 12g mol ^-1, the material with carbon element energy density E ρ that the 1nm calculated thus is thick is 1.073 × 10 ^-12j um ^-2nm ^-1.Then, ablation factor V=0.2nm s is calculated ^-1, namely melting the thick material with carbon element required time of 1nm is completely 5s (see Fig. 4).

Film thickness H

Film thickness H is calculated as the product of ablation factor V and time Tc.In one embodiment, ablation factor is 0.2nm/s, and it is 85 seconds that the film thickness increased after discharge and recharge melts the required time, and therefore film thickness is 17nm (see Fig. 3).

Embodiment

By following examples, more specific description is carried out to the present invention, but the present invention is not by the restriction of these embodiments.

Embodiment 1: the thickness measuring the SEI film of button cell

The preparation of button cell

Prepare containing commercial graphite alkene (xGnP-Grade H with general slurry mixing-casting-drying-pressing process, XG science, USA), acetylene black (DENKA BLACK, Nippon DenkiKagaku, and binder (AX-9258 Japan), ZEON corporation, Japan) battery lead plate.

Battery lead plate is that the circle of 12mm stamps out with diameter, and inserted in 2032 type button cells with the lithium sheet metal as counter electrode by this circle battery lead plate, electrolyte contains 1M LiPF ₆, EC:DMC:EMC (1:1:1 volume ratio) and 2% volume sub-ethylene carbonate as adjuvant.

Raman spectroscopy measurement before non-discharge and recharge

Battery lead plate is placed in Raman spectrometer (NSR-3300, JASCO, Japan).Using 1.3mW633nm He-Ne laser as measurement laser, with the some radius on film be 0.6um, 50 seconds open-assembly times performed measurement.Obtain 1700cm ^-1to 1200cm ^-1measurement range in Raman spectrum.

The charge and discharge process of button cell and electrode sample

2032 type button cells are inserted (BTS-5V5mA, Newware Technology, China) in electrochemical instrument, start the charge-discharge velocity of 0.5C, and be held in atmospheric environment in room temperature.Circulate 30 times.

In the glove box being full of pure argon, 2032 type button cell partition are come.From tank, carefully pull out battery lead plate, and thoroughly clean 3 times to reduce LiPF by N-N-methyl 2-pyrrolidone N- ₆salt.By the electrode after cleaning in a vacuum chamber in 80 DEG C of dryings 6 hours.

Raman Measurement

Battery lead plate after charge and discharge process is placed in same Raman spectrometer (NSR-3300, JASCO, Japan).Same use 1.3mW633nm He-Ne laser, as measurement laser, performed measurement with 50 seconds open-assembly times.Obtain now 1700cm ^-1to 1200cm ^-1measurement range in Raman spectrum.

Then, using 3.7mW633nm He-Ne laser as melting laser, the some radius on film is 0.6um, after exposing 60 seconds, then is switched to the measurement laser of 1.3mW, measures now at 1700cm ^-1to 1200cm ^-1measurement range in Raman spectrum.

Raman line is analyzed

Use G peak height angle value that 3 Raman lines obtained are carried out standardization.By the local minimum points 1475cm in G peak and D spike paddy ^-1as selected wave number σ, and make 1700cm ^-1to 1200cm ^-1baseline in scope.

As seen from Figure 1, without 1475cm during discharge and recharge ^-1place's Raman line is 1.0 (bottom curves) to the relative height of baseline, after discharge and recharge and before not being exposed to and melting laser, the relative height of Raman line is 2.7 (the top curves), and the relative height being exposed to Raman line when melting laser 60 seconds is 1.5 (intermediate curves).Therefore, twice raman spectroscopy measurement after discharge and recharge is respectively 1.7 and 0.5 relative to the relative height change without raman spectroscopy measurement during discharge and recharge.

Time m-height map

Using film be exposed to melt laser time (second) as transverse axis, m-height map when relative height change (absolute unit) is made as the longitudinal axis, by point (0,1.7) and point (60,0.5) correspond on figure, and be linked to be straight line.As seen from Figure 2, when by this straight-line extrapolation to X-axis time, intercept is 85 seconds.This time is melts time Tc completely, its instruction be exposed to melt laser amount to 85 seconds after the SEI film thickness that increases of battery charging and discharging melted laser and all melt.

The derivation of film ablation factor

Film ablation factor is derived by following equation:

$V=\frac{\mathrm{E\ρ}\left(775K\right)}{\frac{p}{{\mathrm{\πr}}^2}\×a}$

Wherein E ρ (775K)=1.07 × 10 ^-12j um ^-2nm ^-1, melt laser power P=3.7mW, π=3.14, some radius r=0.6um, a=6.56 × 10 ^-11, the ablation factor V=0.2nm/s calculated thus.

Film thickness

Film thickness H is ablation factor V (slope of Fig. 3) and the product melting time Tc completely.As seen from Figure 3, the Y-axis value 17nm corresponding to 85 seconds is film thickness.

Below describe the present invention through the specific embodiment and the embodiment, but it will be understood by those skilled in the art that these are not intended to limit scope of the present invention, scope of the present invention should be determined by claims.

Claims (20)

1. use laser Raman spectrometer to measure a method for the thickness of Amorphous solids electrolyte interface (SEI) film of matrix surface, it comprises:

I. starting described SEI film to be exposed to the different time point place of at least two of melting laser, the Raman spectrum measuring laser measurement SEI film described in this time point place is used respectively;

Use the spectral line of the Raman spectrum of described measurement laser determination when ii. not forming SEI film according to the Raman spectrum obtained in i and the described matrix that measures in advance, melt laser described in deriving and described SEI film is melted required time Tc completely; And

Iii. according to time Tc and film ablation factor V, the thickness H of described SEI film is calculated, wherein H=V × Tc.

2. the process of claim 1 wherein, described measurement and the power bracket melting laser are 0.1-10mW.

3. the method any one of claim 1 to 2, wherein, described measurement and the scope melting the spot diameter of laser on film are 0.1-3.0 micron.

4. the method any one of claims 1 to 3, wherein, melts laser described in the energy density of described measurement laser is less than.

5. the method for claim 4, wherein, described measurement laser described some radius is the some radius of described measurement laser on film.

6. the method for claim 4, wherein, melts laser described some radius melts the some radius of laser on film described in being.

7. the method any one of claim 1 to 6, wherein, described measurement and melt laser and all derive from He-Ne laser instrument.

8. the method any one of claim 1 to 7, wherein, described use is measured laser measurement and is comprised described matrix or described SEI film to be exposed to and measure a period of time that laser reaches 10 seconds to 120 seconds.

9. the method any one of claim 1 to 8, wherein, one of described at least two different time points are that accumulative to be exposed to the time of melting laser be the time point of 0.

10. the method any one of claim 1 to 9, wherein, described at least two different time points comprise at least two time points before SEI film melts completely.

Method any one of 11. claims 1 to 10, wherein, uses and measures the Raman spectrum that laser measures described SEI film under the same conditions.

Method any one of 12. claims 1 to 11, wherein, the described Raman line of measurement comprises the Raman migration in certain limit, and wherein, the high-energy point of this scope is 1700cm ^-1to 1650cm ^-1, low-yield point is 1250cm ^-1to 1200cm ^-1.

The method of 13. claims 12, wherein, the scope of described Raman migration is selected from lower group: 1650cm ^-1to 1250cm ^-1, 1660cm ^-1to 1240cm ^-1, 1670cm ^-1to 1230cm ^-1, 1680cm ^-1to 1220cm ^-1, 1690cm ^-1to 1210cm ^-1, and 1700cm ^-1to 1200cm ^-1.

Method any one of 14. claims 1 to 13, wherein, described Raman line comprises G peak and D peak.

Method any one of 15. claims 1 to 14, wherein, all Raman line standardization first will obtained before step I i.

The method of 16. claims 15, wherein, uses G peak height angle value to carry out described standardization.

Method any one of 17. claims 1 to 16, wherein in step I i, melt laser described in being derived by m-difference in height figure during drafting and SEI film is melted required time Tc completely, time described, m-difference in height figure is as follows:

A. its transverse axis represents that described SEI film melts the time t of laser described in adding up to be exposed to, and the longitudinal axis represents Δ h=ht-h, here,

Difference in height between the Raman line that on the Raman line that ht measures when representing time t, wave number σ is corresponding and baseline,

H represents on the Raman line when the described matrix measured in advance does not form SEI film, the difference in height between the Raman line that described wave number σ is corresponding and baseline,

Δh=ht-h>0，

Described wave number σ is the wave number corresponding to point in G peak and the peak-to-peak trough of D; And

B. at least two Raman lines obtained from step I, draw the point (t, ht-h) that it is corresponding on m-difference in height figure when described respectively, and these points are fitted to straight line;

C. melt laser described in the time that the intercept of this straight line and transverse axis represents is and SEI film is melted required time Tc completely.

Method any one of 18. claims 1 to 16, wherein in step I i, melts laser and SEI film is melted required time Tc completely described in deriving as follows:

A. for any two Raman lines obtained from step I, obtain respectively measure the time point of this Raman line add up to be exposed to described in melt time t and the Δ h=ht-h now of laser, here,

Difference in height between the Raman line that on the Raman line that ht measures when representing time t, wave number σ is corresponding and baseline,

H represents on the Raman line when the described matrix measured in advance does not form SEI film, the difference in height between the Raman line that described wave number σ is corresponding and baseline,

Δh=ht-h>0，

Described wave number σ is the wave number corresponding to point in G peak and the peak-to-peak trough of D; And

B. at least two groups obtained (t, Δ h) are carried out linear fit as the solution of equation y=ax+b to this equation, obtain a and b;

C. in the equation y=ax+b tried to achieve, make y=0, obtain x, be described laser and SEI film is melted required time Tc completely.

Method any one of 19. claims 1 to 18, wherein, derive described ablation factor V as follows:

$V=\frac{\mathrm{E\ρ}\left(775K\right)}{\frac{\mathrm{\ρ}}{{\mathrm{\πr}}^2}\×a}$

Here, E ρ represents the energy density of material with carbon element, melt the power of laser described in p represents, melt the some radius of laser on film described in r represents, a is constant=6.56 × 10 ^-11.

The method of 20. claims 19, wherein, absolute temperature is 775K, and gas law constant is 8.314J mol ^-1k ^-1, average carbon density is 2 × 10 ^-12g um ^-3, carbon atom quality is 12g mol ^-1.