JP5446699B2 - Silicon nanosheet, method for producing the same, and lithium ion secondary battery - Google Patents

Description

  The present invention relates to a silicon nanosheet, a method for producing the same, and a lithium ion secondary battery.

In recent years, nanosilicon materials that are expected to be used in fields such as semiconductors, electrical and electronic fields have been developed. For example, in Patent Document 1, a layered polysilane powder represented by the composition formula Si ₆ H ₆ is produced by reacting calcium disilicide with a concentrated hydrochloric acid aqueous solution cooled to −30 ° C. or lower, and the obtained layered polysilane powder and terminal are obtained. A silicon nanosheet is produced by reacting an organic compound having a carbon-carbon unsaturated bond with an organic group using a hydrosilylation reaction catalyst and replacing the hydrogen atom of the layered polysilane with an organic group. The silicon nanosheet produced in this way is in the shape of a flake and has a large shape anisotropy, and therefore is expected to be used in the fields of semiconductors, electrical / electronics, and the like. For example, use for an electrode of a lithium ion secondary battery is conceivable. In that case, a larger interlayer distance is preferable because more lithium ions can be taken in.

JP 2008-69301 A

  However, in the layered polysilane powder, since hydrogen atoms bonded to silicon atoms are easily substituted with hydroxyl groups, it is not always easy to produce the target silicon nanosheet.

  The present invention has been made to solve such problems, and a main object of the present invention is to provide a silicon nanosheet having a relatively large interlayer distance and easy to manufacture.

  The silicon nanosheet of the present invention is a silicon nanosheet having a structure in which a plurality of six-membered rings composed of silicon atoms are connected in a basic skeleton, and the silicon atom has a functional group capable of binding to a metal or a metal oxide. A silicon atom having a hydrocarbon group having a silicon atom bonded through an oxygen atom, a silicon atom bonded to a hydrogen atom, and a silicon atom bonded to a hydroxyl group are mixed.

  The lithium ion secondary battery of the present invention uses the above-described silicon nanosheet of the present invention as an electrode.

  The method for producing a silicon nanosheet of the present invention is a method for producing a silicon nanosheet having a basic skeleton having a structure in which a plurality of six-membered rings composed of silicon atoms are connected, and (a) putting calcium disilicide into a concentrated hydrochloric acid aqueous solution. A step of synthesizing siloxene by stirring at 0 to 80 ° C., and (b) reacting the siloxene with a silane compound having a hydrocarbon group having a functional group capable of binding to a metal or a metal oxide and an alkoxy group. The process of obtaining a silicon nanosheet by this.

  Since the silicon nanosheet of the present invention is flaky and exhibits large shape anisotropy, it can be applied to various fields such as semiconductors, electrical / electronics and the like. Further, since silicon atoms constituting a six-membered ring include those in which a silicon atom having a hydrocarbon group having a functional group capable of bonding to a metal or metal oxide is bonded via an oxygen atom, This keeps the interlayer distance relatively wide. When this property is used as an electrode of a lithium ion secondary battery, a large amount of lithium ions can be taken up. Furthermore, since the above-described hydrocarbon group has a functional group that can be bonded to a metal or a metal oxide, it can be bonded to a metal or a metal oxide via this functional group. For this reason, it can couple | bond with the board | substrate with the surface layer which consists of such a metal or a metal oxide, and can cover a part or all of the surface of this board | substrate, and the possibility of application to various technical fields spreads further. Furthermore, the silicon nanosheet of the present invention can be handled in the air. The cause of the deterioration of such silicon nanosheets is considered to be due to the reaction of moisture and oxygen in the atmosphere with silicon atoms constituting the six-membered ring. In this regard, since the silicon nanosheet of the present invention includes a silicon atom constituting the six-membered ring, in which the silicon atom having the above-described hydrocarbon group is bonded via an oxygen atom. Prevents moisture and oxygen contained in the atmosphere from approaching the silicon atoms constituting the six-membered ring due to steric hindrance such as groups. As a result, it is considered that the deterioration of the silicon nanosheet is suppressed. The silicon nanosheet of the present invention may have a multilayer structure or a structure separated into a single layer (interlayer distance is infinite).

The method for producing the silicon nanosheet of the present invention is suitable for producing the above-described silicon nanosheet of the present invention. In Patent Document 1, layered polysilane (Si ₆ H ₆ ) is used as a raw material before replacing hydrogen atoms bonded to silicon atoms constituting a six-membered ring with organic groups. However, layered polysilane deteriorates immediately in the atmosphere. It was difficult to handle because it was easy to handle and it was necessary to use a very low temperature during synthesis. In the method for producing a silicon nanosheet of the present invention, siloxane (Si ₆ H _6-x (OH) _x : 0 <x ≦ 6) is used as such a raw material instead of layered polysilane. Siloxene is easy to handle because it does not deteriorate immediately in the atmosphere and does not need to be cryogenic at the time of synthesis, so silicon nanosheets can be easily produced.

The structural formula of siloxene is represented by a six-membered ring structure composed of silicon atoms (Si ₆ H _6-x (OH) _x ), but actually a structure in which a plurality of such six-membered rings are connected. Is the basic skeleton. Each six-membered ring does not necessarily have the same x. For example, x is 0, x is 1, x is 2,..., X is 6 and the like.

It is a schematic diagram of the structure of the silicon nanosheet of this invention. It is a graph which shows the measurement result of XRD diffraction. It is a graph which shows the measurement result of XRD diffraction. It is a graph which shows the measurement result of XRD diffraction. 4 is a schematic diagram of a structure of a powder obtained in Experimental Example 1. FIG. It is a graph of IR spectrum data. It is a graph of Raman spectrum data. It is a graph of ¹³ CNMR spectrum data. It is an AFM image of the boundary of the part which the silicon nanosheet has adhered, and the part which has not adhered. It is a graph which shows the characteristic of the cell which used Experimental example 2 for the electrode. It is a graph of IR spectrum data of layered polysilane. It is a graph of the Raman spectrum data of layered polysilane. It is a TEM image of siloxene.

  The silicon nanosheet of the present invention is a silicon nanosheet having a basic skeleton having a structure in which a plurality of six-membered rings composed of silicon atoms are connected. The silicon atom constituting the six-membered ring includes a silicon atom in which a silicon atom having a hydrocarbon group having a functional group capable of bonding to a metal or metal oxide is bonded through an oxygen atom, or a silicon atom bonded to a hydrogen atom. Silicon atoms bonded to atoms and hydroxyl groups are mixed. Silicon atoms (Si) contained in the silicon nanosheet are tetracoordinate atoms that form sp3 bonds with adjacent Si, and three of the Si bonds forming the basic skeleton are bonded to Si, and the remaining 1 The book is bonded to any one of (1) a hydrogen atom, (2) a hydroxyl group, and (3) an oxygen atom bonded to a silicon atom having a hydrocarbon group having a predetermined functional group. FIG. 1 shows a schematic diagram of the structure of such a silicon nanosheet.

  In the silicon nanosheet of the present invention, a silicon atom in which a silicon atom having a hydrocarbon group having a functional group capable of bonding to a metal or a metal oxide is bonded to an oxygen atom is present in a silicon atom constituting a six-membered ring. . Here, examples of the functional group capable of binding to a metal include a mercapto group, a disulfide group, a thioisocyanide group, a selenolate group, a tellurolate group, and a dialkyl selenide group, and a mercapto group is preferable. In this case, the metal is preferably at least one selected from the group consisting of gold, silver, copper, aluminum, platinum and palladium. In addition, examples of the functional group that can be bonded to the metal oxide include a carboxylic acid group, a phosphonic acid group, and a phosphoric ester group, and a carboxylic acid group is preferable. In this case, the metal oxide is selected from the group consisting of titanium oxide, tin oxide, indium oxide, ruthenium oxide, zirconium oxide, titanium oxide, aluminum oxide, tantalum oxide, indium tin oxide (ITO), germanium oxide, and silicon oxide. One or more selected from the above are preferred. Examples of the hydrocarbon group include a chain hydrocarbon group having 1 to 20 carbon atoms and a cyclic hydrocarbon group having 1 to 20 carbon atoms. Examples of chain hydrocarbon groups include methyl, ethyl, propyl, butyl, pentyl, heptyl, octyl, nonyl, decanyl, and other saturated hydrocarbon groups, propenyl groups, butenyl groups, and pentenyl groups. And unsaturated hydrocarbon groups such as alkenyl groups such as a group, heptenyl group, octenyl group, nonenyl group and decenyl group. These may be linear or may have a branch. Examples of the cyclic hydrocarbon group include a saturated hydrocarbon group such as a cyclopropyl group, a cyclopentyl group, and a cyclohexyl group, an unsaturated hydrocarbon group such as a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group, and a phenyl group and a naphthyl group. And aromatic hydrocarbon groups. Among these, a chain hydrocarbon group having 1 to 20 carbon atoms is preferable. Such a hydrocarbon group has the above-described functional group, and the bonding position of the functional group is preferably a terminal. Furthermore, the silicon atom having the hydrocarbon group described above has the remaining two bonds in addition to the bond that is bonded to the hydrocarbon group. The remaining two bonds may be bonded to, for example, a hydrogen atom, a hydroxyl group, or an alkoxy group, or may be bonded to another silicon atom constituting a six-membered ring via an oxygen atom. . Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, an s-butoxy group, and a t-butoxy group.

The silicon nanosheet of the present invention has the following physicochemical properties. That is, in the IR spectrum, Si-OR (R is a hydrocarbon group) (around 1100 cm ^-1) wavenumber derived from, Si-H from the wavenumber (2100 cm around ^-1), wave number from a hydrocarbon (3000 cm ^{- 1} )). In addition, when the silicon nanosheet of this invention has Si-OH partially, a peak is seen also in 900 cm < ^-1 > vicinity (wave number derived from Si-OH). Further, in the Raman spectrum, the wave number six-membered ring composed of a backbone i.e. a silicon atom is derived from a plurality continuous structure (around 370 cm ^-1, 490 cm around ^-1, around 630 cm ^-1), wave number from hydrocarbon It has a peak (around 2800 cm ⁻¹ ). Furthermore, in thermogravimetric analysis (TG), in addition to weight loss due to moisture, weight loss at temperatures higher than 100 ° C., that is, weight loss due to hydrocarbon groups is observed. In a TEM (transmission electron microscope) diffractogram, a diffraction image showing that the Si atom is a hexagonal crystal is seen.

  The thickness of the silicon nanosheet of the present invention is not particularly limited, but is 10 nm or less. Moreover, the lamination period when the silicon nanosheet of the present invention has a multilayer structure is larger than the lamination period of siloxane, preferably 0.65 nm or more, more preferably 0.7 nm or more. With such an interlayer distance, lithium ions can be sufficiently taken in when used as an electrode of a lithium ion secondary battery.

  The method for producing a silicon nanosheet of the present invention is a method for producing a silicon nanosheet having a basic skeleton having a structure in which a plurality of six-membered rings composed of silicon atoms are connected, and (a) putting calcium disilicide into a concentrated hydrochloric acid aqueous solution. A step of synthesizing siloxene by stirring at 0 to 80 ° C., and (b) reacting the siloxene with a silane compound having a hydrocarbon group having a functional group capable of binding to a metal or a metal oxide and an alkoxy group. The process of obtaining a silicon nanosheet by this.

In the step (a), the molar ratio (HCl / CaS ₂ ) between hydrogen chloride and calcium disilicide is preferably 1 to 1000, and more preferably 10 to 100. The reaction time is preferably several hours to several days. This reaction is preferably performed in a dark room because the Si—Si bond may be oxidized to light to change into a Si—O—Si bond. After completion of the reaction, the precipitate can be filtered and fractionated to obtain syloxene.

  In the step (b), siloxene is reacted with a silane compound having a hydrocarbon group having a functional group capable of binding to a metal or metal oxide and an alkoxy group. Here, examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, an s-butoxy group, and a t-butoxy group. In this reaction, it is considered that the alkoxy group of the silane compound is hydrolyzed to become a hydroxyl group, which is bonded to the hydroxyl group of siloxene by a dehydration condensation reaction. Here, in the step (b), the siloxene and the silane compound may be reacted by heating the siloxene and the silane compound. The heating temperature at this time is not particularly limited, but is preferably 100 ° C. or higher and lower than 150 ° C. When the temperature is lower than 100 ° C., the reaction between siloxane and the silane compound becomes insufficient, and when the reaction product is dispersed in the solvent, the modified organic substance may be detached and the layer may return to the original state (becomes only siloxane). . Further, at 150 ° C. or higher, the hydrocarbon group may be thermally decomposed, the silicon atom forming the six-membered ring may be oxidized, or the six-membered ring may be collapsed. Such a heating step is preferably performed in an autoclave. In addition, the hydrocarbon group having a functional group is as described above.

[Experimental Example 1]
1 g of calcium disilicide (CaSi ₂ ) powder was mixed at a ratio of 100 mL of concentrated hydrochloric acid aqueous solution (concentration 10 N) and stirred at room temperature for 3 days to obtain a yellow crude product (see the following formula (1)). . In order to remove calcium chloride from the obtained crude product, the crude product was washed with concentrated aqueous hydrochloric acid. Thereafter, it was further washed with acetone and vacuum-dried. Siloxene (Si ₆ H _6-x (OH) _x : 0 <x ≦ 6) was thus obtained. For the synthesis of siloxene, see International Publication 2006/009073.
3CaSi ₂ + 6HCl + xH ₂ O → Si ₆ H _6-x (OH) _x + 3CaCl ₂ + xH ₂ … (1)

  0.02 g of the siloxene powder thus obtained and 100 μL of mercaptopropyltrimethoxysilane (MPTMS) placed in a Teflon cylindrical container (Teflon is a registered trademark, the same shall apply hereinafter) are placed in an autoclave and allowed to stand at 100 ° C. for 24 hours. Thereafter, the powder was taken out in an inert gas atmosphere.

[Experiment 2]
0.02 g of siloxene powder and 100 μL of MPTMS in a Teflon cylindrical container were placed in an autoclave and allowed to stand at 150 ° C. for 24 hours, after which the powder was taken out in an inert gas atmosphere. Siloxene powder was synthesized in the same manner as in Experimental Example 1.

[Experiment 3]
0.02 g of siloxene powder was mixed with a solution consisting of 30 μL of MPTMS and 10 mL of chloroform and stirred at room temperature for 24 hours, after which chloroform was removed by an evaporator to obtain a powder. Siloxene powder was synthesized in the same manner as in Experimental Example 1.

[XRD diffraction]
The XRD diffractions of the powders obtained in Experimental Examples 1 to 3 and the siloxene obtained in Experimental Example 1 were compared. RINT-TTR manufactured by Rigaku Corporation was used for XRD diffraction. The measurement conditions were CuKα as a radiation source, voltage 50 kV, current 300 mA, DS 0.5, SS 0.5, and RS 0.15. The result is shown in FIG. The peak attributed to the stacking period is 14.5 ° (stacking period 0.61 nm) for siloxane, 12.1 ° (stacking period 0.73 nm) in Experimental Example 1, and 10.8 ° (stacking period 0) in Experimental Example 2. .82 nm) and 8.2 in Example 3 (lamination cycle 1.08 nm) and 14.5 ° (lamination cycle 0.61 nm). That is, it turned out that the lamination period of the powder obtained in Experimental Examples 1 to 3 is wider than the lamination period of siloxane. Here, the lamination period corresponds to the distance between the center lines of two adjacent layers, and corresponds to the sum of the interlayer distance and the layer thickness. In Experimental Example 2, a broad peak having a high intensity from 20 ° to 30 ° was detected in addition to the peak attributed to the 10.8 ° stacking period. This suggests that the layer structure of siloxene was broken and silica was by-produced. From this, it was judged that Experimental Examples 1 and 3 were preferable to Experimental Example 2.

  Next, the powders obtained in Experimental Examples 1 and 3 were filtered and washed with chloroform, dried, and similarly subjected to XRD diffraction. The results are shown in FIGS. In the powder after washing in Experimental Example 1, the peak position did not change before and after washing, as is apparent from FIG. That is, the interlayer distance was maintained before and after cleaning. On the other hand, in the powder after washing of Experimental Example 3, as is clear from FIG. 4, the 8.2 ° peak before washing almost disappeared, and the peak at the same position as siloxane was left. From this result, in Experimental Example 1, the silanol group of siloxene and the silanol group of MPTMS (generated from the alkoxyl group by hydrolysis) were combined by a dehydration condensation reaction in the heating step, and thus MPTMS was retained without being lost even by washing with chloroform. It is considered. Therefore, the structure of the powder obtained in Experimental Example 1 is schematically shown in FIG. In addition, it is thought that the methoxy group of MPTMS is hydrolyzed into a hydroxyl group before bonding with the silanol group of siloxene. On the other hand, in Experimental Example 3, since the above-described dehydration condensation reaction did not occur and MPTMS was simply intruded between the layers of siloxane, it is considered that MPTMS was lost by washing with chloroform. From the above, it was confirmed that the powder obtained in Experimental Example 1 was the product of the present invention.

[Thermogravimetric change (TG)]
The powder obtained in Experimental Example 1 was measured for thermogravimetric change (TG). As a measuring device, a thermogravimetric analyzer Thermo plus TG8120 manufactured by RIGAKU was used. Further, a Pt pan was used, N ₂ was flowed at 0.5 L / min, and the rate of temperature increase was 2 ° C./min. . As a result, a weight reduction of about 1 wt% was observed by 100 ° C., and a weight reduction of about 6 wt% was observed by 100 to 350 ° C. It is considered that the former is due to moisture and the latter is due to mercaptopropyl.

[IR spectrum]
The IR spectrum of the powder obtained in Experimental Example 1 was measured. The measuring apparatus used was a Magna 760 type Fourier transform infrared spectrometer and a Nic-Plan type infrared microscope manufactured by Nicorey. The wave number resolution was 4 cm ⁻¹ , the number of integrations was 50 times, and the transmission method (a method of placing a sample on a diamond plate for measurement) was employed. The obtained IR spectrum data is shown in FIG. As shown in FIG. 6, the detected peak due to Si-OH or Si-OR around 1100 cm ^-1, is detected peak derived from Si-H in the vicinity of 2100 cm ^-1, the alkyl group in the vicinity of 3000 cm ^-1 A derived peak was detected. FIG. 6 also shows siloxane data.

[Raman spectrum]
The Raman spectrum of the powder obtained in Experimental Example 1 was measured. The measuring device used was an NRS-3300 laser Raman spectrometer manufactured by JASCO. The excitation wavelength was 532 nm, the objective lens was 20 times, the exposure time was 30 seconds, the laser power was 2.2 mW, and measurement was performed in a quartz cell (inert gas atmosphere). The obtained Raman spectrum data is shown in FIG. As shown in FIG. 7, 370 cm around ^-1, 490 cm around ^-1, 630 cm around ^-1, 730 cm around ^-1, six-membered ring composed of a basic skeleton namely silicon atoms in the vicinity of 2100 cm ^-1 is continuous multiple structures ( As described later, a peak derived from vibration of the Si main chain) was detected, and a peak derived from an alkyl group was detected in the vicinity of 2800 cm ⁻¹ . In the Raman spectrum, Si—OH appears near 3600 cm ⁻¹ and O—Si—O appears near 1100 to 1000 cm ⁻¹ . However, the peak is not detected in this Raman spectrum. The reason is presumed that the sensitivity to Si—O in Raman is weaker than that in IR. Note that FIG. 7 also shows siloxane data.

[ ¹³ CNMR spectrum]
The powder obtained in Experimental Example 1 was measured for ¹³ CNMR spectrum. The measuring apparatus used was an AVANCE 400 nuclear magnetic resonance apparatus manufactured by Bruker. The probe was 7 mm, the rotation speed was 4 kHz, the number of integrations was 9000 times, the pulse repetition was 5 seconds, and the measurement frequency was 100.6 MHz. The obtained ¹³ C NMR spectrum data is shown in FIG. As shown in FIG. 8, peaks derived from the three carbons of mercaptopropyl were detected.

[Thickness of silicon nanosheet]
0.05 g of the powder obtained in Experimental Example 1 was put in 2 mL of dichloromethane and dispersed by applying ultrasonic waves for 10 minutes. The lower 2/3 of the substrate prepared by sputtering iridium on the silicon wafer was dipped in the dispersion solution, gently lifted, washed with running water with ion-exchanged water, and allowed to stand in the atmosphere for drying. In the dried silicon wafer, the boundary between the part to which the dispersion solution was attached and the part to which the dispersion solution was not attached was observed with an atomic force microscope (AFM). The result is shown in FIG. From this result, it was found that the step difference between the portion where the dispersion solution was adhered and the portion where the dispersion solution was not adhered was about 0.7 nm. This is estimated to correspond to the thickness of one silicon nanosheet in which an organic group derived from MPTMS is modified on a basic skeleton in which a plurality of six-membered rings composed of silicon atoms are connected.

[Charge / discharge capacity]
The electrode was produced as follows. First, MPTMS-modified siloxene prepared in Experimental Example 2, Lion ECP (carbon), and Daikin F-104 (tetrafluoroethylene resin) were kneaded at 14: 5: 1 (weight ratio). The kneading was performed using a mortar in a dew point-90 ° C. inert gas atmosphere. Next, 10 mg of the kneaded body gathered in a film shape was taken and pressed flat with a mortar into a stainless steel wire mesh φ0.12 mm × 吋 50 made by Iseya Wire Mesh Industry cut into φ15 mm, and was vacuumed using a high-frequency induction heating furnace The electrode was prepared by drying at 110 ° C. for 2 hours.

The battery was manufactured as follows using a pressure cell. That is, the electrode produced as described above was used as the working electrode. As the counter electrode, a 0.4 mm thick metal lithium plate made by Honjo Metal cut out to φ18 mm was used. As the electrolytic solution, an electrolytic solution for Li secondary battery 1M LiPF ₆ in EC: DEC = 3/7 (volume ratio) manufactured by Toyama Pharmaceutical Co., Ltd. was used. E25MMS manufactured by Tonen Chemical was used as the separator. Then, a cell was assembled from these in a dew point-90 ° C. inert gas atmosphere.

  The capacity of the battery was measured as follows. That is, the pressure type cell assembled as described above is set in a battery charging / discharging device HJR-1010SM8 manufactured by Hokuto Denko, and charging / discharging is repeated 10 cycles in the range of 0.2-3V by applying 0.7 mA. The charge / discharge capacity of was measured. The measurement results are shown in FIG. From FIG. 10, it was found that the capacity tended to decrease as the number of cycles increased, but gradually became stable and exhibited a capacity of about 120 mAh / g.

[Others]
The IR spectrum of layered polysilane (Si ₆ H ₆ ), which is a raw material of Patent Document 1, was also measured. The IR spectrum data is shown in FIG. FIG. 11 also shows IR spectrum data of syloxene. Both the IR spectra of both, the peak around 2100 cm ^-1 derived from Si-H stretch was compared by focusing on the peak of 1100 cm ^-1 derived from Si-OH stretching, peak derived from Si-H stretching is Both were about the same strength. On the other hand, the peak derived from Si-OH stretching was very strong in siloxene, but only weak in layered polysilane. From this, it was confirmed that siloxane has both Si-H and Si-OH. In addition, it is considered that the reason why the peak derived from the Si—OH stretching was detected in the layered polysilane was generated due to the influence of moisture when measured in the atmosphere.

FIG. 12 is a Raman spectrum (actual measurement) of the layered polysilane. The peak derived from Si—H of the Raman spectrum was identified by performing simulation (model structure is Si ₂₄ H ₃₆ ) using Hartley-Fock / 6-31G (d) on the Raman spectrum of the layered polysilane. As a result, the vibration peak Si backbone 370,490,630cm ^-1, 730cm ^-1 is swinging vibration of Si-H adjacent peaks of 840 cm ^-1 is H-Si-H bending, 2100 cm ^- It was inferred that ¹ was Si—H stretching.

  It was confirmed by TEM that siloxene retained a basic skeleton composed of a six-membered ring of silicon atoms. Specifically, as shown in FIG. 13, when siloxane was observed with TEM, a periodic structure of Si (basic skeleton was a six-membered ring of silicon atoms) was confirmed by a diffractogram.

  In addition, this invention is not limited to the Example mentioned above at all, and as long as it belongs to the technical scope of this invention, it cannot be overemphasized that it can implement with a various aspect.

Claims (9)

A silicon nanosheet having a basic skeleton with a structure in which a plurality of six-membered rings composed of silicon atoms are connected,
The silicon atom includes a silicon atom in which a silicon atom having a hydrocarbon group having a functional group capable of bonding to a metal or a metal oxide is bonded through an oxygen atom, a silicon atom bonded to a hydrogen atom, and a silicon bonded to a hydroxyl group. Atoms are mixed,
Silicon nanosheet. The functional group is a mercapto group or a carboxylic acid group.
The silicon nanosheet according to claim 1. The hydrocarbon group is a chain hydrocarbon group having 1 to 20 carbon atoms,
The silicon nanosheet according to claim 1 or 2. The silicon nanosheet according to any one of claims 1 to 3, which has the following physicochemical properties.
IR spectrum: It has peaks in wave numbers derived from Si-OR (R is a hydrocarbon group), wave numbers derived from Si-H, and wave numbers derived from hydrocarbons.
Raman spectrum: It has a peak in the wave number derived from the basic skeleton and the wave number derived from a hydrocarbon.
Thermogravimetric analysis: In addition to weight loss due to moisture, weight loss at temperatures higher than 100 ° C. is observed.
TEM diffractogram: A diffraction image showing that the Si atom is hexagonal is observed.   The lithium ion secondary battery which used the silicon nanosheet of any one of Claims 1-4 for the electrode. A method for producing a silicon nanosheet having a basic skeleton with a structure in which a plurality of six-membered rings composed of silicon atoms are connected,
(A) synthesizing siloxene by placing calcium disilicide in concentrated aqueous hydrochloric acid and stirring at 0 to 80 ° C .;
(B) obtaining a silicon nanosheet by reacting the siloxane with a silane compound having a hydrocarbon group having a functional group capable of binding to a metal or metal oxide and an alkoxy group;
Of silicon nanosheets containing In the step (b), the siloxene and the silane compound are reacted by heating the siloxene and the silane compound.
The manufacturing method of the silicon nanosheet of Claim 6. The functional group is a mercapto group or a carboxylic acid group.
The manufacturing method of the silicon nanosheet of Claim 6 or 7. The hydrocarbon group is a chain hydrocarbon group having 1 to 20 carbon atoms,
The manufacturing method of the silicon nanosheet of any one of Claims 6-8.