Negative electrode active material production apparatus and negative electrode active material production method

Abstract

To provide a negative electrode active material production apparatus capable of producing a negative electrode active material that can be increased in capacity while maintaining battery characteristics.SOLUTION: Negative electrode active material particles include a porous carbon structure. In the interior of the porous carbon structure, amorphous low valence nano silicon oxide, polycrystalline silicon and an oxide thereof, or both are dispersed as a dispersed substance. The low valence nano silicon oxide includes SiOx in each of the states of x<1.0, and the low valence nano silicon oxide is 50 nm or less on average. A negative electrode active material production apparatus has a structure where the raw material gas of the dispersed substance is supplied to the porous carbon structure held in the interior. When a design pressure is represented as P [MPaG], the internal volume V [m3] of the interior of the apparatus is in the range of PV≤0.004. The negative electrode active material production apparatus has a heating mechanism, and the heating mechanism is capable of heating in the range of 300-1,200°C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a negative electrode active material and a method for manufacturing the same.

Background Art

[0002] In recent years, small electronic devices typified by mobile terminals have become widely popular, and further miniaturization, weight reduction, and longer life are strongly demanded. In response to such market demands, the development of secondary batteries that are particularly small, lightweight, and capable of obtaining a high energy density has been promoted. The application of this secondary battery is not limited to small electronic devices, but is also being studied for large electronic devices typified by automobiles and power storage systems typified by houses.

[0003] Among them, lithium ion secondary batteries are highly expected because they can be easily miniaturized and have a higher capacity, and can obtain a higher energy density than lead batteries and nickel cadmium batteries.

[0004] The above lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution together with a separator, and the negative electrode contains a negative electrode active material involved in charge and discharge reactions.

[0005] As this negative electrode active material, carbon-based active materials are widely used. On the other hand, further improvement in battery capacity is required from recent market demands. In order to improve the battery capacity, the use of silicon as a negative electrode active material has been studied. This is because the theoretical capacity of silicon (4199 mAh / g) is more than 10 times larger than the theoretical capacity of graphite (372 mAh / g), so a significant improvement in battery capacity can be expected. The development of silicon materials as negative electrode active materials has been studied not only for elemental silicon but also for compounds typified by alloys and oxides. In addition, the shape of the active material has been studied from the standard coating type for carbon-based active materials to an integrated type that is directly deposited on the current collector.

[0006] However, when silicon is used as the main raw material for the negative electrode active material, the negative electrode active material expands and contracts during charge and discharge, so it is prone to cracking mainly in the vicinity of the surface layer of the negative electrode active material. In addition, ionic substances are generated inside the active material, making the negative electrode active material prone to cracking. When the surface layer of the negative electrode active material cracks, a new surface is thereby generated, increasing the reaction area of the active material. At this time, the decomposition reaction of the electrolytic solution occurs on the new surface, and a film that is a decomposition product of the electrolytic solution is formed on the new surface, consuming the electrolytic solution. For this reason, the cycle characteristics are likely to deteriorate.

[0007] So far, various studies have been conducted on the negative electrode active material materials and electrode configurations for lithium-ion secondary batteries mainly composed of silicon materials in order to improve the initial battery efficiency and cycle characteristics.

[0008] Specifically, for the purpose of obtaining good cycle characteristics and high safety, silicon and amorphous silicon dioxide are simultaneously deposited using the vapor phase method (see, for example, Patent Document 1). In addition, in order to obtain a high battery capacity and safety, a carbon material (electron conductive material) is provided on the surface layer of the silicon oxide particles (see, for example, Patent Document 2). Furthermore, in order to improve the cycle characteristics and obtain high input / output characteristics, an active material containing silicon and oxygen is produced, and an active material layer with a high oxygen ratio near the current collector is formed (see, for example, Patent Document 3). Also, in order to improve the cycle characteristics, oxygen is contained in the silicon active material, and it is formed so that the average oxygen content is 40 at% or less and the oxygen content increases in a place close to the current collector (see, for example, Patent Document 4).

[0009] In addition, in order to improve the first charge-discharge efficiency, a nano-composite containing Si phase, SiO2, M y O metal oxide is used (see, for example, Patent Document 5). Also, for improving the cycle characteristics, SiO x(0.8 ≦ x ≦ 1.5, particle size range = 1 μm to 50 μm) is mixed with a carbon material and fired at a high temperature (see, for example, Patent Document 6). Further, in order to improve cycle characteristics, the molar ratio of oxygen to silicon in the negative electrode active material is set to 0.1 to 1.2, and the active material is controlled within a range where the difference between the maximum value and the minimum value of the molar ratio near the interface between the active material and the current collector is 0.4 or less (see, for example, Patent Document 7). Further, in order to improve the battery load characteristics, a metal oxide containing lithium is used (see, for example, Patent Document 8). Further, in order to improve cycle characteristics, a hydrophobic layer such as a silane compound is formed on the surface layer of the silicon material (see, for example, Patent Document 9).

[0010] Further, in order to improve cycle characteristics, silicon oxide is used, and conductivity is imparted by forming a graphite film on its surface layer (see, for example, Patent Document 10). In Patent Document 10, regarding the shift value obtained from the Raman spectrum of the graphite film, broad peaks appear at 1330 cm -1 and 1580 cm -1 , and the intensity ratio I 1330 / I 1580 is such that 1.5 < I 1330 / I 1580 < 3. Further, in order to improve high battery capacity and cycle characteristics, particles having a silicon microcrystalline phase dispersed in silicon dioxide are used (see, for example, Patent Document 11). Further, in order to improve overcharge and overdischarge characteristics, a silicon oxide in which the atomic ratio of silicon to oxygen is controlled to 1:y (0 < y < 2) is used (see, for example, Patent Document 12).

[0011] Further, Hitachi Maxell started shipping a rectangular secondary battery for smartphones that adopted a nanosilicon composite in June 2010 in a lithium ion secondary battery using silicon oxide (see, for example, Non-Patent Document 1). The silicon oxide proposed by Hohl is a composite material of Si 0+ ~Si 4+ and has various oxidation states (Non-Patent Document 2). Also, Kapaklis proposed a disproportionation structure that is divided into Si and SiO2 by applying a heat load to silicon oxide (Non-Patent Document 3).

[0012] Miyachi et al. have focused on Si and SiO2 that contribute to charge and discharge among silicon oxides having disproportionated structures (Non-Patent Document 4), and Yamada et al. have proposed the following reaction formula between silicon oxide and Li (Non-Patent Document 5). 2SiO(Si + SiO2) + 6.85Li + + 6.85e - → 1.4Li 3.75 Si + 0.4Li4SiO4+ 0.2SiO2 In the reaction formula, Si and SiO2 constituting the silicon oxide react with Li and are divided into Li silicide, Li silicate, and a part of unreacted SiO2.

[0013] The Li silicate generated here is generally said to be irreversible and a stable substance that does not release Li after once formed. The capacity per mass calculated from this reaction formula has a value close to the experimental value and is recognized as the reaction mechanism of silicon oxide. Kim et al. have identified the irreversible component associated with the charge and discharge of silicon oxide, Li silicate as Li4SiO4, 7 using Li-MAS-NMR and 29 Si-MAS-NMR (Non-Patent Document 6).

[0014] This irreversible capacity is the most problematic aspect of silicon oxide and improvement is required. Therefore, Kim et al. have significantly improved the initial efficiency as a battery using the Li pre-doping method of forming Li silicate in advance and have fabricated a negative electrode that can withstand actual use (Non-Patent Document 7). Also, a method of treating the powder instead of doping the electrode with Li has been proposed and improvement of the irreversible capacity has been realized (Patent Document 13).

[0015] On the other hand, Li metal used for Li doping has extremely large upper and lower limits of price depending on the market situation and has many problems when considered for industrialization. Therefore, using silane gas in porous carbon, CVD-Si-C in which nano-silicon is generated inside can achieve a higher energy density than Li-doped SiO (Patent Documents 14 and 15).

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

Patent Document 12

Patent Document 13

Patent Document 14

Patent Document 15

Non - Patent Documents

[0017]

Non - Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Non-Patent Document 7

Non-Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0018] As described above, in recent years, small electronic devices typified by mobile terminals have been promoted to have higher performance and more functions, and the lithium-ion secondary battery, which is the main power source thereof, is required to increase the battery capacity. As one method for solving this problem, the development of a lithium-ion secondary battery including a negative electrode using a silicon material as a main material is desired.

[0019] In addition, a lithium-ion secondary battery using a silicon material is desired to have initial charge / discharge characteristics and cycle characteristics that are almost equivalent to those of a lithium-ion secondary battery using a carbon-based active material. Therefore, by using a silicon oxide modified by insertion and partial desorption of Li as a negative electrode active material, the cycle characteristics and the initial charge / discharge characteristics have been improved. These days, mainly silicon oxide is used, and Li is contained in advance to generate Li silicate, thereby reducing the irreversible capacity, which is a demerit of silicon oxide, and actually starting to be put on the market. Even when a battery is prototyped by replacing 100% of a carbon negative electrode material with Li-SiO-C (Non-Patent Document 8) using Li for this silicon oxide, the capacity improvement only remains in the latter half of the 20% range compared to the carbon negative electrode material. This means that further improvement in battery capacity is required in consideration of the higher performance (such as 5G) of small electronic devices and the increased driving range of electric vehicles.

[0020] Therefore, CVD-Si-C with little irreversible capacity has been developed, but it has been found that the high-rate chargeability and the battery cycle characteristics are insufficient due to the reaction between Si and the electrolytic solution.

[0021] The present invention has been made in view of the above problems, and an object thereof is to provide a manufacturing apparatus for a negative electrode active material that can manufacture a negative electrode active material capable of increasing the capacity while maintaining battery characteristics.

Means for Solving the Problems

[0022] In order to solve the above problems, the present invention provides a manufacturing apparatus for a negative electrode active material having negative electrode active material particles. The negative electrode active material particles contained in the negative electrode active material to be manufactured include a porous carbon structure. Inside the porous carbon structure, amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nanosilicon oxide and polycrystalline silicon and its oxide are dispersed as a dispersed substance. The low-valence nanosilicon oxide includes each state of SiOx where x < 1.0. The low-valence nanosilicon oxide has an average particle size of 50 nm or less as determined by image processing in a cross-sectional TEM image. The manufacturing apparatus for the negative electrode active material has a structure capable of holding the porous carbon structure inside, and has a structure in which a raw material gas of the dispersed substance is supplied to the porous carbon structure held inside. In the manufacturing apparatus for the negative electrode active material, when the design pressure is P [MPaG], the internal volume V [m 3 is configured to fall within the range of PV ≤ 0.004. The manufacturing apparatus for the negative electrode active material has a heating mechanism, and the heating mechanism can heat in the range of 300 to 1200 °C. A manufacturing apparatus for a negative electrode active material is provided, which is characterized in the above.

[0023] The manufacturing apparatus for the negative electrode active material of the present invention can efficiently manufacture a negative electrode active material in which amorphous low-valence nanosilicon oxide is dispersed inside a porous carbon structure. Since the negative electrode active material that can be manufactured has amorphous low-valence nanosilicon oxide dispersed inside a porous carbon structure, the adverse effect due to the expansion of the internal low-valence nanosilicon oxide can be reduced due to the presence of the porous carbon structure. Also, general SiO is Si 4+Although it becomes an irreversible component, since the negative electrode active material that can be manufactured using the manufacturing apparatus for a negative electrode active material of the present invention includes each state of SiOx: x < 1.0, an irreversible capacity lower than that of general SiO can be maintained. Further, since the Si—O bond can suppress the decomposition of the electrolytic solution, it is possible to reduce the SEI (Solid Electrolyte Interphase) deposited on the surface layer portion. Further, since the particle size of the low-valence number nanosilicon oxide (the particle size obtained by image processing in the cross-sectional TEM image of the low-valence number nanosilicon oxide) is 50 nm or less on average, it is easy to assume that the Si—O bond is appropriately formed.

[0024] In this case, the design pressure P is in the range of 0.001 to 1 MPaG, and the volume V is in the range of 0.0001 to 1 m 3 It is preferably in the range of.

[0025] The manufacturing apparatus for a negative electrode active material of the present invention having such a design pressure and volume can more efficiently manufacture a negative electrode active material in which an amorphous low-valence number nanosilicon oxide is dispersed inside a porous carbon structure.

[0026] Further, in the manufacturing apparatus for a negative electrode active material of the present invention, it is preferable that the raw material gas is a silane-based gas. At this time, the silane-based gas can be at least one of monosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

[0027] The manufacturing apparatus for a negative electrode active material using these silane-based gases as the raw material gas can more efficiently manufacture a negative electrode active material in which an amorphous low-valence number nanosilicon oxide is dispersed inside a porous carbon structure.

[0028] Further, the manufacturing apparatus for a negative electrode active material of the present invention preferably has a stirring mechanism for stirring the porous carbon structure held inside. At this time, it is preferable that the stirring mechanism has one or more mechanisms selected from a screw, a stirring blade, and a blade.

[0029] A manufacturing apparatus for a negative electrode active material having such a stirring mechanism can easily control the stirring of the content during the reaction, and can more efficiently manufacture a negative electrode active material in which an amorphous low-valence nanosilicon oxide is dispersed inside a porous carbon structure.

[0030] Moreover, it is preferable that it has a mechanism for rotating the entire manufacturing apparatus of the negative electrode active material. Also, it is preferable that it has a mechanism for tilting the entire manufacturing apparatus of the negative electrode active material.

[0031] A manufacturing apparatus for a negative electrode active material having such a rotation mechanism or tilting mechanism can easily control the stirring of the content during the reaction by rotation or tilting, and can more efficiently manufacture a negative electrode active material in which an amorphous low-valence nanosilicon oxide is dispersed inside a porous carbon structure.

[0032] Moreover, it is preferable that the manufacturing apparatus for a negative electrode active material of the present invention has a gas diffusion device at the tip of a raw material gas introduction pipe for introducing the raw material gas. At this time, it is preferable that the gas diffusion device has one or more mechanisms selected from a sparger, a sintered metal, and a mesh.

[0033] A manufacturing apparatus for a negative electrode active material having such a gas diffusion device can easily supply the raw material gas more uniformly, so it can easily control the reaction, and can more efficiently manufacture a negative electrode active material in which an amorphous low-valence nanosilicon oxide is dispersed inside a porous carbon structure.

[0034] Moreover, the present invention is a method for manufacturing a negative electrode active material having negative electrode active material particles using the manufacturing apparatus for a negative electrode active material according to any one of the above, the method including a step of preparing a porous carbon structure, A step of depositing silicon inside the porous carbon structure by flowing a silane-based gas under heating with respect to the porous carbon structure; a step of cooling the material having silicon deposited inside the porous carbon structure to 50°C or lower; after the cooling, oxygen diluted 20-fold with nitrogen gas is introduced into the material having silicon deposited inside the porous carbon structure while adjusting to maintain the temperature of the material having silicon deposited inside the porous carbon structure at 50°C or lower, thereby changing at least a part of the silicon into a low-valence nanosilicon oxide, and thereby manufacturing negative electrode active material particles in which amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nanosilicon oxide and polycrystalline silicon and its oxide are dispersed as a dispersed substance inside the porous carbon structure. A method for manufacturing a negative electrode active material is provided, characterized in that.

[0035] With such a method for manufacturing a negative electrode active material, as described above, a negative electrode active material in which amorphous low-valence nanosilicon oxide is dispersed inside the porous carbon structure can be manufactured simply and efficiently.

Effects of the Invention

[0036] The manufacturing apparatus for the negative electrode active material of the present invention can efficiently manufacture a negative electrode active material in which amorphous low-valence nanosilicon oxide is dispersed inside the porous carbon structure. Further, since the negative electrode active material that can be manufactured has amorphous low-valence nanosilicon oxide dispersed inside the porous carbon structure, the adverse effect due to the expansion of the internal low-valence nanosilicon oxide can be reduced due to the presence of the porous carbon structure. Also, general SiO is Si 4+Although it becomes an irreversible component, the negative electrode active material that can be manufactured using the manufacturing apparatus for a negative electrode active material of the present invention contains each state of SiOx: x < 1.0, so that an irreversible capacity lower than that of general SiO can be maintained. In addition, since the Si - O bond can suppress the decomposition of the electrolytic solution, it becomes possible to reduce the SEI (Solid Electrolyte Interphase) deposited on the surface layer portion. Further, since the particle size of the low - valence number nano - silicon oxide (the particle size obtained by image processing in the cross - sectional TEM image of the low - valence number nano - silicon oxide) is 50 nm or less on average, it is easy to assume that the Si - O bond is appropriately formed. As a result, the negative electrode using the negative electrode active material of the present invention can achieve high initial efficiency, high capacity, high input characteristics, and high cycle characteristics.

Brief Description of the Drawings

[0037]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0038] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

[0039] As described above, as one method for increasing the battery capacity of a lithium - ion secondary battery, using a negative electrode in which a low - valence number nano - silicon oxide is used as a main material in a carbon structure as the negative electrode of a lithium - ion secondary battery has been considered. A lithium - ion secondary battery using this active material is desired to have a high battery capacity while showing battery characteristics almost equivalent to those of a lithium - ion secondary battery using a carbon - based active material.

[0040] Therefore, the present inventors have intensively studied to obtain a negative electrode active material that can improve the initial charge-discharge characteristics and increase the battery capacity while obtaining high cycle characteristics when used as a negative electrode of a secondary battery, and have reached the present invention.

[0041] In particular, in CVD-Si-C as disclosed in Patent Documents 14 and 15, there has been a problem that the reaction with the electrolytic solution is too large. In the present invention, in order to suppress such a reaction with the electrolytic solution, the Si part is converted into a Si-O phase, and by using a siloxane bond peculiar to silicon oxide, not only the reaction decomposition of the electrolytic solution is significantly suppressed, but also the Si-O material having a siloxane bond has good Li acceptability. Therefore, a manufacturing apparatus for a negative electrode active material capable of manufacturing a negative electrode active material that can ensure fast charging has been developed.

[0042] [Manufacturing Apparatus for Negative Electrode Active Material of the Present Invention] The manufacturing apparatus for a negative electrode active material of the present invention is a manufacturing apparatus for a negative electrode active material for manufacturing a negative electrode active material having negative electrode active material particles. The negative electrode active material particles contained in the negative electrode active material to be manufactured include a structure of porous carbon. Inside the structure of the porous carbon, an amorphous low-valence nano silicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nano silicon oxide and polycrystalline silicon and its oxide are dispersed as a dispersed substance. The low-valence nano silicon oxide includes each state of SiOx: x < 1.0. The low-valence nano silicon oxide has an average particle size of 50 nm or less obtained by image processing in a cross-sectional TEM image. The manufacturing apparatus for the negative electrode active material has a structure capable of holding the structure of the porous carbon inside, and has a structure in which a raw material gas of the dispersed substance is supplied to the structure of the porous carbon held inside. In the manufacturing apparatus for the negative electrode active material, when the design pressure is P [MPaG], the internal volume V of the apparatus is V [m 3It is configured to fall within the range of PV ≤ 0.004, and the manufacturing apparatus for the negative electrode active material has a heating mechanism that can heat within the range of 300 to 1200°C. A manufacturing apparatus for a negative electrode active material is characterized by this.

[0043] Fig. 1 shows a cross-sectional view showing an example of the configuration of the manufacturing apparatus for the negative electrode active material of the present invention. The shape of the manufacturing apparatus 1 for the negative electrode active material can be, for example, cylindrical. Further, the manufacturing apparatus 1 for the negative electrode active material has a raw material gas introduction pipe 3. Further, the manufacturing apparatus 1 for the negative electrode active material can hold a reactant 5 inside. As the reactant 5, it is a porous carbon structure before the reaction. The manufacturing apparatus 1 for the negative electrode active material has a structure in which a raw material gas of a dispersant is supplied from the raw material gas introduction pipe 3 to the porous carbon structure held inside in this way. Further, when the design pressure is P [MPaG], the internal volume V [m 3 is configured to fall within the range of PV ≤ 0.004. Further, the manufacturing apparatus 1 for the negative electrode active material has a heating mechanism 6 that can heat within the range of 300 to 1200°C.

[0044] [Negative electrode active material manufacturable by the manufacturing apparatus for the negative electrode active material of the present invention] The negative electrode active material manufacturable by the manufacturing apparatus for the negative electrode active material of the present invention contains negative electrode active material particles. These negative electrode active material particles contain a porous carbon structure, and inside the porous carbon structure, amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both amorphous low-valence nanosilicon oxide and polycrystalline silicon and its oxide, are dispersed as a dispersant. This low-valence nanosilicon oxide includes each state of SiOx: x < 1.0, and the particle size obtained by image processing in a cross-sectional TEM image is 50 nm or less on average.

[0045] Such a negative electrode active material has amorphous low-valence nanosilicon oxide dispersed inside a porous carbon structure. Therefore, due to the presence of the porous carbon structure, the adverse effects caused by the expansion of the internal low-valence nanosilicon oxide can be reduced. Also, in general SiO, Si 4+ becomes an irreversible component. However, in the negative electrode active material that can be manufactured by the manufacturing apparatus for the negative electrode active material of the present invention, since it includes each state of SiOx: x < 1.0, an irreversible capacity lower than that of general SiO can be maintained. Further, since the Si—O bond can suppress the decomposition of the electrolytic solution, it is possible to reduce the SEI (Solid Electrolyte Interphase) deposited on the surface layer portion. In the present invention, it is only necessary that amorphous low-valence nanosilicon oxide is dispersed inside the porous carbon structure, and some of the nanosilicon oxide may have crystallinity.

[0046] As described later, the negative electrode active material that can be manufactured by the manufacturing apparatus for the negative electrode active material of the present invention can be manufactured as a Si—Ox material having a siloxane bond in the Si phase in order to suppress the decomposition reaction of the electrolytic solution, which is insufficient for CVD-Si-C generated from general silane gas. The purpose of intentionally creating the Si—O bond is that while the Si—Si bond promotes the decomposition of the electrolytic solution, the Si—O bond has a gentler reaction with the electrolytic solution compared to Si—Si. Further, since the Si—O bond can suppress the decomposition of the electrolytic solution, it is possible to reduce the SEI deposited on the surface layer portion of CVD-Si-C. As a result, the battery cycle characteristics are improved. Also, the grain boundaries of the grains having Si—Si bonds lower the Li diffusivity, while the Si—O bond has good Li diffusivity and improves the high-rate chargeability. Since the main site contributing to the main charge and discharge of the material of the present invention is the low-valence nanosilicon oxide, it can be defined as CVD-SiOx-C with respect to CVD-Si-C. Thus, the produced active material can have a high energy density and high-rate chargeability while maintaining the cycle characteristics of the battery.

[0047] In addition, since tetravalent Si that constitutes SiO becomes an irreversible component, in the negative electrode active material that can be manufactured by the manufacturing apparatus for the negative electrode active material of the present invention, it is preferable that the low-valence nanosilicon oxide is in a substantially composite state of 0 valence, 1 valence, and 2 valence. In particular, it is preferable that this low-valence nanosilicon oxide is substantially dominated by 1 to 2 valences. By making SiOx of 2 valences or less dominant, although the irreversible capacity is larger than that of silicon alone, an irreversible capacity lower than that of general SiO can be maintained.

[0048] The manufacturing apparatus 1 for the negative electrode active material has a design pressure P in the range of 0.001 to 1 MPaG and a volume V in the range of 0.0001 to 1 m 3 It is preferably in the range of. The manufacturing apparatus for the negative electrode active material of the present invention having such a design pressure and volume can more efficiently manufacture a negative electrode active material in which an amorphous low-valence nanosilicon oxide is dispersed inside the porous carbon structure.

[0049] In addition, the manufacturing apparatus 1 for the negative electrode active material preferably can introduce a silane-based gas as a raw material gas from the raw material gas introduction pipe 3. In particular, the silane-based gas can be at least one of monosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. The manufacturing apparatus for the negative electrode active material using these silane-based gases as the raw material gas can more efficiently manufacture a negative electrode active material in which an amorphous low-valence nanosilicon oxide is dispersed inside the porous carbon structure.

[0050] In addition, the manufacturing apparatus 1 for the negative electrode active material preferably has a stirring mechanism 7 for stirring the porous carbon structure held inside. At this time, it is preferable that the stirring mechanism has one or more mechanisms selected from a screw, a stirring blade, and a blade. The manufacturing apparatus for the negative electrode active material having such a stirring mechanism 7 can easily control the stirring of the content during the reaction and can more efficiently manufacture a negative electrode active material in which an amorphous low-valence nanosilicon oxide is dispersed inside the porous carbon structure.

[0051] Further, it is preferable that the manufacturing apparatus 1 of the negative electrode active material has a mechanism 8 for rotating the entire apparatus of the manufacturing apparatus 1 of the negative electrode active material and a mechanism 9 for inclining the entire apparatus of the manufacturing apparatus 1 of the negative electrode active material. The manufacturing apparatus 1 of the negative electrode active material having such a rotation mechanism 8 and an inclination mechanism 9 can easily control the stirring of the content during the reaction by rotation or inclination, and can more efficiently manufacture a negative electrode active material in which an amorphous low-valence nanosilicon oxide is dispersed inside the structure of the porous carbon.

[0052] Further, it is preferable that the manufacturing apparatus 1 of the negative electrode active material has a gas diffusion device 4 at the tip of a raw material gas introduction pipe 3 for introducing a raw material gas. At this time, it is preferable that the gas diffusion device 4 has one or more mechanisms selected from a sparger, a sintered metal, and a mesh.

[0053] The manufacturing apparatus of the negative electrode active material having such a gas diffusion device 4 can easily supply the raw material gas more uniformly, so that the reaction can be easily controlled, and a negative electrode active material in which an amorphous low-valence nanosilicon oxide is dispersed inside the structure of the porous carbon can be manufactured more efficiently.

[0054] In the negative electrode active material that can be manufactured by the manufacturing apparatus of the negative electrode active material of the present invention, the grain size of 0-valent Si constituting the low-valence nanosilicon oxide calculated using Scherrer's formula from the peaks measured by X-ray diffraction measurement of the negative electrode active material particles is preferably in the range of 1 nm to 5 nm. It is preferable to have such a grain size of 0-valent Si having a substantially amorphous structure.

[0055] The calculation of the crystallite size by XRD can be performed, for example, under the following conditions. For a broad peak, it can be performed, for example, under the following conditions using analysis software TOPAS. XRD measurement · Apparatus: D2 PHASER manufactured by Bruker · X-ray source: Cu · Divergence slit: 0.5° · Incident side Soller: 4° · Receiving side Soller: 4° Calculation of Crystallite Size · Analysis Software: DIFFRAC.TOPAS · Analysis Method: Peak Fitting Method · Emission Profile: CuKa5.lam · Function: FP (First Principle) Function · Refinement Option: Select “Caluculate Error” and “Use Extrapolation”

[0056] The valence of low-valence nanosilicon oxides can be quantified by NMR (nuclear magnetic resonance) and XPS (X-ray photoelectron spectroscopy).

[0057] The NMR measurement for determining the valence of low-valence nanosilicon oxides can be carried out, for example, under the following conditions. 29 Si MAS NMR (Magic Angle Spinning Nuclear Magnetic Resonance) · Instrument: Bruker 700 NMR spectrometer · Probe: 4mm HR-MAS rotor 50μL · Sample Rotation Speed: 10kHz · Measurement Environment Temperature: 25°C

[0058] The XPS measurement can be carried out, for example, under the following conditions. XPS · Instrument: X-ray photoelectron spectrometer · X-ray Source: Monochromatic Al Kα ray · X-ray Spot Diameter: 100μm · Ar Ion Gun Sputtering Conditions: 0.5kV 2mm×2mm

[0059] In addition, in the negative electrode active material that can be manufactured by the manufacturing apparatus for a negative electrode active material of the present invention, it is preferable that the low-valence nano silicon oxide dispersed in the porous carbon structure increases from the center to the surface layer of the porous carbon structure as x increases. In the present invention, since a low-valence nano silicon oxide is dispersed in the porous carbon structure, it tends to increase from the center to the surface layer of the porous carbon structure during manufacturing (the oxygen composition ratio increases). Since the oxidation ratio of silicon is large on the surface, the decomposition of the electrolyte can be more effectively suppressed, and since the oxidation ratio of silicon is small inside the active material, the battery capacity can be further increased.

[0060] <Negative electrode for non-aqueous electrolyte secondary battery> Next, the configuration of a negative electrode for a non-aqueous electrolyte secondary battery (hereinafter also referred to as a "negative electrode") including a negative electrode active material that can be manufactured by the manufacturing apparatus for a negative electrode active material of the present invention will be described.

[0061] [Configuration of negative electrode] FIG. 2 shows a cross-sectional view of a negative electrode including a negative electrode active material that can be manufactured by the manufacturing apparatus for a negative electrode active material of the present invention. As shown in FIG. 2, the negative electrode 10 has a configuration in which a negative electrode active material layer 12 is provided on a negative electrode current collector 11. This negative electrode active material layer 12 may be provided on both sides or only one side of the negative electrode current collector 11. Furthermore, in the negative electrode of the non-aqueous electrolyte secondary battery of the present invention, the negative electrode current collector 11 may not be provided.

[0062] [Negative electrode current collector] The negative electrode current collector 11 is made of an excellent conductive material and has mechanical strength. Examples of the conductive material that can be used for the negative electrode current collector 11 include copper (Cu) and nickel (Ni). This conductive material is preferably a material that does not form an intermetallic compound with lithium (Li).

[0063] The negative electrode current collector 11 preferably contains carbon (C) and sulfur (S) in addition to the main element. This is because the physical strength of the negative electrode current collector is improved. In particular, when there is an active material layer that expands during charging, if the current collector contains the above elements, there is an effect of suppressing electrode deformation including the current collector. The content of the above-mentioned contained elements is not particularly limited, but among them, it is preferably 100 mass ppm or less respectively. This is because a higher deformation suppression effect can be obtained. Due to such a deformation suppression effect, the cycle characteristics can be further improved.

[0064] Also, the surface of the negative electrode current collector 11 is preferably roughened. Desirably, the ten-point average roughness Rz of the surface is 1.5 μm or more and 5 μm or less. The roughened negative electrode current collector is, for example, a metal foil that has been subjected to electrolytic treatment, embossing treatment, or chemical etching treatment.

[0065] [Negative electrode active material layer] The negative electrode active material layer 12 may contain a plurality of types of negative electrode active materials such as carbon-based active materials in addition to the silicon-based active material particles of the present invention. Furthermore, for battery design, it may also contain other materials such as a thickening agent (also referred to as a "binder" or "adhesive") and a conductive auxiliary agent.

[0066] [Manufacturing method of negative electrode active material and negative electrode] Subsequently, an example of the manufacturing method of the negative electrode active material of the non-aqueous electrolyte secondary battery of the present invention and the negative electrode using the same will be described.

[0067] First, a method for manufacturing the negative electrode active material contained in the negative electrode initially will be described. The method for manufacturing the negative electrode active material of the present invention is a method for manufacturing a negative electrode active material having negative electrode active material particles using the above-described manufacturing apparatus for the negative electrode active material of the present invention, and includes a step of preparing a porous carbon structure, and flowing a silane-based gas over the porous carbon structure under heating to deposit silicon inside the porous carbon structure, a step of cooling the material having silicon deposited inside the porous carbon structure to 50°C or lower, and after the cooling, introducing oxygen diluted 20-fold with nitrogen gas into the material having silicon deposited inside the porous carbon structure while adjusting the temperature of the material having silicon deposited inside the porous carbon structure to be maintained at 50°C or lower, thereby changing at least a part of the silicon into a low-valence nanosilicon oxide. Thus, a negative electrode active material particle in which amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nanosilicon oxide and polycrystalline silicon and its oxide are dispersed as a dispersed substance is manufactured inside the porous carbon structure. This is a method for manufacturing a negative electrode active material, characterized by this.

[0068] With such a method for manufacturing a negative electrode active material, as described above, a negative electrode active material in which amorphous low-valence nanosilicon oxide is dispersed can be manufactured simply and efficiently inside the porous carbon structure.

[0069] Referring to Steps S1 to S4 in FIG. 4, each step of the method for manufacturing the negative electrode active material will be described.

[0070] First, a porous carbon structure is prepared (Step S1). The porous carbon structure prepared here preferably has a carbon-carbon double bond at least in part. Further, the porous carbon structure prepared here is dominated by Type I in the IUPAC classification, and its surface area is 1400 m 2 / g or more, and the pore volume is 1 cm 3It is preferably / g or more. By classifying according to such IUPAC classification, surface area, and pore volume, deposition of silicon can be carried out more efficiently in a larger amount. Also, for IUPAC classification, surface area, and pore volume, the following measurement methods can be used. · Measure the specific surface area / pore distribution by the constant volume method based on the gas adsorption method using Shimadzu TriStar II Plus. The conditions are as follows. · Gas used: Nitrogen · Environment: Under liquid nitrogen · Pressure operating range: P / P0 · Adsorption 0~0.998 · Desorption 0.998~0.10 · Pretreatment Vacuum 200°C 1 hour

[0071] Next, by flowing a silane-based gas, which is a raw material gas, over the porous carbon structure prepared in step S1 under heating, silicon is deposited inside the porous carbon structure (step S2).

[0072] Note that after step S1 and before step S2, it is preferable to store the porous carbon structure in the manufacturing apparatus 1 (vacuum vessel) and perform evacuation. The degree of vacuum can be, for example, up to about -100 kPa, but is not limited thereto. Also, after evacuation, it is preferable to repressurize with nitrogen and heat to about 350 to 450°C using an external heater in a state where nitrogen is flowing. This heating can be 5 minutes to 1 hour. By performing such preheating in the presence of evacuation and nitrogen, nucleation for silicon deposition in step S2 and removal of hydrogen and water adhering to the porous carbon structure can be performed, so that silicon deposition in step S2 can be carried out more reliably.

[0073] The deposition of silicon in step S2 can be carried out, for example, by flowing a silane-based gas at about 400°C to 500°C. The deposition time can be, for example, 30 minutes to 10 hours. At this time, the silane-based gas as the raw material gas can be at least one of monosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. The manufacturing apparatus for the negative electrode active material using these silane-based gases as the raw material gas can more efficiently manufacture a negative electrode active material in which amorphous low-valence nanosilicon oxide is dispersed inside the porous carbon structure.

[0074] Next, the material with silicon deposited inside the porous carbon structure is cooled to 50°C or lower (step S3). In this step, it is preferable to cool while flowing nitrogen gas, for example. In this cooling, it can be cooled to room temperature, for example.

[0075] After the above cooling (step S3), next, in a state where the temperature of the material with silicon deposited inside the porous carbon structure is adjusted to maintain 50°C or lower, oxygen diluted with nitrogen gas is introduced into the material with silicon deposited inside the porous carbon structure to change at least a part of the silicon into low-valence nanosilicon oxide (step S4). By this step, an Si-O bond can be formed. Note that the temperature to be maintained here is more preferably 35°C or lower.

[0076] The dilution of oxygen with nitrogen can be, for example, 5 to 50 times, and preferably 10 to 30 times. This dilution ratio can typically be 20 times.

[0077] Also, in this step S4, when the internal temperature rises and exceeds 50°C, silicon dioxide is partially generated, which is not preferable as the negative electrode active material. Therefore, in this step S4, it is necessary to adjust so that the temperature of the material is maintained below 50°C. Further, the material temperature in step S4 is preferably, for example, 25°C or higher, more preferably 30°C or higher, in order to facilitate the progress of the oxidation reaction and the formation of Si-O bonds.

[0078] The oxidation time (flow time of oxygen diluted with nitrogen gas) in this step S4 can be, for example, 30 minutes or more and 5 hours or less, preferably 1 hour or more and 3 hours or less. Further, after the flow of oxygen diluted with nitrogen gas, it is also possible to switch to the flow of nitrogen gas and further cool. The flow of only nitrogen gas can be, for example, 30 minutes or more and 2 hours or less.

[0079] In the oxidation by the flow of oxygen diluted with the above nitrogen gas, it is preferable to adjust so that the low-valence nanosilicon oxide dispersed in the porous carbon structure increases x from the center to the surface layer of the porous carbon structure. In the porous carbon structure, the pore structure tends to have a larger cross-sectional area on the particle surface and a smaller cross-sectional area toward the particle interior. Therefore, by performing oxidation by the flow of oxygen diluted with nitrogen gas as in the case of using the manufacturing apparatus of the present invention, it naturally tends to increase x from the center to the surface layer of the porous carbon structure.

[0080] Thereafter, the material is taken out from the storage container. By the above steps, negative electrode active material particles in which amorphous low-valence nanosilicon oxide is dispersed can be produced inside the porous carbon structure.

[0081] <Lithium Ion Secondary Battery> Next, as a specific example of a non-aqueous electrolyte secondary battery using the negative electrode active material of the present invention described above, a laminated film type lithium ion secondary battery will be described.

[0082] [Configuration of a laminated film type secondary battery] The laminated film type lithium ion secondary battery 30 shown in Fig. 3 mainly has a wound electrode body 31 housed inside a sheet-like exterior member 35. This wound electrode body 31 has a separator between the positive electrode and the negative electrode and is wound. There are also cases where a separator is provided between the positive electrode and the negative electrode and a laminate is housed. In both types of electrode bodies, a positive electrode lead 32 is attached to the positive electrode and a negative electrode lead 33 is attached to the negative electrode. The outermost peripheral portion of the electrode body is protected by a protective tape.

[0083] The positive and negative electrode leads 32 and 33 are led out, for example, in one direction from the inside to the outside of the exterior member 35. The positive electrode lead 32 is formed of a conductive material such as aluminum, and the negative electrode lead 33 is formed of a conductive material such as nickel or copper.

[0084] The exterior member 35 is, for example, a laminated film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order. In this laminated film, the outer peripheral edges of the fusion layers of the two films are fused or bonded together with an adhesive or the like so that the fusion layer faces the electrode body 31. The fusion part is a film such as polyethylene or polypropylene, and the metal part is an aluminum foil or the like. The protective layer is nylon or the like, for example.

[0085] A close contact film 34 is inserted between the exterior member 35 and the positive and negative electrode leads to prevent outside air from entering. This material is, for example, polyethylene, polypropylene, or a polyolefin resin.

[0086] The positive electrode has a positive electrode active material layer on both sides or one side of the positive electrode current collector, for example, in the same manner as the negative electrode 10 in Fig. 2.

[0087] The positive electrode current collector is formed of a conductive material such as aluminum, for example.

[0088] The positive electrode active material layer contains any one or more of positive electrode materials capable of intercalating and deintercalating lithium ions, and may contain other materials such as a positive electrode binder, a positive electrode conductive assistant, a dispersant, etc. according to the design. In this case, the details regarding the positive electrode binder and the positive electrode conductive assistant are the same as those of the negative electrode binder and the negative electrode conductive assistant described above, for example.

[0089] As the positive electrode material, a lithium-containing compound is desirable. Examples of this lithium-containing compound include a composite oxide composed of lithium and a transition metal element, or a phosphate compound having lithium and a transition metal element. Among these positive electrode materials, a compound having at least one of nickel, iron, manganese, and cobalt is preferable. As these chemical formulas, for example, Li x M1O2 or Li y M2PO4. In the formula, M1 and M2 represent at least one transition metal element. The values of x and y represent different values depending on the charge and discharge state of the battery, but are generally represented by 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

[0090] Examples of the composite oxide having lithium and a transition metal element include lithium cobalt composite oxide (Li x CoO2), lithium nickel composite oxide (Li x NiO2), lithium nickel cobalt composite oxide, etc. Examples of the lithium nickel cobalt composite oxide include lithium nickel cobalt aluminum composite oxide (NCA), lithium nickel cobalt manganese composite oxide (NCM), etc.

[0091] Examples of the phosphate compound having lithium and a transition metal element include lithium iron phosphate compound (LiFePO4) or lithium iron manganese phosphate compound (LiFe 1-u Mn u PO4 (0 < u < 1)), etc. By using these positive electrode materials, a high battery capacity can be obtained, and excellent cycle characteristics can also be obtained.

[0092] [Negative electrode] The negative electrode has the same configuration as the negative electrode 10 for a lithium-ion secondary battery shown in FIG. 2 described above. For example, it has negative electrode active material layers on both sides of a current collector. It is preferable that the negative electrode charging capacity is larger than the capacitance (charging capacity as a battery) obtained from the positive electrode active material agent. Thereby, precipitation of lithium metal on the negative electrode can be suppressed.

[0093] The positive electrode active material layer is provided on a part of both sides of the positive electrode current collector. Similarly, the negative electrode active material layer is also provided on a part of both sides of the negative electrode current collector. In this case, for example, the negative electrode active material layer provided on the negative electrode current collector has a region where there is no opposing positive electrode active material layer. This is for performing a stable battery design.

[0094] In the region where the above-described negative electrode active material layer and positive electrode active material layer do not face each other, it is hardly affected by charge and discharge. Therefore, the state of the negative electrode active material layer is maintained as it is immediately after formation, and thereby the composition of the negative electrode active material and the like can be accurately examined with good reproducibility without depending on the presence or absence of charge and discharge.

[0095] [Separator] The separator separates the positive electrode and the negative electrode and allows lithium ions to pass through while preventing a current short circuit due to contact between the two electrodes. This separator is formed of, for example, a porous membrane made of a synthetic resin or a ceramic, and may have a laminated structure in which two or more porous membranes are laminated. Examples of the synthetic resin include polytetrafluoroethylene, polypropylene, and polyethylene.

[0096] [Electrolyte] At least a part of the active material layer or the separator is impregnated with a liquid electrolyte (electrolyte solution). This electrolyte solution has an electrolyte salt dissolved in a solvent and may contain other materials such as additives.

[0097] As the solvent, for example, a non-aqueous solvent can be used. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, 1,2-dimethoxyethane, or tetrahydrofuran. Among these, it is desirable to use at least one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. This is because better properties can be obtained. In this case, by combining a high-viscosity solvent such as ethylene carbonate or propylene carbonate with a low-viscosity solvent such as dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate, more excellent properties can be obtained. This is because the dissociation property and ion mobility of the electrolyte salt are improved.

[0098] When using an alloy-based negative electrode, it is particularly desirable that the solvent contains at least one of a halogenated chain carbonate ester or a halogenated cyclic carbonate ester. Thereby, during charge and discharge, particularly during charging, a stable film is formed on the surface of the negative electrode active material. Here, the halogenated chain carbonate ester is a chain carbonate ester having a halogen as a constituent element (at least one hydrogen is substituted by a halogen). Also, the halogenated cyclic carbonate ester is a cyclic carbonate ester having a halogen as a constituent element (that is, at least one hydrogen is substituted by a halogen).

[0099] The type of halogen is not particularly limited, but fluorine is preferred. This is because it forms a better-quality film than other halogens. Also, the larger the number of halogens, the more desirable. This is because the resulting film is more stable and the decomposition reaction of the electrolyte solution is reduced.

[0100] Examples of the halogenated chain carbonate ester include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, etc. Examples of the halogenated cyclic carbonate ester include 4-fluoro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one, etc.

[0101] As a solvent additive, it is preferable to contain an unsaturated carbon-bonded cyclic carbonate. This is because a stable film is formed on the surface of the negative electrode during charge and discharge, and the decomposition reaction of the electrolyte can be suppressed. Examples of the unsaturated carbon-bonded cyclic carbonate include vinylene carbonate or vinyl ethylene carbonate.

[0102] Also, as a solvent additive, it is preferable to contain sultone (cyclic sulfonic acid ester). This is because the chemical stability of the battery is improved. Examples of sultone include propane sultone and propene sultone.

[0103] Furthermore, the solvent preferably contains an acid anhydride. This is because the chemical stability of the electrolyte is improved. Examples of the acid anhydride include propane disulfonic anhydride.

[0104] The electrolyte salt can contain any one or more of light metal salts such as lithium salts, for example. Examples of the lithium salt include lithium hexafluorophosphate (LiPF6) and lithium tetrafluoroborate (LiBF4).

[0105] The content of the electrolyte salt is preferably 0.5 mol / kg or more and 2.5 mol / kg or less with respect to the solvent. This is because high ionic conductivity can be obtained.

Examples

[0106] Hereinafter, the present invention will be described more specifically by showing examples and comparative examples of the present invention, but the present invention is not limited to these examples.

[0107] (Example 1-1) According to the following procedure, a negative electrode active material was prepared, and further, a laminate film type lithium ion secondary battery 30 shown in Figure 3 was prepared.

[0108] A heat-resistant temperature 500 °C storage container (also referred to as a reaction container or a vacuum container) made of nickel alloy (trade name Hastelloy), with a design pressure of 0.1 MPaG, cylindrical shape, diameter 30 mm × height 450 mm, was used to produce the negative electrode active material. First, a porous carbon material (porous carbon structure) with a surface area (BET specific surface area) of 2483 m 2 / g, pore volume of 1.35 cm 3 / g, and particle size (D50) = 11 μm was prepared. Next, this porous carbon material was stored in the above storage container and evacuated to -90 kPa. Next, the pressure was restored with nitrogen, and while nitrogen was flowing, an external heater was used to heat it to 400 °C. After 30 minutes of heating, the temperature was raised to 415 °C, monosilane gas was flowed, and deposition was carried out at an internal pressure of 0.001 MPaG for 4 hours. The monosilane gas used at this time was diluted with hydrogen at a ratio of 1:9. Then, it was cooled to room temperature while flowing nitrogen gas. After the temperature was lowered to 25 °C, oxygen diluted 20 times with nitrogen was introduced, and the material temperature was adjusted to be 50 °C or lower to form Si-O bonds. Next, nitrogen containing oxygen was flowed for 2 hours, and when the material temperature reached 30 °C or lower, it was switched to nitrogen gas and flowed for 60 minutes, and then the material was taken out from the storage container to obtain the negative electrode active material.

[0109] [Fabrication of Negative Electrode] The negative electrode active material (active material containing CVD-SiOx-C) fabricated as described above, graphite, conductive assistant 1 (carbon nanotube, CNT), conductive assistant 2 (carbon fine particles with a median diameter of about 50 nm), sodium polyacrylate, and carboxymethyl cellulose (hereinafter referred to as CMC) were mixed at a dry mass ratio of 9.3:83.7:1:1:4:1, and then diluted with pure water to obtain a negative electrode mixture slurry.

[0110] Also, an electrolytic copper foil with a thickness of 15 μm was used as the negative electrode current collector. This electrolytic copper foil contained carbon and sulfur at concentrations of 70 mass ppm, respectively. Finally, the negative electrode mixture slurry was applied to the negative electrode current collector and dried in a vacuum atmosphere at 100 °C for 1 hour. The deposition amount (also referred to as areal density) of the negative electrode active material layer per unit area on one side of the negative electrode after drying was 7.0 mg / cm2 It was

[0111] [Assembly of Coin Cells for Testing] Next, after mixing the solvents ethylene carbonate (EC) and dimethyl carbonate (DMC), the electrolyte salt (lithium hexafluorophosphate: LiPF6) was dissolved to prepare an electrolyte solution. In this case, the composition of the solvent was EC:DMC = 30:70 by volume ratio, and the content of the electrolyte salt was 1 mol / kg with respect to the solvent. As additives, vinylene carbonate (VC) and fluoroethylene carbonate (FEC) were added in amounts of 1.0% by mass and 2.0% by mass, respectively.

[0112] Next, a coin cell was assembled as follows. First, a Li foil with a thickness of 1 mm was punched out to a diameter of 16 mm and attached to an aluminum clad.

[0113] Next, the previously obtained negative electrode was punched out to a diameter of 15 mm, and this was placed facing the Li foil attached to the aluminum clad through a separator. After injecting the electrolyte solution, a 2032 coin cell was fabricated.

[0114] [Measurement of Initial Efficiency] The initial efficiency was measured under the following conditions. First, for the fabricated coin cell for initial efficiency test, the charging rate was set to be equivalent to 0.03C, and charging (initial charge) was performed in the CCCV mode. The CV was 0V and the termination current was 0.04 mA. Next, the discharging rate was similarly set to 0.03C, and CC discharging (initial discharge) was performed with the discharge termination voltage set to 1.2V.

[0115] When examining the initial charge-discharge characteristics, the initial efficiency (which may also be referred to as the initial efficiency hereinafter) was calculated. The initial efficiency was calculated from the formula: Initial efficiency (%) = (Initial discharge capacity / Initial charge capacity) × 100.

[0116] [Manufacture of Lithium-Ion Secondary Battery and Battery Evaluation] Based on the obtained initial data, the positive electrode was designed so that the utilization rate of the negative electrode would be 95%. The utilization rate was calculated based on the following formula from the capacities of the positive and negative electrodes obtained with the counter electrode Li. Utilization rate = (positive electrode capacity - negative electrode loss) / (negative electrode capacity - negative electrode loss) × 100 Based on this design, lithium-ion secondary batteries (lithium-ion secondary batteries as shown in Fig. 3) of each of the examples and comparative examples were manufactured. Battery evaluations were performed on the lithium-ion secondary batteries of each of the examples and comparative examples.

[0117] The cycle characteristics were examined as follows. First, for battery stabilization, charge and discharge were performed at 0.2C for 2 cycles in an atmosphere of 25°C, and the discharge capacity of the second cycle was measured. The battery cycle characteristics were calculated from the discharge capacity of the third cycle, and the battery test was stopped at 1000 cycles. Charge and discharge were performed at a charge rate of 0.7C and a discharge rate of 0.5C. The charge voltage was 4.3V, the discharge cut-off voltage was 2.5V, and the charge cut-off rate was 0.07C. Also, for the high-rate charge characteristics, the battery cycle characteristics were calculated from the discharge capacity of the third cycle, and the battery test was stopped at 500 cycles. Charge and discharge were performed at a charge rate of 4C and a discharge rate of 0.5C. The charge cut-off voltage was 4.3V, the discharge cut-off voltage was 2.5V, and the charge cut-off rate was 0.07C.

[0118] The configuration and operating conditions of the manufacturing apparatus of Example 1-1 are shown in Tables 1 and 2.

[0119]

Table 1

[0120]

Table 2

[0121] The negative electrode active material manufactured in Example 1-1 had the following characteristics. · 1000-cycle retention rate... 80% · Specific capacity at 1.2V... 1940 mAh / g · Initial efficiency at 1.2V... 88% · 500-cycle retention rate at 4C charge... 80% · Si 0+Grain size... 1.4 nm · Diameter of low-valence part SiOx... 25 nm · Valence of SiOx... 0 to 2 valence, 0 < x < 0.7 Thus, in Example 1-1, a good negative electrode active material could be produced.

[0122] [Examples 2-1 to 2-11] The configurations and operating conditions of the production apparatuses of Examples 2-1 to 2-11 are shown in Tables 3 and 4. Note that Example 1-1 is also shown. As shown in the tables, the processing temperature and operating pressure were changed compared with the production apparatus of the negative electrode active material of Example 1-1.

[0123]

Table 3

[0124]

Table 4

[0125] In Examples 2-1 to 2-11, good samples equivalent to those of Example 1-1 were obtained in all cases. Therefore, since it was found that good samples could be obtained at a processing temperature of 400 to 450 °C, it was found that the heat-resistant temperature of the production apparatus 1 for the negative electrode active material may be a material with a temperature of 500 °C. Also, since the system internal pressure is sufficient at 0.01 MPaG, it was found that the design pressure may be 0.1 MPaG.

[0126] [Examples 3-1 to 3-6, Comparative Example 3-1] The configurations and operating conditions of the production apparatuses of Examples 3-1 to 3-6 and Comparative Example 3-1 are shown in Tables 5 and 6. Note that Example 1-1 is also shown. As shown in the tables, the reaction vessel size and design pressure of the production apparatus 1 for the negative electrode active material were changed compared with the production apparatus of the negative electrode active material of Example 1-1.

[0127]

Table 5

[0128] [Table 6]

[0129] In Examples 3-1 to 3-4, good samples equivalent to those of Example 1-1 were obtained in all cases. Therefore, it was found that there was no problem even if the size of the reaction vessel of the negative electrode active material manufacturing apparatus 1 was enlarged in a cylindrical shape, and there was no problem even if the ratio of the diameter to the length was different. In Examples 3-5 to 3-6, in order to increase the internal pressure of the system of the manufacturing apparatus 1, the design pressure was increased and the treatment was performed. By increasing the internal pressure of the system, the supply gas flow rate increased and powder scattering increased, leading to a decrease in the recovery amount. However, good samples equivalent to those of Example 1-1 were obtained.

[0130] In Comparative Example 3-1, by increasing the design pressure, the plate thickness of the container increased, leading to an increase in cost, and it was judged that it was not realistic because it took a long time to manufacture the container, so the manufacture was abandoned.

[0131] [Examples 4-1 to 4-5] The configurations and operating conditions of the manufacturing apparatuses of Examples 4-1 to 4-6 are shown in Tables 7 and 8. Note that Example 1-1 is also shown. As shown in the tables, the heat-resistant temperature was increased compared to the negative electrode active material manufacturing apparatus of Example 1-1. This was achieved by changing the material of the reaction vessel to stainless steel or heat-resistant cast steel, or by using it in combination with a nickel alloy.

[0132] [Table 7]

[0133] [Table 8]

[0134] In Examples 4-1 to 4-6, good samples equivalent to those of Example 1-1 were obtained in all cases. Therefore, good samples were obtained without any particular influence even when the container material was changed.

[0135] [Examples 5-1 to 5-3] The configurations and operating conditions of the manufacturing apparatuses of Examples 5-1 to 5-3 are shown in Tables 9 and 10. Note that Example 1-1 is also shown. As shown in the tables, in Examples 5-1 to 5-3, chlorosilane gas was initially supplied at 1050°C, and then monosilane gas was supplied at 415°C. As the chlorosilane gas, trichlorosilane was used in Example 5-1, dichlorosilane was used in Example 5-2, and a gas in which dichlorosilane and trichlorosilane were each half was used in Example 5-3. The material of the manufacturing apparatus 1 of Examples 5-1 to 5-3 was heat-resistant cast steel resistant to chlorine.

[0136]

Table 9

[0137]

Table 10

[0138] In Examples 5-1 to 5-3, good samples equivalent to those of Example 1-1 were obtained in all cases. Therefore, it was found that chlorosilane gas can be used as a raw material at about 1000°C.

[0139] [Examples 6-1 to 6-3] The configurations and operating conditions of the manufacturing apparatuses of Examples 6-1 to 6-3 are shown in Tables 11 and 12. Note that Example 1-1 is also shown. As shown in the tables, a stirring mechanism was added to the shaft in the reaction vessel compared to the manufacturing apparatus of the negative electrode active material of Example 1-1. A screw, stirring blades, and a blade were used in each example.

[0140]

Table 11

[0141]

Table 12

[0142] In Examples 6-1 to 6-3, good samples equivalent to those in Example 1-1 were obtained in all cases. Also, when a screw (Example 6-1), an agitator blade (Example 6-2), and a blade (Example 6-3) were used in each example, the screw (Example 6-1) was able to suppress the variation the most. It is considered that a screw capable of stirring the entire powder was good.

[0143] [Examples 7-1 to 7-2] The configurations and operating conditions of the production apparatuses of Examples 7-1 to 7-2 are shown in Tables 13 and 14. Note that Example 1-1 is also shown. As shown in the tables, in Example 7-1, a rotation mechanism for rotating the reaction vessel itself was added compared to the production apparatus for the negative electrode active material of Example 1-1. In Example 7-2, a rotation mechanism for rotating the reaction vessel itself and a screw as a stirring mechanism were added compared to the production apparatus for the negative electrode active material of Example 1-1.

[0144]

Table 13

[0145]

Table 14

[0146] [Examples 8-1 to 8-8] The configurations and operating conditions of the production apparatuses of Examples 8-1 to 8-8 are shown in Tables 15 and 16. Note that Examples 6-1 and 7-2 are also shown. As shown in the tables, a mechanism that can tilt the entire reaction vessel was added compared to the production apparatus for the negative electrode active material of Example 6-1 or Example 7-2.

[0147]

Table 15

[0148]

Table 16

[0149] In Examples 8-1 to 8-8, good samples equivalent to those of Example 1-1 were obtained in all cases. Further, by inclining, the movement of powder in the system was promoted, and the uniformity was dramatically improved. As a result, the variation in the inclination accuracy was suppressed near the angle of repose of the powder.

[0150] [Examples 9-1 to 9-3] The configurations and operating conditions of the manufacturing apparatuses of Examples 9-1 to 9-3 are shown in Tables 17 and 18. Note that Example 1-1 is also shown together. As shown in the tables, a gas diffusion mechanism was added to the tip of the gas introduction nozzle compared with the manufacturing apparatus for the negative electrode active material of Example 1-1. As the gas diffusion mechanism, a sparger, a sintered metal, and a mesh were added.

[0151]

Table 17

[0152]

Table 18

[0153] In Examples 9-1 to 9-3, good samples equivalent to those of Example 1-1 were obtained in all cases. Further, as a result of adding a gas diffusion mechanism to the tip of the gas introduction nozzle, improvements in uniformity were observed for all of the sparger, the sintered metal, and the mesh. It is considered that the gas was dispersed by the diffusion mechanism and spread more uniformly in the system.

[0154] This specification includes the following aspects. [1]: A manufacturing apparatus for a negative electrode active material for manufacturing a negative electrode active material having negative electrode active material particles, The negative electrode active material particles contained in the negative electrode active material to be manufactured include a structure of porous carbon, Inside the structure of the porous carbon, amorphous low-valence nano silicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nano silicon oxide and polycrystalline silicon and its oxide, are dispersed as a dispersion substance. The low-valence nano silicon oxide includes each state where SiOx: x < 1.0. The low-valence nano silicon oxide has a particle size obtained by image processing in a cross-sectional TEM image of an average of 50 nm or less. The manufacturing apparatus of the negative electrode active material has a structure capable of holding the structure of the porous carbon inside, and has a structure in which a raw material gas of the dispersion substance is supplied to the structure of the porous carbon held inside. In the manufacturing apparatus of the negative electrode active material, when the design pressure is P [MPaG], the internal volume V [m 3 is configured to be within the range of PV ≤ 0.004. The manufacturing apparatus of the negative electrode active material has a heating mechanism, and the heating mechanism can heat in the range of 300 to 1200 °C. A manufacturing apparatus of a negative electrode active material characterized by this. [2]: The manufacturing apparatus of the negative electrode active material according to [1] above, wherein the design pressure P is in the range of 0.001 to 1 MPaG, and the volume V is in the range of 0.0001 to 1 m 3 [3]: The manufacturing apparatus of the negative electrode active material according to [1] or [2] above, wherein the raw material gas is a silane-based gas. [4]: The manufacturing apparatus of the negative electrode active material according to [3] above, wherein the silane-based gas is at least one of monosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. [5]: The manufacturing apparatus of the negative electrode active material according to any one of [1] to [4] above, which has a stirring mechanism for stirring the structure of the porous carbon held inside. [6]: The manufacturing apparatus of the negative electrode active material according to [5] above, wherein the stirring mechanism has one or more mechanisms selected from a screw, a stirring blade, and a blade. [7]: The manufacturing apparatus for the negative electrode active material according to any one of [1] to [6] above, having a mechanism for rotating the entire apparatus of the manufacturing apparatus for the negative electrode active material. [8]: The manufacturing apparatus for the negative electrode active material according to any one of [1] to [7] above, having a mechanism for tilting the entire apparatus of the manufacturing apparatus for the negative electrode active material. [9]: The manufacturing apparatus for the negative electrode active material according to any one of [1] to [8] above, having a gas diffusion device at the tip of the raw material gas introduction pipe for introducing the raw material gas.

[10] : The manufacturing apparatus for the negative electrode active material according to [9] above, wherein the gas diffusion device has one or more mechanisms selected from a sparger, a sintered metal, and a mesh.

[11] : A method for manufacturing a negative electrode active material having negative electrode active material particles, using the manufacturing apparatus for the negative electrode active material according to any one of [1] to

[10] above, preparing a porous carbon structure; depositing silicon inside the porous carbon structure by flowing a silane-based gas over the porous carbon structure under heating; cooling the material having silicon deposited inside the porous carbon structure to 50°C or lower; after the cooling, introducing oxygen diluted 20-fold with nitrogen gas into the material having silicon deposited inside the porous carbon structure while adjusting to maintain the temperature of the material having silicon deposited inside the porous carbon structure at 50°C or lower, thereby changing at least a part of the silicon into a low-valence nanosilicon oxide; and thereby manufacturing negative electrode active material particles in which amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nanosilicon oxide and polycrystalline silicon and its oxide are dispersed as a dispersed substance inside the porous carbon structure.

[0155] Note that the present invention is not limited to the above-described embodiments. The above embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Explanation of Reference Numerals

[0156] 1... Manufacturing apparatus for negative electrode active material, 3... Raw material gas introduction pipe, 4... Gas diffusion device, 5... Reactant, 6... Heating mechanism, 7... Stirring mechanism, 8... Rotating mechanism, 9... Tilting mechanism, 10... Negative electrode, 11... Negative electrode current collector, 12... Negative electrode active material layer, 30... Lithium ion secondary battery (laminate film type), 31... Electrode body, 32... Positive electrode lead (positive electrode aluminum lead), 33... Negative electrode lead (negative electrode nickel lead), 34... Adhesive film, 35... Exterior member.

Claims

1. An apparatus for manufacturing a negative electrode active material having negative electrode active material particles, comprising: The negative electrode active material particles contained in the negative electrode active material to be manufactured include a porous carbon structure; Inside the porous carbon structure, amorphous low-valence nano silicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nano silicon oxide and polycrystalline silicon and its oxide, are dispersed as a dispersion substance; The low-valence nano silicon oxide includes each state of SiO x: x < 1.0; The low-valence nano silicon oxide has a particle size determined by image processing in a cross-sectional TEM image of 50 nm or less on average; The apparatus for manufacturing the negative electrode active material has a structure capable of holding the porous carbon structure inside, and has a structure in which a raw material gas of the dispersion substance is supplied to the porous carbon structure held inside; In the manufacturing apparatus for the negative electrode active material, when the design pressure is P [MPaG], the internal volume V [m ３ of the apparatus is configured to fall within the range of PV ≤ 0.004, The apparatus for manufacturing the negative electrode active material has a heating mechanism, and the heating mechanism is capable of heating in the range of 300 to 1200 °C. The apparatus for manufacturing the negative electrode active material is characterized by this.

2. The design pressure P is in the range of 0.001 to 1 MPaG, and the volume V is in the range of 0.0001 to 1 m ３ The manufacturing apparatus for a negative electrode active material according to claim 1, characterized in that it is in the range of

3. The apparatus for manufacturing a negative electrode active material according to claim 1, wherein the raw material gas is a silane-based gas.

4. The apparatus for manufacturing a negative electrode active material according to claim 3, wherein the silane-based gas is at least one of monosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

5. The apparatus for manufacturing a negative electrode active material according to claim 1, further comprising a stirring mechanism for stirring the porous carbon structure held inside.

6. The apparatus for manufacturing a negative electrode active material according to claim 5, wherein the stirring mechanism includes one or more mechanisms selected from a screw, a stirring blade, and a blade.

7. The apparatus for manufacturing a negative electrode active material according to claim 1, further comprising a mechanism for rotating the entire apparatus of the apparatus for manufacturing the negative electrode active material.

8. The apparatus for manufacturing a negative electrode active material according to claim 1, further comprising a mechanism for tilting the entire apparatus of the apparatus for manufacturing the negative electrode active material.

9. The apparatus for manufacturing a negative electrode active material according to claim 1, further comprising a gas diffusion device at the tip of a raw material gas introduction pipe for introducing the raw material gas.

10. The manufacturing apparatus for a negative electrode active material according to claim 9, wherein the gas diffusion device has one or more mechanisms selected from a sparger, a sintered metal, and a mesh.

11. A method for manufacturing a negative electrode active material having negative electrode active material particles, using the manufacturing apparatus for a negative electrode active material according to claims 1 to 10, comprising: preparing a porous carbon structure; depositing silicon inside the porous carbon structure by flowing a silane-based gas under heating to the porous carbon structure; cooling the material having silicon deposited inside the porous carbon structure to 50°C or lower; introducing oxygen diluted 20-fold with nitrogen gas into the material having silicon deposited inside the porous carbon structure in a state where the temperature of the material having silicon deposited inside the porous carbon structure is adjusted to maintain 50°C or lower after the cooling, thereby changing at least a part of the silicon into a low-valence nanosilicon oxide; and thereby manufacturing negative electrode active material particles in which amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nanosilicon oxide and polycrystalline silicon and its oxide are dispersed as a dispersed substance inside the porous carbon structure.

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