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

Abstract

The present invention is a negative electrode active material production apparatus for producing a negative electrode active material which has negative electrode active material particles, wherein: the 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 is / are dispersed as a dispersed substance; the low valence nano silicon oxide includes SiOx in each of the states of x<1.0; the low valence nano silicon oxide is not more than 50 nm on average; the negative electrode active material production apparatus has a structure which makes it possible to hold the porous carbon structure in the interior thereof and has such a structure as to supply a starting material gas of the dispersed substance to the porous carbon structure held in said interior; in the negative electrode active material production apparatus, 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 said heating mechanism is capable of heating in the range of 300-1,200°C. Thus, provided is a negative electrode active material production apparatus which is capable of producing a negative electrode active material that, while maintaining battery characteristics, makes it possible to increase the capacity.

Description

Apparatus for manufacturing negative electrode active material and method for manufacturing negative electrode active material

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

[0002] In recent years, small electronic devices such as mobile terminals have become widespread, and there is a strong demand for further miniaturization, weight reduction, and longer life. In response to such market demands, development of secondary batteries that are small, lightweight, and capable of achieving high energy density has been progressing. The application of these secondary batteries is being considered not only for small electronic devices but also for large electronic devices such as automobiles and power storage systems such as those for homes.

[0003] Among these, lithium-ion secondary batteries are attracting great attention because they can be easily made small and have a high capacity, and can provide a higher energy density than lead batteries and nickel-cadmium batteries.

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

[0005] While carbon-based active materials are widely used as negative electrode active materials, recent market demands have led to a demand for further improvements in battery capacity. To improve battery capacity, the use of silicon as a negative electrode active material has been considered. This is because the theoretical capacity of silicon (4199 mAh / g) is more than 10 times greater than that of graphite (372 mAh / g), and a significant improvement in battery capacity can be expected. The development of silicon materials as negative electrode active materials is being considered not only for silicon itself, but also for alloys and compounds such as oxides. Furthermore, the active material shape is being considered, ranging from the standard coated type for carbon-based active materials to an integrated type in which the material is deposited directly on the current collector.

[0006] However, when silicon is used as the primary raw material for the negative electrode active material, the negative electrode active material expands and contracts during charging and discharging, making it prone to cracking, primarily near the surface of the negative electrode active material. Furthermore, ionic substances are generated within the active material, making it prone to cracking. When the surface layer of the negative electrode active material cracks, a new surface is created, increasing the reactive area of ​​the active material. At this time, the electrolyte decomposes on the new surface, and a coating of the electrolyte decomposition product is formed on the new surface, consuming the electrolyte. This can lead to a deterioration in cycle performance.

[0007] To date, various studies have been conducted on negative electrode active materials and electrode configurations for lithium-ion secondary batteries that are primarily made of silicon materials in order to improve the initial battery efficiency and cycle characteristics.

[0008] Specifically, to achieve good cycle characteristics and high safety, silicon and amorphous silicon dioxide are simultaneously deposited using a vapor-phase method (see, for example, Patent Document 1). Furthermore, to achieve high battery capacity and safety, a carbon material (electron conductor) is provided on the surface of silicon oxide particles (see, for example, Patent Document 2). Furthermore, to improve cycle characteristics and achieve high input / output characteristics, an active material containing silicon and oxygen is prepared, and an active material layer with a high oxygen ratio near the current collector is formed (see, for example, Patent Document 3). Furthermore, to improve cycle characteristics, oxygen is incorporated into the silicon active material, and the silicon active material is formed so that the average oxygen content is 40 at% or less and the oxygen content is higher near the current collector (see, for example, Patent Document 4).

[0009] In addition, in order to improve the initial charge / discharge efficiency, Si phase, SiO ２ , M ｙ In order to improve cycle characteristics, nanocomposites containing SiO2 and metal oxides are used (see, for example, Patent Document 5). 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). 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 so that the difference between the maximum and minimum molar ratios near the interface between the active material and the current collector is 0.4 or less (see, for example, Patent Document 7). To improve battery load characteristics, a lithium-containing metal oxide is used (see, for example, Patent Document 8). To improve cycle characteristics, a hydrophobic layer such as a silane compound is formed on the surface of the silicon material (see, for example, Patent Document 9).

[0010] In addition, in order to improve cycle characteristics, silicon oxide is used and a graphite coating is formed on the surface thereof to impart conductivity (see, for example, Patent Document 10). In Patent Document 10, the shift value obtained from the RAMAN spectrum of the graphite coating is 1330 cm －１ and 1580 cm －１ A broad peak appears at the peak intensity ratio I １３３０ / I １５８０ is 1.5<I １３３０ / I １５８０ <3. In order to achieve high battery capacity and improved cycle characteristics, particles having a silicon microcrystalline phase dispersed in silicon dioxide are used (see, for example, Patent Document 11). In addition, in order to improve overcharge and overdischarge characteristics, silicon oxide is used in which the atomic ratio of silicon to oxygen is controlled to 1:y (0<y<2) (see, for example, Patent Document 12).

[0011] In addition, Hitachi Maxell began shipping lithium ion secondary batteries using silicon oxide in June 2010, which are rectangular secondary batteries for smartphones that use nanosilicon composites (see, for example, Non-Patent Document 1). ０＋ ~Si ４＋ It is a composite material with various oxidation states (Non-Patent Document 2). Kapaklis also reported that by applying a thermal load to silicon oxide, Si and SiO ２ proposed a disproportionated structure that is divided into

[0012] Miyachi et al. have reported that among silicon oxides with disproportionated structures, Si and SiO contribute to charge and discharge. ２ have focused on the above (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 + SiO ２ ) + 6.85Li ＋ + 6.85e － → 1.4 Li ３．７５ Si + 0.4Li ４ SiO ４ + 0.2SiO ２ In the reaction formula, silicon oxide is composed of Si and SiO ２ reacts with Li to form Li silicide, Li silicate, and some unreacted SiO ２ Divided into two.

[0013] The Li silicate produced here is irreversible, and once formed, it is generally said to be a stable substance that does not release Li. The capacity per mass calculated from this reaction formula is close to the experimental value, and is recognized as the reaction mechanism of silicon oxide. Kim et al. ４ SiO ４ As, ７ Li-MAS-NMR ２９ The identification was carried out using Si-MAS-NMR (Non-Patent Document 6).

[0014] This irreversible capacity is the weakest point of silicon oxides, and improvement is needed. Kim et al. have used a Li pre-doping method to form Li silicate in advance, significantly improving the initial efficiency of the battery and producing a negative electrode that can withstand practical use (Non-Patent Document 7). They have also proposed a powder treatment method instead of Li doping the electrode, which has improved the irreversible capacity (Patent Document 13).

[0015] On the other hand, the price of Li metal used for Li doping fluctuates greatly depending on the market situation, and there are many issues when it comes to industrialization. Therefore, CVD-Si-C, which uses silane gas to create porous carbon and generates nanosilicon inside, has achieved a higher energy density than Li-doped SiO (Patent Documents 14 and 15).

[0016] JP 2001-185127 A JP 2002-042806 A JP 2006-164954 A JP 2006-114454 A JP 2009-070825 A JP 2008-282819 A JP 2008-251369 A JP 2008-177346 A JP 2007-234255 A JP 2009-212074 A JP 2009-205950 A JP 06-325765 A JP 2015-156355 A U.S. Pat. No. 10,608,254 U.S. Pat. No. 11,165,054

[0017] Battery Industry Association Newsletter "Denchi" May 1, 2010 issue, p. 10 A. Hohl, T. Wieder, PA van Aken, TE Weirich, G. Denninger, M. Vidal, S. Oswald, C. Deneke, J. Mayer, and H. Fuess: J. Non-Cryst. Solids, 320, (2003), 255.V. Kapaklis, J. Non-Crystalline Solids, 354 (2008) 612Mariko Miyachi, Hironori Yamamoto, and Hidemasa Kawai, J. Electrochem. Soc. 2007 volume 154, issue 4, A376-A380M. Yamada, A. Inaba, A. Ueda, K. Matsumoto, T. Iwasaki, T. Ohzuku, J. Electrochem. Soc., 159, A1630 (2012) Taeahn Kim, Sangjin Park, and Seung M. Oh, J. Electrochem. Soc. volume 154, (2007), A1112-A1117. Hye Jin Kim, Sunghun Choi, Seung Jong Lee, Myung Won Seo, Jae Goo Lee, Erhan Deniz, Yong Ju Lee, Eun Kyung Kim, and Jang Wook Choi, Nano Lett. 2016, 16, 282-288. Frontiers of Development of Automotive Lithium-ion Batteries, pp. 96-111, CMC Publishing, published November 27, 2020.

[0018] As mentioned above, in recent years, small electronic devices such as mobile terminals have become more powerful and multifunctional, and the lithium-ion secondary batteries that serve as their main power sources are required to have larger battery capacities. One method to solve this problem is to develop lithium-ion secondary batteries with a negative electrode that uses silicon as the main material.

[0019] Furthermore, lithium-ion secondary batteries using silicon materials are expected to have initial charge-discharge characteristics and cycle characteristics comparable to those of lithium-ion secondary batteries using carbon-based active materials. Therefore, by using silicon oxide modified by Li insertion and partial deintercalation as the negative electrode active material, cycle characteristics and initial charge-discharge characteristics have been improved. Recently, by incorporating Li in advance and forming Li silicate, primarily silicon oxide, the irreversible capacity, a disadvantage of silicon oxide, has been reduced, and this has actually begun to be commercialized. Even when a prototype battery was fabricated by replacing 100% of this silicon oxide with Li—SiO—C (Non-Patent Document 8), which uses Li, with carbon anode material, the capacity improvement was only in the high 20% range compared to carbon anode material. This means that further improvements in battery capacity are required when considering the increasing performance of small electronic devices (5G, etc.) and the improvement in driving range of electric vehicles.

[0020] Therefore, CVD-Si-C, which has a low irreversible capacity, has been developed, but it is known that the reaction between Si and the electrolyte results in insufficient high-speed charging and battery cycle characteristics.

[0021] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an apparatus for manufacturing a negative electrode active material that can manufacture a negative electrode active material that can increase capacity while maintaining battery characteristics.

[0022] In order to solve the above-mentioned problems, the present invention provides an apparatus for producing an anode active material having anode active material particles, wherein the anode active material particles contained in the anode active material to be produced include a porous carbon structure, and amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nanosilicon oxide and the polycrystalline silicon and their oxides are dispersed inside the porous carbon structure as a dispersed material, the low-valence nanosilicon oxide includes each state of SiOx:x<1.0, and the low-valence nanosilicon oxide has an average particle size of 50 nm or less as determined by image processing of a cross-sectional TEM image, the apparatus for producing an anode 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 material is supplied to the porous carbon structure held inside, and in the apparatus for producing an anode active material, when a design pressure is P [MPaG], an internal volume V [m ３ ] is configured so that the value of PV≦0.004 is within the range of PV≦0.004, and the manufacturing apparatus for a negative electrode active material has a heating mechanism that can heat the material in the range of 300 to 1200°C.

[0023] The negative electrode active material manufacturing apparatus of the present invention can efficiently manufacture a negative electrode active material in which amorphous low-valence nano-silicon oxide is dispersed inside a porous carbon structure. Since the negative electrode active material that can be manufactured has amorphous low-valence nano-silicon oxide dispersed inside a porous carbon structure, the presence of the porous carbon structure can reduce the adverse effects caused by the expansion of the internal low-valence nano-silicon oxide. In addition, general SiO is Si ４＋However, the anode active material that can be produced using the anode active material production apparatus of the present invention includes the SiOx:x<1.0 state, and therefore maintains a lower irreversible capacity than general SiO. Furthermore, the Si-O bond can suppress the decomposition of the electrolyte, making it possible to reduce the SEI (Solid Electrolyte Interphase) that accumulates in the surface layer. Furthermore, since the particle size of the low-valence nanosilicon oxide (particle size determined by image processing of a cross-sectional TEM image of the low-valence nanosilicon oxide) is an average of 50 nm or less, it is easy to ensure 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 preferable that the range is:

[0025] The negative electrode active material manufacturing apparatus of the present invention with such a design pressure and volume can more efficiently manufacture a negative electrode active material in which amorphous low-valent nano silicon oxide is dispersed inside a porous carbon structure.

[0026] In the apparatus for producing a negative electrode active material of the present invention, the raw material gas is preferably a silane-based gas, and the silane-based gas may be at least one of monosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

[0027] A negative electrode active material manufacturing apparatus that uses these silane-based gases as raw material gases can more efficiently manufacture negative electrode active materials in which amorphous low-valent nanosilicon oxide is dispersed inside a porous carbon structure.

[0028] The negative electrode active material manufacturing apparatus of the present invention preferably has a stirring mechanism for stirring the porous carbon structure held therein, and in this case, the stirring mechanism preferably has one or more mechanisms selected from a screw, a stirring blade, and a blade.

[0029] A negative electrode active material manufacturing apparatus having such a stirring mechanism makes it easier to control the stirring of the contents during the reaction, and can more efficiently produce a negative electrode active material in which amorphous low-valent nanosilicon oxide is dispersed inside the porous carbon structure.

[0030] The negative electrode active material manufacturing apparatus preferably has a mechanism for rotating the entire apparatus, and preferably has a mechanism for tilting the entire apparatus.

[0031] A negative electrode active material manufacturing device having such a rotation mechanism or tilt mechanism can easily control the stirring of the contents during the reaction by rotation or tilting, and can more efficiently produce a negative electrode active material in which amorphous low-valent nanosilicon oxide is dispersed inside the porous carbon structure.

[0032] The negative electrode active material manufacturing apparatus of the present invention preferably has a gas diffusion device at the tip of the raw material gas inlet pipe for introducing the raw material gas, and in this case, the gas diffusion device preferably has one or more mechanisms selected from a sparger, a sintered metal, and a mesh.

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

[0034] The present invention also provides a method for producing a negative electrode active material having negative electrode active material particles using any of the above-mentioned negative electrode active material production apparatuses, the method comprising the steps of: preparing a porous carbon structure; depositing silicon inside the porous carbon structure by flowing a silane-based gas through the porous carbon structure under heating; cooling the material with silicon deposited inside the porous carbon structure to 50°C or less; and, after the cooling, converting at least a portion of the silicon into low-valence nanosilicon oxide by introducing oxygen diluted 20 times with nitrogen gas into the material with silicon deposited inside the porous carbon structure while adjusting the temperature of the material with silicon deposited inside the porous carbon structure to maintain 50°C or less, thereby producing 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 dispersed substances inside the porous carbon structure.

[0035] Such a method for producing a negative electrode active material makes it possible to simply and efficiently produce a negative electrode active material in which amorphous low-valent nanosilicon oxide is dispersed inside a porous carbon structure, as described above.

[0036] The negative electrode active material manufacturing apparatus of the present invention can efficiently manufacture a negative electrode active material in which amorphous low-valence nano-silicon oxide is dispersed inside a porous carbon structure. Furthermore, since the negative electrode active material that can be manufactured has amorphous low-valence nano-silicon oxide dispersed inside a porous carbon structure, the presence of the porous carbon structure can reduce the adverse effects caused by the expansion of the internal low-valence nano-silicon oxide. Furthermore, general SiO is Si ４＋However, the anode active material that can be produced using the anode active material production apparatus of the present invention includes the SiOx:x<1.0 state, and therefore maintains a lower irreversible capacity than general SiO. Furthermore, the Si—O bond can suppress the decomposition of the electrolyte, thereby reducing the solid electrolyte interphase (SEI) that accumulates in the surface layer. Furthermore, since the particle size of the low-valence nanosilicon oxide (particle size determined by image processing of a cross-sectional TEM image of the low-valence nanosilicon oxide) is an average of 50 nm or less, it is easy to ensure that the Si—O bond is appropriately formed. As a result, anode electrodes using the anode active material of the present invention can achieve high initial efficiency, high capacity, high input characteristics, and high cycle characteristics.

[0037] Fig. 1 is a cross-sectional view showing an example of the configuration of an apparatus for manufacturing a negative electrode active material of the present invention. Fig. 2 is a cross-sectional view showing the configuration of a negative electrode containing the negative electrode active material of the present invention. Fig. 3 is an exploded view showing an example of the configuration (laminate film type) of a lithium ion secondary battery containing the negative electrode active material of the present invention. Fig. 4 is a flow chart showing an example of a method for manufacturing a negative electrode active material using the apparatus for manufacturing a negative electrode active material of the present invention.

[0038] Hereinafter, the present invention will be described in detail with reference to the preferred embodiments, but the present invention is not limited to these.

[0039] As mentioned above, one method for increasing the battery capacity of lithium-ion secondary batteries is to use a negative electrode with a carbon structure mainly made of low-valent nanosilicon oxide. Lithium-ion secondary batteries using this active material are expected to have high battery capacity while exhibiting battery characteristics similar to those of lithium-ion secondary batteries using carbon-based active materials.

[0040] Therefore, the present inventors conducted extensive research to obtain a negative electrode active material that, when used as a negative electrode of a secondary battery, can achieve high cycle characteristics, improve initial charge-discharge characteristics, and increase battery capacity, and have arrived at the present invention.

[0041] In particular, the CVD-Si-C disclosed in Patent Documents 14 and 15 has an issue of excessive reactivity with the electrolyte. In the present invention, in order to suppress such a reaction with the electrolyte, the Si portion is converted to a Si-O phase, and the siloxane bond specific to silicon oxide is used, thereby significantly suppressing the reactive decomposition of the electrolyte. Furthermore, since the Si-O material having the siloxane bond has good Li acceptability, an apparatus for manufacturing anode active material has been developed that can produce anode active material that can ensure high-speed charging.

[0042] [Apparatus for manufacturing a negative electrode active material of the present invention] The apparatus for manufacturing a negative electrode active material of the present invention is an apparatus for manufacturing a negative electrode active material having negative electrode active material particles, wherein the negative electrode active material particles contained in the negative electrode active material to be manufactured comprise a porous carbon structure, and amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nanosilicon oxide and polycrystalline silicon and their oxides are dispersed inside the porous carbon structure as a dispersed material, the low-valence nanosilicon oxide includes each state of SiOx:x<1.0, and the low-valence nanosilicon oxide has an average particle size of 50 nm or less as determined by image processing of a cross-sectional TEM image, the apparatus for manufacturing a 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 material is supplied to the porous carbon structure held inside, and the apparatus for manufacturing a negative electrode active material has an internal volume V [m ３ ] is configured so that the value of PV≦0.004 is within the range of PV≦0.004, and the manufacturing apparatus for a negative electrode active material is characterized in that it has a heating mechanism that can heat the material in the range of 300 to 1200°C.

[0043] FIG. 1 shows a cross-sectional view illustrating an example of the configuration of an apparatus for manufacturing anode active material according to the present invention. The shape of the apparatus for manufacturing anode active material 1 can be, for example, cylindrical. The apparatus for manufacturing anode active material 1 also has a raw material gas inlet pipe 3. The apparatus for manufacturing anode active material 1 can hold a reactant 5 inside. The reactant 5 is a porous carbon structure before reaction. The apparatus for manufacturing anode active material 1 has a structure in which a raw material gas of a dispersed material is supplied to the porous carbon structure thus held inside from the raw material gas inlet pipe 3. Furthermore, the apparatus for manufacturing anode active material 1 has an internal volume V [m ３ ] is configured to be in the range of PV≦0.004. The negative electrode active material manufacturing apparatus 1 also has a heating mechanism 6, which is capable of heating in the range of 300 to 1200°C.

[0044] [Negative electrode active material producible by the negative electrode active material manufacturing apparatus of the present invention] The negative electrode active material producible by the negative electrode active material manufacturing apparatus of the present invention includes negative electrode active material particles. The negative electrode active material particles include a porous carbon structure, and amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both amorphous low-valence nanosilicon oxide and polycrystalline silicon and their oxides are dispersed within the porous carbon structure as dispersed materials. The low-valence nanosilicon oxide includes SiOx:x<1.0 and has an average particle size of 50 nm or less as determined by image processing of a cross-sectional TEM image.

[0045] Such a negative electrode active material has amorphous low-valence nano silicon oxide dispersed inside the porous carbon structure, and the presence of the porous carbon structure can reduce the adverse effects caused by the expansion of the low-valence nano silicon oxide inside. ４＋However, the anode active material that can be produced by the anode active material production apparatus of the present invention includes the states of SiOx:x<1.0, and therefore can maintain a lower irreversible capacity than general SiO. Furthermore, the Si-O bond can suppress decomposition of the electrolyte, making it possible to reduce the solid electrolyte interface (SEI) that accumulates in the surface layer. Note that, in the present invention, it is sufficient that the amorphous low-valent nanosilicon oxide is dispersed inside the porous carbon structure, and some of the nanosilicon oxide may be crystalline.

[0046] As described below, the anode active material that can be produced using the anode active material production apparatus of the present invention can be produced as a Si-Ox material having siloxane bonds in the Si phase to suppress the decomposition reaction of the electrolyte, which is insufficient with CVD-Si-C produced from general silane gas. The purpose of intentionally creating Si-O bonds is that while Si-Si bonds promote the decomposition of the electrolyte, Si-O bonds react more slowly with the electrolyte than Si-Si bonds. Furthermore, since Si-O bonds can suppress the decomposition of the electrolyte, it is possible to reduce the SEI that accumulates on the surface layer of the CVD-Si-C. As a result, battery cycle characteristics are improved. Furthermore, while grain boundaries with Si-Si bonds reduce Li diffusivity, Si-O bonds improve Li diffusivity and improve high-speed charging. The material of the present invention can be defined as CVD-SiOx-C in contrast to CVD-Si-C because the portion that primarily contributes to charge and discharge is a low-valence nanosilicon oxide. The active material thus produced can have high energy density and high-speed charging properties while maintaining the cycle characteristics of the battery.

[0047] Furthermore, since the tetravalent Si that constitutes SiO is an irreversible component, in the anode active material that can be produced by the anode active material production apparatus of the present invention, it is preferable that the low-valence nanosilicon oxide is substantially in a composite state of zero valence, monovalent, and divalent. In particular, it is preferable that this low-valence nanosilicon oxide is substantially predominantly monovalent to divalent. By making SiOx of divalent or less predominant, the irreversible capacity is larger than that of silicon alone, but it is possible to maintain a lower irreversible capacity than general SiO.

[0048] The negative electrode active material manufacturing apparatus 1 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 The negative electrode active material manufacturing apparatus of the present invention having such a design pressure and volume can more efficiently manufacture a negative electrode active material in which amorphous low-valent nano silicon oxide is dispersed inside the porous carbon structure.

[0049] Furthermore, the negative electrode active material manufacturing apparatus 1 is preferably capable of introducing a silane-based gas as a raw material gas from the raw material gas inlet pipe 3. In particular, the silane-based gas may be at least one of monosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. A negative electrode active material manufacturing apparatus using such a silane-based gas as a raw material gas can more efficiently manufacture a negative electrode active material in which amorphous low-valent nanosilicon oxide is dispersed inside a porous carbon structure.

[0050] Furthermore, the negative electrode active material manufacturing apparatus 1 preferably has a stirring mechanism 7 that stirs the porous carbon structure held therein. In this case, the stirring mechanism preferably has one or more mechanisms selected from a screw, a stirring impeller, and a blade. A negative electrode active material manufacturing apparatus having such a stirring mechanism 7 can easily control the stirring of the contents during the reaction, and can more efficiently produce a negative electrode active material in which amorphous low-valent nano silicon oxide is dispersed inside the porous carbon structure.

[0051] It is also preferable that the negative electrode active material manufacturing apparatus 1 has a mechanism 8 for rotating the entire apparatus and a mechanism 9 for tilting the entire apparatus. The negative electrode active material manufacturing apparatus 1 having such a rotation mechanism 8 and tilt mechanism 9 can easily control the stirring of the contents during the reaction by rotation or tilting, and can more efficiently manufacture a negative electrode active material in which amorphous low-valent nano silicon oxide is dispersed inside the porous carbon structure.

[0052] Furthermore, the negative electrode active material manufacturing apparatus 1 preferably has a gas diffusion device 4 at the tip of a raw material gas inlet pipe 3 for introducing a raw material gas. In this case, the gas diffusion device 4 preferably has one or more mechanisms selected from a sparger, a sintered metal, and a mesh.

[0053] A negative electrode active material manufacturing apparatus having such a gas diffusion device 4 can more uniformly supply raw material gas, making it easier to control the reaction and more efficiently manufacturing a negative electrode active material in which amorphous low-valent nano-silicon oxide is dispersed inside a porous carbon structure.

[0054] In the negative electrode active material that can be produced by the negative electrode active material production apparatus of the present invention, the grain size of zero-valent Si constituting the low-valent nanosilicon oxide, calculated using the Scherrer equation from the peak measured by X-ray diffraction measurement of the negative electrode active material particles, is preferably in the range of 1 nm to 5 nm. Such a grain size of zero-valent Si that is substantially amorphous is preferable.

[0055] Calculation of crystallite size by XRD can be performed, for example, under the following conditions. For broad peaks, analysis software TOPAS can be used, for example, under the following conditions. XRD measurement: Apparatus: Bruker D2 PHASER X-ray source: Cu Divergence slit: 0.5° Incident side solar: 4° Receiving side solar: 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 "Calculate Error" and "Use Extrapolation"

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

[0057] The NMR measurement for measuring the valence of the low-valence nano silicon oxide can be carried out, for example, under the following conditions. ２９ Si MAS NMR (Magic Angle Spinning Nuclear Magnetic Resonance) Apparatus: Bruker 700 NMR spectrometer, Probe: 4 mm HR-MAS rotor 50 μL, Sample rotation speed: 10 kHz, Measurement environment temperature: 25° C.

[0058] The XPS measurement can be carried out, for example, under the following conditions: XPS Apparatus: X-ray photoelectron spectrometer, X-ray source: monochromated Al Kα ray, X-ray spot diameter: 100 μm, Ar ion gun sputtering conditions: 0.5 kV 2 mm×2 mm.

[0059] Furthermore, in the negative electrode active material that can be produced by the negative electrode active material production apparatus of the present invention, it is preferable that the low-valence nanosilicon oxide dispersed in the porous carbon structure has x increasing from the center of the porous carbon structure to the surface. In the present invention, since low-valence nanosilicon oxide is dispersed in the porous carbon structure, x tends to increase (the oxygen content increases) from the center of the porous carbon structure to the surface during production. Because the silicon oxidation rate is high at the surface, decomposition of the electrolyte can be more effectively suppressed, while the silicon oxidation rate is low inside the active material, allowing for greater battery capacity.

[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 "negative electrode") containing a negative electrode active material that can be produced by the negative electrode active material production apparatus of the present invention will be described.

[0061] [Configuration of Negative Electrode] Fig. 2 shows a cross-sectional view of a negative electrode containing a negative electrode active material that can be produced by the negative electrode active material production apparatus of the present invention. As shown in Fig. 2, the negative electrode 10 has a negative electrode active material layer 12 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, the negative electrode of the nonaqueous electrolyte secondary battery of the present invention does not necessarily have to have the negative electrode current collector 11.

[0062] [Negative electrode current collector] The negative electrode current collector 11 is made of a highly conductive material that has excellent mechanical strength. Examples of conductive materials 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 elements. This is because the physical strength of the negative electrode current collector is improved. In particular, when an active material layer that expands during charging is included, if the current collector contains the above elements, it is effective in suppressing deformation of the electrode including the current collector. The contents of the above contained elements are not particularly limited, but are preferably 100 mass ppm or less each. This is because a higher deformation suppression effect can be obtained. Such a deformation suppression effect can further improve cycle characteristics.

[0064] The surface of the negative electrode current collector 11 is preferably roughened, and the ten-point average roughness Rz of the surface is preferably 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 an electrolytic treatment, an embossing treatment, or a chemical etching treatment.

[0065] [Negative Electrode Active Material Layer] The negative electrode active material layer 12 may contain multiple types of negative electrode active materials, such as a carbon-based active material, in addition to the silicon-based active material particles of the present invention. Furthermore, in terms of battery design, it may also contain other materials such as a thickener (also referred to as a "binding agent" or "binder") and a conductive additive.

[0066] [Negative Electrode Active Material and Method for Producing Negative Electrode] Next, an example of a method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery of the present invention and a negative electrode using the same will be described.

[0067] First, a method for producing the negative electrode active material contained in the negative electrode will be described. The method for producing a negative electrode active material of the present invention is a method for producing a negative electrode active material having negative electrode active material particles using the above-mentioned negative electrode active material production apparatus of the present invention, and includes the steps of: preparing a porous carbon structure; depositing silicon inside the porous carbon structure by flowing a silane-based gas through the porous carbon structure under heating; cooling the material with silicon deposited inside the porous carbon structure to 50°C or less; and, after the cooling, converting at least a portion of the silicon into low-valence nanosilicon oxide by introducing oxygen diluted 20 times with nitrogen gas into the material with silicon deposited inside the porous carbon structure while adjusting the temperature of the material with silicon deposited inside the porous carbon structure to maintain 50°C or less, thereby producing 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 dispersed substances inside the porous carbon structure.

[0068] Such a method for producing a negative electrode active material makes it possible to simply and efficiently produce a negative electrode active material in which amorphous low-valent nanosilicon oxide is dispersed inside a porous carbon structure, as described above.

[0069] Each step of the method for producing the negative electrode active material will be described with reference to steps S1 to S4 in FIG.

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

[0071] Next, a silane-based gas, which is a source gas, is flowed into the porous carbon structure prepared in step S1 under heating, thereby depositing silicon inside the porous carbon structure (step S2).

[0072] After step S1 and before step S2, it is preferable to store the porous carbon structure in a manufacturing apparatus 1 (vacuum container) and evacuate it. The degree of vacuum can be, for example, but is not limited to, about -100 kPa. After evacuating, it is preferable to restore pressure with nitrogen and heat to about 350 to 450°C using an external heater while nitrogen is flowing. This heating can be performed for 5 minutes to 1 hour. By performing such evacuation and preheating in the presence of nitrogen, nucleation for silicon deposition in step S2 and removal of hydrogen and water attached to the porous carbon structure can be performed, thereby more reliably carrying out silicon deposition in step S2.

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

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

[0075] After the cooling (step S3), the temperature of the material with silicon deposited inside the porous carbon structure is adjusted to maintain 50°C or less. Then, oxygen diluted with nitrogen gas is introduced into the material with silicon deposited inside the porous carbon structure, converting at least a portion of the silicon into low-valence nano-silicon oxide (step S4). This step allows the formation of Si—O bonds. It is more preferable to maintain the temperature at 35°C or less.

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

[0077] Furthermore, in step S4, if the internal temperature rises and exceeds 50°C, silicon dioxide will be formed in some parts, which is undesirable as a negative electrode active material. Therefore, in step S4, it is necessary to adjust the temperature of the material so that it remains at 50°C or lower. Furthermore, in order to facilitate the oxidation reaction and the formation of Si—O bonds, the material temperature in step S4 is preferably set to, for example, 25°C or higher, and more preferably 30°C or higher.

[0078] The oxidation time in step S4 (flow time of oxygen diluted with nitrogen gas) can be, for example, 30 minutes to 5 hours, preferably 1 hour to 3 hours. After the flow of oxygen diluted with nitrogen gas, the flow can be switched to nitrogen gas for further cooling. The flow of nitrogen gas alone can be, for example, 30 minutes to 2 hours.

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

[0080] The material is then removed from the storage container. Through the above steps, negative electrode active material particles can be produced in which amorphous low-valent nano-silicon oxide is dispersed inside the porous carbon structure.

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

[0082] [Configuration of Laminate Film Type Secondary Battery] The laminate film type lithium ion secondary battery 30 shown in Fig. 3 mainly comprises a wound electrode body 31 housed inside a sheet-like exterior member 35. This wound electrode body 31 has a separator between the positive and negative electrodes and is wound. There are also cases where a separator is between the positive and negative electrodes and a laminate is housed. In either type of electrode body, 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 periphery of the electrode body is protected by protective tape.

[0083] The positive and negative electrode leads 32, 33 are, for example, led out 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 laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order, and the outer peripheral edges of the fusion layers of the two films of this laminate film are fused together or attached with an adhesive or the like so that the fusion layer faces the electrode body 31. The fusion portion is, for example, a film such as polyethylene or polypropylene, and the metal portion is, for example, aluminum foil. The protection layer is, for example, nylon or the like.

[0085] An adhesive film 34 is inserted between the exterior member 35 and the positive and negative electrode leads to prevent outside air from entering, and is made of, for example, polyethylene, polypropylene, or polyolefin resin.

[0086] The positive electrode has a positive electrode active material layer on one or both sides of a positive electrode current collector, similar to the negative electrode 10 in FIG. 2, for example.

[0087] The positive electrode current collector is made of a conductive material such as aluminum.

[0088] The positive electrode active material layer contains one or more positive electrode materials capable of absorbing and releasing lithium ions, and may contain other materials such as a positive electrode binder, a positive electrode conductive additive, a dispersant, etc. Depending on the design, the positive electrode binder and the positive electrode conductive additive may be similar in detail to, for example, the negative electrode binder and the negative electrode conductive additive already described.

[0089] The positive electrode material is preferably a lithium-containing compound. Examples of the lithium-containing compound include a composite oxide made of lithium and a transition metal element, or a phosphate compound containing lithium and a transition metal element. Among these positive electrode materials, compounds containing at least one of nickel, iron, manganese, and cobalt are preferred. Their chemical formulas are, for example, Li ｘ M １ O ２ Or Li ｙ M ２ P.O. ４ In the formula, M １ , M ２ represents at least one transition metal element. The values ​​of x and y vary depending on the charge / discharge state of the battery, but are generally expressed as 0.05≦x≦1.10 and 0.05≦y≦1.10.

[0090] Examples of composite oxides containing lithium and transition metal elements include lithium cobalt composite oxide (Li ｘ CoO ２ ), lithium nickel composite oxide (Li ｘ NiO ２ ), lithium nickel cobalt composite oxide, etc. Examples of the lithium nickel cobalt composite oxide include lithium nickel cobalt aluminum composite oxide (NCA) and lithium nickel cobalt manganese composite oxide (NCM).

[0091] Examples of phosphate compounds containing lithium and a transition metal element include lithium iron phosphate compounds (LiFePO ４ ) or lithium iron manganese phosphate compound (LiFe １－ｕ Mn ｕ P.O. ４ (0<u<1)). By using these positive electrode materials, it is possible to obtain a high battery capacity and also excellent cycle characteristics.

[0092] [Negative Electrode] The negative electrode has a configuration similar to that of the lithium-ion secondary battery negative electrode 10 shown in Fig. 2, and has, for example, negative electrode active material layers on both sides of a current collector. This negative electrode preferably has a negative electrode charge capacity greater than the electrical capacity (charge capacity as a battery) obtained from the positive electrode active material. This can suppress the deposition of lithium metal on the negative electrode.

[0093] The positive electrode active material layer is provided on a portion of both sides of the positive electrode current collector, and similarly, the negative electrode active material layer is provided on a portion 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 the opposing positive electrode active material layer is not present. This is for the purpose of designing a stable battery.

[0094] The region where the negative electrode active material layer and the positive electrode active material layer do not face each other is hardly affected by charging and discharging, and therefore the state of the negative electrode active material layer is maintained as it was immediately after formation, allowing the composition of the negative electrode active material to be accurately determined with good reproducibility, regardless of whether charging and discharging are performed.

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

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

[0097] The solvent can be, for example, a non-aqueous solvent. Examples of non-aqueous solvents include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, 1,2-dimethoxyethane, and tetrahydrofuran. Among these, it is desirable to use at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. This is because better properties can be obtained. In this case, more advantageous properties can be obtained 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. This is because the dissociation property and ion mobility of the electrolyte salt are improved.

[0098] When an alloy-based negative electrode is used, it is particularly desirable to use a solvent containing at least one of a halogenated chain carbonate or a halogenated cyclic carbonate. This allows a stable coating to be formed on the surface of the negative electrode active material during charge and discharge, particularly during charging. Here, the halogenated chain carbonate is a chain carbonate having a halogen as a constituent element (i.e., at least one hydrogen atom is substituted with a halogen). Furthermore, the halogenated cyclic carbonate is a cyclic carbonate having a halogen as a constituent element (i.e., at least one hydrogen atom is substituted with a halogen).

[0099] Although the type of halogen is not particularly limited, fluorine is preferred because it forms a better coating than other halogens. Furthermore, the more halogens there are, the more desirable they are because the resulting coating is more stable and the decomposition reaction of the electrolyte is reduced.

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

[0101] It is preferable that the solvent additive contains an unsaturated carbon-bond cyclic carbonate. This is because a stable coating is formed on the negative electrode surface during charge and discharge, and the decomposition reaction of the electrolyte can be suppressed. Examples of the unsaturated carbon-bond cyclic carbonate include vinylene carbonate and vinylethylene carbonate.

[0102] It is also preferable that the solvent additive contains sultone (cyclic sulfonic acid ester), which improves the chemical stability of the battery. Examples of sultones include propane sultone and propene sultone.

[0103] Furthermore, it is preferable that the solvent contains an acid anhydride, because this improves the chemical stability of the electrolyte solution. Examples of acid anhydrides include propanedisulfonic acid anhydride.

[0104] The electrolyte salt may include, for example, one or more light metal salts such as lithium salts. Examples of the lithium salt include lithium hexafluorophosphate (LiPF ６ ), lithium tetrafluoroborate (LiBF ４ ) etc.

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

[0106] EXAMPLES The present invention will be explained in more detail below by showing examples and comparative examples of the present invention, but the present invention is not limited to these examples.

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

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

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

[0110] The negative electrode current collector was a 15 μm-thick electrolytic copper foil. This electrolytic copper foil contained carbon and sulfur at concentrations of 70 mass ppm each. Finally, the negative electrode mixture slurry was applied to the negative electrode current collector and dried at 100°C for 1 hour in a vacuum atmosphere. After drying, the deposition amount of the negative electrode active material layer per unit area on one side of the negative electrode (also referred to as area density) was 7.0 mg / cm. ２ It was.

[0111] [Assembly of Test Coin Battery] Next, solvents ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed, and then an electrolyte salt (lithium hexafluorophosphate: LiPF ６ The electrolyte solution was prepared by dissolving EC and DMC in a solvent with a volume ratio of 30:70, and the electrolyte salt content was 1 mol / kg relative to the solvent. Vinylene carbonate (VC) and fluoroethylene carbonate (FEC) were added as additives in amounts of 1.0% by mass and 2.0% by mass, respectively.

[0112] Next, a coin battery was assembled as follows: First, a Li foil having 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 opposite a Li foil attached to an aluminum clad via a separator. After injection of an electrolyte, a 2032 coin battery was fabricated.

[0114] [Measurement of Initial Efficiency] The initial efficiency was measured under the following conditions. First, the coin battery prepared for the initial efficiency test was charged (initial charge) in CCCV mode at a charge rate equivalent to 0.03 C. The CV was 0 V and the cut-off current was 0.04 mA. Next, CC discharge (initial discharge) was performed at a discharge rate of 0.03 C and a discharge cut-off voltage of 1.2 V.

[0115] When examining the initial charge-discharge characteristics, the initial efficiency (hereinafter sometimes referred to as initial efficiency) was calculated using the formula: initial efficiency (%) = (initial discharge capacity / initial charge capacity) × 100.

[0116] [Production of Lithium-Ion Secondary Batteries and Battery Evaluation] From the obtained initial data, a counter positive electrode was designed so that the utilization rate of the negative electrode would be 95%. The utilization rate was calculated from the capacity of the positive and negative electrodes obtained with the counter electrode Li, based on the following formula: Utilization rate = (positive electrode capacity - negative electrode loss) / (negative electrode capacity - negative electrode loss) x 100 Based on this design, lithium-ion secondary batteries (lithium-ion secondary batteries as shown in Figure 3) of the Examples and Comparative Examples were produced. Battery evaluation was performed on each of the lithium-ion secondary batteries of the Examples and Comparative Examples.

[0117] The cycle characteristics were investigated as follows. First, to stabilize the battery, two charge / discharge cycles were performed at 0.2 C in an atmosphere of 25°C, and the discharge capacity at the second cycle was measured. The battery cycle characteristics were calculated from the discharge capacity at the third cycle, and the battery test was stopped after 1,000 cycles. Charging and discharging were performed at 0.7 C and 0.5 C. The charging voltage was 4.3 V, the discharge cut-off voltage was 2.5 V, and the charge cut-off rate was 0.07 C. Furthermore, the fast charging characteristics were calculated from the discharge capacity at the third cycle, and the battery test was stopped after 500 cycles. Charging and discharging were performed at 4 C and 0.5 C. The charge cut-off voltage was 4.3 V, the discharge cut-off voltage was 2.5 V, and the charge cut-off rate was 0.07 C.

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

[0119]

[0120]

[0121] The negative electrode active material produced in Example 1-1 had the following properties: 1000 cycle retention rate: 80% Single capacity at 1.2 V: 1940 mAh / g Initial efficiency at 1.2 V: 88% 500 cycle retention rate at 4 C charge: 80% Si ０＋ Grain size of SiOx: 1.4 nm Diameter of low valence portion SiOx: 25 nm Valence of SiOx: 0 to 2, 0<x<0.7 In this way, 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 manufacturing apparatuses of Examples 2-1 to 2-11 are shown in Tables 3 and 4. The configurations and operating conditions of Example 1-1 are also shown. As shown in the tables, the processing temperature and operating pressure were changed compared to the manufacturing apparatus for the negative electrode active material of Example 1-1.

[0123]

[0124]

[0125] In Examples 2-1 to 2-11, good samples equivalent to those in Example 1-1 were obtained. Therefore, it was found that good samples could be obtained at a processing temperature of 400 to 450°C, and therefore it was found that the heat-resistant temperature of the negative electrode active material manufacturing apparatus 1 could be made of a material with a temperature limit of 500°C. Furthermore, it was found that a system pressure of 0.01 MPaG was sufficient, and therefore the design pressure could be 0.1 MPaG.

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

[0127]

[0128]

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

[0130] In Comparative Example 3-1, increasing the design pressure would have increased the thickness of the vessel, leading to increased costs and a long time required to manufacture the vessel, so it was determined to be unrealistic and production 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. The configurations and operating conditions of Example 1-1 are also shown. As shown in the tables, the heat-resistant temperature was increased compared to the manufacturing apparatus for the negative electrode active material 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 a nickel alloy in combination.

[0132]

[0133]

[0134] In Examples 4-1 to 4-6, good samples equivalent to those in Example 1-1 were obtained. Therefore, good samples were obtained without any particular effect 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. 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 in Example 5-2, and a gas mixture of dichlorosilane and trichlorosilane in half and half in Example 5-3. Heat-resistant cast steel that is resistant to chlorine was used as the material for the manufacturing apparatus 1 of Examples 5-1 to 5-3.

[0136]

[0137]

[0138] In Examples 5-1 to 5-3, good samples equivalent to those in Example 1-1 were obtained. 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 listed. As shown in the tables, compared to the manufacturing apparatus for the negative electrode active material of Example 1-1, a stirring mechanism was added to the shaft inside the reaction vessel. A screw, stirring blade, and blade were used in each example.

[0140]

[0141]

[0142] In Examples 6-1 to 6-3, good samples equivalent to those in Example 1-1 were obtained. Furthermore, when a screw (Example 6-1), a stirring 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 believed that a screw capable of stirring the entire powder was effective.

[0143] [Examples 7-1 to 7-2] The configurations and operating conditions of the manufacturing apparatuses of Examples 7-1 and 7-2 are shown in Tables 13 and 14. The configurations and operating conditions of Example 1-1 are 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 manufacturing 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 manufacturing apparatus for the negative electrode active material of Example 1-1.

[0144]

[0145] In Examples 7-1 and 7-2, good samples equivalent to those in Example 1-1 were obtained. Furthermore, it was found that the powder movement was limited when using only a rotating mechanism (Example 7-1), but the effect was further enhanced when used in combination with a screw (Example 7-2). A baffle plate may be attached to the reaction vessel itself.

[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. Examples 6-1 and 7-2 are also listed. As shown in the tables, compared to the negative electrode active material production apparatus of Example 6-1 or Example 7-2, a mechanism that allows the entire reaction vessel to be tilted was added.

[0147]

[0148]

[0149] In Examples 8-1 to 8-8, good samples equivalent to those in Example 1-1 were obtained. The tilting also promoted the movement of powder within the system, dramatically improving uniformity. The tilt accuracy was found to be stable 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. The configurations and operating conditions of Example 1-1 are also shown. As shown in the tables, compared to the manufacturing apparatus for the negative electrode active material of Example 1-1, a gas diffusion mechanism was added to the tip of the gas introduction nozzle. A sparger, sintered metal, and mesh were added as the gas diffusion mechanism.

[0151]

[0152]

[0153] In Examples 9-1 to 9-3, good samples equivalent to those in Example 1-1 were obtained. Furthermore, adding a gas diffusion mechanism to the tip of the gas introduction nozzle resulted in improvements in uniformity for the sparger, sintered metal, and mesh. It is believed that the gas was dispersed by the diffusion mechanism, allowing it to be distributed more uniformly throughout the system.

[0154] The present specification includes the following aspects. [1]: A negative electrode active material manufacturing apparatus for manufacturing a negative electrode active material having negative electrode active material particles, wherein the negative electrode active material particles contained in the negative electrode active material to be manufactured include a porous carbon structure, and amorphous low-valence nanosilicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valence nanosilicon oxide and polycrystalline silicon and their oxides are dispersed as a dispersed material inside the porous carbon structure, the low-valence nanosilicon oxide includes each state of SiOx:x<1.0, and the low-valence nanosilicon oxide has an average particle size of 50 nm or less as determined by image processing of a cross-sectional TEM image, the negative electrode active material manufacturing apparatus has a structure capable of holding the porous carbon structure inside, and has a structure in which a raw material gas of the dispersed material is supplied to the porous carbon structure held inside, and the negative electrode active material manufacturing apparatus has an internal volume V [m ３ ] is configured so that PV≦0.004, and the manufacturing apparatus for a negative electrode active material has a heating mechanism that can heat in the range of 300 to 1200°C. [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[3]: The apparatus for producing an anode active material according to [1] above, wherein the raw material gas is a silane-based gas. [4]: ​​The apparatus for producing an anode active material according to [3] above, wherein the silane-based gas is at least one of monosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. [5]: The apparatus for producing an anode active material according to any of [1] to [4] above, which has a stirring mechanism for stirring the porous carbon structure held therein. [6]: The apparatus for producing an anode active material according to [5] above, wherein the stirring mechanism has one or more mechanisms selected from a screw, a stirring impeller, and a blade. [7]: The apparatus for producing an anode active material according to any of [1] to [6] above, which has a mechanism for rotating the entire apparatus for producing an anode active material. [8]: The apparatus for producing an anode active material according to any of [1] to [7] above, which has a mechanism for tilting the entire apparatus for producing an anode active material. [9]: The apparatus for producing a negative electrode active material according to any one of [1] to [8] above, which has a gas diffusion device at the tip of a raw material gas inlet pipe for introducing the raw material gas.

[10] : The apparatus for producing a 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 producing a negative electrode active material having negative electrode active material particles using the negative electrode active material production apparatus according to any one of [1] to

[10] above, comprising the steps of: preparing a porous carbon structure; depositing silicon inside the porous carbon structure by flowing a silane-based gas through the porous carbon structure under heating; cooling the material with silicon deposited inside the porous carbon structure to 50°C or less; and, after the cooling, converting at least a portion of the silicon into low-valence nano-silicon oxide by introducing oxygen diluted 20 times with nitrogen gas into the material with silicon deposited inside the porous carbon structure while adjusting the temperature of the material with silicon deposited inside the porous carbon structure to maintain 50°C or less, thereby A method for producing a negative electrode active material, characterized by producing negative electrode active material particles in which amorphous low-valent nanosilicon oxide, or polycrystalline silicon and its oxide, or both the amorphous low-valent nanosilicon oxide and polycrystalline silicon and its oxide are dispersed as dispersed substances inside the porous carbon structure.

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

Claims

1. A manufacturing apparatus for a negative electrode active material having negative electrode active material particles, wherein the negative electrode active material particles contained in the negative electrode active material to be manufactured include a porous carbon structure, and inside the porous carbon structure, 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 dispersion substance, the low-valence nano silicon oxide includes each state of SiO x: 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 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 is configured to be in the range of PV ≤ 0.004, and the manufacturing apparatus for 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. A manufacturing apparatus for a negative electrode active material, characterized in that.

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

4. The manufacturing apparatus for 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 manufacturing apparatus for a negative electrode active material according to claim 1, which has a stirring mechanism for stirring the structure of the porous carbon held therein.

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

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

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

9. The manufacturing apparatus for a negative electrode active material according to claim 1, which has 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 any one of claims 1 to 10, the method comprising: preparing a porous carbon structure; depositing silicon inside the porous carbon structure by flowing a silane-based gas under heating with respect 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 nano silicon oxide; and thereby manufacturing negative electrode active material particles in which 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 inside the porous carbon structure.

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