JP6852691B2 - Oxygen-containing silicon material and its manufacturing method - Google Patents

Description

The present invention relates to oxygen-containing silicon materials.

Silicon is known to be used as a component of semiconductors, solar cells, secondary batteries, etc. Therefore, research on silicon is being actively conducted.

For example, Patent Document 1 describes _{that a layered silicon compound containing CaSi 2} and an acid to remove Ca as a main component was synthesized, and that the layered silicon compound was heated at 300 ° C. or higher to generate hydrogen. It describes the production of the detached silicon material and the lithium ion secondary battery containing the silicon material as a negative electrode active material.

International Publication No. 2014/08608

When a silicon material is used as the negative electrode active material of the secondary battery, it is the silicon itself that exhibits the function as the negative electrode active material when the charge carrier is occluded and released. Therefore, in order to improve the function of storing and releasing charge carriers, it is necessary to increase the purity of the silicon material. However, in a secondary battery using a silicon material having a high proportion of silicon as a negative electrode active material, although the initial efficiency indicated by (initial discharge capacity) / (initial charge capacity) is improved, when charging and discharging are repeated. It was found that the capacity of the battery was greatly reduced.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a silicon material and a method for producing the same, which can optimize the capacity retention rate of a secondary battery.

The present inventor repeated trial and error to study a method for producing a silicon material. As a result, it was found that a secondary battery using a silicon material containing an element other than silicon to some extent has an excellent capacity retention rate.
The present invention relates to an oxygen-containing silicon material focusing on oxygen as an element other than silicon, and particularly provides a production method capable of controlling the oxygen content of the oxygen-containing silicon material.

Oxygen-containing silicon material of the present invention, oxygen mass% _(W O%) is the 16 _<W O _<27, characterized in that silicon mass% _{(W Si%)} is _{62 <W} Si _<81.

One aspect of the method for producing an oxygen-containing silicon material of the present invention is
a-1) _{A step of reacting CaSi 2} with an acid aqueous solution at 15 to 50 ° C. to synthesize an oxygen-containing layered silicon compound containing layered polysilane.
b) A step of synthesizing an oxygen-containing silicon material by heating the oxygen-containing layered silicon compound at 300 ° C. or higher.
It is characterized by including.

Another aspect of the method for producing an oxygen-containing silicon material of the present invention is
a-2-1) _{A step of reacting CaSi 2} with an acid aqueous solution at -20 to 10 ° C.
a-2-2) Following the step a-2-1), a step of synthesizing an oxygen-containing layered silicon compound containing layered polysilane at a temperature of the reaction solution of 15 to 50 ° C.
b) A step of synthesizing an oxygen-containing silicon material by heating the oxygen-containing layered silicon compound at 300 ° C. or higher.
It is characterized by including.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an oxygen-containing silicon material and a method for producing the same, which can optimize the capacity retention rate of the secondary battery.

It is a graph which shows the relationship between the integrated capacity and the discharge capacity of each lithium ion secondary battery in evaluation example 2. It is a graph which shows the relationship between the integrated capacity and the discharge capacity of each lithium ion secondary battery in evaluation example 9.

Hereinafter, embodiments for carrying out the present invention will be described. Unless otherwise specified, the numerical range "a to b" described in the present specification includes the lower limit a and the upper limit b in the range. Then, a numerical range can be constructed by arbitrarily combining these upper and lower limit values and the numerical values listed in the examples. Further, a numerical value arbitrarily selected from these numerical values can be set as a new upper limit value or lower limit value.

Oxygen-containing silicon material of the present invention, oxygen mass% _(W O%) is the 16 _<W O _<27, characterized in that silicon mass% _{(W Si%)} is _{62 <W} Si _<81.

The oxygen-containing silicon material of the present invention can be used as a negative electrode active material for a secondary battery such as a lithium ion secondary battery. Since the oxygen-containing silicon material of the present invention has an appropriate ratio of oxygen to silicon, the secondary battery provided with the oxygen-containing silicon material of the present invention satisfies all of the capacity retention rate, the capacity, and the initial efficiency in a well-balanced manner. ..

An oxygen-containing silicon material having an excessively low mass% of oxygen and an excessively high% by mass of silicon is excellent in capacity and initial efficiency as a negative electrode active material, but is inferior in capacity retention rate. On the other hand, an oxygen-containing silicon material having an excessively high oxygen mass% and an excessively low silicon mass% is inferior in capacity and initial efficiency as a negative electrode active material.

Oxygen mass% in the oxygen-containing silicon material of the present invention _(W O%) is preferably 16.5 ≦ _{W O} ≦ 26.5, and more preferably 17 ≦ _{W O} ≦ 26, is 18 ≦ _{W O} ≦ 25.5 and particularly preferably from 19 ≦ _{W O} ≦ 25.
_{The silicon mass% (W Si} %) in the oxygen-containing silicon material of the present invention preferably satisfies 65 ≦ W _Si ≦ 80, _{more preferably 68 ≦ W Si} ≦ 79, and 70 ≦ W _Si ≦. It is more preferable to satisfy 78, and it is particularly preferable to satisfy _{70 ≦ W Si ≦ 76.}

The oxygen-containing silicon material of the present invention may contain elements other than oxygen and silicon. Al is preferable as such an element. The oxygen-containing silicon material of the present invention containing Al has reduced resistance. Therefore, it can be said that the oxygen-containing silicon material of the present invention containing Al is excellent in function as a negative electrode active material.

Further, it is known that under the charge / discharge conditions of the secondary battery, the constituent components of the electrolytic solution are decomposed to form an SEI (Solid Electrolyte Interphase) film containing oxygen on the surface of the negative electrode active material. Here, when the negative electrode active material contains silicon, there is a concern that the silicon will be oxidized by oxygen contained in the SEI film and deteriorate.
However, since the oxygen-containing silicon material of the present invention containing Al contains Al, it is considered that oxidative deterioration of silicon is suppressed. The reason is that Al has a lower electronegativity than silicon and is considered to preferentially and stably bond with oxygen, and the Al—O bond between Al and oxygen is more stable than the Si—O bond. In addition, it can be said that oxygen having formed a stable Al—O bond is less likely to be involved in the oxidation of silicon having a higher electronegativity than Al.
Therefore, a secondary battery containing the oxygen-containing silicon material of the present invention containing Al as a negative electrode active material can be expected to have a long life.

_{The Al mass% (W Al} %) in the oxygen-containing silicon material of the present invention preferably satisfies 0 <W _Al <1, _{more preferably 0 <W Al} ≤ 0.8, and 0.01. It is more preferable to satisfy ≦ W _Al ≦ 0.6, and it is particularly preferable to satisfy _{0.05 ≦ W Al ≦ 0.4.}

The oxygen-containing silicon material of the present invention may contain impurities derived from the manufacturing process and impurities derived from the raw material. As will be described later, an acid is used in the method for producing an oxygen-containing silicon material of the present invention. The element derived from the anion of the acid is likely to be contained as an impurity in the oxygen-containing silicon material of the present invention.
In the oxygen-containing silicon material of the present invention, the element mass% (W _X %) derived from the anion of the acid is preferably a small value. When W _X % is large, the irreversible capacity of the oxygen-containing silicon material increases, so that the initial efficiency decreases. _{0 <W X} <8 can be exemplified as the range of W _X%. The range of W _{X % preferably satisfies 0 <W X} <6, _{more preferably 0 <W X} ≤ 4, further preferably 0 <W _X ≤ 3, and 0 <. It is particularly preferable to satisfy _{W X ≦ 2.} When the acid anion is halogen, the element mass% (W _X %) derived from the acid anion is read as halogen mass% (W _X%).

Ca and Fe can be exemplified as impurities that can be contained in the oxygen-containing silicon material of the present invention. Ca is derived from the raw material CaSi _2. Fe is an impurity in the raw material.

_{The Ca mass% (W Ca} %) in the oxygen-containing silicon material of the present invention is preferably a small value. _{The Ca mass% (W Ca} %) in the oxygen-containing silicon material of the present invention preferably satisfies 0 ≦ W _Ca <5, _{more preferably 0 ≦ W Ca} ≦ 1, and 0 ≦ W _Ca ≦. It is more preferable to satisfy 0.5, and it is particularly preferable to satisfy _{0 ≦ W Ca ≦ 0.3.} Considering the ease of mixing Ca and the difficulty of removing _Ca , it is assumed that the _{mass% of Ca (W Ca} %) in the oxygen-containing silicon material of the present invention is 0 <W Ca.

_{The Fe mass% (W Fe} %) in the oxygen-containing silicon material of the present invention is preferably a small value. _{The Fe mass% (W Fe} %) in the oxygen-containing silicon material of the present invention preferably satisfies 0 ≦ W _Fe ≦ 3, _{more preferably 0 ≦ W Fe} ≦ 1, and 0 ≦ W _Fe ≦. It is more preferable to satisfy 0.5, _{particularly preferably 0 ≦ W Fe} ≦ 0.3, and most preferably 0 ≦ W _Fe ≦ 0.1. Considering the ease of mixing Fe and the difficulty of removing it, it is assumed that the _{Fe mass% (W Fe} %) in the Al-containing silicon material of the present invention is 0 <W _Fe.
Further, the relationship between Al mass% (W _Al %) and Fe mass% (W _{Fe %) preferably satisfies W Al} > W _Fe, and more preferably W _Al > 2 × W _Fe .

From the viewpoint of structure, the oxygen-containing silicon material of the present invention preferably has a structure in which a plurality of plate-shaped silicon bodies are laminated in the thickness direction. This laminated structure can be confirmed by observation with a scanning electron microscope or the like. Considering that the oxygen-containing silicon material of the present invention is used as the negative electrode active material of the lithium ion secondary battery, the plate-shaped silicon body has a thickness of 10 nm for efficient insertion and desorption reaction of lithium ions. Those in the range of ~ 100 nm are preferable, and those in the range of 20 nm to 50 nm are more preferable. The length of the plate-shaped silicon body in the major axis direction is preferably in the range of 0.1 μm to 50 μm. Further, the plate-shaped silicon body preferably has (length in the major axis direction) / (thickness) in the range of 2 to 1000. The laminated structure of the plate-shaped silicon body is considered to be a remnant of the Si layer in _{the raw material CaSi 2.}

The oxygen-containing silicon material of the present invention may contain either amorphous silicon or silicon crystals, or may contain both. The size of the silicon crystal is preferably nano-sized. Specifically, the size of the silicon crystal is preferably in the range of 0.5 nm to 300 nm, more preferably in the range of 1 nm to 100 nm, further preferably in the range of 1 nm to 50 nm, and particularly preferably in the range of 1 nm to 10 nm. preferable. The size of the silicon crystal is calculated from Scheller's equation using the half width of the diffraction peak on the Si (111) plane of the obtained XRD chart obtained by performing X-ray diffraction measurement (XRD measurement) on the silicon material. To.

The ratio of crystalline to amorphous in silicon of the oxygen-containing silicon material of the present invention is 0: 100 to 100: 0, 1:99 to 50:50, 0: 100 to 30:70, 5:95 to 30: The range of 70, 10:90 to 20:80 can be exemplified.

The oxygen-containing silicon material of the present invention is preferably in a powder state, and is preferably an aggregate of particles showing a constant particle size distribution. The average particle size of the oxygen-containing silicon material of the present invention is preferably in the range of 0.5 to 30 μm, more preferably in the range of 1 to 20 μm, and even more preferably in the range of 2 to 10 μm. In the present specification, the average particle size means _{D 50} when measured with a general laser diffraction type particle size distribution measuring device.

The BET specific surface area in the oxygen-containing silicon material of the present invention, within the scope of 0.5~15m ² / g, in the range of 0.5 to 10 m ² / g, in the range of 1 to 10 m ² / g,. 3 to The range of 10 m ² / g can be exemplified.

Next, the method for producing the oxygen-containing silicon material of the present invention (hereinafter, may be simply referred to as “the production method of the present invention”) will be described.
The key to the production method of the present invention is to set the temperature of the reaction solution to 15 to 50 ° C. in the step of reacting _{CaSi 2 with an acid aqueous solution to synthesize an oxygen-containing layered silicon compound containing layered polysilane.} The purpose is to control the oxygen content of the oxygen-containing layered silicon compound containing layered polysilane and the oxygen-containing silicon material of the present invention.

One aspect of the production method of the present invention is
a-1) A step of _{reacting CaSi 2} with an acid aqueous solution at 15 to 50 ° C. to synthesize an oxygen-containing layered silicon compound containing layered polysilane (hereinafter, simply referred to as “a-1) step”. ),
b) The step of synthesizing the oxygen-containing silicon material by heating the oxygen-containing layered silicon compound at 300 ° C. or higher (hereinafter, simply referred to as “b) step” may be referred to. ), Is included.

When a hydrogen chloride aqueous solution (hydrochloric acid) is used as the acid aqueous solution in the step a-1), the reaction represented by the following formula (1) proceeds, and then on _{the surface of Si 6} H ₆ which is a layered polysilane, for example. It is considered that the reaction represented by the formula (2) proceeds. Therefore, it can be said that step a-1) is a key step for determining the oxygen content of the oxygen-containing layered silicon compound containing layered polysilane and the oxygen-containing silicon material of the present invention.
Equation (1) 3CaSi ₂ + 6HCl → Si ₆ H ₆ + 3CaCl ₂
Equation (2) Si ₆ H ₆ + 3H ₂ O → Si ₆ H ₃ (OH) ₃ + 3H ₂ ↑

The temperature of the step a-1) is preferably in the range of 18 to 45 ° C, more preferably in the range of 20 to 40 ° C. a-1) In order to control the temperature of the process, a constant temperature device such as a constant temperature bath may be used. Examples of the processing time of the step a-1) include 1 to 50 hours, 5 to 40 hours, and 10 to 30 hours.

Instead of the a-1) step, the following a-2-1) step and a-2-2) step may be adopted.
a-2-1) _{Step of reacting CaSi 2} with an acid aqueous solution at -20 to 10 ° C a-2-2) Continuing from the above a-2-1) step, the reaction solution is layered at a temperature of 15 to 50 ° C. Step of synthesizing oxygen-containing layered silicon compound containing polysilane

In the step a-2-1), it is considered that the reaction represented by the formula (1) mainly proceeds, and in the step a-2-2), the reaction represented by the formula (2) is considered to proceed mainly. Therefore, it can be said that the a-2-2) step is a key step for determining the oxygen content in the oxygen-containing layered silicon compound containing the layered polysilane and the oxygen-containing silicon material of the present invention.

Examples of the timing for switching the a-2-1) step to the a-2-2) step include the time when the heat generated from the reaction has settled down and the time when the foaming from the reaction solution has settled down. In order to switch the a-2-1) step to the a-2-2) step, the temperature of the constant temperature device used in the a-2-1) step may be raised, or the temperature may be increased in the a-2-1) step. The constant temperature device may be replaced with another constant temperature device adjusted in advance within the temperature range of 15 to 50 ° C.

The temperature of the a-2-1) step is preferably in the range of −10 to 5 ° C., more preferably in the range of −5 to 5 ° C. Specific examples of the time of the a-2-1) step include 10 minutes, 20 minutes, 1 hour, or 2 hours after the mixing of _{CaSi 2 and the acid aqueous solution is completed.}
The temperature of the a-2-2) step is preferably in the range of 18 to 45 ° C, more preferably in the range of 20 to 40 ° C. Specific examples of the time of the a-2-2) step include 1 to 50 hours, 5 to 40 hours, and 10 to 30 hours.

Hereinafter, _{the steps of reacting CaSi 2} with an aqueous acid solution to synthesize an oxygen-containing layered silicon compound containing layered polysilane may be collectively referred to as step a).

_{CaSi 2} , which is a raw material, generally has a structure in which a Ca layer and a Si layer are laminated. CaSi ₂ may be synthesized by a known production method, or a commercially available product may be adopted. _{a) CaSi 2} used in the step is preferably pulverized in advance and powdered.

CaSi ₂ preferably contains Al. The Al content is preferably less than 4.5%, more preferably in the range of 0.01 to 3%, further preferably in the range of 0.05 to 2%, and in the range of 0.1 to 1%. Is particularly preferable.

Acids include hydrofluoric acid, hydrochlorite, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, methanesulfonic acid, tetrafluoroboric acid, hexafluorophosphate, hexafluoro. Examples thereof include arsenic acid, fluoroantimonic acid, hexafluorosilicic acid, hexafluorogermanic acid, hexafluorotin (IV) acid, trifluoroacetic acid, hexafluorotitanic acid, hexafluorozyric acid, trifluoromethanesulfonic acid and fluorosulfonic acid. To. These acids may be used alone or in combination.

It is preferable to use an acid in an amount capable of supplying 2 mol or more of protons to 1 mol of CaSi _2. The reason for using water as a solvent in the a) step is that it _{is easy to remove unnecessary substances such as CaCl 2} from a technical point of view, and it is extremely important to introduce oxygen into the layered polysilane produced in the step a). It's an easy point.

The concentration of the acid in the aqueous acid solution is preferably 5 to 36% by mass, more preferably 5 to 30% by mass, further preferably 10 to 30% by mass, particularly preferably 13 to 25% by mass, and 15 to 20% by mass. Is the most preferable. If the acid concentration is too low, the reaction will proceed slowly and the production efficiency will decrease. On the other hand, if the concentration of the acid is too high, an element derived from the anion of the acid is contained in a large amount in the oxygen-containing silicon material of the present invention.

a) The reaction conditions in the step are preferably under an atmosphere of an inert gas such as nitrogen, helium, or argon, and preferably under stirring conditions.

a) In order to isolate the oxygen-containing layered silicon compound obtained in the step, a filtration step, a washing step, and a drying step may be carried out as appropriate. In order to control the amount of oxygen in the oxygen-containing layered silicon compound, it is preferable to carry out these steps in an atmosphere of an inert gas such as nitrogen, helium or argon.

Next, b) step will be described. b) The step is a step of heating the oxygen-containing layered silicon compound at 300 ° C. or higher.

From a chemical point of view, the step b) is a step of synthesizing an oxygen-containing silicon material by removing hydrogen or the like from the oxygen-containing layered silicon compound by heating. b) The reaction formula when hydrogen is separated from the layered polysilane in the step is as follows.
Si ₆ H ₆ → 6 Si + 3H ₂ ↑

b) The step is preferably carried out in a non-oxidizing atmosphere having a lower oxygen content than in a normal atmosphere. Examples of the non-oxidizing atmosphere include a reduced pressure atmosphere including a vacuum and an inert gas atmosphere such as nitrogen, helium, and argon. The heating temperature is preferably in the range of 300 ° C. to 1000 ° C., more preferably in the range of 500 ° C. to 900 ° C., and even more preferably in the range of 600 ° C. to 800 ° C. If the heating temperature is too low, hydrogen may not be sufficiently released. On the other hand, if the heating temperature is too high, crystallization of silicon in the oxygen-containing silicon material may proceed excessively, leading to deterioration of the performance as the negative electrode active material. The heating time may be appropriately set according to the heating temperature, and it is also preferable to determine the heating time while measuring the amount of hydrogen or the like that escapes from the reaction system. By appropriately selecting the heating temperature and the heating time, the ratio of amorphous silicon and silicon crystals contained in the produced oxygen-containing silicon material and the size of the silicon crystals can be adjusted, and further, the silicon crystals are produced. It is also possible to prepare the shape and size of a nano-level-thick layer containing amorphous silicon and silicon crystals contained in the oxygen-containing silicon material.

The oxygen-containing silicon material of the present invention may be pulverized and classified into particles having a constant particle size distribution.

As described above, the oxygen-containing silicon material of the present invention can be used as a negative electrode active material for a secondary battery such as a lithium ion secondary battery. In that case, it is preferable to use the oxygen-containing silicon material of the present invention coated with carbon. This is because the carbon coating improves the conductivity.
As a carbon coating method, a mechanical milling method in which a mixture of an oxygen-containing silicon material and a carbon powder is stirred and integrated under strong pressure, or carbon generated from a carbon source is vapor-deposited on the oxygen-containing silicon material. A CVD (chemical vapor deposition) method for causing the vehicle to be subjected to can be exemplified.

The CVD method is preferable as the carbon coating method because the surface of the oxygen-containing silicon material can be uniformly coated with a thin carbon layer. Then, among the CVD methods, a thermal CVD method in which a gaseous organic substance as a carbon source is decomposed by heat to generate carbon is preferable.

Carbon _mass% (W _C%) is the oxygen-containing silicon material of the present invention which is a carbon coating, it is preferable to satisfy 1 ≦ W _C ≦ 10, more preferably satisfies 3 ≦ W _C ≦ 9, 5 ≦ W is more desirable to satisfy the _C ≦ 8. For the content of elements other than carbon in the carbon-coated oxygen-containing silicon material of the present invention, the numerical range described in the oxygen-containing silicon material of the present invention is incorporated.

Hereinafter, a secondary battery including the oxygen-containing silicon material of the present invention as a negative electrode active material will be described by taking a lithium ion secondary battery as an example. The lithium ion secondary battery containing the oxygen-containing silicon material of the present invention as a negative electrode active material is hereinafter referred to as the lithium ion secondary battery of the present invention. Specifically, the lithium ion secondary battery of the present invention includes a positive electrode, a negative electrode containing the oxygen-containing silicon material of the present invention as a negative electrode active material, an electrolytic solution, and a separator if necessary.

The positive electrode has a current collector and a positive electrode active material layer bonded to the surface of the current collector.

A current collector is a chemically inert electron conductor that keeps current flowing through the electrodes during the discharge or charging of a lithium-ion secondary battery. Collectors include at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel. Metallic materials can be exemplified. The current collector may be coated with a known protective layer. A current collector whose surface is treated by a known method may be used as the current collector.

The current collector can take the form of foil, sheet, film, linear, rod, mesh or the like. Therefore, as the current collector, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, or a stainless steel foil can be preferably used. When the current collector is in the form of a foil, a sheet, or a film, the thickness thereof is preferably in the range of 1 μm to 100 μm.

The positive electrode active material layer contains a positive electrode active material and, if necessary, a conductive auxiliary agent and / or a binder.

As the positive electrode active material, a layered compound _{Li a Ni b Co c Mn d} D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is Li, Fe, Cr, Cu, At least one element selected from Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, 1.7 ≦ f ≦ 3. _{), Li a Ni b Co c} Al d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is Li, Fe, Cr, Cu, Zn, Ca, Mg, S , Si, Na, K, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, at least one element, 1.7 ≦ f ≦ 3), Li ₂ MnO _3. Can be done. Further, as the positive electrode active material, _{a spinel such as LiMn 2} O ₄ and a solid solution composed of a mixture of the spinel and the layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (M in the formula is Co, Ni, Mn, A polyanionic compound represented by (selected from at least one of Fe) and the like can be mentioned. Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as the positive electrode active material may have the above composition formula as the basic composition, and those in which the metal element contained in the basic composition is replaced with another metal element can also be used. Further, as the positive electrode active material, a positive electrode active material material that does not contain lithium ions that contributes to charging and discharging, for example, sulfur alone, a compound that combines sulfur and carbon, a metal sulfide such as _{TiS 2 , V 2} O ₅ , MnO _{Oxides such as 2} , polyaniline and anthraquinone, compounds containing these aromatics in their chemical structures, conjugated materials such as conjugated diacetic acid-based organic substances, and other known materials can also be used. Further, a compound having a stable radical such as nitroxide, nitronylnitroxide, galbinoxyl, phenoxyl and the like may be adopted as the positive electrode active material. When a lithium-free positive electrode active material is used, it is necessary to add ions to the positive electrode and / or the negative electrode in advance by a known method. Here, in order to add the ion, a metal or a compound containing the ion may be used.

The conductive auxiliary agent is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be arbitrarily added when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent. The conductive auxiliary agent may be a chemically inert electron high conductor, and examples thereof include carbon black, graphite, vaporized carbon fiber (Vapor Grown Carbon Fiber), and various metal particles, which are carbonaceous fine particles. To. Examples of carbon black include acetylene black, Ketjen black (registered trademark), furnace black, and channel black. These conductive auxiliary agents can be added to the active material layer alone or in combination of two or more.

The mixing ratio of the conductive auxiliary agent in the active material layer is preferably 1: 0.005 to 1: 0.5, and 1: 0.01 to 1: 0 in terms of mass ratio. It is more preferably .2, and even more preferably 1: 0.02 to 1: 0.15. This is because if the amount of the conductive auxiliary agent is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary agent is too large, the moldability of the active material layer is deteriorated and the energy density of the electrode is lowered.

The binder serves to anchor the active material or the conductive auxiliary agent to the surface of the current collector and maintain the conductive network in the electrode. Examples of the binder include fluororesins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins and poly ( Examples thereof include acrylic resins such as meta) acrylic acid, styrene-butadiene rubber (SBR), and carboxymethyl cellulose. These binders may be used alone or in combination of two or more.

The mixing ratio of the binder in the active material layer is preferably 1: 0.05 to 1: 0.3, preferably 1: 0.01 to 1: 0, in terms of mass ratio. It is more preferably .2, and even more preferably 1: 0.02 to 1: 0.15. This is because if the amount of the binder is too small, the moldability of the electrode is lowered, and if the amount of the binder is too large, the energy density of the electrode is lowered.

The negative electrode has a current collector and a negative electrode active material layer bonded to the surface of the current collector. As the current collector, the one described in the positive electrode may be appropriately adopted. The negative electrode active material layer contains a negative electrode active material and, if necessary, a conductive auxiliary agent and / or a binder.

The negative electrode active material may be any one containing the oxygen-containing silicon material of the present invention, and only the oxygen-containing silicon material of the present invention may be adopted, or the oxygen-containing silicon material of the present invention and a known negative electrode active material may be adopted. May be used together.

As the conductive auxiliary agent and the binder used for the negative electrode, those described for the positive electrode may be appropriately and appropriately adopted in the same blending ratio.

Further, a crosslinked polymer obtained by cross-linking a carboxyl group-containing polymer such as polyacrylic acid or polymethacrylic acid with a polyamine such as diamine disclosed in International Publication No. 2016/06382 may be used as a binder.

Examples of the diamine used in the crosslinked polymer include alkylenediamines such as ethylenediamine, propylenediamine and hexamethylenediamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, isophoronediamine and bis (4-aminocyclohexyl) methane. Saturated carbocyclic diamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, bis (4-aminophenyl) sulfone, benzidine, o-trizine, 2,4- Examples thereof include aromatic diamines such as tolylene diamine, 2,6-tolylene diamine, xylylene diamine and naphthalene diamine.

In order to form an active material layer on the surface of the current collector, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used to collect current. The active material may be applied to the surface of the body. Specifically, the active material, the solvent, and if necessary, the binder and / or the conductive auxiliary agent are mixed to prepare a slurry. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The slurry is applied to the surface of the current collector and then dried. The dried one may be compressed in order to increase the electrode density.

The electrolytic solution contains a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent.

As the non-aqueous solvent, cyclic carbonates, cyclic esters, chain carbonates, chain esters, ethers and the like can be used. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, and examples of the cyclic ester include gamma-butyrolactone, 2-methyl-gamma-butyrolactone, acetyl-gamma-butyrolactone, and gamma-valerolactone. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, and ethyl methyl carbonate, and examples of the chain ester include propionic acid alkyl ester, malonic acid dialkyl ester, and acetate alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. As the non-aqueous solvent, a compound in which some or all of the chemical structure of the specific solvent is replaced with fluorine may be adopted.

Examples of the electrolyte include lithium salts such _{as LiClO 4} , LiAsF ₆ , LiPF _{6 , LiBF 4} , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (FSO ₂ ) _2.

As the electrolytic solution, 0.5 to 3.5 mol of lithium salts such as _{LiClO 4} , LiPF ₆ , LiBF ₄ , and LiN (FSO ₂ ) ₂ are added to a non-aqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, and diethyl carbonate. Examples thereof include solutions dissolved at concentrations of / L, 1 to 3 mol / L, and 1.6 to 2.5 mol / L.

The separator separates the positive electrode and the negative electrode, and allows lithium ions to pass through while preventing a short circuit due to contact between the two electrodes. Examples of the separator include polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, synthetic resin such as polyaramid (Aromatic polyamide), polyester and polyacrylonitrile, polysaccharides such as cellulose and amylose, and natural substances such as fibroin, keratin, lignin and sverin. Examples thereof include a porous body using one or more electrically insulating materials such as a polymer and ceramics, a non-woven fabric, and a woven fabric. Further, the separator may have a multi-layer structure.

Next, a method for manufacturing the lithium ion secondary battery of the present invention using the positive electrode, the negative electrode and the electrolytic solution will be described.

For example, the separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. The electrode body may be either a laminated type in which a positive electrode, a separator and a negative electrode are stacked, or a wound type in which a laminated body of a positive electrode, a separator and a negative electrode is wound. After connecting the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collector lead or the like, an electrolytic solution is added to the electrode body to form a lithium ion secondary battery. Good.

The shape of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical type, a square type, a coin type, and a laminated type can be adopted.

The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from a lithium ion secondary battery for all or part of its power source, and may be, for example, an electric vehicle or a hybrid vehicle. When a lithium-ion secondary battery is mounted on a vehicle, a plurality of lithium-ion secondary batteries may be connected in series to form an assembled battery. In addition to vehicles, devices equipped with lithium-ion secondary batteries include various battery-powered home appliances such as personal computers and mobile communication devices, office devices, and industrial devices. Further, the lithium ion secondary battery of the present invention includes wind power generation, solar power generation, hydraulic power generation and other power storage devices and power smoothing devices for electric power systems, power supply sources for power and / or auxiliary machinery such as ships, aircraft, and aircraft. Power supply sources for spacecraft and / or auxiliary equipment, auxiliary power sources for vehicles that do not use electricity as power sources, power sources for mobile household robots, power sources for system backup, power sources for non-disruptive power supply devices, It may be used as a power storage device that temporarily stores the electric power required for charging in a charging station for an electric vehicle or the like.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. As long as it does not deviate from the gist of the present invention, it can be carried out in various forms with modifications, improvements, etc. that can be made by those skilled in the art.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

(Example 1)
a) Step a-1) Step A CaSi ₂ powder containing Fe as an impurity was prepared.
A reaction vessel containing 35% by mass hydrochloric acid was placed in a constant temperature bath at 18 ° C. After confirming that the temperature of hydrochloric acid reached 18 ° C., the CaSi ₂ powder was gradually added to hydrochloric acid under a nitrogen gas atmosphere and stirring conditions. After adding the CaSi ₂ powder, stirring was continued for 2 hours, and then the reaction solution was filtered. The residue was washed with distilled water, further washed with methanol, and dried under reduced pressure to obtain the oxygen-containing layered silicon compound of Example 1.

b) Step The oxygen-containing layered silicon compound of Example 1 was heated at 900 ° C. for 1 hour in a nitrogen gas atmosphere to obtain an oxygen-containing silicon material. This was used as the oxygen-containing silicon material of Example 1.

The negative electrode and the lithium ion secondary battery of Example 1 were manufactured as follows.

Polyacrylic acid having a weight average molecular weight of 800,000 was dissolved in N-methyl-2-pyrrolidone to prepare a polyacrylic acid solution containing 10% by mass of polyacrylic acid. Further, 0.2 g (1.0 mmol) of 4,4'-diaminodiphenylmethane was dissolved in 0.4 mL of N-methyl-2-pyrrolidone to prepare a 4,4'-diaminodiphenylmethane solution. Under stirring conditions, the entire amount of the 4,4'-diaminodiphenylmethane solution was added dropwise to 7 mL of the polyacrylic acid solution (corresponding to 9.5 mmol in terms of acrylic acid monomer), and the obtained mixture was added dropwise at room temperature for 30 minutes. Stirred. Then, using a Dean-Stark apparatus, the mixture was stirred at 130 ° C. for 3 hours to allow the dehydration reaction to proceed, thereby producing a binder solution.

72.5 parts by mass of the oxygen-containing silicon material of Example 1 as the negative electrode active material, 13.5 parts by mass of acetylene black as the conductive auxiliary agent, and 14 parts by mass of the solid content as the binder. Then, an appropriate amount of N-methyl-2-pyrrolidone was mixed to prepare a slurry. A copper foil was prepared as a current collector for the negative electrode. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. N-Methyl-2-pyrrolidone was removed by drying the copper foil coated with the slurry. Then, the negative electrode of Example 1 in which the negative electrode active material layer was formed was manufactured by pressing and baking at 180 ° C.

_{A solution prepared by dissolving LiPF 6} at a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 was used as an electrolytic solution.

The negative electrode was cut to a diameter of 11 mm and used as an evaluation electrode. A metal lithium foil having a thickness of 500 μm was cut to a diameter of 13 mm and used as a counter electrode. As a separator, a glass filter (Hoechst Celanese Co., Ltd.) and a single-layer polypropylene celgard 2400 (Polypore Co., Ltd.) were prepared. Two types of separators were sandwiched between the counter electrode and the evaluation electrode in the order of the counter electrode, the glass filter, the celgard 2400, and the evaluation electrode to form an electrode body. This electrode body was housed in a coin-type battery case CR2032 (Hosen Co., Ltd.). The electrolytic solution was injected into the battery case, the battery case was sealed, and the lithium ion secondary battery of Example 1 was manufactured.

(Example 2)
a) In the step, the oxygen-containing layered silicon compound, the oxygen-containing silicon material, the negative electrode, and the lithium ion secondary battery of Example 2 were prepared in the same manner as in Example 1 except that the temperature of the constant temperature bath was set to 40 ° C. Manufactured.

(Comparative Example 1)
a) In the step, the oxygen-containing layered silicon compound, the oxygen-containing silicon material, the negative electrode, and the lithium ion secondary battery of Comparative Example 1 were prepared in the same manner as in Example 1 except that the temperature of the constant temperature bath was set to 0 ° C. Manufactured.

(Comparative Example 2)
a) In the step, the oxygen-containing layered silicon compound, the oxygen-containing silicon material, the negative electrode, and the lithium ion secondary battery of Comparative Example 2 were prepared in the same manner as in Example 1 except that the temperature of the constant temperature bath was set to 60 ° C. Manufactured.

(Evaluation example 1)
Elemental analysis of Si, Cl, Fe and Ca was performed on the oxygen-containing silicon materials of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 using a fluorescent X-ray analyzer (XRF). went. Further, using an oxygen / nitrogen / hydrogen analyzer (inert gas melting method), an element targeting oxygen with respect to the oxygen-containing silicon materials of Example 1, Example 2, Comparative Example 1 and Comparative Example 2. Analysis was carried out.
The results of these elemental analyzes are shown in Table 1 as mass%. From Table 1, it can be seen that as the temperature of the step a) increases, the silicon content decreases and the oxygen content increases.

(Evaluation example 2)
The lithium ion secondary batteries of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 are charged to 0.01 V at a current of 0.2 mA and then discharged to 1.0 V at a current of 0.2 mA. The initial charge / discharge was performed.
Further, the lithium ion secondary batteries of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 after the initial charge / discharge are charged to 0.01 V at a current of 0.5 mA, and then charged at a current of 0.5 mA. The charge / discharge cycle of discharging to 1.0 V was performed 50 times.

The initial efficiency and capacity retention rate were calculated by the following formulas.
Initial efficiency (%) = 100 x (initial discharge capacity) / (initial charge capacity)
Capacity retention rate (%) = 100 x (discharge capacity at 50 cycles) / (discharge capacity at 1 cycle)
The results of initial efficiency and volume retention are shown in Table 2 together with some of the results of elemental analysis. Further, FIG. 1 shows the relationship between the integrated capacity and the discharge capacity of each lithium ion secondary battery in 50 charge / discharge cycles.

From the results of the initial efficiency in Table 2, it can be seen that the value of the initial efficiency in the lithium ion secondary battery of Comparative Example 2 is remarkably low. It can be said that the oxygen-containing silicon material having a higher silicon mass% and a lower oxygen mass% than the oxygen-containing silicon material of Comparative Example 2 has excellent initial efficiency. In terms of production conditions, it can be said that a) the temperature of the step is less than 60 ° C., which is a suitable condition for producing an oxygen-containing silicon material having excellent initial efficiency.

From the results of the capacity retention rate in Table 2, it can be seen that the value of the capacity retention rate in the lithium ion secondary battery of Comparative Example 1 is remarkably low. From the results of the elemental analysis in Table 2, it is considered that there is a significant difference in capacity retention rate between the oxygen-containing silicon material having an oxygen mass% of 16% or less and the oxygen-containing silicon material having an oxygen mass% of more than 16%.
In terms of production conditions, it can be said that a) the temperature of the step is more than 0 ° C., which is advantageous for introducing oxygen and is a condition for producing an oxygen-containing silicon material having an excellent capacity retention rate.

Further, from the graph of FIG. 1 showing the relationship between the integrated capacity and the discharge capacity of each lithium ion secondary battery, it can be seen that the oxygen-containing silicon materials of Examples 1 and 2 are particularly excellent negative electrode active materials. ..

(Evaluation example 3)
The BET specific surface area of the oxygen-containing silicon materials of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 was measured.
In addition, Raman spectroscopy of each oxygen-containing silicon material was measured with a Raman spectroscope. In each Raman spectroscopic spectrum, a peak derived from silicon crystals was observed near ^{520 cm -1} , and a peak derived from amorphous silicon was observed near ^{480 cm -1.} A sample in which amorphous silicon and silicon crystals were mixed at a weight ratio of 1: 1 was measured, and the ratio of silicon crystals to amorphous silicon was calculated from the intensity ratio of each peak based on the measurement results of the sample.
The above results are shown in Table 3.

From Table 3, it can be said that the BET specific surface area of the oxygen-containing silicon material tends to increase as the temperature of the step a) increases, but it becomes almost constant at 40 ° C. or higher. It is considered that the ratio of silicon crystals and amorphous silicon in the oxygen-containing silicon material does not correlate with the temperature of a) step.

(Example 3)
_{CaSi 2} powder containing Al was prepared as follows.
Ca, Al and Si were weighed into a carbon crucible. The elemental composition ratio of Ca and Si was 1: 2, and the amount of Al added was 1% with respect to the total mass of Ca, Al and Si. The carbon crucible was heated at around 1300 ° C. with a high-frequency induction heating device in an argon gas atmosphere to prepare a molten metal containing Ca, Al and Si. The molten metal was cooled by pouring it into a predetermined mold to form a solid. The solid was pulverized to obtain CaSi ₂ powder, which was then subjected to step a).

a) Step a-2-1) Step A reaction vessel containing 18% by mass hydrochloric acid was placed in a constant temperature bath at 0 ° C. After confirming that the temperature of hydrochloric acid became 0 ° C., the CaSi ₂ powder was gradually added to hydrochloric acid under a nitrogen gas atmosphere and stirring conditions. After adding the CaSi ₂ powder, stirring was continued for 15 minutes.
a-2-2) Step After the a-2-1) step, the temperature of the constant temperature bath was raised to 20 ° C. at a rate of 1 ° C./min, and the reaction solution was stirred overnight. Then, the reaction solution was filtered. The residue was washed with distilled water, further washed with methanol, and dried under reduced pressure to obtain the oxygen-containing layered silicon compound of Example 3.

b) Step The oxygen-containing layered silicon compound of Example 3 was heated at 900 ° C. for 1 hour in a nitrogen gas atmosphere to obtain an oxygen-containing silicon material. This was used as the oxygen-containing silicon material of Example 3.

Hereinafter, the negative electrode and the lithium ion secondary battery of Example 3 were manufactured by the same method as in Example 1.

(Example 4)
In the step a-2-2), the oxygen-containing layered silicon compound and oxygen-containing of Example 4 were carried out in the same manner as in Example 3 except that the temperature of the constant temperature bath was raised to 30 ° C. at a rate of 1 ° C./min. Silicon material, negative electrode and lithium ion secondary battery were manufactured.

(Example 5)
In the step a-2-2), the oxygen-containing layered silicon compound and oxygen-containing of Example 5 were carried out in the same manner as in Example 3 except that the temperature of the constant temperature bath was raised to 40 ° C. at a rate of 1 ° C./min. Silicon material, negative electrode and lithium ion secondary battery were manufactured.

(Example 6)
a) The oxygen-containing layered silicon compound, oxygen-containing silicon material, negative electrode, and lithium ion secondary battery of Example 6 were produced in the same manner as in Example 3 except that the steps were as follows.
a-1) Step A reaction vessel containing 18% by mass hydrochloric acid was placed in a constant temperature bath at 20 ° C. After confirming that the temperature of hydrochloric acid reached 20 ° C., CaSi ₂ powder was gradually added to hydrochloric acid under a nitrogen gas atmosphere and stirring conditions. After adding the CaSi ₂ powder, the reaction solution was stirred overnight. Then, the reaction solution was filtered. The residue was washed with distilled water, further washed with methanol, and dried under reduced pressure to obtain the oxygen-containing layered silicon compound of Example 6.

(Comparative Example 3)
In the step a-2-2), the oxygen-containing layered silicon compound and the oxygen-containing silicon material of Comparative Example 3 were prepared in the same manner as in Example 3 except that the temperature of the constant temperature bath was not raised and the temperature was maintained at 0 ° C. A negative electrode and a lithium ion secondary battery were manufactured.

(Comparative Example 4)
In the step a-2-2), the oxygen-containing layered silicon compound of Comparative Example 4 and oxygen-containing were contained in the same manner as in Example 3 except that the temperature of the constant temperature bath was raised to 60 ° C. at a rate of 1 ° C./min. Silicon material, negative electrode and lithium ion secondary battery were manufactured.

(Evaluation example 4)
Elemental analysis was performed on the oxygen-containing silicon materials of Examples 3 to 6 and Comparative Examples 3 to 4 in the same manner as in Evaluation Example 1. The results of these elemental analyzes are shown in Table 4 as mass%.

From the results in Table 4, it can be seen that the oxygen content increases as the reaction temperature in step a-2-2) increases. It is considered that the reaction rate of the following formula (2) can be controlled depending on the temperature of the a-2-2) step.
Equation (2) Si ₆ H ₆ + 3H ₂ O → Si ₆ H ₃ (OH) ₃ + 3H ₂ ↑

Further, as compared with the oxygen-containing silicon material of Example 1 using 35% by mass hydrochloric acid, Cl in the oxygen-containing silicon materials of Examples 3 to 5 and Comparative Examples 3 to 4 using 18% by mass hydrochloric acid. It can be seen that the content is extremely low.

(Evaluation example 5)
The lithium ion secondary batteries of Examples 3 to 6 and Comparative Examples 3 to 4 are charged to 0.01 V at a current of 0.2 mA and then discharged to 1.0 V at a current of 0.2 mA. The initial charge / discharge was performed.
Further, the lithium ion secondary batteries of Examples 3 to 5 and Comparative Examples 3 to 4 after the initial charge / discharge are charged to 0.01 V at a current of 0.5 mA, and then charged at a current of 0.5 mA. The charge / discharge cycle of discharging to 1.0 V was performed 50 times.

The initial efficiency and capacity retention rate were calculated by the following formulas.
Initial efficiency (%) = 100 x (initial discharge capacity) / (initial charge capacity)
Capacity retention rate (%) = 100 x (discharge capacity at 50 cycles) / (discharge capacity at 1 cycle)
The results of initial charge capacity, initial discharge capacity, initial efficiency, and capacity retention rate are shown in Tables 5 and 6 together with some of the results of elemental analysis.

From the results in Tables 5 and 6, it can be seen that the values of the initial charge capacity, the initial discharge capacity, and the initial efficiency of Comparative Example 4 in which the temperature of the step a-2-2) is 60 ° C. are extremely low. As a result, since the temperature of the a-2-2) step was 60 ° C., the reaction of the formula (2), which is an oxygen introduction reaction, proceeded excessively, and the oxygen content in the oxygen-containing silicon material was high. It can be said that the fact that it was too expensive was reflected.
Further, from the results in Table 6, it can be seen that the value of the capacity retention rate of Comparative Example 3 in which the temperature of the step a-2-2) is 0 ° C. is extremely low. As a result, since the temperature of the a-2-2) step was 0 ° C., the reaction of the formula (2), which is an oxygen introduction reaction, was slowed down, and the silicon content in the oxygen-containing silicon material was high. It can be said that the fact that it was too expensive was reflected.

From Tables 5 and 6, _{the temperature at the time of adding the CaSi 2} powder was 0 ° C., and then the temperature was raised to 20 ° C., and the temperature at the time of _{adding the CaSi 2 powder was 20 ° C., which was 20 ° C.} It can be said that the maintained Example 6 showed the same result in terms of battery characteristics. _{From the viewpoint of work safety, it is rational to adopt a manufacturing method in which when CaSi 2} powder, which causes a relatively violent reaction, is charged, the reaction proceeds under low temperature conditions and the temperature gradually rises. ..

(Example 7)
_{CaSi 2} powder containing Al was prepared as follows.
Ca, Al and Si were weighed into a carbon crucible. The elemental composition ratio of Ca and Si was 1: 2, and the amount of Al added was 1% with respect to the total mass of Ca, Al and Si. The carbon crucible was heated at around 1300 ° C. with a high-frequency induction heating device in an argon gas atmosphere to prepare a molten metal containing Ca, Al and Si. The molten metal was cooled by pouring it into a predetermined mold to form a solid. The solid was pulverized to obtain CaSi ₂ powder, which was then subjected to step a).

a) Step a-2-1) Step A reaction vessel containing 18% by mass hydrochloric acid was placed in a constant temperature bath at 0 ° C. After confirming that the temperature of hydrochloric acid became 0 ° C., the CaSi ₂ powder was gradually added to hydrochloric acid under a nitrogen gas atmosphere and stirring conditions. After adding the CaSi ₂ powder, stirring was continued for 15 minutes.

a-2-2) Step After the a-2-1) step, the temperature of the constant temperature bath was raised to 20 ° C. at a rate of 1 ° C./min, and the reaction solution was stirred overnight. Then, the reaction solution was filtered. The residue was washed with distilled water, further washed with methanol, and dried under reduced pressure to obtain the oxygen-containing layered silicon compound of Example 7.

b) Step The oxygen-containing layered silicon compound of Example 7 was heated at 900 ° C. for 1 hour in a nitrogen gas atmosphere to obtain an oxygen-containing silicon material. The oxygen-containing silicon material was pulverized using a jet mill to obtain a powder having an average particle size of 5 μm.
This powder was used as the oxygen-containing silicon material of Example 7.

-Carbon coating step The oxygen-containing silicon material of Example 7 was placed in a rotary kiln type reactor, and thermal CVD was performed under the conditions of 880 ° C. and a residence time of 60 minutes under the aeration of a propane-argon mixed gas to achieve carbon coating. An oxygen-containing silicon material was obtained. This was used as the carbon-coated-oxygen-containing silicon material of Example 7.

The negative electrode and the lithium ion secondary battery of Example 7 were manufactured as follows.

Polyacrylic acid having a weight average molecular weight of 800,000 was dissolved in N-methyl-2-pyrrolidone to prepare a polyacrylic acid solution containing 10% by mass of polyacrylic acid. Further, 0.2 g (1.0 mmol) of 4,4'-diaminodiphenylmethane was dissolved in 0.4 mL of N-methyl-2-pyrrolidone to prepare a 4,4'-diaminodiphenylmethane solution. Under stirring conditions, the entire amount of the 4,4'-diaminodiphenylmethane solution was added dropwise to 7 mL of the polyacrylic acid solution (corresponding to 9.5 mmol in terms of acrylic acid monomer), and the obtained mixture was added dropwise at room temperature for 30 minutes. Stirred. Then, using a Dean-Stark apparatus, the mixture was stirred at 130 ° C. for 3 hours to allow the dehydration reaction to proceed, thereby producing a binder solution.

The above-mentioned binding in an amount of 78.5 parts by mass of the carbon-coated-oxygen-containing silicon material of Example 7 as the negative electrode active material, 10.5 parts by mass of acetylene black as the conductive auxiliary agent, and 11 parts by mass of the solid content as the binder. A slurry was prepared by mixing the agent solution and an appropriate amount of N-methyl-2-pyrrolidone. A copper foil was prepared as a current collector for the negative electrode. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. N-Methyl-2-pyrrolidone was removed by drying the copper foil coated with the slurry. Then, the negative electrode of Example 7 in which the negative electrode active material layer was formed was manufactured by pressing and baking at 180 ° C.

_{LiNi 82/100 Co 14/100 Al 4/100 O 2} 96 parts by mass as a positive electrode active material, acetylene black 2 parts by weight as a conductive additive, polyvinylidene fluoride 2 parts as a binder, and an appropriate amount of N- methyl -2-Pyrrolidone was mixed to prepare a slurry. Aluminum foil was prepared as a current collector for the positive electrode. The slurry was applied in a film form on the surface of the aluminum foil using a doctor blade. N-Methyl-2-pyrrolidone was removed by drying the aluminum foil coated with the slurry. Then, by pressing and baking at 120 ° C., a positive electrode having a positive electrode active material layer formed on the surface of the positive electrode current collector was manufactured.

Dimethyl carbonate, ethyl methyl carbonate and fluoroethylene carbonate were mixed at a volume ratio of 63:27:10 to prepare a mixed organic solvent. _{LiPF 6} was dissolved in a mixed organic solvent at a concentration of 2 mol / L to prepare an electrolytic solution.

A polyethylene porous membrane was prepared as a separator.

A separator was sandwiched between the positive electrode and the negative electrode of Example 7 to form an electrode plate group. This group of plates was covered with a set of two laminated films, the three sides were sealed, and then the electrolytic solution was injected into the bag-shaped laminated film. By sealing the remaining one side, a lithium ion secondary battery was obtained in which the four sides were hermetically sealed and the electrode plate group and the electrolytic solution were sealed. This battery was used as the lithium ion secondary battery of Example 7.

(Example 8)
In the step a-2-2), the oxygen-containing layered silicon compound and oxygen-containing of Example 8 were carried out in the same manner as in Example 7 except that the temperature of the constant temperature bath was raised to 40 ° C. at a rate of 1 ° C./min. Silicone materials, carbon-coated-oxygen-containing silicon materials, negative electrodes and lithium-ion secondary batteries were manufactured.

(Comparative Example 5)
In the step a-2-2), the oxygen-containing layered silicon compound and the oxygen-containing silicon material of Comparative Example 5 were prepared in the same manner as in Example 7 except that the temperature of the constant temperature bath was not raised and the temperature was maintained at 0 ° C. Carbon-coated-oxygen-containing silicone materials, negative electrodes and lithium-ion secondary batteries were manufactured.

(Comparative Example 6)
In the step a-2-2), the oxygen-containing layered silicon compound and oxygen-containing of Comparative Example 6 were carried out in the same manner as in Example 7 except that the temperature of the constant temperature bath was raised to 60 ° C. at a rate of 1 ° C./min. Silicone materials, carbon-coated-oxygen-containing silicon materials, negative electrodes and lithium-ion secondary batteries were manufactured.

(Comparative Example 7)
The negative electrode and lithium ion of Comparative Example 7 were used in the same manner as in Example 7 except that carbon-coated SiO (Shin-Etsu Chemical Co., Ltd.), which is a carbon-coated-oxygen-containing silicon material, was used as the negative electrode active material. The next battery was manufactured.

(Evaluation example 6)
Elemental analysis was performed on the carbon-coated-oxygen-containing silicon materials of Examples 7 to 8 and Comparative Examples 5 to 7 in the same manner as in Evaluation Example 1. However, elemental analysis of carbon was performed using a carbon / sulfur analyzer.
The results of these elemental analyzes are shown in Table 7 as mass%.

(Evaluation example 7)
The lithium ion secondary batteries of Examples 7 to 8 and Comparative Examples 5 to 7 were charged to a voltage of 4.28 V under the condition of 25 ° C., and then discharged to a voltage of 3 V. The initial discharge capacity was measured.
Further, the voltage of each lithium ion secondary battery adjusted to SOC 15% was measured when the lithium ion secondary battery was discharged at a constant current for 10 seconds under the condition of 25 ° C. The measurement was performed under multiple conditions with varying currents. From the obtained results, for each lithium ion secondary battery having an SOC of 15%, a constant current (mA) at which the discharge time up to a voltage of 2.5 V was 10 seconds was calculated, and 2.5 V was multiplied by the current value. The value was 25 ° C. for 10 seconds output (mW).
Further, the voltage of each lithium ion secondary battery adjusted to SOC 15% was measured when the lithium ion secondary battery was discharged at a constant current for 5 seconds under the condition of 0 ° C. The measurement was performed under multiple conditions with varying currents. From the obtained results, for each lithium ion secondary battery having an SOC of 15%, a constant current (mA) at which the discharge time up to a voltage of 2.5 V was 5 seconds was calculated, and 2.5 V was multiplied by the current value. The value was set to 0 ° C. for 5 seconds.
The above results are shown in Table 8.

From Table 8, it can be seen that Comparative Example 6 and Comparative Example 7 having a high oxygen content have a low initial discharge capacity. It can be said that Examples 7 and 8 in which the oxygen content and the silicon content are in an appropriate range are excellent in all the results of the initial discharge capacity, the 25 ° C. output and the 0 ° C. output.
Further, from the results of Comparative Example 6 and Comparative Example 7 in which the oxygen content and the silicon content are the same, it can be seen that the lithium ion secondary battery of Comparative Example 6 is superior in battery characteristics. The _{oxygen-containing silicon material made from CaSi 2} has a unique structure in which a plurality of plate-shaped silicon bodies are laminated in the thickness direction, which is not observed in general SiO. When Comparative Example 6 and Comparative Example 7 were compared, the reason why the lithium ion secondary battery of Comparative Example 6 was superior in output characteristics was that the oxygen-containing silicon material of Comparative Example 6 had a plurality of plates. It is considered that the silicon body has a structure in which the silicon bodies are laminated in the thickness direction.

(Example 9)
_{CaSi 2} powder containing Al was prepared as follows.
Ca, Al and Si were weighed into a carbon crucible. The elemental composition ratio of Ca and Si was 1: 2, and the amount of Al added was 1% with respect to the total mass of Ca, Al and Si. The carbon crucible was heated at around 1300 ° C. with a high-frequency induction heating device in an argon gas atmosphere to prepare a molten metal containing Ca, Al and Si. The molten metal was cooled by pouring it into a predetermined mold to form a solid. The solid was pulverized to obtain CaSi ₂ powder, which was then subjected to step a).

a) Step a-2-1) Step A reaction vessel containing 18% by mass hydrochloric acid was placed in a constant temperature bath at 0 ° C. After confirming that the temperature of hydrochloric acid became 0 ° C., the CaSi ₂ powder was gradually added to hydrochloric acid under a nitrogen gas atmosphere and stirring conditions. After adding the CaSi ₂ powder, stirring was continued for 15 minutes.

a-2-2) Step After the a-2-1) step, the temperature of the constant temperature bath was raised to 20 ° C. at a rate of 1 ° C./min, and the reaction solution was stirred overnight. Then, the reaction solution was filtered. The residue was washed with distilled water, further washed with methanol, and dried under reduced pressure to obtain the oxygen-containing layered silicon compound of Example 9.

b) Step The oxygen-containing layered silicon compound of Example 9 was heated at 900 ° C. for 1 hour in a nitrogen gas atmosphere to obtain an oxygen-containing silicon material. The oxygen-containing silicon material was pulverized using a jet mill to obtain a powder having an average particle size of 5 μm.
This powder was used as the oxygen-containing silicon material of Example 9.

-Carbon coating step The oxygen-containing silicon material of Example 9 was placed in a rotary kiln type reactor, and thermal CVD was performed under the conditions of 880 ° C. and a residence time of 60 minutes under the aeration of a propane-argon mixed gas to achieve carbon coating. An oxygen-containing silicon material was obtained. This was used as the carbon-coated-oxygen-containing silicon material of Example 9.

The negative electrode and the lithium ion secondary battery of Example 9 were manufactured as follows.

Polyacrylic acid having a weight average molecular weight of 800,000 was dissolved in N-methyl-2-pyrrolidone to prepare a polyacrylic acid solution containing 10% by mass of polyacrylic acid. Further, 0.2 g (1.0 mmol) of 4,4'-diaminodiphenylmethane was dissolved in 0.4 mL of N-methyl-2-pyrrolidone to prepare a 4,4'-diaminodiphenylmethane solution. Under stirring conditions, the entire amount of the 4,4'-diaminodiphenylmethane solution was added dropwise to 7 mL of the polyacrylic acid solution (corresponding to 9.5 mmol in terms of acrylic acid monomer), and the obtained mixture was added dropwise at room temperature for 30 minutes. Stirred. Then, using a Dean-Stark apparatus, the mixture was stirred at 130 ° C. for 3 hours to allow the dehydration reaction to proceed, thereby producing a binder solution.

The above-mentioned binding in an amount of 78.5 parts by mass of the carbon-coated-oxygen-containing silicon material of Example 9 as the negative electrode active material, 10.5 parts by mass of acetylene black as the conductive auxiliary agent, and 11 parts by mass of the solid content as the binder. A slurry was prepared by mixing the agent solution and an appropriate amount of N-methyl-2-pyrrolidone. A copper foil was prepared as a current collector for the negative electrode. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. N-Methyl-2-pyrrolidone was removed by drying the copper foil coated with the slurry. Then, the negative electrode of Example 9 in which the negative electrode active material layer was formed was manufactured by pressing and baking at 180 ° C.

_{A solution prepared by dissolving LiPF 6} at a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 was used as an electrolytic solution.

The negative electrode was cut to a diameter of 11 mm and used as an evaluation electrode. A metal lithium foil having a thickness of 500 μm was cut to a diameter of 13 mm and used as a counter electrode. As a separator, a glass filter (Hoechst Celanese Co., Ltd.) and a single-layer polypropylene celgard 2400 (Polypore Co., Ltd.) were prepared. Two types of separators were sandwiched between the counter electrode and the evaluation electrode in the order of the counter electrode, the glass filter, the celgard 2400, and the evaluation electrode to form an electrode body. This electrode body was housed in a coin-type battery case CR2032 (Hosen Co., Ltd.). The electrolytic solution was injected into the battery case, the battery case was sealed, and the lithium ion secondary battery of Example 9 was manufactured.

(Example 10)
In the step a-2-2), the oxygen-containing layered silicon compound and oxygen-containing of Example 10 were carried out in the same manner as in Example 9 except that the temperature of the constant temperature bath was raised to 40 ° C. at a rate of 1 ° C./min. Silicone materials, carbon-coated-oxygen-containing silicon materials, negative electrodes and lithium-ion secondary batteries were manufactured.

(Comparative Example 8)
In the step a-2-2), the oxygen-containing layered silicon compound and the oxygen-containing silicon material of Comparative Example 8 were prepared in the same manner as in Example 9 except that the temperature of the constant temperature bath was not raised and the temperature was maintained at 0 ° C. Carbon-coated-oxygen-containing silicone materials, negative electrodes and lithium-ion secondary batteries were manufactured.

(Comparative Example 9)
In the step a-2-2), the oxygen-containing layered silicon compound and oxygen-containing of Comparative Example 9 were carried out in the same manner as in Example 9 except that the temperature of the constant temperature bath was raised to 60 ° C. at a rate of 1 ° C./min. Silicone materials, carbon-coated-oxygen-containing silicon materials, negative electrodes and lithium-ion secondary batteries were manufactured.

(Evaluation example 8)
Elemental analysis was performed on the carbon-coated-oxygen-containing silicon materials of Examples 9 to 10 and Comparative Examples 8 to 9 in the same manner as in Evaluation Example 6. The results of these elemental analyzes are shown in Table 9 as mass%.

(Evaluation example 9)
A charge / discharge test was performed on the lithium ion secondary batteries of Examples 9 to 10 and Comparative Examples 8 to 9 in the same manner as in Evaluation Example 2. The results are shown in Table 10. Further, FIG. 2 shows the relationship between the integrated capacity and the discharge capacity of each lithium ion secondary battery in 50 charge / discharge cycles.

From the results of Table 10 and FIG. 2, the lithium ion secondary batteries provided with the oxygen-containing silicon materials of Examples 9 and 10 in which the oxygen mass% and the silicon mass% are in the appropriate ranges maintain the initial efficiency and capacity. It can be said that the rate and integrated capacity are well-balanced and satisfied.

(Example 11)
_{CaSi 2} powder containing Al was prepared as follows.
Ca, Al and Si were weighed into a carbon crucible. The elemental composition ratio of Ca and Si was 1: 2, and the amount of Al added was 1% with respect to the total mass of Ca, Al and Si. The carbon crucible was heated at around 1300 ° C. with a high-frequency induction heating device in an argon gas atmosphere to prepare a molten metal containing Ca, Al and Si. The molten metal was cooled by pouring it into a predetermined mold to form a solid. The solid was pulverized to obtain CaSi ₂ powder, which was then subjected to step a).

a) Step a-2-1) Step A reaction vessel containing 18% by mass hydrochloric acid was placed in a constant temperature bath at 0 ° C. After confirming that the temperature of hydrochloric acid became 0 ° C., the CaSi ₂ powder was gradually added to hydrochloric acid under a nitrogen gas atmosphere and stirring conditions. After adding the CaSi ₂ powder, stirring was continued for 15 minutes.

a-2-2) Step After the a-2-1) step, the temperature of the constant temperature bath was raised to 40 ° C. at a rate of 1 ° C./min, and the reaction solution was stirred overnight. Then, the reaction solution was filtered. The residue was washed with distilled water, further washed with methanol, and dried under reduced pressure to obtain the oxygen-containing layered silicon compound of Example 11.

b) Step The oxygen-containing layered silicon compound of Example 11 was heated at 700 ° C. for 1 hour in a nitrogen gas atmosphere to obtain an oxygen-containing silicon material. The oxygen-containing silicon material was pulverized using a jet mill to obtain a powder having an average particle size of 5 μm.
This powder was used as the oxygen-containing silicon material of Example 11.

-Carbon coating step The oxygen-containing silicon material of Example 11 was placed in a rotary kiln type reactor and subjected to thermal CVD under the conditions of 700 ° C. and a residence time of 60 minutes under aeration of a hexane-argon mixed gas to achieve carbon coating. An oxygen-containing silicon material was obtained. This was used as the carbon-coated-oxygen-containing silicon material of Example 11.

The negative electrode and the lithium ion secondary battery of Example 11 were manufactured as follows.

72.5 parts by mass of the carbon-coated-oxygen-containing silicon material of Example 11 as the negative electrode active material, 13.5 parts by mass of acetylene black as the conductive auxiliary agent, 14 parts by mass of the polyamide-imide as the binder, and an appropriate amount of N-methyl. -2-Pyrrolidone was mixed to prepare a slurry. A copper foil was prepared as a current collector for the negative electrode. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. N-Methyl-2-pyrrolidone was removed by drying the copper foil coated with the slurry. Then, by pressing and baking at 180 ° C., the negative electrode of Example 11 in which the negative electrode active material layer was formed was manufactured.

_{A solution prepared by dissolving LiPF 6} at a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 was used as an electrolytic solution.

The negative electrode was cut to a diameter of 11 mm and used as an evaluation electrode. A metal lithium foil having a thickness of 500 μm was cut to a diameter of 13 mm and used as a counter electrode. As a separator, a glass filter (Hoechst Celanese Co., Ltd.) and a single-layer polypropylene celgard 2400 (Polypore Co., Ltd.) were prepared. Two types of separators were sandwiched between the counter electrode and the evaluation electrode in the order of the counter electrode, the glass filter, the celgard 2400, and the evaluation electrode to form an electrode body. This electrode body was housed in a coin-type battery case CR2032 (Hosen Co., Ltd.). The electrolytic solution was injected into the battery case, the battery case was sealed, and the lithium ion secondary battery of Example 11 was manufactured.

(Example 12)
_{In the step of preparing the CaSi 2} powder containing Al, the same method as in Example 11 was carried out except that the amount of Al added was 0.5% with respect to the total mass of Ca, Al and Si. The oxygen-containing layered silicon compound of Example 12, the oxygen-containing silicon material, the carbon-coated-oxygen-containing silicon material, the negative electrode, and the lithium ion secondary battery were manufactured.

(Example 13)
In the step of preparing _{the CaSi 2} powder containing Al, the oxygen-containing layered silicon of Example 13 was prepared in the same manner as in Example 11 except _{that the CaSi 2 powder containing no Al was prepared without adding Al.} Compounds, oxygen-containing silicon materials, carbon-coated-oxygen-containing silicon materials, negative electrodes and lithium-ion secondary batteries were manufactured.

(Example 14)
b) The same method as in Example 11 except that the heating temperature of the step was 900 ° C. and the conditions of the carbon coating step were 880 ° C. and a residence time of 60 minutes under the aeration of a propane-argon mixed gas. , Oxygen-containing layered silicon compound, oxygen-containing silicon material, carbon-coated-oxygen-containing silicon material, negative electrode and lithium ion secondary battery of Example 14 were produced.

(Example 15)
b) The same method as in Example 13 except that the heating temperature of the step was 900 ° C. and the conditions of the carbon coating step were 880 ° C. and a residence time of 60 minutes under the aeration of a propane-argon mixed gas. , Oxygen-containing layered silicon compound, oxygen-containing silicon material, carbon-coated-oxygen-containing silicon material, negative electrode and lithium ion secondary battery of Example 15 were produced.

(Evaluation example 10)
Elemental analysis was performed on the carbon-coated-oxygen-containing silicon materials of Examples 11 to 15 in the same manner as in Evaluation Example 6. The results of these elemental analyzes are shown in Table 11 as mass%.

(Evaluation example 11)
The BET specific surface area of the carbon-coated-oxygen-containing silicon material of Examples 11 to 15 was measured. The results are shown in Table 12 together with the features of the manufacturing method other than a) step.

(Evaluation example 12)
The lithium ion secondary batteries of Examples 11 to 15 are initially charged and discharged by charging to 0.01 V at a current of 0.2 mA and then discharging to 1.0 V at a current of 0.2 mA. went.
Further, the lithium ion secondary batteries of Examples 11 to 15 after the initial charge / discharge are charged to 0.01 V at a current of 0.5 mA, and then discharged to 1.0 V at a current of 0.5 mA. The charge / discharge cycle of the above was performed 50 times.

The initial efficiency and capacity retention rate were calculated by the following formulas.
Initial efficiency (%) = 100 x (initial discharge capacity up to 0.8V) / (initial charge capacity)
Capacity retention rate (%) = 100 x (discharge capacity at 50 cycles) / (discharge capacity at 1 cycle)
The above results are shown in Table 13 together with data such as elemental analysis of the carbon-coated-oxygen-containing silicon material.

From the results in Table 13, it can be said that a suitable carbon-coated-oxygen-containing silicon material having an oxygen mass% exhibits excellent properties as a negative electrode active material. It can also be seen that the oxygen mass%, silicon mass% and Al mass% of the carbon-coated-oxygen-containing silicon material affect the capacity retention rate of the secondary battery.

Claims (13)

a-1) _{A step of reacting CaSi 2} with an acid aqueous solution at 15 to 50 ° C. to synthesize an oxygen-containing layered silicon compound containing layered polysilane.
b) A step of synthesizing an oxygen-containing silicon material by heating the oxygen-containing layered silicon compound at 300 ° C. or higher.
Only contains the CaSi ₂ is contained Al, and the negative electrode including an oxygen-containing silicon material, wherein the Al mass% in the oxygen-containing silicon material _{(W Al%)} is 0 _{<W Al} <1 Manufacturing method of active material. a-2-1) _{A step of reacting CaSi 2} with an acid aqueous solution at -20 to 10 ° C.
a-2-2) Following the step a-2-1), a step of synthesizing an oxygen-containing layered silicon compound containing layered polysilane at a temperature of the reaction solution of 15 to 50 ° C.
b) A step of synthesizing an oxygen-containing silicon material by heating the oxygen-containing layered silicon compound at 300 ° C. or higher.
Only contains the CaSi ₂ is contained Al, and the negative electrode including an oxygen-containing silicon material, wherein the Al mass% in the oxygen-containing silicon material _{(W Al%)} is 0 _{<W Al} <1 Manufacturing method of active material. The method for producing a negative electrode active material containing an oxygen-containing silicon material according to claim 1 or 2, wherein the acid concentration in the aqueous acid solution is in the range of 5 to 30% by mass. The oxygen-containing silicon according to claim 3, wherein the oxygen-containing silicon material contains an element derived from the anion of the acid, and the mass% (W _X %) of the _{element in the oxygen-containing silicon material is 0 <W X} <6. A method for producing a negative electrode active material including a material. Method of preparing a negative active material containing an oxygen-containing silicon material according to any one of claims 1 to 4 oxygen _mass% (W _O%) is 16 <W O _<27 in the oxygen-containing silicon material. The method for producing a negative electrode active material containing an oxygen-containing silicon material according to any one of claims 1 to 5, wherein the silicon mass% (W _Si %) in the oxygen-containing silicon material is 62 <W _{Si <81.} The negative electrode active material containing the oxygen-containing silicon material according to any one of claims 1 to 6 , wherein the ratio of silicon crystals to amorphous silicon in the oxygen-containing silicon material is in the range of 0: 100 to 30:70. Manufacturing method. a-1) _{A step of reacting CaSi 2} with an acid aqueous solution at 40 to 50 ° C. to synthesize an oxygen-containing layered silicon compound containing layered polysilane.
b) A step of synthesizing an oxygen-containing silicon material by heating the oxygen-containing layered silicon compound at 300 ° C. or higher.
A method for producing a negative electrode active material containing an oxygen-containing silicon material. a-2-1) _{A step of reacting CaSi 2} with an acid aqueous solution at -20 to 10 ° C.
a-2-2) Following the step a-2-1), a step of synthesizing an oxygen-containing layered silicon compound containing layered polysilane at a temperature of the reaction solution of 30 to 50 ° C.
b) A step of synthesizing an oxygen-containing silicon material by heating the oxygen-containing layered silicon compound at 300 ° C. or higher.
A method for producing a negative electrode active material containing an oxygen-containing silicon material. a-1) _{A step of reacting CaSi 2} with an acid aqueous solution at 15 to 50 ° C. to synthesize an oxygen-containing layered silicon compound containing layered polysilane.
b) A step of synthesizing an oxygen-containing silicon material by heating the oxygen-containing layered silicon compound at 300 ° C. or higher.
Only including, a manufacturing method of the negative electrode active material containing an oxygen-containing silicon material, wherein the concentration of the acid in the aqueous acid solution is in the range of 5 to 30 mass%. a-2-1) _{A step of reacting CaSi 2} with an acid aqueous solution at -20 to 10 ° C.
a-2-2) Following the step a-2-1), a step of synthesizing an oxygen-containing layered silicon compound containing layered polysilane at a temperature of the reaction solution of 15 to 50 ° C.
b) A step of synthesizing an oxygen-containing silicon material by heating the oxygen-containing layered silicon compound at 300 ° C. or higher.
Only including, a manufacturing method of the negative electrode active material containing an oxygen-containing silicon material, wherein the concentration of the acid in the aqueous acid solution is in the range of 5 to 30 mass%. A method for producing a negative electrode, which uses a negative electrode active material containing an oxygen-containing silicon material produced by the production method according to any one of claims 1 to 11. A method for manufacturing a secondary battery, which uses a negative electrode manufactured by the manufacturing method according to claim 12.

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