JP6765984B2 - Method for manufacturing negative electrode active material for non-aqueous electrolyte secondary battery and method for manufacturing negative electrode for non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, a method for producing a negative electrode for a non-aqueous electrolyte secondary battery, and a method for producing a non-aqueous electrolyte secondary battery.

In recent years, small electronic devices represented by mobile terminals and the like have become widespread, and further miniaturization, weight reduction, and long life are strongly required. In response to such market demands, the development of a secondary battery that is particularly compact, lightweight, and capable of obtaining a high energy density is being promoted. This secondary battery is being considered for application not only to small electronic devices but also to large electronic devices such as automobiles and electric power storage systems such as houses.

Among them, lithium-ion secondary batteries are highly expected because they are compact and easy to increase in capacity, and can obtain higher energy density than lead batteries and nickel-cadmium batteries.

The lithium ion secondary battery includes an electrolytic solution together with a positive electrode, a negative electrode, and a separator. This negative electrode contains a negative electrode active material involved in the charge / discharge reaction.

While carbon materials are widely used as negative electrode active materials, recent market demands require further improvement in battery capacity. As an element for improving the battery capacity, the use of silicon as the negative electrode active material is being studied. This is because the theoretical capacity of silicon (4199 mAh / g) is more than 10 times larger than the theoretical capacity of graphite (372 mAh / g), so that a significant improvement in battery capacity can be expected. The development of Kay material as a negative electrode active material is being studied not only for silicon alone, but also for compounds such as alloys and oxides. The shape of the active material has been studied from the standard coating type of carbon material to the integrated type that deposits directly on the current collector.

However, when silicon is used as the main raw material as the negative electrode active material, the negative electrode active material particles expand and contract during charging and discharging, so that the vicinity of the surface layer of the negative electrode active material particles is liable to crack. In addition, an ionic substance is generated inside the active material, and the negative electrode active material particles are easily broken. The cracking of the surface layer of the negative electrode active material particles creates a new surface, and the reaction area of the negative electrode active material particles increases. At this time, the decomposition reaction of the electrolytic solution occurs on the new surface, and the electrolytic solution is consumed because a film which is a decomposition product of the electrolytic solution is formed on the new surface. Therefore, the cycle characteristics of the battery tend to deteriorate.

So far, in order to improve the initial efficiency and cycle characteristics of the battery, various studies have been made on the negative electrode material for lithium ion secondary batteries and the electrode configuration, which are mainly made of Kay material.

Specifically, silicon and amorphous silicon dioxide are simultaneously deposited using the vapor phase method for the purpose of obtaining good cycle characteristics and high safety (see, for example, Patent Document 1). Further, in order to obtain high battery capacity and safety, a carbon material (electron conductive material) is provided on the surface layer of the silicon oxide particles (see, for example, Patent Document 2). Further, in order to improve the cycle characteristics and obtain high input / output characteristics, an active material containing silicon and oxygen is prepared, and an active material layer having a high oxygen ratio in the vicinity of the current collector is formed (for example). , Patent Document 3). Further, in order to improve the cycle characteristics, oxygen is contained in 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 high near the current collector. (See, for example, Patent Document 4).

Further, Si phase in order to improve the initial charge-discharge efficiency is used nanocomposites containing SiO 2, _M y _O metal oxide (e.g., see Patent Document 5). Further, in order to improve the initial charge / discharge efficiency, a Li-containing substance is added to the negative electrode, and Li is decomposed at a high negative electrode potential to return Li to the positive electrode by predoping (see, for example, Patent Document 6).

Further, in order to improve the cycle characteristics, SiOx (0.8 ≦ x ≦ 1.5, particle size range = 1 μm to 50 μm) and a carbon material are mixed and fired at a high temperature (see, for example, Patent Document 7). Further, in order to improve the 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 molar ratio of oxygen amount to silicon amount in the vicinity of the interface between the active material and the current collector is set. The active material is controlled within a range in which the difference between the maximum value and the minimum value of is 0.4 or less (see, for example, Patent Document 8). Further, in order to improve the battery load characteristics, a metal oxide containing lithium is used (see, for example, Patent Document 9). Further, in order to improve the cycle characteristics, a hydrophobic layer such as a silane compound is formed on the surface layer of the Kay material (see, for example, Patent Document 10).

Further, in order to improve the cycle characteristics, silicon oxide is used and a graphite film is formed on the surface layer thereof to impart conductivity (see, for example, Patent Document 11). In this case, in Patent Document 11, with respect to the shift value obtained from the Raman spectra for graphite coating, with broad peaks appearing at 1330 cm ^-1 and 1580 cm ^-1, their intensity ratio _I 1330 _{/ I 1580} is 1.5 <I ₁₃₃₀ / I ₁₅₈₀ <3.

Further, in order to improve the high battery capacity and cycle characteristics, particles having a silicon microcrystalline phase dispersed in silicon dioxide are used (see, for example, Patent Document 12). Further, in order to improve the overcharge and overdischarge characteristics, a silicon oxide in which the atomic number ratio of silicon and oxygen is controlled to 1: y (0 <y <2) is used (see, for example, Patent Document 13). ..

Further, in order to increase the battery capacity and improve the initial efficiency, there is a method in which the alloy-based material is brought into contact with a solution containing an alkali metal and a polycyclic aromatic compound, and further immersed in a liquid that desorbs the alkali metal element (for example,). See Patent Document 14).

Japanese Unexamined Patent Publication No. 2001-185127 JP-A-2002-042806 Japanese Unexamined Patent Publication No. 2006-164954 Japanese Unexamined Patent Publication No. 2006-114454 Japanese Unexamined Patent Publication No. 2009-070825 Special Table 2013-513206 Japanese Unexamined Patent Publication No. 2008-282819 Japanese Unexamined Patent Publication No. 2008-251369 Japanese Unexamined Patent Publication No. 2008-177346 JP-A-2007-234255 Japanese Unexamined Patent Publication No. 2009-21204 JP-A-2009-205950 Japanese Patent No. 2997741 Japanese Unexamined Patent Publication No. 2005-235439

As mentioned above, in recent years, small electronic devices such as mobile terminals have been promoted to have higher performance and more functions, and secondary batteries, which are the main power sources thereof, especially lithium ion secondary batteries, have a battery capacity. Is required to increase. As one method for solving this problem, it is desired to develop a non-aqueous electrolyte secondary battery composed of a negative electrode using a Kay material as a main material. Further, a non-aqueous electrolyte secondary battery using a Kay material is desired to have cycle characteristics close to those of a non-aqueous electrolyte secondary battery using a carbon material.

Therefore, the thermal Li insertion reaction, the electrical Li insertion reaction, the Li insertion reaction by the immersion method (oxidation-reduction method), and the like have been used independently to improve the cycle maintenance rate and the initial efficiency of the battery. However, since the modified silicon oxide was modified using Li, its water resistance is relatively low. Therefore, there is a problem that the stabilization of the slurry containing the modified silicon oxide, which is produced at the time of manufacturing the negative electrode, tends to be insufficient.

The present invention has been made in view of the above-mentioned problems, and provides a method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, which can increase the battery capacity and improve the initial efficiency and cycle characteristics. The purpose is. Another object of the present invention is to provide a method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery using such a negative electrode active material for a non-aqueous electrolyte secondary battery. Another object of the present invention is to provide a method for manufacturing a non-aqueous electrolyte secondary battery using such a negative electrode for a non-aqueous electrolyte secondary battery.

In order to achieve the above object, the present invention is a method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery containing silicon compound particles containing lithium.
A step of preparing silicon compound particles containing a silicon compound (SiO _x : 0.5 ≦ x ≦ 1.6) and
A step of mixing the silicon compound particles with a simple substance of lithium or a lithium compound and heating to obtain the first lithium-containing silicon compound particles.
A step of obtaining the second lithium-containing silicon compound particles by contacting the first lithium-containing silicon compound particles with a solution A containing lithium and the solvent is an ether solvent.
Provided is a method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, which comprises.

Since the negative electrode active material containing silicon compound particles containing lithium produced by the method for producing the negative electrode active material of the present invention is a silicon-based active material mainly composed of a silicon compound, the battery capacity can be increased. it can. Further, since this silicon compound is represented by the general formula SiO _x (however, 0.5 ≦ x ≦ 1.6) and the silicon compound particles contain lithium, the cycle characteristics can be improved. it can.

Further, in the method for producing a negative electrode active material of the present invention, as a step of inserting lithium (Li), a step of obtaining first lithium-containing silicon compound particles (hereinafter, also referred to as a heated Li insertion step) and a second lithium-containing step. The irreversible capacity of different sites in the silicon compound particles can be selectively modified by going through two types of steps of obtaining the silicon compound particles (hereinafter, also referred to as a dipping Li insertion step). This makes it possible to improve the initial efficiency of the non-aqueous electrolyte secondary battery using the negative electrode active material, and further prevent the growth of silicon crystallites due to the insertion of Li and the gelation during slurrying. Further, by performing the heating Li insertion step first and then the immersion Li insertion step, it is possible to prevent the heat-sensitive Li-containing chemical species generated in the immersion Li insertion step from being destroyed by heating.

Further, it is preferable to have a step of forming a carbon film on the silicon compound particles before the step of obtaining the first lithium-containing silicon compound particles.

Since the silicon compound particles have a carbon film as described above, the decrease in conductivity due to Li insertion can be stopped to some extent.

Further, in the step of preparing the silicon compound particles, it is preferable to prepare the silicon compound particles having a silicon crystallite size of 3 nm or more and 10 nm or less.

By appropriately adjusting the Si crystallite size in the silicon compound particles in this way, the initial efficiency can be improved and the cycle characteristics can be maintained.

Further, in the step of obtaining the first lithium-containing silicon compound particles, the heating temperature is preferably 400 ° C. or higher. The heating temperature at this time is more preferably 400 ° C. or higher and 800 ° C. or lower, and particularly preferably 600 ° C. or higher and 800 ° C. or lower.

By setting the heating temperature within the above range, it is possible to suppress the crystal growth of silicon in the silicon compound particles and prevent the cycle maintenance rate from deteriorating. In addition, lithium can be sufficiently inserted, and the initial efficiency can be sufficiently improved.

Further, in the step of obtaining the second lithium-containing silicon compound particles, it is preferable that the contact time with the solution A is 3 minutes or more.

By contacting the solution A for 3 minutes or more, Li can be more sufficiently inserted into the silicon compound particles.

Further, as the solution A, solution A ₁ or lithium containing lithium and _one or more selected from a linear polyphenylene compound and its derivative, and a polycyclic aromatic compound and its derivative, and the solvent is an ether solvent, and It is preferable to use solution A ₂ containing amines and the solvent being an ether solvent.

If a solution such as these is used as the solution A containing lithium, more uniform Li can be inserted into the silicon compound particles, and Li can be efficiently inserted. Hereinafter, "one or more selected from linear polyphenylene compounds and derivatives thereof and polycyclic aromatic compounds and derivatives thereof" is also referred to as "linear polyphenylene compounds and the like".

In this case, as the solution A, it is preferable to use the solution A _1.

When the solution A ₁ is used, Li can be inserted particularly efficiently.

In this case, as the solution A _1, comprises lithium, and include one or more selected from linear polyphenylene compounds and derivatives thereof, it is preferable to use a solution in which the solvent is an ether solvent.

Thus, as a solution A _1, it is particularly preferred to use those containing one or more selected from linear polyphenylene compounds and derivatives thereof.

Further, the total content of one or more selected from the linear polyphenylene compound and its derivative and the polycyclic aromatic compound and its derivative measured by TPD-MS of the second lithium-containing silicon compound particle is 1 mass ppm or more 4000. The mass is preferably ppm or less.

By setting the total content of the linear polyphenylene compound or the like within the above range, the surface stability of the second lithium-containing silicon compound particles is improved by the linear polyphenylene compound or the like.

Further, after the step of obtaining the second lithium-containing silicon compound particles, the second lithium-containing silicon compound particles contain one or more selected from an ether-based material, a ketone-based material, and an ester-based material as a solvent. It is preferable to have a step of contacting the solution B containing a compound having a quinoid structure in the molecule as a solute.

The compound having a quinoid structure in the molecule, which is the solute of the solution B, extracts Li from the silicon compound particles containing active Li in the above solvent to form a salt of Li and a quinone analog, which is a solvent. Since it dissolves in, Li can be withdrawn until it reaches an equilibrium state.

In this case, it is preferable that the compound having a quinoid structure in the molecule is benzoquinone, quinodimethane, quinodiimine, or a derivative thereof.

As the solute of the solution B, those such as these can be used. Among the compounds having a quinoid structure in the molecule, in particular, by using these compounds, it is possible to efficiently extract active Li from silicon compound particles containing active Li in a solvent.

Further, the second lithium-containing silicon compound particle has a peak derived from the (011) plane of Li ₄ SiO ₄ and a peak derived from the (001) plane of Li ₂ SiO ₃ in the XRD spectrum of the particles. It is preferable that the particle is used.

By coexisting Li ₄ SiO ₄ and Li ₂ SiO ₃ in the second lithium-containing silicon compound particles, Li ₄ SiO ₄ is eluted from the second lithium-containing silicon compound particles when the negative electrode slurry (particularly an aqueous slurry) is produced. Can be sufficiently suppressed.

Further, it is preferable that the lithium content of the second lithium-containing silicon compound particles is 4% by mass or more and 30% by mass or less.

By appropriately adjusting the lithium content of the second lithium-containing silicon compound particles in this way, the discharge capacity can be appropriately adjusted while increasing the initial efficiency.

Further, the present invention is a method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery containing silicon compound particles containing lithium.
A step of preparing silicon compound particles containing a silicon compound (SiO _x : 0.5 ≦ x ≦ 1.6) and
A step of mixing the silicon compound particles with a simple substance of lithium or a lithium compound and heating to obtain the first lithium-containing silicon compound particles.
A step of forming an electrode containing the first lithium-containing silicon compound particles, and
A step of contacting the first lithium-containing silicon compound particles contained in the electrode with a solution A containing lithium and the solvent being an ether solvent to obtain an electrode containing the second lithium-containing silicon compound particles.
Provided is a method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery, which comprises.

Since the negative electrode containing silicon compound particles containing lithium produced by the method for producing a negative electrode of the present invention contains a silicon-based active material mainly composed of a silicon compound, the battery capacity can be increased. Further, since this silicon compound is represented by the general formula SiO _x (however, 0.5 ≦ x ≦ 1.6) and the silicon compound particles contain lithium, the cycle characteristics can be improved. it can.

Further, in the method for producing a negative electrode of the present invention, there are two types of steps for inserting lithium (Li): a step of obtaining first lithium-containing silicon compound particles and a step of obtaining an electrode containing a second lithium-containing silicon compound particles. It is possible to selectively modify the irreversible capacity of different sites in the silicon compound particles. This makes it possible to improve the initial efficiency of the non-aqueous electrolyte secondary battery using the negative electrode, and further prevent the growth of silicon crystallites due to Li insertion and gelation during slurry formation. Further, by first performing the step of obtaining the first lithium-containing silicon compound particles and then performing the step of obtaining the electrode containing the second lithium-containing silicon compound particles, the electrode containing the second lithium-containing silicon compound particles is performed. It is possible to prevent the heat-sensitive Li-containing chemical species generated in the process of obtaining the above-mentioned chemical species from being destroyed by heating.

Further, it is preferable to have a step of forming a carbon film on the silicon compound particles before the step of obtaining the first lithium-containing silicon compound particles.

Since the silicon compound particles have a carbon film as described above, the decrease in conductivity due to Li insertion can be stopped to some extent.

Further, in the step of preparing the silicon compound particles, it is preferable to prepare the silicon compound particles having a silicon crystallite size of 3 nm or more and 10 nm or less.

By appropriately adjusting the Si crystallite size in the silicon compound particles in this way, the initial efficiency can be improved and the cycle characteristics can be maintained.

Further, in the step of obtaining the first lithium-containing silicon compound particles, the heating temperature is preferably 400 ° C. or higher. The heating temperature at this time is more preferably 400 ° C. or higher and 800 ° C. or lower, and particularly preferably 600 ° C. or higher and 800 ° C. or lower.

By setting the heating temperature within the above range, it is possible to suppress the crystal growth of silicon in the silicon compound particles and prevent the cycle maintenance rate from deteriorating. In addition, lithium can be sufficiently inserted, and the initial efficiency can be sufficiently improved.

Further, in the step of obtaining the electrode containing the second lithium-containing silicon compound particles, it is preferable that the contact time with the solution A is 3 minutes or more.

By contacting the solution A for 3 minutes or more, Li can be more sufficiently inserted into the silicon compound particles.

Further, as the solution A, solution A ₁ or lithium containing lithium and _one or more selected from a linear polyphenylene compound and its derivative, and a polycyclic aromatic compound and its derivative, and the solvent is an ether solvent, and It is preferable to use solution A ₂ containing amines and the solvent being an ether solvent.

If a solution such as these is used as the solution A containing lithium, more uniform Li can be inserted into the silicon compound particles, and Li can be efficiently inserted.

In this case, as the solution A, it is preferable to use the solution A _1.

When the solution A ₁ is used, Li can be inserted particularly efficiently.

In this case, as the solution A _1, comprises lithium, and include one or more selected from linear polyphenylene compounds and derivatives thereof, it is preferable to use a solution in which the solvent is an ether solvent.

Thus, as a solution A _1, it is particularly preferred to use those containing one or more selected from linear polyphenylene compounds and derivatives thereof.

Further, the total content of one or more selected from the linear polyphenylene compound and its derivative and the polycyclic aromatic compound and its derivative measured by TPD-MS of the second lithium-containing silicon compound particle is 1 mass ppm or more 4000. The mass is preferably ppm or less.

By setting the total content of the linear polyphenylene compound or the like within the above range, the surface stability of the second lithium-containing silicon compound particles is improved by the linear polyphenylene compound or the like.

Further, after the step of obtaining the electrode containing the second lithium-containing silicon compound particles, one selected from an ether-based material, a ketone-based material, and an ester-based material using the second lithium-containing silicon compound particles as a solvent. Including the above, it is preferable to have a step of contacting the solution B containing a compound having a quinoid structure in the molecule as a solute.

The compound having a quinoid structure in the molecule, which is the solute of the solution B, extracts Li from the silicon compound particles containing active Li in the above solvent to form a salt of Li and a quinone analog, which is a solvent. Since it dissolves in, Li can be withdrawn until it reaches an equilibrium state.

In this case, it is preferable that the compound having a quinoid structure in the molecule is benzoquinone, quinodimethane, quinodiimine, or a derivative thereof.

As the solute of the solution B, those such as these can be used. Among the compounds having a quinoid structure in the molecule, in particular, by using these compounds, it is possible to efficiently extract active Li from silicon compound particles containing active Li in a solvent.

Further, the second lithium-containing silicon compound particle has a peak derived from the (011) plane of Li ₄ SiO ₄ and a peak derived from the (001) plane of Li ₂ SiO ₃ in the XRD spectrum of the particles. It is preferable that the particle is used.

By coexisting Li ₄ SiO ₄ and Li ₂ SiO ₃ in the second lithium-containing silicon compound particles, Li ₄ SiO ₄ is eluted from the second lithium-containing silicon compound particles when the negative electrode slurry (particularly an aqueous slurry) is produced. Can be sufficiently suppressed.

Further, it is preferable that the lithium content of the second lithium-containing silicon compound particles is 4% by mass or more and 30% by mass or less.

By appropriately adjusting the lithium content of the second lithium-containing silicon compound particles in this way, the discharge capacity can be appropriately adjusted while increasing the initial efficiency.

Further, in the present invention, the negative electrode active material for a non-aqueous electrolyte secondary battery is produced by the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, and the negative electrode active material for the non-aqueous electrolyte secondary battery is used. Provided is a method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery, which comprises manufacturing a negative electrode for a non-aqueous electrolyte secondary battery.

Further, in the present invention, a negative electrode for a non-aqueous electrolyte secondary battery is manufactured by the method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery of the present invention, and the negative electrode for a non-aqueous electrolyte secondary battery is used to produce a non-aqueous electrolyte secondary battery. Provided is a method for manufacturing a non-aqueous electrolyte secondary battery, which comprises manufacturing the above.

As described above, in the method for producing a negative electrode active material of the present invention, it is possible to selectively modify the irreversible capacity of different sites in the silicon compound particles. This makes it possible to improve the initial efficiency of the non-aqueous electrolyte secondary battery using the negative electrode active material, and further prevent the growth of silicon crystallites due to the insertion of Li and the gelation during slurrying. Therefore, the negative electrode manufactured by using the negative electrode active material and the non-aqueous electrolyte secondary battery manufactured by using this negative electrode have good battery characteristics.

The method for producing a negative electrode active material of the present invention can produce a negative electrode active material having a high capacity and good cycle characteristics and initial charge / discharge characteristics when used in a non-aqueous electrolyte secondary battery.

Further, the same characteristics can be obtained in the secondary battery containing the negative electrode active material produced by the method for producing the negative electrode active material of the present invention. Further, the same effect can be obtained in electronic devices, electric tools, electric vehicles, power storage systems, etc. using this secondary battery.

It is a flow chart which shows an example of the manufacturing method of the negative electrode active material for a non-aqueous electrolyte secondary battery of this invention. It is schematic cross-sectional view which shows an example of the structure of the negative electrode manufactured by the manufacturing method of the negative electrode for a non-aqueous electrolyte secondary battery of this invention. It is an exploded view which shows an example of the structure of the non-aqueous electrolyte secondary battery (laminate film type lithium ion secondary battery) manufactured by using the manufacturing method of the secondary battery of this invention.

Hereinafter, the present invention will be described in more detail.

As described above, as one method for increasing the battery capacity of the non-aqueous electrolyte secondary battery, it has been studied to use a negative electrode using a Kay material as a main material as a negative electrode of the non-aqueous electrolyte secondary battery.

A non-aqueous electrolyte secondary battery using this Kay material is desired to have cycle characteristics close to those of a non-aqueous electrolyte secondary battery using a carbon material, but a non-aqueous electrolyte secondary battery using a carbon material and No negative electrode material showing equivalent cycle stability has been proposed. In addition, since the initial efficiency of the silicon compound containing oxygen is lower than that of the carbon material, the improvement of the battery capacity is limited accordingly.

Therefore, the cycle maintenance rate and the initial efficiency of the battery have been improved by using the silicon oxide modified by inserting and partially removing Li as the negative electrode active material. However, when Li insertion is performed using only the thermal Li insertion reaction, the silicon crystallites in the silicon compound particles grow with the Li insertion, the cycle characteristics deteriorate, and the Li insertion reaction by the immersion method When Li is inserted using only Li, the Li-containing chemical species generated in the silicon compound particles by Li insertion increase the alkalinity at the time of preparing the negative electrode slurry, cut the molecular chain of the binder (binding agent), and the slurry There is a problem that it is difficult to make a slurry because it causes a low viscosity and reacts with a binder of a negative electrode slurry and a solvent molecule.

Therefore, the present inventors have made extensive studies on a method for producing a negative electrode active material, which can obtain a high battery capacity, good cycle characteristics and initial efficiency when used in a non-aqueous electrolyte secondary battery. It led to the invention.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is a flow chart showing an example of a method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention.

First, the overall flow of the implementation procedure will be described. In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, first, as shown in FIG. 1, silicon compound particles containing a silicon compound (SiO _x : 0.5 ≦ x ≦ 1.6) are prepared. (Step 1).

Next, as shown in FIG. 1, the silicon compound particles prepared in step 1 and the carbon material can be composited (step 2). However, this step is not essential.

Subsequently, as shown in FIG. 1, lithium alone or a lithium compound is mixed with the silicon compound particles prepared in step 1 or the silicon compound particles in which the carbon material is composited in step 2, and heated to contain the first lithium. Obtain silicon compound particles (step 3: heating Li insertion step).

Subsequently, as shown in FIG. 1, the first lithium-containing silicon compound particles obtained in step 3 are brought into contact with a solution A containing lithium and the solvent is an ether solvent to contain a second lithium. Obtain silicon compound particles (step 4: immersion Li insertion step).

Subsequently, as shown in FIG. 1, the second lithium-containing silicon compound particles obtained in step 4 contain at least one selected from an ether-based material, a ketone-based material, and an ester-based material as a solvent, and are a solute. It can be brought into contact with solution B containing a compound having a quinoid structure in the molecule (step 5). However, this step is not essential.

Since the negative electrode active material containing silicon compound particles containing lithium produced by the method for producing the negative electrode active material of the present invention is a silicon-based active material mainly composed of a silicon compound, the battery capacity can be increased. it can. Further, since this silicon compound is represented by the general formula SiO _x (however, 0.5 ≦ x ≦ 1.6) and the silicon compound particles contain lithium, the cycle characteristics can be improved. it can. Further, by including Li in the silicon compound particles, the irreversible capacity is reduced at the time of initial charging / discharging of the battery containing the silicon-based active material.

Further, in the method for producing a negative electrode active material of the present invention, Li is thermally inserted into the silicon compound particles and then a dipping Li insertion step is performed to perform thermal Li insertion and rhythmic Li insertion (room temperature). By dipping Li insertion) that can be performed in the vicinity, Li can be inserted into different sites of the silicon compound particles. Thereby, the initial efficiency of the non-aqueous electrolyte secondary battery using the negative electrode active material can be improved.

Further, by going through the two types of Li insertion steps in this way, it is possible to reduce the demerits while taking advantage of the advantages of each Li insertion step. For example, the negative electrode active material has less growth of silicon crystallites than the negative electrode active material obtained by performing only the heating Li insertion step as the Li insertion step. Further, the negative electrode active material has a Li compound (Li-containing chemical species) that is thermodynamically stable in the silicon compound particles as compared with the negative electrode active material obtained by performing only the immersion Li insertion step as the Li insertion step. It will include many. As a result, the problem when the negative electrode active material is mixed with a binder, a solvent, etc. to prepare a negative electrode slurry, that is, this Li compound increases the alkalinity of the slurry, cuts the molecular chain of the binder, and lowers the viscosity of the slurry. It is possible to prevent the problem that the Li compound reacts with these binders, solvent molecules, etc., and the slurry gels or overheats due to the reaction heat. Therefore, the negative electrode manufactured by using the negative electrode active material and the non-aqueous electrolyte secondary battery manufactured by using this negative electrode have good battery characteristics.

When the heating Li insertion step is performed after the immersion Li insertion step, the initial efficiency cannot be sufficiently improved. This is because when Li is inserted by the immersion Li insertion method, Li-containing chemical species that are deactivated by heat are generated in the silicon compound particles. Further, in this case, the capacity retention rate is also lowered. This is because by heating the silicon active material containing a larger amount of Li, disproportionation proceeds and Si crystallites grow.

Subsequently, the method for producing the negative electrode active material of the present invention will be described more specifically.

<1. Manufacturing method of negative electrode active material>
First, silicon compound particles containing a silicon compound (SiO _x : 0.5 ≦ x ≦ 1.6) are prepared (step 1 in FIG. 1). Such a silicon compound represented by the general formula SiO _x (however, 0.5 ≦ x ≦ 1.6) can be produced, for example, by the following method. First, a raw material that generates silicon oxide gas is heated in the presence of an inert gas or under reduced pressure in a temperature range of 900 ° C. to 1600 ° C. to generate silicon oxide gas. In this case, a mixture of metallic silicon powder and silicon dioxide powder can be used as the raw material, and considering the presence of surface oxygen of the metallic silicon powder and trace oxygen in the reaction furnace, the mixed molar ratio is 0.8 <metal. It is desirable that the range is silicon powder / silicon dioxide powder <1.3. The gas generated from the raw material is deposited on the adsorption plate. Subsequently, the deposits are taken out in a state where the temperature in the reactor is lowered to 100 ° C. or lower, and pulverized and pulverized using a ball mill, a jet mill or the like. The crystallinity of the silicon compound particles, such as the size of Si crystallinity, can be controlled by adjusting the charging range (mixed molar ratio) and the heating temperature of the raw material. Crystallinity can also be controlled by heat treatment after the formation of silicon compound particles.

In this step 1, it is preferable to prepare silicon compound particles having a silicon crystallite size of 3 nm or more and 10 nm or less. When the crystallite size is 10 nm or less, the expansion and contraction of the silicon compound particles due to charging and discharging becomes small, and the capacity retention rate increases. When the crystallite size is 3 nm or more, the improvement rate of the initial efficiency by Li insertion becomes sufficient. Therefore, by setting the crystallite size within this range, the capacity retention rate and the initial efficiency can be improved. The crystallite size can be calculated from the half-value width (half-value width) of the diffraction peak caused by the Si (111) crystal plane obtained by X-ray diffraction.

Moreover, it is preferable that x is close to 1 as the composition of the silicon compound to be produced. This is because high cycle characteristics can be obtained. Further, the composition of the silicon compound in the present invention does not necessarily mean 100% purity, and may contain a trace amount of impurity elements.

Further, a carbon material may be compounded with the silicon compound particles (step 2 in FIG. 1). Examples of the compounding method include a method of forming a carbon film on the surface of silicon compound particles by a thermal CVD (Chemical Vapor Deposition) method, and a method of physically mixing silicon compound particles and a carbon material. By combining a carbon material with silicon compound particles, it is possible to impart high conductivity. In particular, since the silicon compound particles have a carbon film, the decrease in conductivity due to Li insertion can be suppressed to some extent.

In particular, a thermal CVD method is desirable as a method for forming a carbon film on the surface of silicon compound particles. In the thermal CVD method, first, the silicon compound particles are set in the furnace. Subsequently, the furnace is filled with hydrocarbon gas to raise the temperature inside the furnace. By raising the temperature inside the furnace, the hydrocarbon gas is decomposed and a carbon film is formed on the surface of the silicon compound particles. The decomposition temperature of the hydrocarbon gas is not particularly limited, but is preferably 1200 ° C. or lower, and particularly preferably 1050 ° C. or lower. This is because it is possible to suppress unintended disproportionation of silicon compound particles.

When a carbon film is formed by the thermal CVD method, for example, by adjusting the pressure and temperature in the furnace, the carbon film can be formed on the surface layer of the powder material while adjusting the coverage and thickness of the carbon film. ..

The hydrocarbon gas used in the thermal CVD method is not particularly limited, but it is desirable that 3 ≧ n in the C _n H _m composition. This is because the manufacturing cost can be lowered and the physical properties of the decomposition products are good.

Subsequently, the silicon compound particles prepared in step 1 or the silicon compound particles in which the carbon material is composited in step 2 are mixed with lithium alone or a lithium compound and heated to obtain the first lithium-containing silicon compound particles (FIG. 1). Step 3: Heating Li insertion step).

In this way, by mixing the silicon compound particles with lithium alone or the lithium compound and heating the particles, Li can be inserted into the silicon compound particles and Li can be diffused to the inside. This is because heating gives sufficient energy for the Li atom to diffuse in the silicon compound particles. As a result, the Li compound is generated in the silicon compound particles, and the Li compound becomes a thermodynamically stable chemical species to some extent. That is, in the heating Li insertion step, Li is inserted and the active Li compound is stabilized by heating, so that it does not easily react with water used for producing an aqueous slurry. Therefore, the first lithium-containing silicon compound particles thus obtained can be safely handled in the subsequent steps.

In the heating Li insertion step, the heating temperature is preferably 400 ° C. or higher. The heating temperature at this time is more preferably 400 ° C. or higher and 800 ° C. or lower, and particularly preferably 600 ° C. or higher and 800 ° C. or lower. When the heating temperature is 800 ° C. or lower, it is possible to suppress the crystal growth of silicon in the silicon compound particles and prevent the cycle maintenance rate from deteriorating. When the heating temperature is 400 ° C. or higher, a thermally stable Li compound is produced, and the initial efficiency can be sufficiently improved even when applied to an aqueous slurry.

In the heating Li insertion step, lithium simple substance or a lithium compound is used as the Li source, but a mixture thereof can also be used. Specific examples of the Li source include lithium metal, lithium hydride, lithium nitride and the like. These Li sources are preferable because they have high activity and the lithium insertion reaction can proceed more easily. These can be used alone or in combination of two or more. In the present invention, any material containing at least a part of a lithium compound or the like can be used as a Li source.

The heating time in the heating Li insertion step is not particularly limited, but can be, for example, 1 minute or more and 10 hours or less.

The lithium content of the silicon compound particles after the heating Li insertion step is preferably 4% by mass or more and 20% by mass or less in terms of lithium with respect to the silicon compound. If the amount is 4% by mass or more, sufficient improvement in initial efficiency can be expected, and if it is 20% by mass or less, the heating temperature may be excessively increased or the heating time may be excessively lengthened in the heating Li insertion step. Therefore, it is possible to prevent the growth of silicon crystallites in the silicon compound particles from progressing, and it is possible to prevent deterioration of the cycle maintenance rate.

Subsequently, the first lithium-containing silicon compound particles obtained in step 3 are brought into contact with a solution A containing lithium and the solvent is an ether solvent to obtain second lithium-containing silicon compound particles (FIG. 6). Step 4: Immersion Li insertion step). By inserting Li by the immersion Li insertion method in this way, Li is inserted at a site different from the Li inserted by the heating Li insertion method, so that the initial efficiency can be further improved and the heating Li insertion method can be used. It is possible to alleviate the growth of silicon crystallites.

The solution A contains lithium and contains at least one selected from a linear polyphenylene compound and its derivative, and a polycyclic aromatic compound and its derivative, and the solvent is an ether solvent. Solution A ₁ or lithium and amines. It is preferable to use the solution A ₂ containing the above and the solvent is an ether solvent.

In this way, when the method of inserting lithium by contacting the solution A with the silicon compound particles is used, the disproportionation inside the silicon compound particles is increased as compared with the case of using, for example, the above-mentioned heating Li insertion method. It is suppressed and the cycle characteristics are further improved. Further, since lithium is dissolved in a solution by being complexed with a linear polyphenylene compound or the like or amines, more uniform Li insertion into silicon compound particles can be performed. Among them, it is particularly preferable to use a solution A ₁ comprising lithium and straight chain polyphenylene compounds. This insertion reaction of lithium with a solution A ₁ handled at around room temperature, yet because lithium is dissolved in a solution complexed with such linear polyphenylene compounds, in order to enable a more uniform Li insertion into silicon compound particles .. Further, by using an ether solvent as the solvent, the complex of lithium with a linear polyphenylene compound or the like or amines is more stable, so that lithium can be efficiently inserted into the silicon compound particles. Particularly solutions A ₁ Among comprises lithium, and include one or more selected from linear polyphenylene compounds and derivatives thereof, it is preferable to use a solution in which the solvent is an ether solvent.

In the selective modification by such a method, the temperature is not raised significantly in the process of inserting Li into the silicon compound particles, so that the formation of crystalline Li silicate can be suppressed. If the formation of crystalline Li silicate can be suppressed, the Li ion conductivity in the silicon compound particles will be improved, and further, crystallization in the silicon compound particles will be difficult to proceed, so that the cycle characteristics will be further improved.

As the ether solvent used for the solutions A, A ₁ and A ₂ , diethyl ether, tert-butyl methyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or A mixed solvent of these can be used. Of these, tetrahydrofuran, dioxane and 1,2-dimethoxyethane are particularly preferable. These solvents are preferably dehydrated and preferably deoxygenated.

As the linear polyphenylene compounds and derivatives thereof contained in the solution A _1, it can be used biphenyl, terphenyl, and one or more selected from these derivatives. As the polycyclic aromatic compound and a derivative thereof contained in the solution A _1, using naphthalene, anthracene, phenanthrene, naphthacene, pentacene, pyrene, picene, triphenylene, coronene, chrysene, and one or more selected from these derivatives be able to.

The total concentration of such linear polyphenylene compound in the solution _{A ^1,} preferably between 5 mol / L from 10 -3 mol / ^L, more preferably between 10 -1 mol / L of 3 mol / L. When the total concentration of the linear polyphenylene compound or the like is 10 ^-3 mol / L or more, the reaction between the lithium metal and the linear polyphenylene compound or the like can easily proceed, and the reaction time can be shortened. When the total concentration of the linear polyphenylene compound or the like is 5 mol / L or less, the reaction product of the linear polyphenylene compound or the like and the lithium metal is unlikely to adhere to the silicon compound particles, and the silicon compound powder can be easily separated. .. Further, when the negative electrode active material is a non-aqueous electrolyte secondary battery, the reaction residue does not flow out to the electrolytic solution, and deterioration of battery characteristics due to side reactions can be suppressed. Further, the lithium metal is preferably contained in an amount of 0.5 equivalent or more with respect to the linear polyphenylene compound or the like, and a part thereof may not be dissolved.

Further, as the amines contained in the solution A ₂ , dimethylamine, ethylamine, diethylamine, ethylenediamine, triethylenetriamine and the like can be used.

The time for contacting the silicon compound particles with the solution A, A ₁ or A ₂ is preferably 3 minutes or more, and more preferably 3 minutes or more and 100 hours or less. If the contact time is 3 minutes or more, a sufficient amount of lithium dope can be obtained. Further, when the contact time reaches 100 hours, the lithium insertion into the silicon compound particles reaches an almost equilibrium state. The reaction temperature is preferably −20 ° C. to 200 ° C., more preferably 0 ° C. to 50 ° C. Of these, the reaction temperature is particularly preferably around 20 ° C. In the temperature range as described above, the reaction rate is unlikely to decrease, and the precipitation of the lithium compound due to the side reaction is unlikely to occur, so that the reaction rate of the lithium insertion reaction into the silicon compound particles is improved.

In addition, the total content of the linear polyphenylene compound and the like measured by TPD-MS (Temperature Projection-Mass Spectroscopy) of the second lithium-containing silicon compound particles is 1 mass ppm or more and 4000 mass. It is preferably ppm or less. By setting the total content of the linear polyphenylene compound or the like within the above range, the surface stability of the second lithium-containing silicon compound particles is improved by the linear polyphenylene compound or the like. Therefore, when the negative electrode active material containing such silicon compound particles is used as the negative electrode active material of the lithium ion secondary battery, it has a high battery capacity, and good cycle characteristics and initial charge / discharge characteristics can be obtained. Here, in the measurement of TPD-MS, for example, 50 mg of a sample is placed in a silica cell, the temperature is raised from room temperature to 1000 ° C. at a rate of 10 ° C./min in a helium gas flow of 50 mL / min, and the sample is generated. This can be performed by analyzing the resulting gas with a mass spectrometer (manufactured by Shimadzu Corporation, GC / MS QP5050A).

Further, the second lithium-containing silicon compound particles are derived from the peak derived from the (011) plane of Li ₄ SiO ₄ and the (001) plane of Li ₂ SiO ₃ in the XRD (X-ray diffraction) spectrum of the particles. It is preferable that the peak has a peak. Li ₄ SiO ₄ has a large amount of Li with respect to Si, so that the initial efficiency is further improved, but it is easily dissolved in water. Therefore, in order to sufficiently suppress the negative electrode slurry Li ₄ SiO ₄ (particularly aqueous slurries) during the production is to elute from the second lithium-containing silicon compound particles, Li ₄ SiO ₄ to the second lithium-containing silicon compound particles in And Li ₂ SiO ₃ coexist. This improves the battery characteristics.

The lithium content of the second lithium-containing silicon compound particles is preferably 4% by mass or more and 30% by mass or less in terms of lithium with respect to the silicon compound. When the lithium content is 4% by mass or more, the initial efficiency is sufficiently improved. When the lithium content is 30% by mass or less, a non-aqueous electrolyte secondary battery having a high discharge capacity can be manufactured.

Further, the second lithium-containing silicon compound particles obtained in step 4 contain at least one selected from an ether-based material, a ketone-based material, and an ester-based material as a solvent, and have a quinoid structure in the molecule as a solute. It may be brought into contact with solution B containing the compound (step 5 in FIG. 1).

The compound having a quinoid structure in the molecule, which is the solute of the solution B, extracts Li from the silicon compound particles containing active Li in the above solvent to form a salt of Li and a quinone analog, which is a solvent. Since it dissolves in, Li can be extracted until it reaches an equilibrium state.

Further, in a solvent such as an ether-based material, a ketone-based material, and an ester-based material, the activity of protons contained in the solvent molecule is low, and especially in an ether-based solvent, the activity is particularly low, so that silicon in which lithium is inserted. Side reactions in the elimination reaction of Li from the compound particles are unlikely to occur.

In this way, in step 5, the active Li is almost completely inactivated by bringing the solution B into contact with the silicon compound particles. This facilitates the application of the silicon-based active material containing Li to the aqueous slurry.

As the ether-based material used as the solvent of the solution B, diethyl ether, tert-butyl methyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether, or a mixture thereof. A solvent or the like can be used.

As the ketone material used as the solvent of the solution B, acetone and acetophenone, a mixed solvent thereof and the like can be used.

As the ester-based material used as the solvent of the solution B, methyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, a mixed solvent thereof and the like can be used.

Further, a mixed solvent or the like in which two or more of the above ether-based materials, ketone-based materials, and ester-based materials are combined may be used.

Further, as the compound having a quinoid structure in the molecule used as the solute of the solution B, benzoquinone, quinodimethane, quinodiimine, or a derivative thereof can be used. The quinoid structure, also called a quinone structure or simply a quinoid, is a structure in which the inner ring double bond of an ordinary aromatic compound is reduced by one and instead has two outer ring double bonds at the para or ortho position. .. The quinoid structure in the molecule used as the solute of the solution B may be either p-quinoid or o-quinoid. The "compound having a quinoid structure in the molecule" is, for example, a compound having a structure represented by the following formula (1) or formula (2) in the molecule.

R ¹ , R ² , R ³ and R ⁴ of the above formula (1) may independently represent a hydrogen atom or a substituent, or R ¹ and R ² or R ^{3 respectively.} And R ⁴ bond with each other to form a ring, particularly an aromatic ring, which may have a substituent with the carbon atom to which each of R ¹ , R ² , R ³ and R ⁴ is bonded. You may be. Examples of this aromatic ring include a benzene ring and a naphthalene ring. For example, X ¹ and X ² may represent an oxygen atom, and the atom contains a nitrogen atom, and the nitrogen atom forms a double bond with the carbon constituting the carbon ring represented by the above formula (1). It may represent a group, or may represent an atomic group containing a carbon atom and the carbon atom forms a double bond with the carbon constituting the carbon ring represented by the above formula (1).

R ⁵ , R ⁶ , R ⁷ and R ⁸ of the above formula (2) may independently represent a hydrogen atom or a substituent, and R ⁵ and R ⁶ and R ⁶ and R ⁷ Alternatively, a ring in which R ⁷ and R ⁸ may be bonded to each other and have a substituent together with a carbon atom to which each of R ⁵ , R ⁶ , R ⁷ and R ⁸ is bonded, in particular. It may form an aromatic ring. Examples of this aromatic ring include a benzene ring and a naphthalene ring. Similar to the above formula (1), X ³ and X ⁴ may represent, for example, an oxygen atom, and include a nitrogen atom, and the nitrogen atom is a carbon constituting the carbon ring represented by the above formula (2). It may represent an atomic group forming a double bond, or an atom containing a carbon atom and the carbon atom forms a double bond with the carbon constituting the carbon ring represented by the above formula (2). It may represent a group.

Preferable compounds having a quinoid structure in the molecule that can be used in the present invention, more specifically, p-benzoquinone, o-benzoquinone, naphthoquinone, anthraquinone, tetracyanoquinodimethane, N, N'. -Dicyanoquinodiimine and derivatives thereof.

The concentration of the solute in the solution B used in the reaction (compound having a quinoid structure in the molecule) ^is good battery characteristics can be obtained if 10 -3 mol / L or more 1 × ¹⁰ 0 mol / L or less.

Further, the obtained first or second lithium-containing silicon compound particles may be washed with water or the like to remove excess Li.

As described above, the negative electrode active material can be produced by the method for producing the negative electrode active material of the present invention. The negative electrode active material produced in this manner can constitute a negative electrode as described below.

<2. Manufacturing method of negative electrode for non-aqueous electrolyte secondary battery>
Next, a method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery of the present invention will be described. In the method for producing a negative electrode for a non-aqueous electrolyte secondary battery of the present invention, the negative electrode active material for a non-aqueous electrolyte secondary battery is produced by the above method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, and the non-water electrolyte secondary battery is produced. This is a method of manufacturing a negative electrode for a non-aqueous electrolyte secondary battery using a negative electrode active material for an electrolyte secondary battery. First, the configuration of the negative electrode thus obtained will be described.

[Construction of negative electrode]
As shown in FIG. 2, the negative electrode 10 has a negative electrode active material layer 12 on the negative electrode current collector 11. The negative electrode active material layer 12 may be provided on both sides or only one side of the negative electrode current collector 11.

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

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

The surface of the negative electrode current collector 11 may or may not be roughened. The negative electrode current collector whose surface is roughened is, for example, an electrolytic treatment, an embossing treatment, or a chemically etched metal foil. The negative electrode current collector whose surface is not roughened is, for example, a rolled metal foil.

[Negative electrode active material layer]
The silicon-based active material produced by the method for producing a negative electrode active material of the present invention serves as a material constituting the negative electrode active material layer 12. The negative electrode active material layer 12 contains a silicon-based active material, and may further contain other materials such as a negative electrode binder and a negative electrode conductive auxiliary agent in terms of battery design. As the negative electrode active material, a carbon-based active material or the like may be contained in addition to the silicon-based active material.

Such a negative electrode can be produced by a coating method using a silicon-based active material produced by the above-mentioned method for producing a negative electrode active material of the present invention. The coating method is a method in which silicon-based active material particles are mixed with the following binders, and if necessary, the following conductive aids and carbon-based active materials are mixed, and then dispersed in an organic solvent or water for coating. ..

In this case, first, the silicon-based active material produced by the method for producing the negative electrode active material of the present invention is mixed with a solvent such as a conductive auxiliary agent, a binder, and water to obtain an aqueous slurry. At this time, if necessary, a carbon-based active material may also be mixed. Next, the aqueous slurry is applied to the surface of the negative electrode current collector 11 and dried to form the negative electrode active material layer 12 of FIG.

As the conductive auxiliary agent, for example, any one or more of carbon black, acetylene black, graphite such as scaly graphite, kechen black, carbon nanotubes, carbon nanofibers and the like can be used. These conductive auxiliaries are preferably in the form of particles having a median diameter smaller than that of silicon compound particles containing lithium. In that case, for example, acetylene black can be selected as the conductive auxiliary agent.

Further, as the binder, for example, carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid and the like can be used.

Further, as the carbon-based active material, for example, pyrolytic carbons, cokes, glassy carbon fibers, calcined organic polymer compounds, carbon blacks and the like can be used. As a result, it is possible to reduce the electrical resistance of the negative electrode active material layer 12 and relax the expansion stress associated with charging.

Further, in the present invention, there is a step of preparing silicon compound particles containing a silicon compound (SiO _x : 0.5 ≦ x ≦ 1.6), and the silicon compound particles are mixed with lithium alone or a lithium compound and heated. After the step of obtaining the first lithium-containing silicon compound particles, the step of forming the electrode containing the first lithium-containing silicon compound particles is performed, and the first lithium-containing silicon compound particles contained in the electrode are obtained from lithium. The negative electrode may be produced by performing a step of obtaining an electrode containing the second lithium-containing silicon compound particles by contacting the solution A which contains the above and the solvent is an ether solvent. In the method for producing a negative electrode for a non-aqueous electrolyte secondary battery of the present invention, similarly to the above-mentioned method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, after the step of preparing silicon compound particles and after the first step. A step of forming a carbon film may be provided before the step of obtaining one lithium-containing silicon compound particle. Further, after the step of obtaining the electrode containing the second lithium-containing silicon compound particles, there may be a step of contacting the solution B. In order to bring the solutions A and B into contact with the silicon compound particles in the electrode, for example, the electrode is immersed (impregnated) in the solutions A and B, or the solutions A and B are sprinkled on the electrode. The solutions A and B may be brought into contact with the silicon compound particles contained in the above. The details of other manufacturing conditions and the like in the method for manufacturing the negative electrode are the same as the above-described method for manufacturing the negative electrode active material of the present invention.

<3. Manufacturing method of non-aqueous electrolyte secondary battery>
Next, a method for manufacturing the non-aqueous electrolyte secondary battery of the present invention will be described. In the method for manufacturing a non-aqueous electrolyte secondary battery of the present invention, a negative electrode for a non-aqueous electrolyte secondary battery is manufactured by the above method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery of the present invention, and the negative electrode for the non-aqueous electrolyte secondary battery is manufactured. It is a method of manufacturing a non-aqueous electrolyte secondary battery using. Hereinafter, the method for producing a non-aqueous electrolyte secondary battery of the present invention will be more concretely described by taking as an example the case of producing a laminated film type lithium ion secondary battery (hereinafter, also referred to as a laminated film type secondary battery). To explain.

[Structure of laminated film type secondary battery]
The laminated film type secondary battery 30 shown in FIG. 3 is mainly a sheet-shaped exterior member 35 in which a wound electrode body 31 is housed. The wound electrode body 31 has a separator between the positive electrode and the negative electrode, and is wound. Further, there is also a case where a separator is provided between the positive electrode and the negative electrode and the laminated body is housed. In both electrode bodies, the positive electrode lead 32 is attached to the positive electrode, and the negative electrode lead 33 is attached to the negative electrode. The outermost peripheral portion of the electrode body is protected by a protective tape.

The positive and negative electrode leads are led out in one direction from the inside of the exterior member 35 toward the outside, for example. 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.

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

An adhesive film 34 is inserted between the exterior member 35 and the positive and negative electrode leads to prevent outside air from entering. This material is, for example, polyethylene, polypropylene, polyolefin resin.

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

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

The positive electrode active material layer contains any one or more of the positive electrode materials capable of occluding and releasing lithium ions, and contains other materials such as a binder, a conductive auxiliary agent, and a dispersant depending on the design. You can go out. In this case, the details regarding the binder and the conductive auxiliary agent are the same as those of the negative electrode binder and the negative electrode conductive auxiliary agent described above.

A lithium-containing compound is desirable as the positive electrode material. Examples of the lithium-containing compound include a composite oxide composed of lithium and a transition metal element, and a phosphoric acid compound having lithium and a transition metal element. Among these positive electrode materials, a compound having at least one of nickel, iron, manganese, and cobalt is preferable. These chemical formulas are represented by, for example, Li _x M ₁ O ₂ or Li _y M ₂ PO ₄ . In the formula, M ₁ and M ₂ represent at least one transition metal element. The values of x and y show different values depending on the battery charge / discharge state, but are generally shown by 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Examples of the composite oxide having lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel composite oxide (Li _x NiO ₂ ), and phosphoric acid having lithium and a transition metal element. Examples of the compound include a lithium iron phosphate compound (LiFePO ₄ ) and a lithium iron manganese phosphate compound (LiFe _1-u Mn _u PO ₄ (0 <u <1)). This is because when these positive electrode materials are used, a high battery capacity can be obtained and also excellent cycle characteristics can be obtained.

[Negative electrode]
The negative electrode has the same configuration as the negative electrode 10 of FIG. 2 described above, and has, for example, negative electrode active material layers 12 on both sides of the negative electrode current collector 11. It is preferable that the negative electrode has a larger negative electrode charge capacity than the electric capacity (charge capacity as a battery) obtained from the positive electrode active material. This is because the precipitation of lithium metal on the negative electrode can be suppressed.

The positive electrode active material layer is provided on a part of both sides of the positive electrode current collector, and the negative electrode active material layer is also provided on a part of both sides of the negative electrode current collector. In this case, for example, the negative electrode active material layer provided on the negative electrode current collector is provided with a region in which the opposite positive electrode active material layer does not exist. This is for stable battery design.

In the non-opposing region, that is, the region where the negative electrode active material layer and the positive electrode active material layer do not face each other, the influence of charging and discharging is hardly affected. Therefore, the state of the negative electrode active material layer is maintained as it is immediately after formation. As a result, the composition of the negative electrode active material can be accurately investigated with good reproducibility regardless of the presence or absence of charge / discharge.

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

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

As the solvent, for example, a non-aqueous solvent can be used. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methylpropyl 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 characteristics can be obtained. Further, in this case, more superior characteristics 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 dissociability and ion mobility of the electrolyte salt are improved.

It is preferable to contain unsaturated carbon-bonded cyclic carbonate as a solvent additive. This is because a stable film is formed on the surface of the negative electrode during charging and discharging, and the decomposition reaction of the electrolytic solution can be suppressed. Examples of the unsaturated carbon-bonded cyclic carbonate include vinylene carbonate and vinyl acetate.

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

Further, the solvent preferably contains an acid anhydride. This is because the chemical stability of the electrolytic solution is improved. Examples of the acid anhydride include propanedisulfonic anhydride.

The electrolyte salt can include, for example, any one or more of light metal salts such as lithium salts. Examples of the lithium salt include the following materials. Examples thereof include lithium hexafluorophosphate (LiPF ₆ ) and lithium tetrafluoroboate (LiBF ₄ ).

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

[Manufacturing method of laminated film type secondary battery]
First, a positive electrode is prepared using the above-mentioned positive electrode material. First, the positive electrode active material is mixed with a binder, a conductive auxiliary agent, etc., if necessary, to form a positive electrode mixture, and then dispersed in an organic solvent to prepare a positive electrode mixture slurry. Subsequently, the mixture slurry is applied to the positive electrode current collector with a coating device such as a knife roll or a die coater having a die head, and dried with hot air to obtain a positive electrode active material layer. Finally, the positive electrode active material layer is compression-molded with a roll press or the like. At this time, heating may be performed. Further, compression and heating may be repeated a plurality of times.

Next, using the same work procedure as the production of the negative electrode 10 described above, a negative electrode active material layer is formed on the negative electrode current collector to produce a negative electrode (see FIG. 2).

The positive electrode and the negative electrode are manufactured by the same manufacturing procedure as described above. In this case, the active material layers can be formed on both sides of the positive electrode and the negative electrode current collectors. At this time, as shown in FIG. 2, the active material coating lengths on both sides of both electrodes may be deviated.

Subsequently, the electrolytic solution is prepared. Subsequently, the positive electrode lead 32 of FIG. 3 is attached to the positive electrode current collector by ultrasonic welding or the like, and the negative electrode lead 33 is attached to the negative electrode current collector. Subsequently, the positive electrode and the negative electrode are laminated or wound via a separator to prepare a wound electrode body, and a protective tape is adhered to the outermost peripheral portion thereof. Next, the wound body is molded so as to have a flat shape. Subsequently, after sandwiching the wound electrode body between the folded film-shaped exterior members 35, the insulating portions of the exterior members are adhered to each other by a heat fusion method, and the wound electrode body is opened in only one direction. Is enclosed. The adhesion film 34 is inserted between the positive electrode lead 32 and the negative electrode lead 33 and the exterior member 35. A predetermined amount of the electrolytic solution prepared above is charged from the open portion, and vacuum impregnation is performed. After impregnation, the open portion is bonded by a vacuum heat fusion method.

As described above, the laminated film type secondary battery 30 can be manufactured.

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

(Example 1-1)
First, a silicon-based active material was prepared as follows.

First, a raw material (vaporization starting material) in which metallic silicon and silicon dioxide are mixed is installed in a reaction furnace, and the material vaporized in an atmosphere of 10 Pa of vacuum is deposited on an adsorption plate, cooled sufficiently, and then deposited. The material (SiO _x : x = 0.5) was taken out and crushed with a jet mill. Then, the surface of the silicon compound particles was coated with a carbon film by performing thermal CVD using methane gas.

As shown in Table 1 below, it is calculated from the half-value width (half-value width) of the diffraction peak caused by the Si (111) crystal plane obtained by X-ray diffraction in the above-mentioned silicon compound particles after the carbon coating. The crystal face size of silicon was 3.77 nm. The amount of carbon coated was 5% by mass with respect to the silicon compound particles.

Subsequently, 4.5% by mass of metal Li powder (average particle size of less than 200 μm) was mixed with the silicon compound particles after coating the carbon film in an inert atmosphere with respect to the silicon compound, and the obtained mixture was placed in a pot. And fired at 400 ° C. to obtain the first lithium-containing silicon compound particles.

Subsequently, the obtained first lithium-containing silicon compound particles, the lithium piece and biphenyl tetrahydrofuran (hereinafter, THF also referred) was immersed in a solution obtained by dissolving (solution A _1). Solution A _{1 of} Example 1-1 is prepared by dissolving biphenyl in a THF solvent at a concentration of 1 mol / L, and then adding 10% by mass of lithium pieces to this mixed solution of THF and biphenyl. Made. The temperature of the solution when immersing the first lithium-containing silicon compound particles was 20 ° C., and the immersion time was 10 hours. Then, the silicon compound particles were collected by filtration. Through the above treatment, lithium was inserted into the first lithium-containing silicon compound particles to obtain second lithium-containing silicon compound particles.

Subsequently, the obtained second lithium-containing silicon compound particles were immersed in a solution (solution B) in which p-benzoquinone was dissolved in THF at a concentration of 1 mol / L. The immersion time was 2 hours. Then, the silicon compound particles were collected by filtration.

Next, the silicon compound particles after being immersed in the solution B were washed, and the washed silicon compound particles were dried under reduced pressure. As described above, the silicon-based active material was produced.

Subsequently, a test cell composed of the electrode containing the silicon-based active material produced as described above and the counter electrode lithium was prepared, and the initial charge / discharge characteristics in the initial charge / discharge were investigated. In this case, a 2032 type coin battery was assembled as a test cell.

Electrodes containing silicon-based active material particles were prepared as follows. First, graphite, prepared silicon-based active material particles, conductive auxiliary agent 1 (carbon nanotube, CNT), conductive auxiliary agent 2 (carbon fine particles having a median diameter of about 50 nm), conductive auxiliary agent 3 (scaly graphite), styrene butadiene. Rubber (styrene-butadiene copolymer, hereinafter referred to as SBR) and carboxymethyl cellulose (hereinafter, referred to as CMC) are mixed at a dry mass ratio of 82: 9: 1.5: 1: 1: 2.5: 3, and then pure. It was diluted with water to prepare a negative electrode mixture slurry. That is, the mass ratio of the graphite mixed as the active material and the silicon-based active material is about 9: 1. The above SBR and CMC are negative electrode binders (negative electrode binders). Subsequently, the mixture slurry was applied to both sides of the current collector with a coating device and then dried. As this current collector, an electrolytic copper foil (thickness = 20 μm) was used. Finally, it was fired at 90 ° C. for 1 hour in a vacuum atmosphere. As a result, a negative electrode active material layer was formed.

The electrolytic solution of the test cell was prepared as follows. After mixing the solvent (4-fluoro-1,3-dioxolan-2-one (FEC), ethylene carbonate (EC) and dimethyl carbonate (DMC)), an electrolyte salt (lithium hexafluorophosphate: LiPF ₆ ) is added. It was dissolved to prepare an electrolytic solution. In this case, the composition of the solvent was FEC: EC: DMC = 10: 20: 70 in terms of volume ratio, and the content of the electrolyte salt was 1.0 mol / kg with respect to the solvent.

As the counter electrode, a metal lithium foil having a thickness of 0.5 mm was used. Further, as a separator, polyethylene having a thickness of 20 μm was used.

Subsequently, the bottom cover, lithium foil, and separator of the 2032 type coin battery are overlaid and 150 mL of the electrolytic solution is injected, and then the negative electrode and the spacer (thickness 1.0 mm) are overlapped and 150 mL of the electrolytic solution is injected. Then, the spring and the upper pig of the coin battery were pumped up in this order and crimped with an automatic coin cell caulking machine to produce a 2032 type coin battery.

Subsequently, the produced 2032 type coin battery is charged at a constant current density of 0.2 mA / cm ² until it reaches 0.0 V, and when the voltage reaches 0.0 V, the current density reaches 0.0 V constant voltage. was charged to reach 0.02 mA / cm ^2, when the discharge was discharged until the voltage reached 1.2V at a constant current density of 0.2 mA / cm ^2. Then, the initial charge / discharge characteristics in this initial charge / discharge were investigated. For the initial charge / discharge characteristics, the initial efficiency (initial efficiency) (%) = (initial discharge capacity / initial charge capacity) × 100 was calculated.

Subsequently, in order to evaluate the cycle characteristics of the non-aqueous electrolyte secondary battery using the negative electrode active material produced by the method for producing the negative electrode active material of the present invention, the laminated film type secondary battery as shown in FIG. 3 is subsequently evaluated. 30 was prepared as follows.

First, a positive electrode used for a laminated film type secondary battery was prepared. The positive electrode active material is 95 parts by mass of LiCoO _2, which is a lithium cobalt composite oxide, 2.5 parts by mass of a positive electrode conductive auxiliary agent (acetylene black), and 2.5 parts by mass of a positive electrode binder (polyvinylidene fluoride: Pvdf). Was mixed to obtain a positive electrode mixture. Subsequently, the positive electrode mixture was dispersed in an organic solvent (N-methyl-2-pyrrolidone: NMP) to prepare a paste-like slurry. Subsequently, the slurry was applied to both sides of the positive electrode current collector with a coating device having a die head, and dried with a hot air drying device. At this time, a positive electrode current collector having a thickness of 15 μm was used. Finally, compression molding was performed with a roll press.

As the negative electrode, one prepared by the same procedure as the electrode containing the silicon-based active material of the above test cell was used.

As the electrolytic solution, one prepared by the same procedure as the electrolytic solution in the above test cell was used.

Next, a laminated film type lithium ion secondary battery was assembled as follows. First, an aluminum lead was ultrasonically welded to one end of the positive electrode current collector, and a nickel lead was welded to the negative electrode current collector. Subsequently, the positive electrode, the separator, the negative electrode, and the separator were laminated in this order and wound in the longitudinal direction to obtain a wound electrode body. The winding end portion was fixed with PET protective tape. As the separator, a laminated film of 12 μm sandwiched between a film containing porous polypropylene as a main component and a film containing porous polyethylene as a main component was used. Subsequently, after sandwiching the electrode body between the exterior members, the outer peripheral edges excluding one side were heat-sealed to each other, and the electrode body was housed inside. As the exterior member, a nylon film, an aluminum foil, and an aluminum laminated film in which a polypropylene film was laminated were used. Subsequently, the electrolytic solution prepared from the opening was injected, impregnated in a vacuum atmosphere, and then heat-sealed and sealed.

The cycle characteristics (maintenance rate%) of the laminated film type lithium ion secondary battery produced in this manner were investigated.

The cycle characteristics were investigated as follows. First, in order to stabilize the battery, charging and discharging were performed for two cycles in an atmosphere of 25 ° C., and the discharge capacity of the second cycle was measured. Subsequently, charging and discharging were performed until the total number of cycles reached 100 cycles, and the discharge capacity was measured each time. Finally, the discharge capacity in the 100th cycle was divided by the discharge capacity in the second cycle (× 100 for% display) to calculate the capacity retention rate. As cycling conditions, a constant current density until reaching 4.3V, and charged at 2.5 mA / cm ^2, current density reached 0.25 mA / cm ² at 4.3V constant voltage at the stage of reaching the voltage 4.3V Charged up to. At the time of discharge, the battery was discharged at a constant current density of ^2.5 mA / cm ² until the voltage reached 3.0 V.

(Examples 1-2 to 1-5, Comparative Examples 1-1 and 1-2)
A negative electrode active material (silicon-based active material) was produced in the same manner as in Example 1-1 except that _x of SiO _x was changed. Then, the battery characteristics were evaluated in the same manner as in Example 1-1.

The initial charge / discharge characteristics of the test cells (coin batteries) produced in Examples 1-1 to 1-5 and Comparative Examples 1-1 and 1-2 and the capacity retention rate of the laminated film type secondary battery were examined. The result shown in 1 was obtained. The initial discharge capacity was 1360 mAh / g in Examples 1-3.

As can be seen from Table 1, in the silicon compound represented by SiOx, when the value of x was out of the range of 0.5 ≦ x ≦ 1.6, the battery characteristics deteriorated. For example, as shown in Comparative Example 1-1, when there is not enough oxygen (x = 0.3), the capacity retention rate of the secondary battery is significantly deteriorated. On the other hand, as shown in Comparative Example 1-2, when the amount of oxygen was large (x = 1.8), the conductivity of the silicon compound was lowered and the capacity retention rate of the secondary battery was lowered.

(Example 2-1 and Comparative Examples 2-1 to 2-5)
A negative electrode active material was prepared in the same manner as in Examples 1-3 except that the Li insertion method and the presence or absence of the carbon film of the silicon compound particles were changed. Then, the battery characteristics were evaluated in the same manner as in Examples 1-3. In Comparative Example 2-1 Li was not inserted.

When the initial charge / discharge characteristics of the test cells of Example 2-1 and Comparative Examples 2-1 to 2-5 and the capacity retention rate of the laminated film type secondary battery were examined, the results shown in Table 2 were obtained. The results of Examples 1-3 above are also shown in Tables 2 to 8 below.

As can be seen from Table 2, as the Li insertion method, the contact method (the contact method is a method of contacting a Li metal and a Si compound), the heated Li insertion method, and the immersion Li insertion method are used, respectively. When used alone, the improvement in initial efficiency (initial efficiency) was insufficient. This is because the amount of sites in the silicon compound particles that can be modified by these methods is fixed, and there is a limit to the improvement in initial efficiency. Further, when the immersion Li insertion method is performed first and then the heating Li insertion method is performed (Comparative Example 2-5), the initial efficiency is improved, but the capacity retention rate is lowered. This is because heating a silicon active material containing a larger amount of Li promotes disproportionation, causes Si crystallites to grow, and lowers the capacity retention rate. In addition, Comparative Example 2-5 had a poorer initial efficiency result than Example 1-3. It is considered that this is because the Li-containing chemical species produced by the immersion Li insertion method is sensitive to heat and is destroyed during heat doping. In addition, when the carbon film was included, both the capacity retention rate and the initial efficiency were better. This is because the carbon film suppresses the increase in powder resistivity due to Li insertion.

(Examples 3-1 to 3-8)
A negative electrode active material was prepared in the same manner as in Examples 1-3, except that the crystallinity of the silicon compound particles prepared before the Li insertion step was changed. Then, the battery characteristics were evaluated in the same manner as in Examples 1-3.

When the initial charge / discharge characteristics of the test cells (coin batteries) produced in Examples 3-1 to 3-8 and the capacity retention rate of the laminated film type secondary battery were examined, the results shown in Table 3 were obtained.

As can be seen from Table 3, when the crystallinity of the silicon compound particles was changed, good battery characteristics were obtained in the range of Si (111) crystallite size of 3 nm or more and 10 nm or less. When the crystallite size is 10 nm or less, the expansion and contraction of the silicon compound particles due to charging and discharging becomes small, and the capacity retention rate increases. When the crystallite size is 3 nm or more, the improvement rate of the initial efficiency by Li insertion becomes sufficient. Therefore, by setting the crystallite size within this range, the capacity retention rate and the initial efficiency can be improved. In Example 3-8, the peak of the Si (111) plane was broad, and the minute region of silicon was substantially amorphous.

(Examples 4-1 to 4-5)
A negative electrode active material was prepared in the same manner as in Examples 1-3 except that the amount of Li inserted into the silicon compound particles was changed. Then, the battery characteristics were evaluated in the same manner as in Examples 1-3.

When the initial charge / discharge characteristics of the test cells (coin batteries) produced in Examples 4-1 to 4-5 and the capacity retention rate of the laminated film type secondary battery were examined, the results shown in Table 4 were obtained.

As can be seen from Table 4, when the lithium content is 4% by mass or more, the initial efficiency is sufficiently improved. Further, when the lithium content is 30% by mass or less, a non-aqueous electrolyte secondary battery having a high initial discharge capacity of 1000 mAh / g or more can be manufactured. Therefore, in order to balance the initial efficiency and the initial discharge capacity, it is preferable to adjust the lithium content between them.

(Examples 5-1 to 5-9)
A negative electrode active material was produced in the same manner as in Examples 1-3 except that the type of Li source, the compounding mass ratio of the Li source, and the heating temperature were changed in the heating Li insertion step. Then, the battery characteristics were evaluated in the same manner as in Examples 1-3.

When the initial charge / discharge characteristics of the test cells (coin batteries) produced in Examples 5-1 to 5-9 and the capacity retention rate of the laminated film type secondary battery were examined, the results shown in Table 5 were obtained.

As can be seen from Table 5, as the Li source, Li metal, preferable to use the LiH or Li ₃ N good battery characteristics. Since these Li sources have high activity and Li insertion occurs smoothly to the inside, they react uniformly to the inside of the silicon compound particles, and the growth of silicon crystallites can be suppressed. Therefore, both high initial efficiency and capacity retention rate can be achieved. The heating temperature is preferably 400 ° C. or higher and 800 ° C. or lower, and particularly preferably 600 ° C. or higher and 800 ° C. or lower. When the heating temperature is 800 ° C. or lower, it is possible to suppress the crystal growth of silicon in the silicon compound particles and prevent the cycle maintenance rate from deteriorating. When the heating temperature is 400 ° C. or higher, the lithium insertion process is sufficiently completed, and the initial efficiency can be sufficiently improved. Further, as the XRD peak of Li silicate, it is preferable that both the peak derived from the (011) plane of Li ₄ SiO ₄ and the peak derived from the (001) plane of Li ₂ SiO ₃ are detected. Li ₄ SiO ₄ has a large amount of Li with respect to Si, so that the initial efficiency is further improved, but it is easily dissolved in water. Therefore, in order to sufficiently suppress the negative electrode slurry Li ₄ SiO ₄ (particularly aqueous slurries) during the production is to elute from the second lithium-containing silicon compound particles, Li ₄ SiO ₄ to the second lithium-containing silicon compound particles in And Li ₂ SiO ₃ coexist. This improves the battery characteristics.

(Examples 6-1 to 6-17)
Examples 1-3 and Example 1-3, except that the aromatic compound species, the solvent species, the concentration of the aromatic compound, the immersion time in the solution A, and the temperature of the solution A of the solution A containing Li were changed as shown in Table 6. Similarly, a negative electrode active material was prepared. Then, the battery characteristics were evaluated in the same manner as in Examples 1-3.

(Comparative Example 6-1)
In Comparative Example 6-1, an ether solvent was not used as the solution A. Other than that, a negative electrode active material was prepared in the same manner as in Examples 1-3. Then, the battery characteristics were evaluated in the same manner as in Examples 1-3.

Table 6 shows the initial charge / discharge characteristics of the test cells (coin batteries) produced in Examples 6-1 to 6-17 and Comparative Example 6-1 and the capacity retention rate of the laminated film type secondary battery. Results were obtained.

In the immersion Li insertion step, the first lithium-containing silicon compound particles are brought into contact with the solution A containing lithium and the solvent is an ether solvent to obtain the second lithium-containing silicon compound particles. In this step, as the solution A containing lithium, it is preferable to use the solution A ₁ containing lithium and a linear polyphenylene compound or the like, or the solution A ₂ containing lithium and amines, of which the solution A ₁ is used. Is particularly preferred. This is because the solution A ₁ can be handled near room temperature. Further, in particular, when comparing Examples 1-3, 6-1 and 6-2, the battery characteristics were further improved in the case of Example 1-3 in which biphenyl was used as the polyphenylene compound. This is because the complex formed by the reaction of lithium and biphenyl is highly active and stable, so that the insertion of lithium into the silicon compound particles continues at a faster rate.

In addition, the battery characteristics were improved when the ether solvent was used as compared with Comparative Example 6-1 which did not use the ether solvent. This is because the complex of lithium and the linear polyphenylene compound or the like can stably exist in the ether solvent, so that lithium insertion into the silicon compound particles can be easily sustained. Furthermore, the battery characteristics are better when THF is used (Examples 1-3) than when diethyl ether or tert-butyl methyl ether is used as the ether solvent (Examples 6-3 and 6-4). Has improved. This is because in THF, which has a relatively high dielectric constant among ether solvents, a complex of lithium and a linear polyphenylene compound or the like exists particularly stably, so that lithium insertion into silicon compound particles is likely to be sustained. is there.

The total concentration of the linear polyphenylene compound and the like in the solution A is preferably between ^10-3 mol / L and 5 mol / L. Compared with the case where the total concentration of the linear polyphenylene compound or the like as in Example 6-5 is less than 10 ^-3 mol / L, the total concentration of the linear polyphenylene compound or the like is 10 ^-3 mol / L or more and 5 mol / L or less. In the case of (for example, Examples 1-3, 6-6, 6-7), the maintenance rate and the initial efficiency are improved. This is because the insertion of lithium into the silicon compound particles proceeded more efficiently. Further, as compared with the case where the total concentration of the linear polyphenylene compound or the like exceeds 5 mol / L as in Example 6-8, the total concentration of the linear polyphenylene compound or the like is 10 ^-3 mol / L or more and 5 mol / L or less. In some cases, maintenance rate and initial efficiency are improved. This is because when the negative electrode active material is a non-aqueous electrolyte secondary battery, the reaction residue does not flow out to the electrolytic solution, and deterioration of battery characteristics due to side reactions can be suppressed. In Examples 6-8, a part of biphenyl remained undissolved.

Further, the temperature of the solution A is preferably close to 20 ° C. When the temperature of the solution A is around 20 ° C., the reaction rate is unlikely to decrease, and the precipitation of the lithium compound due to the side reaction is unlikely to occur, so that the reaction rate of the lithium insertion reaction from the silicon compound particles is improved. Is. Therefore, as compared with the cases where the temperature of the solution A is higher or lower than 20 ° C. as in Examples 6-9 and 6-10, the example (for example, Example 1-3) having a solution temperature of 20 ° C. However, the battery characteristics became better.

Further, it is desirable that the contact time between the silicon compound powder and the solution A is 3 minutes or more and 100 hours or less. If the contact time is 3 minutes or more (for example, Example 6-15), lithium insertion into the silicon compound particles occurs more sufficiently than when it is less than 3 minutes (Example 6-14). Further, when the contact time reaches 100 hours, the lithium insertion into the silicon compound particles reaches an almost equilibrium state.

(Examples 7-1 to 7-9)
A negative electrode active material was prepared in the same manner as in Example 1-3, except that the solvent type, solute type, and solute concentration of the solution B were changed as shown in Table 7. Then, the battery characteristics were evaluated in the same manner as in Examples 1-3.

When the initial charge / discharge characteristics of the test cells (coin batteries) of Examples 7-1 to 7-9 and the capacity retention rate of the laminated film type secondary battery were examined, the results shown in Table 7 were obtained.

As can be seen from Table 7, as solution B, compounds having a quinoid structure in the molecule (Examples 1-3, 7-1 to 7-6 have a p-quinoid structure, and Examples 7-7 have an o-quinoid structure) are used. When a solute containing the solute was used, better battery characteristics were obtained as compared with the case where the solution B containing the compound having a quinoid structure in the molecule was not used as in Examples 7-8 and 7-9. As the solvent of the solution B, an ether solvent, an ester solvent, and a ketone solvent are preferable, and an ether solvent is particularly preferable. This is because the activity of protons contained in the solvent molecules is low in these solvents, and the activity is particularly low in ether-based solvents, so that side reactions in the reaction between the oxidizing agent and the active lithium in the silicon compound particles are unlikely to occur. .. The concentration of the solute in the solution B used in the reaction ^is, good battery characteristics can be obtained if 10 -3 mol / L or more 1 × ¹⁰ 0 mol / L or less.

(Examples 8-1 to 8-6)
A negative electrode active material was prepared in the same manner as in Examples 1-3, except that the total content of the linear polyphenylene compound and the like of the second lithium-containing silicon compound particles was changed as shown in Table 8. Then, the battery characteristics were evaluated in the same manner as in Examples 1-3. The total content of the linear polyphenylene compound and the like remains in the negative electrode active material by controlling the amount of the linear polyphenylene compound and the like added to each solution used in the lithium insertion step by the redox method, the immersion time, and the like. The amount to be adjusted was changed.

When the initial charge / discharge characteristics of the test cells (coin batteries) of Examples 8-1 to 8-6 and the capacity retention rate of the laminated film type secondary battery were examined, the results shown in Table 8 were obtained.

As can be seen from Table 8, if the total content of the linear polyphenylene compound or the like is in the range of 1 mass ppm or more and 4000 mass ppm or less as in Examples 8-2 to 8-5, the implementation is out of this range. The cycle characteristics and initial charge / discharge characteristics were improved as compared with Examples 8-1 and 8-6. In particular, the battery characteristics were particularly excellent in the range where the total content of the linear polyphenylene compound and the like was 1 mass ppm or more and 1000 mass ppm or less.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any object having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. Is included in the technical scope of.

10 ... Negative electrode, 11 ... Negative electrode current collector, 12 ... Negative electrode active material layer,
30 ... Laminated film type secondary battery, 31 ... Winding electrode body,
32 ... Positive electrode lead (positive electrode aluminum lead),
33 ... Negative electrode lead (negative electrode nickel lead), 34 ... Adhesive film,
35 ... Exterior member.

Claims (30)

A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery containing silicon compound particles containing lithium.
A step of preparing silicon compound particles containing a silicon compound (SiO _x : 0.5 ≦ x ≦ 1.6) and
A step of mixing the silicon compound particles with a simple substance of lithium or a lithium compound and heating to obtain the first lithium-containing silicon compound particles.
A step of obtaining the second lithium-containing silicon compound particles by contacting the first lithium-containing silicon compound particles with a solution A containing lithium and the solvent is an ether solvent.
A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, which comprises. The negative electrode activity for a non-aqueous electrolyte secondary battery according to claim 1, further comprising a step of forming a carbon film on the silicon compound particles before the step of obtaining the first lithium-containing silicon compound particles. Method of manufacturing the substance. The non-aqueous electrolyte according to claim 1 or 2, wherein in the step of preparing the silicon compound particles, the silicon compound particles having a silicon crystallite size of 3 nm or more and 10 nm or less are prepared. A method for manufacturing a negative electrode active material for a secondary battery. The negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the heating temperature is set to 400 ° C. or higher in the step of obtaining the first lithium-containing silicon compound particles. Manufacturing method of active material. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 4, wherein the heating temperature is set to 400 ° C. or higher and 800 ° C. or lower in the step of obtaining the first lithium-containing silicon compound particles. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the heating temperature is set to 600 ° C. or higher and 800 ° C. or lower in the step of obtaining the first lithium-containing silicon compound particles. The non-aqueous electrolyte according to any one of claims 1 to 6, wherein in the step of obtaining the second lithium-containing silicon compound particles, the contact time with the solution A is 3 minutes or more. A method for manufacturing a negative electrode active material for a secondary battery. As the solution A, solution A ₁ or lithium and amines containing lithium and containing at least one selected from a linear polyphenylene compound and its derivative and a polycyclic aromatic compound and its derivative, and the solvent being an ether solvent. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein a solution A ₂ containing an ether solvent is used. Wherein a solution A, method of preparing a negative active material for a nonaqueous electrolyte secondary battery according to claim 8, characterized by using the solution A _1. The non-water solution according to claim 9, wherein the solution A ₁ contains a solution containing lithium, one or more selected from a linear polyphenylene compound and a derivative thereof, and the solvent being an ether solvent. A method for producing a negative electrode active material for an electrolyte secondary battery. The total content of one or more selected from the linear polyphenylene compound and its derivative and the polycyclic aromatic compound and its derivative measured by TPD-MS of the second lithium-containing silicon compound particle is 1 mass ppm or more and 4000 mass ppm. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 8 to 10, wherein the method is as follows. After the step of obtaining the second lithium-containing silicon compound particles, the solute contains the second lithium-containing silicon compound particles as a solvent and contains one or more selected from ether-based materials, ketone-based materials, and ester-based materials. The negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 11, which comprises a step of contacting the solution B containing a compound having a quinoid structure in the molecule. Production method. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 12, wherein the compound having a quinoid structure in the molecule is benzoquinone, quinodimethane, quinodiimine, or a derivative thereof. The second lithium-containing silicon compound particle has a peak derived from the (011) plane of Li ₄ SiO ₄ and a peak derived from the (001) plane of Li ₂ SiO ₃ in the XRD spectrum of the particles. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 13, wherein the negative electrode active material is produced. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 14, wherein the lithium content of the second lithium-containing silicon compound particles is 4% by mass or more and 30% by mass or less. A method for producing a negative electrode active material for use. A method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery containing silicon compound particles containing lithium.
A step of preparing silicon compound particles containing a silicon compound (SiO _x : 0.5 ≦ x ≦ 1.6) and
A step of mixing the silicon compound particles with a simple substance of lithium or a lithium compound and heating to obtain the first lithium-containing silicon compound particles.
A step of forming an electrode containing the first lithium-containing silicon compound particles, and
A step of contacting the first lithium-containing silicon compound particles contained in the electrode with a solution A containing lithium and the solvent being an ether solvent to obtain an electrode containing the second lithium-containing silicon compound particles.
A method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery, which comprises. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 16, further comprising a step of forming a carbon film on the silicon compound particles prior to the step of obtaining the first lithium-containing silicon compound particles. Production method. The non-aqueous electrolyte according to claim 16 or 17, wherein in the step of preparing the silicon compound particles, the silicon compound particles having a silicon crystallite size of 3 nm or more and 10 nm or less are prepared. A method for manufacturing a negative electrode for a secondary battery. The negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 16 to 18, wherein the heating temperature is set to 400 ° C. or higher in the step of obtaining the first lithium-containing silicon compound particles. Manufacturing method. The method for producing a negative electrode for a non-aqueous electrolyte secondary battery according to claim 19, wherein the heating temperature is set to 400 ° C. or higher and 800 ° C. or lower in the step of obtaining the first lithium-containing silicon compound particles. The method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery according to claim 20, wherein the heating temperature is set to 600 ° C. or higher and 800 ° C. or lower in the step of obtaining the first lithium-containing silicon compound particles. The method according to any one of claims 16 to 21, wherein in the step of obtaining the electrode containing the second lithium-containing silicon compound particles, the contact time with the solution A is 3 minutes or more. A method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery. As the solution A, solution A ₁ or lithium and amines containing lithium and containing at least one selected from a linear polyphenylene compound and its derivative and a polycyclic aromatic compound and its derivative, and the solvent being an ether solvent. wherein the method for producing a negative electrode for a nonaqueous electrolyte secondary battery according to claims 16 to any one of claims 22 to solvent is characterized by using a solution a ₂ is an ether-based solvent. Wherein a solution A, method for producing a negative electrode for a nonaqueous electrolyte secondary battery according to claim 23, characterized by using the solution A _1. The non-water solution according to claim 24, wherein the solution A ₁ contains a solution containing lithium, one or more selected from a linear polyphenylene compound and a derivative thereof, and the solvent being an ether solvent. A method for manufacturing a negative electrode for an electrolyte secondary battery. The total content of one or more selected from the linear polyphenylene compound and its derivative and the polycyclic aromatic compound and its derivative measured by TPD-MS of the second lithium-containing silicon compound particle is 1 mass ppm or more and 4000 mass ppm. The method for producing a negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 23 to 25, which comprises the following. After the step of obtaining the electrode containing the second lithium-containing silicon compound particles, one or more selected from ether-based materials, ketone-based materials, and ester-based materials are used as the solvent for the second lithium-containing silicon compound particles. The negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 16 to 26, which comprises a step of contacting the solution B containing a compound having a quinoid structure in the molecule as a solute. Manufacturing method. The method for producing a negative electrode for a non-aqueous electrolyte secondary battery according to claim 27, wherein the compound having a quinoid structure in the molecule is benzoquinone, quinodimethane, quinodiimine, or a derivative thereof. The second lithium-containing silicon compound particle has a peak derived from the (011) plane of Li ₄ SiO ₄ and a peak derived from the (001) plane of Li ₂ SiO ₃ in the XRD spectrum of the particles. The method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 16 to 28. The non-aqueous electrolyte secondary battery according to any one of claims 16 to 29, wherein the lithium content of the second lithium-containing silicon compound particles is 4% by mass or more and 30% by mass or less. Negative electrode manufacturing method.

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