JP2007165061A - Electrode structure for lithium secondary battery and secondary battery having such electrode structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode structure for a lithium secondary battery having a high capacity and a long lifetime; and to provide a lithium secondary battery using the electrode structure and having the high capacity, high energy density, and the long lifetime. <P>SOLUTION: The electrode structure for the lithium secondary battery includes a main active material layer formed from a metal powder selected from silicon, tin and an alloy thereof that can store and discharge and capable of lithium by electrochemical reaction, and a binder of an organic polymer; and an electrode structure comprising a current collector. The main active material layer is formed at least by a powder of a support material for supporting the electron conduction of the main active material layer in addition to the metal powder. The powder of the support material is a particle having a spherical, pseudo-spherical or pillar shape with an average particle size of 0.3 to 1.35 times the thickness of the main active material layer. The support material is one or more materials selected from a group consisting of graphite, oxides of transition metals and metals that do not electrochemically form alloy with lithium. Organic polymer compounded with a conductive polymer is used for the binder. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrode material for a lithium secondary battery comprising a powder of particles mainly composed of a metal alloyed with lithium by an electrochemical reaction such as silicon and tin, an electrode structure having the electrode material, and the electrode The present invention relates to a secondary battery having a structure.

Recently, since the amount of CO ₂ gas contained in the atmosphere is increasing, it has been pointed out that global warming may occur due to the greenhouse effect. Thermal power plants convert thermal energy obtained by burning fossil fuels into electrical energy. However, it is difficult to construct new thermal power plants because they emit a large amount of CO ₂ gas by combustion. ing. Therefore, as an effective use of power generated by generators such as thermal power plants, surplus power nighttime power is stored in secondary batteries installed in ordinary households and used in the daytime when power consumption is high So-called load leveling has been proposed to level the load.

In addition, for electric vehicle applications that are characterized by not discharging substances related to air pollution including CO ₂ , NO _x , hydrocarbons, etc., development of secondary batteries with high energy density is expected. Furthermore, for power applications of portable devices such as book-type personal computers, video cameras, digital cameras, mobile phones, and PDAs (Personal Digital Assistants), it is urgent to develop a small, lightweight, high-performance secondary battery.

  As such a small, lightweight and high-performance secondary battery, a lithium intercalation compound that deintercalates lithium ions from the interlayer is used as a positive electrode material, and lithium ions are formed from carbon atoms. The development of so-called “lithium ion batteries” of rocking chair type using a carbon material typified by graphite, which can be intercalated between the layers of a six-membered ring network plane, as a negative electrode material has been put into practical use and is generally used. ing.

  However, in this “lithium ion battery”, a negative electrode composed of a carbon material can theoretically intercalate only a maximum of 1/6 lithium atoms per carbon atom. A secondary battery having a high energy density comparable to that of the primary battery cannot be realized. If a negative electrode made of carbon in a “lithium ion battery” is intercalated with a lithium amount greater than the theoretical amount during charging, or if charging is performed under conditions of high current density, lithium metal is dendrited on the surface of the carbon negative electrode. There is a possibility that it will grow into a (dendritic) shape and eventually lead to an internal short circuit between the negative electrode and the positive electrode through repeated charge / discharge cycles. A “lithium ion battery” exceeding the theoretical capacity of a graphite negative electrode will provide a sufficient cycle life. It is not done.

  On the other hand, a high-capacity lithium secondary battery using metallic lithium as a negative electrode has attracted attention as a secondary battery exhibiting a high energy density, but has not yet been put into practical use. This is because the cycle life of charge / discharge is extremely short. The main reasons for the extremely short charge / discharge cycle life are that metal lithium reacts with impurities such as moisture in the electrolyte and an organic solvent to form an insulating film, and the surface of the metal lithium foil is not flat and the electric field is concentrated. It is considered that the lithium metal grows in a dendrite shape due to repeated charge and discharge due to this, causing an internal short circuit between the negative electrode and the positive electrode and reaching the life.

  A lithium alloy made of lithium and aluminum is used for the negative electrode in order to suppress the progress of the reaction between the lithium metal and the water in the electrolyte or the organic solvent, which is a problem of the secondary battery using the lithium metal as the negative electrode. A method has been proposed. However, in this case, since the lithium alloy is hard, it cannot be spirally wound, so that a spiral cylindrical battery cannot be produced, the cycle life is not sufficiently extended, and energy comparable to a battery using metallic lithium as a negative electrode. The current situation is that a wide range of practical applications has not been achieved because the density cannot be obtained sufficiently.

In order to solve the above problems, the present inventors have disclosed Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5 as negative electrodes for lithium secondary batteries made of silicon or tin element. Patent Document 6 is proposed. Patent Document 1 uses a negative electrode in which a metal material that is not alloyed with lithium and an electrode layer formed of a metal that is alloyed with lithium such as silicon or tin and a metal that is not alloyed with nickel or copper is used. We have proposed a lithium secondary battery. In Patent Document 2, a negative electrode formed from an alloy powder of an element such as nickel or copper and an element such as tin is used. In Patent Document 3, particles made of silicon or tin having an average particle size of 0.5 to 60 μm are used. A lithium secondary battery using a negative electrode containing 35% by weight or more, having a porosity of 0.10 to 0.86 and a density of 1.00 to 6.56 g / cm ³ is proposed. Patent Document 4 proposes a lithium secondary battery using a negative electrode having silicon or tin having an amorphous phase. Patent Document 5 proposes a lithium secondary battery using a negative electrode made of non-stoichiometric amorphous tin-transition metal alloy particles. Patent Document 6 proposes a lithium secondary battery using a negative electrode made of non-stoichiometric amorphous silicon-transition metal alloy particles.

  Further, in Patent Document 7, a metal layer or metalloid capable of forming a lithium alloy, particularly a carbon layer on the surface of silicon particles is formed by a thermal decomposition chemical vapor deposition method such as benzene to improve conductivity, thereby improving lithium There has been proposed a lithium secondary battery that suppresses volume expansion during alloying to prevent electrode destruction, and has a high capacity and high charge / discharge efficiency. However, the chemical vapor deposition method using thermal decomposition has problems such as that the surface of silicon particles cannot be uniformly coated, the thermal decomposition temperature is high, and oxidation of silicon particles is likely to occur. By repeating the above, the problem that the internal resistance of the battery increases and the amount of electricity that can be taken out gradually decreases has not been solved as well as the graphite electrode.

Moreover, the negative electrode for a lithium secondary battery formed from a metal powder capable of storing and releasing lithium by an electrochemical reaction and a binder selected from silicon, tin, and an alloy thereof is expanded by charging and discharging of the battery. Shrinkage due to discharge, and expansion and contraction are repeated by repeated charge and discharge, which may cause a decrease in contact between the metal powder particles, dropping of the metal powder particles, and peeling of the electrode layer from the current collector. The reason is considered to be that the lithium alloying reaction during charging with the metal powder particles occurs unevenly. In order to make the non-uniformity of the reaction more uniform, there is also an attempt to improve by mixing carbon particles such as graphite. However, if the amount of Li stored in the negative electrode during charging increases, the metal powder particles and the carbon particles Due to the difference between the storage capacity and the volume expansion, the electrochemical reaction related to charge / discharge does not occur uniformly in the electrode layer. (The metal powder particles are units constituting metal powder, and the carbon particles are units constituting carbon powder.)
Therefore, development of a long-life negative electrode that solves the above problems is desired.
US Pat. No. 6,051,340 US Pat. No. 5,795,679 US Pat. No. 6,432,585 JP-A-11-283627 Japanese Unexamined Patent Publication No. 2000-311681 Japanese Patent Publication WO00 / 17949 JP 2000-215887 A

  Accordingly, the present invention provides an electrode structure for a negative electrode of a lithium secondary battery having a high capacity and a high energy density, in which the capacity is not decreased even by repeated charge and discharge, and a lithium secondary battery having the electrode structure. It is the purpose.

That is, the first invention of the present invention is a binding of an organic polymer and a metal powder selected from silicon, tin, or an alloy containing any one of these elements and capable of storing and releasing lithium by an electrochemical reaction. In an electrode structure composed of a main active material layer made of an agent and a current collector,
(A) In addition to the metal powder, the main active material layer includes at least a support material powder that supports electronic conduction of the main active material layer, and the shape of the powder of the support material is spherical, pseudo-spherical, or columnar. The average particle size is 0.3 to 1.35 times the average thickness of the main active material layer, and the support material is a transition metal oxide selected from graphite, TiO ₂ , MoO ₃ , and WO ₃ , Li and One or more selected from the group consisting of Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and metals selected from these alloys that do not form alloys electrochemically An electrode structure for a lithium secondary battery, characterized by being a material.

According to a second aspect of the present invention, there is provided a metal powder selected from silicon, tin, or an alloy containing any one of these elements and capable of storing and releasing lithium by an electrochemical reaction, and an organic polymer binder. In an electrode structure composed of a main active material layer and a current collector,
(A) In addition to the metal powder, the main active material layer includes at least a support material powder that supports electronic conduction of the main active material layer, and the shape of the powder of the support material is spherical, pseudo-spherical, or columnar. The average particle size is 0.3 to 1.35 times the thickness of the main active material layer, and the support material is a transition metal oxide selected from graphite, TiO ₂ , MoO ₃ , and WO ₃ , Li and electricity One or more materials selected from the group consisting of Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and metals selected from these alloys that do not form alloys chemically And
(B) An electron conductive buffer layer is provided between the current collector and the main active material layer of the electrode structure, and the buffer layer includes at least an organic polymer binder, a conductive polymer, Graphite, Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and a metal that does not form an alloy with Li selected from the group of these alloys, TiO ₂ , MoO ₃ , composed of particles of one or more kinds of materials selected from the group consisting of transition metal oxides selected from WO _3, and the average particle size of the material particles is 0.5 μm to 10 μm.
This is an electrode structure for a lithium secondary battery.

According to a third aspect of the present invention, there is provided a metal powder selected from silicon, tin, or an alloy containing any one of these elements and capable of storing and releasing lithium by an electrochemical reaction, and an organic polymer binder. In an electrode structure composed of a main active material layer and a current collector,
(A) In addition to the metal powder, the main active material layer includes at least a support material powder that supports electronic conduction of the main active material layer, and the shape of the powder of the support material is spherical, pseudo-spherical, or columnar. The average particle size is 0.3 to 1.35 times the thickness of the main active material layer, and the support material is a transition metal oxide selected from graphite, TiO ₂ , MoO ₃ , and WO ₃ , Li and electricity One or more materials selected from the group consisting of Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and metals selected from these alloys that do not form alloys chemically And
(C) A surface coating layer is provided on the surface of the main active material layer of the electrode structure, the surface coating layer has electron conductivity and ion permeability or ion conductivity, and the surface coating layer is at least From the group of organic polymer binders and conductive polymers, amorphous carbon, graphite, Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and alloys thereof A particle composed of one or more materials selected from the group consisting of transition metal oxides selected from metals selected from Li, TiO ₂ , MoO ₃ , and WO ₃ that do not electrochemically form an alloy with Li. An electrode structure for a lithium secondary battery, wherein the secondary particles have an average particle size of 0.5 μm to 10 μm.

According to a fourth aspect of the present invention, there is provided a metal powder selected from silicon, tin, or an alloy containing any one of these elements and capable of storing and releasing lithium by an electrochemical reaction, and an organic polymer binder. In an electrode structure composed of a main active material layer and a current collector,
(A) In addition to the metal powder, the main active material layer includes at least a support material powder that supports electronic conduction of the main active material layer, and the shape of the powder of the support material is spherical, pseudo-spherical, or columnar. The average particle size is 0.3 to 1.35 times the thickness of the main active material layer, and the support material is a transition metal oxide selected from graphite, TiO ₂ , MoO ₃ , and WO ₃ , Li and electricity One or more materials selected from the group consisting of Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and metals selected from these alloys that do not form alloys chemically And
(B) An electron conductive buffer layer is provided between the current collector and the main active material layer of the electrode structure, and the buffer layer includes at least an organic polymer binder, a conductive polymer, Graphite, Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and a metal that does not form an alloy with Li selected from the group of these alloys, TiO ₂ , MoO _3, WO ₃ is composed of particles of one or more materials selected from the group consisting of transition metal oxide selected from the mean particle size of the material particles is 0.5 ~ 10 m,
(C) A surface coating layer is provided on the surface of the main active material layer of the electrode structure, the surface coating layer has electron conductivity and ion permeability or ion conductivity, and the surface coating layer is at least From the group of organic polymer binders and conductive polymers, amorphous carbon, graphite, Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and alloys thereof A particle composed of one or more materials selected from the group consisting of transition metal oxides selected from metals selected from Li, TiO ₂ , MoO ₃ , and WO ₃ that do not electrochemically form an alloy with Li. An electrode structure for a lithium secondary battery, wherein the secondary particles have an average particle size of 0.5 μm to 10 μm.

  The fifth invention of the present invention is a secondary battery comprising a negative electrode using the above electrode structure, a lithium ion conductor and a positive electrode, and utilizing a lithium oxidation reaction and a lithium ion reduction reaction.

The present invention has been made in view of the above circumstances, and the first feature of the present invention is that lithium is stored by an electrochemical reaction selected from silicon, tin, or an alloy containing any one of these elements. In an electrode structure composed of a main active material layer and a current collector made of a releasable metal powder and an organic polymer binder, the main active material layer is added to the metal powder and the main active material layer. It is composed of at least a support material powder that supports the electron conduction of the material layer, and the shape of the powder of the support material is spherical, pseudo-spherical, or columnar, and the average particle size is 0.3 to 1 of the thickness of the main active material layer. .35 times the point. The support material is not electrochemically alloyed with graphite, transition metal oxide (selected from TiO ₂ , MoO ₃ , WO ₃ ), Li (Cu, Ni, Co, Ti, Fe, Cr, Mo , W, Pd, Pt, Au, and alloys thereof (preferably one or more materials selected from the group consisting of metals). The support material is preferably graphite. It is preferable that an average particle diameter of primary particles forming metal powder particles selected from silicon, tin, or an alloy containing any one of these elements in the main active material layer is 0.02 μm to 5 μm. Further, the ten-point average height Rz of the surface roughness of the current collector is preferably 0.7 μm to 3 μm.

Further, as a second feature, a buffer layer is provided between the current collector and the main active material layer of the electrode structure, and has a conductivity, and is less expanded during charging. And at least an organic polymer binder and a conductive polymer, graphite, (Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and alloys thereof. (I) composed of particles of one or more materials selected from the group consisting of metals that do not electrochemically form an alloy with Li, transition metal oxides (selected from TiO ₂ , MoO ₃ , WO ₃ ), The average particle diameter of the material particles is 0.5 μm to 5 μm.

As a third feature, a surface coating layer is provided on the surface of the main active material layer of the electrode structure to reduce concentration of an electric field during charge and discharge, and the surface coating layer has electron conductivity. The surface coating layer includes at least an organic polymer binder, a conductive polymer, amorphous carbon, graphite, (Cu, Ni, Co), and a layer having ion permeability (ion conductivity). , Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and metals that do not electrochemically form an alloy with Li (from TiO ₂ , MoO ₃ , WO ₃₎ It is also preferred that it consists of particles of one or more materials selected from the group consisting of (selected) transition metal oxides, and that the secondary particles have an average particle size of 0.5 μm to 10 μm.

Another feature of the present invention is that the binder of the main active material layer, the adhesion layer, and the coating layer is the same material.
A fourth feature is that a conductive organic polymer is dispersed in the binder.

  Furthermore, a feature of the present invention is a secondary battery including a negative electrode using the electrode structure, an electrolyte, and a positive electrode, and utilizing a lithium oxidation reaction and a lithium ion reduction reaction. The support material powder in the layer has a coefficient of expansion of not more than 1.5 times in the opposite positive electrode direction after charging.

The fifth feature of the present invention is that a metal powder capable of storing and releasing lithium by an electrochemical reaction, a hard carbon (non-graphitizable carbon) powder, or graphite is selected from silicon, tin, and alloys thereof. In an electrode structure composed of a carbon powder and a main active material layer composed of a binder of an organic polymer and a current collector,
A material having a function as a “linkage” that bears a chemical bond or electronic conduction between the metal powder and the carbon powder (herein referred to as a “linkage material”), in which the metal powder and the carbon powder are combined. is there.

  The electrode structure of the present invention can also be used as an electrode of a battery other than a lithium secondary battery or an electrode of a capacitor.

  The lithium secondary battery according to the preferred embodiment of the present invention can achieve a high storage capacity, a high energy density, and a charge / discharge cycle life.

  The present inventors have arrived at the present invention through detailed examination of an alloy-based negative electrode for a lithium secondary battery. In a lithium secondary battery in which an electrode in which an active material layer made of silicon or tin metal or alloy powder and a binder is formed on a current collector of a metal foil is used as a negative electrode, the battery is repeatedly charged and discharged. Increases the internal resistance, resulting in performance degradation. The present inventors have inferred that the following is the cause by observing and analyzing the active material layer of the negative electrode. In the process where the powder of silicon or tin metal or alloy is electrochemically alloyed with lithium by charging, uniform alloying does not occur, and the expansion associated with this lithium alloying occurs unevenly. In the vicinity of the surface of the material layer and in the middle of the active material layer, so-called “soot” and cracks are generated in the region of the active material layer and the current collector interface. The occurrence of “soot” and cracks hinders electron conduction in the active material layer of the negative electrode and increases the electrical resistance of the electrode. This is thought to be due to the fact that silicon or tin metal or alloy powders have very large expansion when alloyed with lithium. In order to suppress expansion due to alloying with lithium, it is possible to suppress the amount of lithium to be alloyed, but the amount of electricity that can be stored is also reduced.

  Accordingly, the present inventors have developed (1) expansion of silicon or tin metal or alloy powder of the active material in order to prevent generation of cracks and “soot” due to non-uniform expansion. However, a support material capable of maintaining electronic conduction is dispersed in the active material layer. (2) In order to improve the electronic conductivity of the binder, a conductive organic polymer is combined with the binder. 3) Electronic conductivity that ensures electronic conduction between the active material layer and the current collector even when the silicon or tin metal or alloy powder of the active material expands between the current collector and the active material layer. (4) In order to suppress non-uniform expansion on the surface of the electrode layer, the expansion due to charging is small compared to the silicon or tin metal or alloy of the active material layer main material, and ion permeation Electrode structure with a surface coating layer that is conductive and electronically conductive It was devised.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 4 and FIG.
In FIG. 1, 100 is a current collector, 101 is silicon, tin, or an alloy particle containing any of these elements, 102 is a conductive auxiliary material particle, 103 is a binder, 104 is a support material particle, 105 is The main active material layer 106 is an electrode structure, and 101 'is particles of silicon, tin, or an alloy containing any one of these elements expanded by alloying with lithium.

  In FIG. 2, 200 is a current collector, 201 is particles of silicon, tin, or an alloy containing any of these elements, 202 is a conductive auxiliary material particle, 203 is a binder, 204 is support material particles, 205 is The main active material layer, 206 is an electron conductive particle, 207 is a binder, 208 is a buffer layer, and 209 is an electrode structure.

  In FIG. 3, 300 is a current collector, 301 is silicon, tin, or particles of an alloy containing any of these elements, 302 is a conductive auxiliary material particle, 303 is a binder, 304 is support material particles, 305 is The main active material layer, 306 is an ion conductive or electron conductive particle, 307 is a binder, 308 is a lithium ion permeable surface coating layer, and 309 is an electrode structure.

  In FIG. 4, 400 is a current collector, 401 is silicon, tin, or particles of an alloy containing any of these elements, 402 is a conductive auxiliary material particle, 403 is a binder, 404 is support material particles, and 405 is Main active material layer, 406 is an electron conductive particle, 407 is a binder, 408 is a buffer layer, 409 is an ion conductive or electron conductive particle, 410 is a binder, 411 is a lithium ion permeable surface coating Layers 412 are electrode structures, and 413 is a surface-roughened current collector.

  In FIG. 5, 500 is a current collector, 501 is particles of silicon, tin, or an alloy containing any of these elements, 502 is a flat conductive auxiliary material particle, 503 is a conductive auxiliary material particle, and 504 is a binder. , 505 is a main active material layer, 506 is an electrode structure, and 501 ′ is particles of silicon or tin expanded by alloying with lithium, or an alloy containing any one of these elements.

  FIG. 1 shows a main active material layer consisting of particles 100 of silicon or tin metal or their alloys, conductive aid particles 102 (helping electronic conduction between the particles), and a binder 103. FIG. 3 is a schematic cross-sectional configuration diagram of an example of an electrode structure 106 formed by introducing a support material 104 having a particle size of the same level as the thickness of a main active material layer 105 that assists electron conduction in a direction. The method of introducing the support material is to mix the support material powder in addition to the silicon or tin metal or their alloy powder, the conductive auxiliary material powder, the binder when forming the main active material on the current collector. It can be done.

  FIG. 1B shows a lithium secondary battery manufactured by combining the electrode structure of FIG. 1A with the positive electrode using the electrode structure of FIG. 1A, and particles of silicon or tin metal or their alloys and lithium FIG. 3 is an imaginary view of a cross section of an electrode structure when the alloy is expanded by an electrochemical reaction.

  (A) of FIG. 5 is a schematic cross-sectional block diagram of the electrode structure which formed the active material layer which introduce | transduced the flat electroconductive auxiliary material particle | grains instead of the support material of FIG. FIG. 5B shows a lithium secondary battery manufactured by combining the electrode structure of FIG. 5A with the positive electrode using the negative electrode structure, and particles of silicon or tin metal or their alloys and lithium. FIG. 6 is a cross-sectional image view of the electrode structure of FIG. 5A when the alloy is expanded by an electrochemical reaction.

  1 (b) and FIG. 5 (b), the electrode structure having the structure shown in FIG. 1 (a) may be expanded by charging as compared with FIG. 5 (a). It can be seen that the presence of the support material particles 104 reduces the decrease in electron conduction during the electrode reaction and suppresses the increase in electrode resistance. In addition, when a conductive polymer is combined with the binder shown in FIG. 1 (b), electronic conduction is maintained through the binder network even during expansion (not shown), thereby improving charge / discharge efficiency. In addition, the charge / discharge cycle life is also extended.

  FIG. 2 is a schematic cross-sectional configuration diagram of an example of an electrode structure in which an electron conductive buffer layer is provided between the current collector and the main active material layer of the electrode structure. Even when charging is performed using the electrode structure of FIG. 2 as a negative electrode of a lithium secondary battery, a buffer layer with small expansion assists electronic conduction between the main active material layer that expands by charging and the current collector. be able to. Further, unlike the electrode structure of FIG. 1 (a), a buffer layer made of an organic polymer binder is provided between the current collector and the main active material layer. The stress at the current collector interface generated during the expansion of the material is relaxed and made uniform. Therefore, a part of the main active material layer is prevented from being easily peeled off from the current collector, and deformation due to the stress of the current collector is also suppressed. At this time, the material of the binder used for the main active material layer and the buffer layer is more preferably the same or the same material because the interface between the buffer layer and the main active material layer is continuously formed.

  FIG. 3 is a schematic cross-sectional configuration diagram of an example of an electrode structure in which a surface coating layer is provided on the surface of the main active material layer in the electrode structure of FIG. Even when charging is performed using the electrode structure of FIG. 3 as the negative electrode of a lithium secondary battery, the surface coating layer 306 is provided which has a low expansion due to charging and has electronic conductivity. Sometimes the electric field strength applied to the surface of the electrode structure in FIG. 3 is made uniform, so that the expansion of the main active material layer can be made uniform, and the electron conduction parallel to the current collector during the electrochemical reaction during the expansion is maintained. Easy to be. For this reason, the electrical resistance of the electrode structure can be further suppressed during expansion due to charging.

  FIG. 4 shows that an electron conductive buffer layer is provided between the current collector of the electrode structure and the main active material layer, and a surface coating layer is provided on the surface of the main active material layer of the electrode structure. 2 is a schematic cross-sectional configuration diagram of an example of an electrode structure. 4A shows an example in which a current collector having a flat surface is used as the current collector, and FIG. 4B shows an example in which a current collector with a roughened surface is used as the current collector. When a current collector that has been subjected to surface roughening is used, the area of the interface can be increased, and the stress generated during charging / discharging between the main active material layer and the current collector can be reduced. However, if the unevenness is large and uneven, the stress applied to the current collector is uneven, and breakage may occur due to repeated charge and discharge. Therefore, the ten-point average height Rz of the surface roughness of the current collector is preferably 0.5 μm to 5 μm, and more preferably 0.7 μm to 3 μm.

[Main active material layer]
The main active material layer of the electrode structure used for the negative electrode of the lithium secondary battery of the present invention is obtained by mixing the main active material with a support material powder, a conductive auxiliary material powder, and a binder, and appropriately adding a binder solvent. Knead to prepare a slurry. Next, the slurry prepared in the current collector is coated on the current collector or a buffer layer described later, dried to form an electrode layer, and then appropriately pressed to adjust the thickness and density of the electrode layer. Thus, an electrode structure is formed. As the coating method, for example, a coater coating method or a screen printing method can be applied. Further, the main material, the support material powder, the conductive auxiliary material, and the binder are pressure-molded on the current collector or a buffer layer described later without adding a solvent to form an electrode material layer. It is also possible. The density of the electrode material layer of the present invention is preferably in the range of 0.7~2.0g / cm ^3, and more preferably in the range of 0.9~1.5g / cm ^3. If the density of the electrode material layer is too high, expansion upon insertion of lithium increases, and peeling from the current collector occurs. On the other hand, if the density of the electrode material layer is too small, the resistance of the electrode is increased, so that the charge / discharge efficiency is lowered and the voltage drop during battery discharge is increased.

(Main active material)
As the main active material constituting the main active material layer, it is preferable to use metal powder particles of silicon, tin or an alloy thereof. The metal powder particles (alloy particles) preferably contain a transition metal element and are combined with carbon. The metal powder particles (alloy particles) are preferably amorphized particles having a crystallite size of preferably 60 nm or less, more preferably 20 nm or less. In the present invention, the size of the crystallite of the particle can be determined by using the following Scherrer formula from the half width and diffraction angle of the peak of an X-ray diffraction curve using CuKα as a radiation source.

Lc = 0.94λ / (βcosθ) (Scherrer equation)
Lc: Crystallite size λ: X-ray beam wavelength β: Half width of peak (radian)
θ: Bragg angle of diffraction line The average particle diameter of primary particles forming the metal powder particles (alloy particles) of the main active material is preferably in the range of 0.05 μm to 5 μm, and in the range of 0.1 μm to 3 μm. It is more preferable that

(Coating with metal powder selected from silicon, tin, and their alloys that can store and release lithium by electrochemical reaction)
The silicon, tin or their alloy particles are coated with a material selected from pitch, pitch coke, petroleum coke, coal tar, fluoranthene, pyrene, chrysene, phenanthrene, anthracene, naphthalene, fluorene, biphenyl, and acenaphthene, and then non-coated. It is preferably carbonized by active gasification and coated with a carbonized layer. Among the carbonized raw materials, pitch, pitch coke, petroleum coke, coal tar, and the like have a low melting point, so that the coating of the main active material particles is facilitated and the carbonization temperature is low. Facilitates coating with a carbonized layer without degrading performance. Furthermore, these materials are inexpensive. The ratio of the carbonized layer of silicon, tin or alloy particles of the carbonized layer coating does not impair the lithium occlusion amount of silicon, tin or alloy particles thereof, assists electronic conduction between particles, and suppresses oxidation. The range of 1 to 10% by weight is preferable, and the range of 2 to 5% by weight is more preferable. Further, in the carbonization process, a reduction reaction for depriving oxygen elements from partially oxidized silicon, tin, or alloy particles occurs, so that oxides that cause an irreversible reaction with lithium can be reduced. As the inert gas used in the carbonization process, a gas selected from argon gas, nitrogen gas, and carbon dioxide gas can be used. The carbonization temperature is preferably in the range of 400 ° C. to 900 ° C., more preferably in the range of 500 ° C. to 800 ° C., where carbonization proceeds and crystallization of silicon, tin, or alloy particles does not proceed easily.

Further, metal powders selected from silicon, tin, and alloys thereof and capable of storing and releasing lithium by an electrochemical reaction are TiO ₂ , MoO ₃ , WO ₃ , and Ti, Mo, W of the metal oxides. It is desirable to coat a part or the whole of the surface with an oxide partially substituted with another metal element. Since the metal oxide has a stable structure and facilitates electrical insertion and removal of Li ions, a metal powder selected from silicon, tin, and alloys thereof is used as a negative electrode main material of a lithium secondary battery. In such a battery, it is possible to prevent Li ions from being reduced and deposited as active Li metal on the metal powder selected from the silicon, tin, and alloys thereof. As a result, a decrease in charge / discharge performance due to repeated charge / discharge of the battery can be suppressed, and the charge / discharge cycle life can be extended.
As coating materials other than the above TiO ₂ , MoO ₃ , and WO ₃ , transition metal oxides such as Li _4/3 Ti _5/3 O ₄ and V ₂ MoO ₈ , and transition metal sulfides such as TiS ₂ and MoS ₂ are also used. it can.

  The coating with the metal oxide can be formed by mixing a metal powder selected from the silicon, tin, and alloys thereof with a pulverizer such as a ball mill. The raw material of the metal oxide, polytitanic acid, polytungstic acid, polymolybdic acid, polytitanic acid peroxide, polytungstic acid peroxide, polymolybdic peroxide solution, and the silicon, tin, and their It can coat | cover by mixing the metal powder selected from an alloy.

  In addition, a carbon-carbon conductive polymer having a conjugated double bond, in which a double bond and a single bond are alternated, and a part of the surface of the metal powder selected from the silicon, tin, and alloys thereof, or It is also desirable to cover the entire surface. When the negative electrode of a lithium secondary battery is configured with a binder, the affinity between the binder and the metal powder selected from the silicon, tin, and alloys thereof is increased and dispersed uniformly in the electrode layer of the negative electrode. Therefore, stable negative electrode performance can be obtained.

  In addition, since the conductive polymer can also electrochemically insert and desorb Li ions, the same effect as that obtained when the metal oxide is coated can be obtained. The conductive polymer is preferably a polymer that is a polymer such as a thiophene derivative, a pyrrole derivative, an aniline derivative, or an acetylene derivative. Furthermore, in order to further increase the affinity with the binder, the conductive polymer is more preferably a complex compound with a surfactant. The coating of the metal powder selected from the silicon, tin, and alloys thereof with the conductive polymer can be formed by mixing the metal powder with a solution of the conductive polymer.

(Support material)
As a support material for the main active material layer, graphite, a transition metal oxide (selected from TiO ₂ , MoO ₃ , WO ₃ ), and Li do not form an alloy electrochemically (Cu, Ni, Co, Ti, One or more materials selected from the group consisting of metals (selected from Fe, Cr, Mo, W, Pd, Pt, Au, and alloys thereof) are preferred and inhibit lithium dendrite growth upon charging. In this respect, graphite and a transition metal oxide (selected from TiO ₂ , MoO ₃ , and WO ₃ ) are more preferable. The transition metal oxide selected from graphite and TiO ₂ , MoO ₃ , and WO ₃ can occlude lithium between layers, and the transition metal oxide selected from graphite, MoO ₃ , and WO ₃ during occlusion of lithium Since the potential difference with metallic lithium is small, it is a more preferable material. Examples of the support material for metal compounds other than TiO ₂ , MoO ₃ and WO ₃ include transition metal oxides such as Li _4/3 Ti _5/3 O ₄ and V ₂ MoO ₈ , and transition metals such as TiS ₂ and MoS _2. Sulfides can also be used.

  From the viewpoint of easily holding the electrolytic solution, graphite is most preferable as the support material of the present invention. The shape of the support material powder is preferably spherical, pseudo-spherical, or columnar. The average particle size (secondary particle) size of the support material is 0.3 to 1.1 of the average thickness of the main active material layer in order to ensure the electron conduction in the main active material layer even during expansion by charging. It is preferably 35 times, and more preferably 0.6 to 1.2 times.

(Conductive auxiliary material)
As the conductive auxiliary material for the main active material layer, carbon materials such as amorphous carbon such as acetylene black and ketjen black and carbon with graphite structure, nickel, copper, silver, titanium, platinum, aluminum, cobalt, iron, chromium, etc. However, graphite is preferable because graphite can hold an electrolyte solution, has electronic conductivity, and has a large specific surface area. As the shape of the conductive auxiliary material, a shape selected from a spherical shape, a flake shape, a filament shape, a fiber shape, a spike shape, a needle shape, and the like can be preferably used. Furthermore, by adopting two or more different types of powders, the packing density at the time of forming the electrode material layer can be increased and the impedance of the electrode structure can be reduced. The average particle (secondary particle) size as the conductive auxiliary material is preferably 10 μm or less, and more preferably 5 μm or less.

As a conductive auxiliary material used for the negative electrode of a lithium secondary battery composed mainly of a metal powder selected from silicon, tin, and alloys thereof and capable of storing and releasing lithium by an electrochemical reaction, in addition to a carbon material It is also preferable to use a metal powder having the characteristics of a so-called super elastic alloy obtained by heat-treating a powder of a Ni—Ti intermetallic compound (for example, at a temperature of 480 ° C. or the like). In a negative electrode lithium secondary battery formed of a metal powder selected from silicon, tin, and alloys thereof, the amount of chargeable electricity is large, and the negative electrode expands and contracts by charging and discharging, but the conductive auxiliary material is used for the negative electrode. As a result, it is possible to suppress a decrease in the current collecting ability of the negative electrode due to repeated expansion and contraction.
Thereby, it can suppress that battery performance falls at the time of repetition of charging / discharging.

(Binder)
The binder material of the main active material layer includes polyamideimide, polyimide, polyimide precursor (polyamic acid before polyimideization or incompletely polyimideized), styrene-butadiene rubber, modified with reduced water absorption Examples thereof include organic polymer materials such as polyvinyl alcohol resins. In particular, it is more preferable to use a polyamideimide or a polyimide precursor (polyamic acid before polyimideization or imperfect polyimideization) for binding the silicon alloy powder. In the case of a polyimide precursor, after the application of the electrode layer, heat treatment is performed in the range of 150 to 300 ° C. to advance the polyimide.

The content of the binder in the main active material layer is preferably 2 to 20% by weight, and more preferably 5 to 10% by weight.
Organics such as polyamideimide, polyimide, polyimide precursor (polyamic acid before polyimide formation, or imperfect polyimide formation), styrene-butadiene rubber, modified polyvinyl alcohol resin with reduced water absorption, etc. Since the polymer material has poor electronic conductivity, it is necessary to add and use a conductive polymer having a -C = C-C = C- carbon-carbon double bond and single bond replacement. It is good for reducing the resistance. Since the conductive polymer has a high affinity with the organic polymer, a more uniform composite is possible. In order to maintain the binding force and reduce the electrical resistance, the ratio of the conductive polymer mixed with the organic polymer material as the binder of the conductive polymer is 1 to 20 with respect to the binder 100 by weight ratio. Is preferable, and 2 to 10 are more preferable for increasing the electric conductivity without decreasing the binding force of the binder. Examples of the conductive polymer include polymer polymers such as a thiophene derivative monomer, a pyrrole derivative monomer, an aniline derivative monomer, an acetylene derivative monomer, and a phenylene derivative monomer. Preferable specific representative examples of the conductive polymer include polythiophene, poly-3-hexylthiophene, poly-2-acetylthiophene, polybenzothiophene, poly2,5-dimethylthiophene, poly-2-ethylthiophene, poly-2-thiophene. Examples thereof include ethyl carboxylate, polythiophene acetonitrile, poly 3,4 ethylenedioxythiophene, polyisothiafunte, polypyrrole, polyaniline, polyparaphenylene, and the like. The method for adding the conductive polymer to the organic polymer that is the binder is to add the binder to the binder in advance before mixing with the active material or the conductive polymer. The electronic conductivity of the binder can be further increased.

[Current collector]
The current collector of the electrode structure of the present invention plays a role of efficiently supplying a current consumed by an electrode reaction during charging or collecting a current generated during discharging. In particular, when the electrode structure is applied to the negative electrode of a secondary battery, the material forming the current collector is preferably a material having high electrical conductivity and inert to battery reaction. Preferable materials include those made of one or more metal materials selected from copper, nickel, iron, stainless steel, titanium, and platinum. As a more preferable material, copper which is inexpensive and has low electric resistance is used. The shape of the current collector is plate-like, but this “plate-like” is not specified in terms of thickness in terms of practical use, and has a form called “foil” having a thickness of about 5 μm to 100 μm. Is also included. Further, a plate-like member such as a mesh, sponge, or fiber, a punching metal, a metal having a three-dimensional concavo-convex pattern formed on both front and back surfaces, an expanded metal, or the like may be employed.

  The plate-like or foil-like metal on which the three-dimensional uneven pattern is formed is, for example, a plate-like or foil-like shape by applying pressure to a metal or ceramic roll provided with a microarray pattern or a line and space pattern on the surface. It can be produced by transferring to a metal. In particular, a negative electrode battery employing a current collector with a three-dimensional uneven pattern formed has a substantial reduction in current density per electrode area during charge / discharge, improved adhesion to the electrode layer, mechanical From the improvement in strength, there are the effects of improving the current characteristics of charge / discharge and improving the charge / discharge cycle life. The current collector on which the three-dimensional uneven pattern is formed can be applied not only to a current collector of a battery electrode but also to an electrode of an electricity storage device such as a capacitor.

  The surface roughness of the current collector preferably has a ten-point average height Rz in the range of 0.5 μm to 5.0 μm in order to maintain the adhesion of the electrode layer formed on the current collector. More preferably, it is in the range of 7 μm to 3.0 μm. When Rz is larger than the upper limit of the above range, the thickness of the electrode layer formed thereon becomes non-uniform, and when charging and discharging are performed in a lithium secondary battery, it is affected by expansion and contraction of the main active material layer. Due to stress, it tends to break. When Rz is smaller than the lower limit of the above range, when charging / discharging is performed in a lithium secondary battery, it tends to peel off at the interface of the current collector due to the stress generated by the expansion and contraction of the main active material layer, The electrical resistance will increase.

[Buffer layer]
The buffer layer of the present invention is provided between the current collector and the main active material layer, and includes at least an organic polymer binder, a conductive polymer, graphite, (Cu, Ni, Co, Ti, Fe). , Cr, Mo, W, Pd, Pt, Au, and a metal that does not form an alloy with Li) (selected from TiO ₂ , MoO ₃ , WO ₃ ) It is composed of one or more kinds of particles of an electron conductive material selected from the group consisting of transition metal oxides.

The buffer layer is prepared by first mixing an electron conductive material powder and a binder, adding a binder solvent as appropriate, and kneading to prepare a slurry. Next, the prepared slurry is applied onto a current collector and dried to form an electrode layer, and then appropriately pressed, and the thickness and density of the electrode layer are adjusted to form an electrode structure. As the coating method, for example, a coater coating method or a screen printing method can be applied. It is also possible to form the electrode material layer by pressure-molding the electron conductive material powder and the binder on the current collector without adding a solvent. The density of the electrode material layer of the present invention is preferably in the range of 0.7~2.0g / cm ^3, and more preferably in the range of 0.9~1.5g / cm ^3.

  The average particle diameter of the electron conductive particles is preferably 0.5 μm to 10 μm in order to uniformly form the buffer layer. Increasing the thickness of the buffer layer (1) increases the overall thickness of the electrode layer, thereby reducing the storage capacity per electrode layer, and (2) the expansion coefficient of the main active material layer during charging. Since the difference is large, a large stress is generated and warped and easily peels off.

  As the binder constituting the buffer layer, it is preferable to use the same or the same material as the binder constituting the active material layer because it is difficult to form an interface. This is because, when stress is generated when the interface is formed, peeling easily occurs at this interface. As the material of the binder, as in the case of the main active material layer, polyamide imide, polyimide, polyimide precursor (before polyimide formation or incomplete polyimide formation), styrene-butadiene rubber, water absorption Organic polymer materials such as modified polyvinyl alcohol resins having reduced properties. The content of the binder in the buffer layer is preferably 2 to 20% by weight, and more preferably 5 to 10% by weight. The organic polymer material has high insulating properties. Therefore, it is preferable to increase the electron conductivity by mixing a conductive polymer. Since the conductive polymer has a high affinity with the organic polymer, a more uniform composite is possible. In order to maintain the binding force and reduce the electrical resistance, the ratio of the conductive polymer mixed with the organic polymer material as the binder of the conductive polymer is 1 to 20 with respect to the binder 100 by weight ratio. Is preferable, and 2 to 10 is more preferable. Examples of the conductive polymer include polymer polymers such as a thiophene derivative monomer, a pyrrole derivative monomer, an aniline derivative monomer, an acetylene derivative monomer, and a phenylene derivative monomer.

(Surface coating layer)
The surface coating layer of the present invention is provided on the surface of the main active material layer, has electron conductivity and ion permeability (ion conductivity), and the surface coating layer includes at least an organic polymer binder. , Conductive polymer, amorphous carbon, graphite, Li (selected from the group of Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and alloys thereof) Li and electricity It is composed of particles of one or more materials selected from the group consisting of metals that do not form alloys chemically, transition metal oxides (selected from TiO ₂ , MoO ₃ , WO ₃ ). As the material of the particles, a transition metal oxide (selected from graphite, TiO ₂ , MoO ₃ , and WO ₃ ) can insert lithium ions, and graphite, MoO ₃ , and WO ₃ have potentials at the time of lithium insertion. This is preferable because it is close to metallic lithium. The average particle size of the secondary particles of the particles is preferably 0.5 μm to 10 μm in order to make the thickness of the electrode layer of the electrode structure uniform. Increasing the thickness of the covering layer increases the thickness of the entire electrode layer, thereby reducing the storage capacity per electrode layer.

  As the binder constituting the surface coating layer, it is preferable to use the same or the same kind of material as the binder constituting the active material layer because it is difficult to form an interface. This is because, when stress is generated when the interface is formed, peeling easily occurs at this interface. As the material of the binder, as in the case of the main active material layer, polyamide imide, polyimide, polyimide precursor (before polyimide formation or incomplete polyimide formation), styrene-butadiene rubber, water absorption Organic polymer materials such as modified polyvinyl alcohol resins having reduced properties. The content of the binder in the surface coating layer is preferably 2 to 20% by weight, and more preferably 5 to 10% by weight. The organic polymer material has a high insulating property. Therefore, a conductive polymer having a carbon-carbon double bond and a single bond substitution of -C = C-C = C- is mixed to provide electronic conductivity. It is preferable to increase. Since the conductive polymer has a high affinity with the organic polymer, a more uniform composite is possible. In order to maintain the binding force and reduce the electrical resistance, the ratio of the conductive polymer mixed with the organic polymer material as the binder of the conductive polymer is 1 to 20 with respect to the binder 100 by weight ratio. Is preferable, and 2 to 10 is more preferable. Examples of the conductive polymer include polymer polymers such as a thiophene derivative monomer, a pyrrole derivative monomer, an aniline derivative monomer, an acetylene derivative monomer, and a phenylene derivative monomer.

[Secondary battery]
The secondary battery according to the present invention includes a negative electrode, an electrolyte, and a positive electrode using the electrode structure having the above-described characteristics, and utilizes a lithium oxidation reaction and a lithium ion reduction reaction. FIG. 6 is a diagram showing a basic configuration of the lithium secondary battery of the present invention. In the secondary battery of FIG. 6, 601 is a negative electrode using the electrode structure of the present invention, 602 is an ion conductor, 603 is a positive electrode, 604 is a negative electrode terminal, 605 is a positive electrode terminal, and 606 is a battery case (housing). .

  In the secondary battery, an electrode group is formed by laminating an ionic conductor between a negative electrode and a positive electrode, and the electrode group is placed in a dry air or dry inert gas atmosphere in which the dew point temperature is sufficiently controlled. After being inserted into the battery case, it is assembled by connecting each electrode and each electrode terminal and sealing the battery case. When using an ionic conductor with a microporous polymer film holding an electrolyte, an electrode group with a microporous polymer film sandwiched between the negative electrode and the positive electrode as a short-circuit preventing separator After forming the battery, the battery is assembled by inserting it into the battery case, connecting each electrode and each electrode terminal, and injecting an electrolyte before sealing the battery case.

The lithium secondary battery using the electrode structure of the present invention for the negative electrode has a high capacity and energy density due to the beneficial effects of the negative electrode, and has a sufficient charge / discharge cycle life.
In the present specification, the case where the electrode structure of the present invention is used as the negative electrode of a lithium secondary battery is described. However, the electrode structure of the present invention can also be applied as an electrode of a capacitor.

(Positive electrode 602)
The positive electrode 602 serving as a counter electrode of a lithium secondary battery using the above-described electrode structure of the present invention as a negative electrode comprises at least a positive electrode material which is a lithium ion source and serves as a lithium ion host material, preferably a lithium ion host material. A layer formed of a positive electrode material and a current collector. Further, the layer formed from the positive electrode material is preferably made of a positive electrode material which becomes a lithium ion host material and a binder, and in some cases, a material obtained by adding a conductive auxiliary material thereto.

  As a positive electrode material that is a lithium ion source and used as a host material for the lithium secondary battery of the present invention, lithium-transition metal oxide, lithium-transition metal sulfide, lithium-transition metal nitride, lithium-transition metal phosphorylation More preferred. Examples of the transition metal element of the transition metal oxide, transition metal sulfide, transition metal nitride, and transition metal phosphate compound are metal elements having a d-shell or f-shell, such as Sc, Y, lanthanoid, and actinoid. , Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pb, Pt, Cu, Ag, Au are used. In particular, Co, Ni, Mn, Fe, Cr, and Ti are preferably used.

  In the above-mentioned lithium-transition metal oxide, lithium-transition metal sulfide, lithium-transition metal nitride, and lithium-transition metal phosphor oxide, a plurality of positive electrode materials obtained by selecting the transition metal element contained are appropriately mixed. By doing so, the performance of the negative electrode which is the electrode structure of the present invention can be drawn, the battery voltage and the storage capacity can be designed, and a lithium secondary battery with high energy density can be obtained.

  When the shape of the positive electrode active material is powder, a binder is used, or a positive electrode active material layer is formed on a current collector by sintering or vapor deposition to produce a positive electrode. Further, when the positive electrode active material powder has low conductivity, it is necessary to appropriately mix a conductive auxiliary material as in the formation of the active material layer of the electrode structure. In addition, the positive electrode active material powder is coated with a material selected from pitch, pitch coke, petroleum coke, coal tar, fluoranthene, pyrene, chrysene, phenanthrene, anthracene, naphthalene, fluorene, biphenyl, and acenaphthene, and then inert gasified. It is preferable to be carbonized and coated with a carbonized layer. Among the carbonized raw materials, pitch, pitch coke, petroleum coke, coal tar, and the like have a low melting point, so that the coating of the positive electrode particles is facilitated, and the carbonization temperature is low, so the performance of the positive electrode material is lowered. Without this, the coating with the carbonized layer can be facilitated, and the contact resistance between the positive electrode material particles can be reduced. Furthermore, these materials are inexpensive. The ratio of the carbonized layer coating is preferably in the range of 1 to 5% by weight in order to assist the electron conduction between particles without impairing the lithium occlusion amount of the positive electrode active material. Examples of the conductive auxiliary material and the binder include a fluororesin such as polyvinylidene fluoride, a polyolefin resin such as polyethylene, a rubber-based resin such as styrene-butadiene rubber, a polyamideimide, a polyimide, a polyimide precursor (the one before polyimideization, Alternatively, those that are imperfectly polyimideized) or modified polyvinyl alcohol resins with reduced water absorption can be used.

  The binder has high insulating properties, and therefore it is preferable to increase the electronic conductivity by mixing a conductive polymer. Since the conductive polymer has a high affinity with the organic polymer, a more uniform composite is possible. In order to maintain the binding force and reduce the electrical resistance, the ratio of the conductive polymer mixed with the organic polymer material as the binder of the conductive polymer is 1 to 20 with respect to the binder 100 by weight ratio. Is preferable, and 2 to 10 is more preferable. Examples of the conductive polymer include polymer polymers such as a thiophene derivative monomer, a pyrrole derivative monomer, an aniline derivative monomer, an acetylene derivative monomer, and a phenylene derivative monomer.

  The current collector material used for the positive electrode is preferably aluminum, titanium, nickel, or platinum, which is a material having high electrical conductivity and is inert to battery reaction. Specifically, nickel, stainless steel, titanium, aluminum Among them, aluminum is more preferable because it is inexpensive and has high electrical conductivity. The shape of the current collector is plate-like, but this “plate-like” is not specified in terms of thickness in terms of practical use, and has a form called “foil” having a thickness of about 5 μm to 100 μm. Is also included. Further, a plate-like member such as a mesh, sponge, or fiber, a punching metal, a metal having a three-dimensional concavo-convex pattern formed on both front and back surfaces, an expanded metal, or the like may be employed. The plate-like or foil-like metal on which the three-dimensional concavo-convex pattern is formed is obtained by applying pressure to a metal or ceramic roll provided with a microarray pattern or a line-and-space pattern on the surface, for example. It can be produced by transferring to a metal. In particular, a positive electrode battery that employs a current collector with a three-dimensional uneven pattern formed has a substantial reduction in current density per electrode area during charge / discharge, improved adhesion to the electrode layer, and mechanical strength. As a result, there is an effect of improving the current characteristics of charge / discharge and improving the charge / discharge cycle life.

(Ion conductor 603)
The ionic conductor of the lithium secondary battery of the present invention includes a separator holding an electrolytic solution (an electrolytic solution prepared by dissolving an electrolyte in a solvent), a solid electrolyte, and a solid obtained by gelling the electrolytic solution with a polymer gel. Lithium ion conductors such as hydrolyzed electrolytes, composites of polymer gels and solid electrolytes can be used.

The conductivity of the ionic conductor used for the secondary battery of the present invention is preferably 1 × 10 ⁻³ S / cm or more, preferably 5 × 10 ⁻³ S / cm or more, as a value at 25 ° C. More preferred.

As the electrolyte, for example, lithium ion (Li ⁺⁾ and Lewis acid ion _{^{(BF - 4, PF - 6}} , AsF - 6, ClO - 4, CF 3 SO - 3, BPh - 4 (Ph: phenyl group)) And a mixed salt thereof. It is desirable that the salt be sufficiently dehydrated and deoxygenated by heating under reduced pressure. Furthermore, an electrolyte prepared by dissolving the lithium salt in a molten salt can also be used.

  Examples of the solvent for the electrolyte include acetonitrile, benzonitrile, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethylformamide, tetrahydrofuran, nitrobenzene, dichloroethane, diethoxyethane, 1,2-dimethoxyethane, Chlorobenzene, γ-butyrolactone, dioxolane, sulfolane, nitromethane, dimethyl sulfide, dimethylsulfoxide, methyl formate, 3-methyl-2-oxazolidinone, 2-methyltetrahydrofuran, 3-propyl sydnone, sulfur dioxide, phosphoryl chloride, thionyl chloride, Sulfuryl chloride or a mixture thereof can be used.

  For example, the solvent may be dehydrated with activated alumina, molecular sieve, phosphorus pentoxide, calcium chloride, or the like, or depending on the solvent, distillation may be performed in the presence of an alkali metal in an inert gas for impurity removal and dehydration. Good. The electrolyte concentration of the electrolyte prepared by dissolving the electrolyte in the solvent is preferably in the range of 0.5 to 2.0 mol / liter because of high ionic conductivity.

  Further, in order to suppress the reaction between the electrode and the electrolytic solution, it is also preferable to add a vinyl monomer that easily causes an electrolytic polymerization reaction to the electrolytic solution. By adding vinyl monomer to the electrolyte, a polymerized film is formed on the surface of the silicon alloy particles of the main active material by the charging reaction of the battery, and the lithium or lithium deposited on the surface of the silicon alloy particles is stored in the silicon alloy particles during charging. Is suppressed from reacting with the organic solvent of the electrolytic solution, etc., so that the charge / discharge cycle life can be extended. If the amount of vinyl monomer added to the electrolytic solution is too small, the above effect is not obtained.If the amount is too large, the ionic conductivity of the electrolytic solution is lowered, and the thickness of the polymer film formed during charging is increased, increasing the resistance of the electrode. The amount of vinyl monomer added to the electrolyte is preferably in the range of 1 to 5% by weight.

  Specific examples of the vinyl monomer include styrene, 2-vinylnaphthalene, 2-vinylpyridine, N-vinyl-2-pyrrolidone, divinyl ether, ethyl vinyl ether, vinyl phenyl ether, methyl methacrylate, methyl acrylate, acrylonitrile, And vinylene carbonate. More preferable examples include styrene, 2-vinylnaphthalene, 2-vinylpyridine, N-vinyl-2-pyrrolidone, divinyl ether, ethyl vinyl ether, vinyl phenyl ether, and vinylene carbonate. When the said vinyl monomer has an aromatic group, since affinity with lithium ion is high, it is preferable. Furthermore, N-vinyl-2-pyrrolidone, divinyl ether, ethyl vinyl ether, vinyl phenyl ether, vinylene carbonate, etc., which have high affinity with the solvent of the electrolytic solution, and a vinyl monomer having an aromatic group may be used in combination. More preferred.

  In order to prevent leakage of the electrolytic solution, it is preferable to use a solid electrolyte or a solidified electrolyte. Examples of the solid electrolyte include glass such as an oxide composed of lithium element, silicon element, oxygen element, phosphorus element, or sulfur element, and a polymer complex of an organic polymer having an ether structure. As the solidified electrolyte, a solution obtained by gelling the electrolytic solution with a gelling agent and solidifying it is preferable. As the gelling agent, it is desirable to use a porous material having a large liquid absorption amount, such as a polymer that swells by absorbing the solvent of the electrolytic solution, or silica gel. Examples of the polymer include polyethylene oxide, polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, and vinylidene fluoride-hexafluoropropylene copolymer. Further, the polymer preferably has a crosslinked structure.

  The separator serves to prevent a short circuit between the negative electrode 601 and the positive electrode 603 in the secondary battery. Moreover, it may have a role of holding the electrolytic solution. The separator needs to have many pores through which lithium ions can move and be insoluble and stable in the electrolyte. Therefore, as the separator, for example, glass, polyolefin such as polypropylene or polyethylene, micropore structure such as fluororesin, or non-woven material is preferably used. Moreover, the metal oxide film which has a micropore, or the resin film which compounded the metal oxide can also be used.

[Battery shape and structure]
Specific examples of the secondary battery of the present invention include a flat shape, a cylindrical shape, a rectangular parallelepiped shape, and a sheet shape. Examples of the battery structure include a single layer type, a multilayer type, and a spiral type. Among them, the spiral cylindrical battery has a feature that the electrode area can be increased by winding a separator between the negative electrode and the positive electrode, and a large current can be passed during charging and discharging. Moreover, a rectangular parallelepiped type or sheet type battery has a feature that a storage space of a device configured by storing a plurality of batteries can be used effectively.

  Hereinafter, the battery shape and structure will be described in more detail with reference to FIGS. FIG. 7 is a cross-sectional view of a single-layer flat (coin-type) battery, and FIG. 8 is a cross-sectional view of a spiral cylindrical battery. The lithium secondary battery having the above shape has basically the same configuration as that shown in FIG. 6 and includes a negative electrode, a positive electrode, an ion conductor, a battery housing, and an output terminal.

  7 and 8, 701 and 803 are negative electrodes, 703 and 806 are positive electrodes, 704 and 808 are negative terminals (negative electrode cap or negative electrode can), 705 and 809 are positive terminals (positive electrode can or positive electrode cap), and 702 and 807. Is an ion conductor, 706 and 810 are gaskets, 801 is a negative electrode current collector, 804 is a positive electrode current collector, 811 is an insulating plate, 812 is a negative electrode lead, 813 is a positive electrode lead, and 814 is a safety valve.

  In the flat type (coin type) secondary battery shown in FIG. 7, an ion conductor 702 in which a positive electrode 703 including a positive electrode material layer and a negative electrode 701 including a negative electrode material layer are formed of, for example, a separator holding at least an electrolyte solution. The laminate is accommodated in a positive electrode can 705 as a positive electrode terminal from the positive electrode side, and the negative electrode side is covered with a negative electrode cap 704 as a negative electrode terminal. And the gasket 706 is arrange | positioned in the other part in a positive electrode can.

In the spiral cylindrical secondary battery shown in FIG. 8, a positive electrode 806 having a positive electrode (material) layer 805 formed on a positive electrode current collector 804 and an electrode layer 802 formed on the negative electrode current collector 801 are provided. The negative electrode 803 provided is opposed to, for example, an ion conductor 807 formed of a separator holding at least an electrolytic solution, and forms a multilayer structure of a cylindrical structure wound in multiple layers. The laminate having the cylindrical structure is accommodated in a negative electrode can 808 serving as a negative electrode terminal. Further, a positive electrode cap 809 as a positive electrode terminal is provided on the opening side of the negative electrode can 808, and a gasket 810 is disposed in another part of the negative electrode can. The electrode stack having a cylindrical structure is separated from the positive electrode cap side by an insulating plate 811. The positive electrode 806 is connected to the positive electrode cap 809 via the positive electrode lead 813. The negative electrode 803 is connected to the negative electrode can 808 via the negative electrode lead 812. A safety valve 814 for adjusting the internal pressure inside the battery is provided on the positive electrode cap side. For the negative electrode 803, the above-described electrode structure of the present invention is used.

Below, an example of the assembly method of the battery shown in FIG.7 and FIG.8 is demonstrated.
(1) The separator (702, 807) is sandwiched between the negative electrode (701, 803) and the formed positive electrode (703, 806), and is assembled into the positive electrode can (705) or the negative electrode can (808).
(2) After injecting the electrolytic solution, the negative electrode cap (704) or the positive electrode cap (809) and the gaskets (706, 810) are assembled.
(3) The battery is completed by caulking (2) above.

It is desirable that the above-described lithium battery material preparation and battery assembly be performed in dry air from which moisture has been sufficiently removed or in a dry inert gas.
The member which comprises the above secondary batteries is demonstrated.

(gasket)
As a material of the gasket (706, 810), for example, a fluororesin, a polyolefin resin, a polyamide resin, a polysulfone resin, and various rubbers can be used. As a battery sealing method, a glass sealing tube, an adhesive, welding, soldering, or the like is used in addition to “caulking” using a gasket as shown in FIGS. Further, as the material of the insulating plate (811) in FIG. 8, various organic resin materials and ceramics are used.

(Outside can)
As an outer can of a battery, it is comprised from the positive electrode can or negative electrode can (705,808) of a battery, and a negative electrode cap or a positive electrode cap (704,809). Stainless steel is suitably used as the material for the outer can. As other materials for the outer can, an aluminum alloy, a titanium clad stainless material, a copper clad stainless material, a nickel-plated steel plate and the like are often used.

  Since the positive electrode can (705) in FIG. 7 and the negative electrode can (808) in FIG. 8 also serve as a battery housing (case) and a terminal, the above stainless steel is preferable. However, if the positive electrode can or negative electrode can does not serve as the battery housing and terminal, the material of the battery case is not only stainless steel but also metals such as zinc, plastics such as polypropylene, or metal or glass fiber and plastic. Composite materials can be used.

(safety valve)
The lithium secondary battery is provided with a safety valve as a safety measure when the internal pressure of the battery increases. As the safety valve, for example, rubber, a spring, a metal ball, a rupture foil, or the like can be used.

  In addition, if the inventors can improve the contact resistance between the metal powder particles and the carbon particles in the main active material layer (electrode layer), the electrochemical reaction in the electrode layer in charge and discharge becomes more uniform. In view of the above, the present inventors added a material that plays a role of “linking” to make the connection between completely different metal powders and carbon particles such as graphite uniform, thereby causing more uniform electrochemical reaction in charge and discharge. I did it. As the connecting material, coal tar pitch, carbonized material of coal tar pitch, and nonionic fluorosurfactant were particularly effective.

  The coal tar pitch has affinity for both the metal powder particles having a hydrophilic surface and the carbon particles having a hydrophobic surface, and the coal tar pitch is added to and mixed with the metal powder and the carbon powder. It is considered that the electron conduction between the powder particles and the carbon particles can be improved. The amount of the coal tar pitch added to the main active material layer is preferably 0.1 to 3% by weight. Since the mechanical strength of the coal tar pitch itself is weak, if the amount added is large, the mechanical strength of the main active material layer (electrode layer) is weakened.

  After adding coal tar pitch to the metal powder and the carbon powder, heat treatment is preferably performed in a temperature range of 400 ° C. to 700 ° C. in an inert gas atmosphere. Thereby, carbonization of the coal tar pitch can be performed, and the metal powder particles and the carbon particles can be joined with amorphous carbon obtained by carbonization of the coal tar pitch, and between the metal powder particles and the carbon particles. Can improve electron conduction.

  As the metal powder particles, those that have been made amorphous are preferable because when used in batteries, the charge / discharge cycle life becomes longer. If the heat treatment temperature of the amorphous metal powder particles is higher than 700 ° C., crystallization is promoted and metal oxides are easily formed due to adsorbed oxygen and adsorbed water. .

The metal powder particles may be previously carbonized after being coated with coal tar pitch.
The amount of coal tar pitch added for carbonization is preferably 1 to 10% by weight. A material in which the metal powder particles and the carbon particles are joined with amorphous carbon obtained by carbonization of coal tar pitch because the amount of amorphous carbon generated during carbonization increases when the addition amount of the coal tar pitch is increased. When the negative electrode is formed and the lithium secondary battery is formed, since the irreversible amount of lithium is increased, the initial charge / discharge coulombic efficiency is lowered.

  The coal tar pitch is preferably one having a high softening point and a high carbonization yield. As said softening temperature, the range of 110-500 degreeC is preferable, and the range of 150-350 degreeC is more preferable. The fixed carbon content of the coal tar pitch is preferably 58 to 90% by weight, and more preferably 65 to 90% by weight. The weight reduction rate of the coal tar pitch at 1000 ° C. is preferably 55% or less. Moreover, it is also preferable that the content of mesophase microspheres contained during the heating of the coal tar pitch is 2 to 80%.

  The nonionic fluorosurfactant has a C—F bond and an ether bond or an ester bond, and can improve the wettability of both a substance having a hydrophilic surface and a substance having a lipophilic surface. Therefore, when forming an electrode layer made of a binder that is the metal powder, the carbon powder, and an organic polymer, it is added so that the metal powder particles and the carbon particles are in contact with each other. The bond between the binder and the bond between the carbon particles and the binder can be improved. The amount of the nonionic fluorosurfactant added to form the electrode layer is preferably 0.01 to 0.5% by weight. Since the surfactant is a substance that does not contribute to the charge / discharge reaction of the battery, when the addition amount is increased, the performance of the battery is deteriorated.

  FIG. 9A is a schematic cross-sectional view showing a relationship between a metal powder particle 901 selected from silicon, tin, and an alloy thereof and a binder 903 that interposes a carbon particle 902. By using the coal powder 901 having a hydrophilic surface and the carbon particles 902 having an oleophilic surface as a connecting material 903 that is easy to bond to the surfaces of both particles, a coal tar pitch or a fluorosurfactant is used. As a result, the metal powder particles and the carbon particles can be easily joined to facilitate electronic conduction. When these materials are used as a negative electrode material for a lithium secondary battery, the charge / discharge coulombic efficiency is increased, The discharge cycle life can be extended, the performance of the original metal material capable of storing high lithium can be utilized, and a high capacity battery can be achieved. When the coal tar pitch and the fluorosurfactant are used simultaneously, a higher effect can be obtained.

  FIG. 9B shows a schematic cross-sectional structure of particles obtained by integrating and compounding metal powder particles 901 and carbon particles 902 selected from silicon, tin, and alloys thereof with a connecting material 903. After mixing the metal powder particles and the carbon particles with a carbonizable material such as coal tar pitch, carbonizing the carbonizable material such as coal tar pitch in an inert gas such as nitrogen or argon gas, The metal powder particles and the carbon particles integrated and composited with carbide are obtained. Electronic conduction between the metal powder particles and the carbon particles is facilitated through the carbide. As a result, when these materials are used as the negative electrode material of a lithium secondary battery, the charge / discharge coulombic efficiency is increased, the charge / discharge cycle life is extended, and the performance of the original metal material capable of highly absorbing lithium is utilized. A capacity battery will be achieved.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Preparation of electrode material)
First, a negative electrode material was prepared.

Example 1
(1) Preparation of negative electrode main active material Silicon, tin, and copper were mixed in an atomic ratio of 82.9: 16.6: 0.5 (weight ratio of 65: 30: 5) and melted in an argon gas atmosphere. After forming the molten metal, Si—Sn—Cu alloy powder was obtained by a water atomization method in which the molten metal was injected with high-pressure water. Next, the obtained Si—Sn—Cu alloy powder was pulverized in isopropyl alcohol by a media mill apparatus using zirconia balls to obtain a fine Si—Sn—Cu alloy powder having an average particle size of 0.3 μm. It was. Next, 15% by weight of graphite powder was added to the obtained Si—Sn—Cu alloy fine powder, and the resultant was pulverized for 10 hours in an argon gas atmosphere using an attritor apparatus in an argon gas atmosphere to compound carbon. An electrode material of Si-Sn-Cu alloy fine powder was obtained. The obtained Si—Sn—Cu alloy-carbon composite powder was found to be an amorphized alloy powder having a crystallite of 30 nm from analysis by an X-ray diffractometer.

(2) Production of negative electrode Si-Sn-Cu alloy-carbon composite powder as the main active material obtained in (1) above, pseudo-spherical artificial graphite powder having an average particle size of 27 μm as a support material, conductive auxiliary After mixing the graphite powder having an average particle diameter of 5 μm and the solid content of the N-methyl-2-pyrrolidone solution of the polyamide precursor (polyamic acid) in a weight ratio of 74: 10: 5: 11, the solvent N-methyl-2-pyrrolidone was added and kneaded to prepare a slurry, and the obtained slurry was applied to a copper foil having a 10-point average height Rz = 0.6 μm and a thickness of 15 μm with a coater device. . Next, heat treatment is performed at 150 ° C. for 30 minutes, further heat treatment is performed at 220 ° C. for 1 hour, and drying is performed at 200 ° C. under reduced pressure to produce a negative electrode structure having an average thickness of 20 μm and a negative electrode layer density of 1.3 g / cm ^3. did.
The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.

(3) Preparation of positive electrode After mixing 5% by weight of graphite powder and 5% by weight of polyvinylidene fluoride powder with lithium-cobalt oxide LiCoO ₂ , N-methyl-2-pyrrolidone was added to prepare a slurry.

The obtained positive electrode material slurry was applied and dried on a current collector of aluminum foil having a thickness of 20 microns, and then the thickness of the positive electrode active material layer on one side was adjusted to 90 μm and the density to 3.3 g / cm ³ with a roll press. Further, aluminum leads were connected with an ultrasonic welder and dried under reduced pressure at 150 ° C. to produce a positive electrode.

(4) Preparation Procedure of Electrolytic Solution A solvent was prepared by mixing ethylene carbonate and diethyl carbonate from which water was sufficiently removed at a volume ratio of 3: 7.
A solution obtained by dissolving 1M (mol / liter) of lithium hexafluorophosphate (LiPF ₆ ) in the obtained solvent was used as an electrolytic solution.

(5) Separator A polyethylene microporous film having a thickness of 16 μm was used as a separator.

(6) Battery assembly The assembly was all performed in a dry atmosphere in which moisture having a dew point of -50 ° C or lower was controlled.
A separator is sandwiched between the negative electrode and the positive electrode prepared in the above operation, and the negative electrode / separator / positive electrode is inserted into a battery case in which a polyethylene / aluminum foil / nylon-structured aluminum laminate film is pocketed, and an electrolyte solution is injected into the electrode. The lead was taken out and heat sealed to produce a battery for evaluation of positive electrode capacity regulation. The outer side of the aluminum laminate film was a nylon film, and the inner side was a polyethylene film.

Example 2
In Example 1, the negative electrode current collector was changed to a copper foil having a 10-point average height Rz = 2.1 μm and a thickness of 15 μm as a negative electrode current collector. Otherwise, an evaluation battery was fabricated in the same manner as in Example 1.

Example 3
A battery for evaluation test was produced by replacing the negative electrode in Example 1 with the negative electrode produced by the following operation.

(1) Preparation of negative electrode First, a solution obtained by dispersing 10% by weight of poly-2-ethylthiophene in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7 was used as a polyamide precursor (polyamic). Acid) in an N-methyl-2-pyrrolidone solution and mixed so that poly-2-ethylthiophene is 10% by weight of the solid content of the polyamide precursor (polyamic acid).

Next, Si—Sn—Cu alloy-carbon composite powder as the main active material, artificial artificial graphite powder having an average particle diameter of 22 μm, graphite powder having an average particle diameter of 5 μm of conductive auxiliary material, poly-2-ethylthiophene-added polyamide A N-methyl-2-pyrrolidone solution of a precursor (polyamic acid) was mixed. At this time, the weight ratio of the solid content of the Si—Sn—Cu alloy-carbon composite powder, the artificial graphite powder having an average particle diameter of 22 μm, the graphite powder having an average particle diameter of 5 μm, and the polyamide precursor (polyamic acid) is 74:10: 5:11. Next, N-methyl-2-pyrrolidone as a solvent was added to the above mixture, kneaded to prepare a slurry, and the obtained slurry was applied to a copper foil having a 10-point average height Rz = 0.6 μm and a thickness of 15 μm. And coated with a coater device. Next, heat treatment was performed at 150 ° C. for 30 minutes, further heat treatment was performed at 220 ° C. for 1 hour, and drying was performed at 200 ° C. under reduced pressure to produce a negative electrode structure having a negative electrode layer density of 1.3 g / cm ³ . .

  The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.

Example 4
An evaluation test battery was prepared by replacing the negative electrode in Example 1 with the negative electrode prepared by the following operation.

(1) Preparation of negative electrode After forming the buffer layer on copper foil with the following operation, the main active material layer was formed.
First, the solid content of the graphite powder having an average particle size of 5 μm and the polyamide precursor (polyamic acid) added with poly-2-ethylthiophene prepared in the same manner as in Example 3 is 93: 7 by weight. Then, N-methyl-2-pyrrolidone is added as a solvent and kneaded to prepare a slurry. The obtained slurry is applied to a copper foil having a 10-point average height Rz = 0.6 μm and a thickness of 15 μm. It was coated with an apparatus and dried at 150 ° C. to form a buffer layer of the present invention with a thickness of 5 μm and a density of 1.2 g / cm ³ . The reason why poly 2-ethylthiophene, which is a conductive polymer, was added to the binder polyamide precursor (polyamic acid) is to impart electron conductivity. Because the particles of graphite powder are small, the binder material cannot be reduced, and the electron conductivity is low, so in the charge / discharge test at high current density, compared to the case of low current density, This is because the charge / discharge efficiency decreases.

Next, Si—Sn—Cu alloy-carbon composite powder as the main active material, pseudo-spherical artificial graphite powder with an average particle size of 22 μm, graphite powder with an average particle size of 5 μm of conductive auxiliary material, polyamide precursor (polyamic acid) The N-methyl-2-pyrrolidone solution was mixed so that the solid content in the weight ratio was 74: 10: 5: 11, then N-methyl-2-pyrrolidone was added as a solvent and kneaded to prepare a slurry. The prepared slurry was applied to the copper foil on which the buffer layer was formed with a coater device. Next, heat treatment was performed at 150 ° C. for 30 minutes, further heat treatment was performed at 220 ° C. for 1 hour, and drying was performed at 200 ° C. under reduced pressure to produce a negative electrode structure having a negative electrode layer density of 1.3 g / cm ³ . .

  The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.

Example 5
A battery for evaluation test was produced by replacing the negative electrode in Example 1 with the negative electrode produced by the following operation.

(1) Production of negative electrode On the electrode structure produced in Example 1, the coating layer of the present invention was formed by the following operation.
First, the solid content of the graphite powder having an average particle size of 5 μm and the polyamide precursor (polyamic acid) added with poly-2-ethylthiophene prepared in the same manner as in Example 3 is 93: 7 by weight. After mixing, N-methyl-2-pyrrolidone as a solvent was added and kneaded to prepare a slurry.

The obtained slurry was applied to the electrode structure obtained in Example 2 with a coater, heat-treated at 150 ° C. for 30 minutes, further heat-treated at 220 ° C. for 1 hour, and dried at 200 ° C. under reduced pressure. The coating layer of the present invention was formed with a thickness of 5 μm and a density of 1.0 g / cm ³ .

  The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.

Example 6
The negative electrode buffer layer of Example 4 (1) was formed by the following operation. That is, the solid content of a solution of a graphite precursor (polyamic acid) added with graphite powder having an average particle diameter of 5 μm, tungsten oxide WO _{3 having} an average particle diameter of 5 μm, and poly-2-ethylthiophene prepared in the same manner as in Example 3 Then, N-methyl-2-pyrrolidone was added as a solvent, and kneaded to prepare a slurry. The obtained slurry was subjected to ten-point average height Rz. = Coating was applied to a copper foil having a thickness of 0.6 μm and a thickness of 15 μm using a coater, and dried at 150 ° C. to form a buffer layer of the present invention with a thickness of 5 μm and a density of 1.3 g / cm ³ .
Subsequent operations were carried out in the same manner as in Example 4 to produce evaluation test batteries.

Example 7
In Example 6, a main active material layer was formed on the buffer layer, heat-treated at 150 ° C. for 30 minutes, and further subjected to heat treatment at 220 ° C. for 1 hour to form a surface coating layer by the following operation. Graphite powder with an average particle diameter of 5 μm, lithium-titanium oxide Li _4/3 Ti _5/3 O ₄ with an average particle diameter of 4 μm prepared from titanium oxide and lithium carbonate as raw materials, in the same manner as in Example 3. After mixing so that the solid content of the prepared polyamide precursor (polyamic acid) solution to which poly-2-ethylthiophene was added was 60: 33: 7 by weight, N-methyl-2-pyrrolidone was used as a solvent. Add and knead to prepare a slurry. The obtained slurry was applied to the electrode structure obtained in Example 2 with a coater, heat-treated at 150 ° C. for 30 minutes, further heat-treated at 220 ° C. for 1 hour, and dried at 200 ° C. under reduced pressure. The coating layer of the present invention was formed with a thickness of 5 μm and a density of 1.1 g / cm ³ to produce a three-layered negative electrode structure.
Thereafter, an evaluation test battery was produced in the same manner as in Example 6.

Example 8
In Example 1, as an electrolyte, 100 parts of a 1M (mol / liter) ethylene carbonate / diethyl carbonate solution of lithium hexafluorophosphate (LiPF ₆ ) of Example 1 by weight was added with 2 parts of styrene and weight. A battery for evaluation test was produced in the same manner as in Example 1 using an electrolytic solution to which 2 parts of vinylene carbonate was added.

Example 9
In Example 2, the binder of Example 3 in which a conductive polymer was added to the binder of the negative electrode was used, and the electrolytic solution containing styrene and vinylene carbonate added in Example 8 was used for the evaluation test. A battery was produced.

Example 10
(1) Preparation of Main Active Material for Negative Electrode The Si—Sn—Cu alloy-carbon composite powder obtained by the preparation of the main active material for negative electrode of Example 1 (melting point: 150 ° C., carbonized at 700 ° C. After coating with coal tar pitch, hold in nitrogen gas atmosphere at 600 ° C. for 1 hour, then heat-treat at 700 ° C. for 1 hour to carbonize the coal tar pitch, and carbon (5% by weight) coated Si—Sn -Cu alloy-carbon composite powder was prepared.

(2) Production of Negative Electrode The carbon-coated Si—Sn—Cu alloy-carbon composite powder obtained in (1) above, which is the main active material, was used as the Si—Sn—Cu alloy in (2) of Example 1. -It replaced with carbon composite powder and the negative electrode was produced by operation similar to (2) of Example 1. FIG.
Next, an evaluation battery was produced in the same manner as in Example 1.

Example 11
In the production of the negative electrode in Example 3, a copper foil having a 10-point average height Rz = 2.1 μm and a thickness of 15 μm was used for the copper foil of the current collector, and the electrolytic solution containing styrene and vinylene carbonate added in Example 8 was used as the electrolytic solution. An evaluation battery was prepared in the same manner as in Example 3 except that the liquid was used.

Reference example 1
In the production of the electrode structure for negative electrode of Example 1, a flat graphite powder (substantially disc-shaped graphite powder having a diameter of about 5 μm and a thickness of about 1 μm) is used instead of the artificial artificial graphite powder having an average particle diameter of 22 μm. The electrode structure for negative electrodes was produced using. Thereafter, an evaluation battery was prepared in the same manner as in Example 1.

Comparative Example 1
A negative electrode structure was prepared by the following operation.
Pseudo-spherical artificial graphite powder having an average particle size of 22 μm as a main active material and a solid content of an N-methyl-2-pyrrolidone solution of a polyamide precursor (polyamic acid) were mixed at a weight ratio of 89:11. Then, N-methyl-2-pyrrolidone was added as a solvent, kneaded to prepare a slurry, and the resulting slurry was applied to a copper foil having a 10-point average height Rz = 0.6 μm and a thickness of 15 μm using a coater device. Coated. Next, heat treatment was performed at 150 ° C. for 30 minutes, heat treatment was further performed at 220 ° C. for 1 hour, and drying was performed at 200 ° C. under reduced pressure to produce a negative electrode structure having a negative electrode layer thickness of 1.4 g / cm ³ . .

The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.
A battery for evaluation test was produced in the same manner as in Example 1 except that the negative electrode was produced.

[Battery evaluation]
Based on the capacity of the positive electrode, charge to 4.2V at a constant current of 1C rate, and when the battery voltage reaches 4.2V, switch to 4.2V constant voltage charging and charge at constant current-constant voltage The test of discharging to a battery voltage of 3.0 V at a constant current of 1 C rate was repeated 100 times. In addition, a pause of 30 minutes was provided during the transition from charging to discharging and from discharging to charging. The ratio of the first discharge amount to the first discharge charge amount (charge / discharge efficiency), the 100th discharge amount and the charge / discharge efficiency are evaluated, and each value of Reference Example 1 is set to 1.00. And evaluated. The evaluation results are summarized in Table 1.

  However, since the battery for evaluation test of Comparative Example 1 has a low storage capacity of the negative electrode, the amount of charge electricity was regulated so as not to exceed the amount of electricity of the negative electrode capacity calculated in advance.

Note that the amount of electricity discharged per electrode layer weight (excluding the weight of the current collector) in Example 1 was a maximum of 1300 mAh / g.
According to the results in Table 1, both the first discharge amount and the charge / discharge efficiency, and the 100th discharge amount and the charge / discharge efficiency are superior in each example as compared to Reference Example 1. all right.

  Even when compared with the battery of Comparative Example 1 using a graphite material as the negative electrode material, the first charge amount and the 100th discharge amount are inferior in the first charge / discharge efficiency. It has been found that the batteries of the inventive examples are excellent.

  Next, in order to increase the battery voltage during battery discharge and to improve safety, a positive electrode material was changed to produce an evaluation test battery.

Example 12
An evaluation test battery was produced in the same manner as in Example 11 except that the positive electrode produced in the following procedure was used as the positive electrode in Example 11.

(3) Preparation of positive electrode 35 wt% spinel type lithium manganese oxide LiMn _1.5 Ni _0.5 O ₄ and 55 wt% zirconium-added lithium cobalt oxide LiCo _0.96 Zr _0.04 O ₂ with 5 wt% graphite powder After mixing 5% by weight of poly (vinylidene fluoride) powder, N-methyl-2-pyrrolidone was added to prepare a slurry.

The obtained positive electrode material slurry was applied and dried on a current collector of aluminum foil having a thickness of 20 microns, and then the thickness of the positive electrode active material layer on one side was adjusted to 90 μm and the density to 3.3 g / cm ³ with a roll press. Further, aluminum leads were connected with an ultrasonic welder and dried under reduced pressure at 150 ° C. to produce a positive electrode.

Example 13
An evaluation test battery was produced in the same manner as in Example 11 except that the positive electrode produced in the following procedure was used as the positive electrode in Example 11.

(1) Preparation of positive electrode 45 wt% LiCo _0.33 Ni _0.34 Mn _0.33 O ₂ , 45 wt% zirconium-added lithium cobalt oxide LiCo _0.96 Zr _0.04 O ₂ , 5 wt% graphite powder and 5 wt% polyfluoride After the viridinidide powder was mixed, N-methyl-2-pyrrolidone was added to prepare a slurry.

The obtained positive electrode material slurry was applied and dried on a current collector of aluminum foil having a thickness of 20 microns, and then the thickness of the positive electrode active material layer on one side was adjusted to 90 μm and the density to 3.3 g / cm ³ with a roll press. Further, aluminum leads were connected with an ultrasonic welder and dried under reduced pressure at 150 ° C. to produce a positive electrode.

Example 14
An evaluation test battery was produced in the same manner as in Example 11 except that the positive electrode produced in the following procedure was used as the positive electrode in Example 11.

(1) Fabrication of positive electrode 40% by weight of spinel type lithium manganese oxide based LiMn _1.5 Ni _0.5 O ₄ and 50% by weight of LiNi _0.34 Co _0.33 Mn _0.33 O ₂ , 5% by weight of graphite powder and 5% by weight of polyfluoride After the viridinidide powder was mixed, N-methyl-2-pyrrolidone was added to prepare a slurry.

The obtained positive electrode material slurry was applied and dried on a current collector of aluminum foil having a thickness of 20 microns, and then the thickness of the positive electrode active material layer on one side was adjusted to 90 μm and the density to 3.3 g / cm ³ with a roll press. Further, aluminum leads were connected with an ultrasonic welder and dried under reduced pressure at 150 ° C. to produce a positive electrode.

Example 15
An evaluation test battery was produced in the same manner as in Example 11 except that the positive electrode produced in the following procedure was used as the positive electrode in Example 11.

(1) Fabrication of positive electrode 5% by weight on 30% by weight of spinel type lithium manganese oxide-based LiMn _1.5 Ni _0.5 O ₄ and 10% by weight of LiMn ₂ O ₄ and 50% by weight of LiNi _0.34 Co _0.33 Mn _0.33 O ₂ The graphite powder and 5 wt% poly (vinylidene fluoride) powder were mixed, and then N-methyl-2-pyrrolidone was added to prepare a slurry.

The obtained positive electrode material slurry was applied and dried on a current collector of aluminum foil having a thickness of 20 microns, and then the thickness of the positive electrode active material layer on one side was adjusted to 90 μm and the density to 3.3 g / cm ³ with a roll press. Further, aluminum leads were connected with an ultrasonic welder and dried under reduced pressure at 150 ° C. to produce a positive electrode.

[Battery evaluation]
The discharge capacity and average discharge voltage of the batteries of Examples 12 to 15 were evaluated by comparing with the batteries obtained in Example 11 and Comparative Example 1 by the following methods.

  Based on the capacity of the positive electrode in Example 11, the battery is charged to 4.6 V at a constant current of 1 C rate, and when the battery voltage reaches 4.6 V, it is switched to 4.6 V constant voltage charging and constant current-constant The test was repeated by charging at a voltage and discharging to a battery voltage of 2.75 V at a constant current of 0.2 C rate. In addition, a pause of 30 minutes was provided during the transition from charging to discharging and from discharging to charging. The fifth discharge amount and the fifth average discharge voltage were determined, and each value of Example 11 was normalized and evaluated. The evaluation results are summarized in Table 2.

  From the results in Table 2 above, by appropriately mixing lithium-manganese-nickel oxide, lithium-cobalt-nickel-manganese oxide, lithium-cobalt oxide, etc., the discharge voltage can be increased and the discharge amount can be increased. I understood.

[Safety evaluation test]
The safety of the batteries of Examples 12 to 15 was evaluated by the following method in comparison with Example 11. Based on the capacity of the positive electrode in Example 11, the battery was charged to 5.0 V with a constant current of 1 C rate. Each battery was then evaluated by Accelerating Rate Calibration (ARC). As a result, the heat generation start temperature was the fastest in the battery of Example 11, and the magnitude of the heat generation rate in the vicinity of 100 ° C. was in the order of Example 11, Example 13, Example 12, Example 14, and Example. The order was as in Example 15. It has been found that the safety is improved by including the manganese compound in the positive electrode.

  As described above, from the results of Table 2 and the safety evaluation test, in the lithium secondary battery of the negative electrode formed from the negative electrode material selected from silicon, tin, or an alloy containing any of these elements, an appropriate combination of the positive electrode materials can be used. It was found that a safe battery with high energy density can be obtained.

Example 16
An evaluation test battery was produced in the same manner as in Example 11 except that the positive electrode produced in the following procedure was used as the positive electrode in Example 11.

(1) Production of positive electrode LiCo _0.33 Ni _0.34 Mn _0.33 O ₂ and zirconium-added lithium cobalt oxide LiCo _0.96 Zr _0.04 O ₂ were mixed at a weight ratio of 50:50, and the melting point was 100 parts by weight (melting point). 3 parts of coal tar pitch (carbonized at 350 ° C. and 700 ° C.) were mixed, treated in argon gas atmosphere at 400 ° C. for 1 hour, then treated at 700 ° C. for 1 hour, and coated with carbide of coal tar pitch. LiCo _0.33 Ni _0.34 Mn _0.33 O ₂ and LiCo _0.96 Zr _0.04 O ₂ were obtained. The content of coal tar pitch carbide in the obtained product was 1% by weight.

Next, after mixing LiCo _0.33 Ni _0.34 Mn _0.33 O ₄ , LiCo _0.96 Zr _0.04 O ₂ , 5 wt% graphite powder and 5 wt% poly (vinylidene fluoride) powder coated with 90 wt% carbonized coal tar pitch N-methyl-2-pyrrolidone was added to prepare a slurry.

The obtained positive electrode material slurry was applied and dried on a current collector of aluminum foil having a thickness of 20 microns, and then the thickness of the positive electrode active material layer on one side was adjusted to 90 μm and the density to 3.3 g / cm ³ with a roll press. Further, aluminum leads were connected with an ultrasonic welder and dried under reduced pressure at 150 ° C. to produce a positive electrode.

The high rate discharge performance of the battery obtained in Example 16 was evaluated by comparing with the battery obtained in Example 11 by the following method.
Based on the capacity of the positive electrode in Example 11, the battery is charged to 4.6 V at a constant current of 1 C rate, and when the battery voltage reaches 4.6 V, it is switched to 4.6 V constant voltage charging and constant current-constant The test of charging at a voltage and discharging to a battery voltage of 2.75 V at a constant current of 2.0 C was repeated, and the fifth discharge amount was determined. As a result, the discharge amount of the battery of Example 16 was 1.2 times that of the battery of Example 11. From this, it was found that carbonization of the coal tar pitch to coat the positive electrode active material particles improves the performance in efficient discharge with increased current density.

Reference example 2
(1) Preparation of silicon alloy used as main material of negative electrode layer The metal powder used for forming the negative electrode layer was obtained by using a metal silicon powder in isopropyl alcohol using a media mill of zirconia beads and having an average particle size of 0.2 μm. To obtain a fine silicon powder.

  To the obtained silicon fine powder, tin powder, copper powder, boron powder, and graphite powder were mixed at a weight ratio of 58.5: 27.0: 4.5: 1.0: 9.0, A stainless steel ball was pulverized for 24 hours in an argon gas atmosphere using an attritor apparatus to obtain an electrode material of Si—Sn—Cu—B alloy fine powder combined with carbon.

(2) Production of negative electrode Si-Sn-Cu alloy-carbon composite powder as the main active material obtained in (1) above, pseudo-spherical artificial graphite powder having an average particle diameter of 27 μm, and average particle of conductive auxiliary material After mixing the graphite powder having a diameter of 5 μm and the solid content of the polyamide-imide N-methyl-2-pyrrolidone solution in a weight ratio of 74: 10: 5: 11, N-methyl-2-pyrrolidone was used as a solvent. The slurry was added and kneaded to prepare a slurry, and the obtained slurry was coated on a copper foil having a 10-point average height Rz = 0.6 μm and a thickness of 15 μm with a coater device. Subsequently, it heat-processed for 30 minutes at 150 degreeC, and it dried under reduced pressure at 200 degreeC, and produced the electrode structure for negative electrodes with a density of 1.3 g / cm < ³ > of 20 micrometers of average thickness negative electrode layers.

  The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.

(3) Preparation of positive electrode After mixing 5% by weight of graphite powder and 5% by weight of polyvinylidene fluoride powder with lithium-cobalt oxide LiCoO ₂ , N-methyl-2-pyrrolidone was added to prepare a slurry.

The obtained positive electrode material slurry was applied and dried on a current collector of aluminum foil having a thickness of 20 microns, and then the thickness of the positive electrode active material layer on one side was adjusted to 90 μm and the density to 3.3 g / cm ³ with a roll press. Further, aluminum leads were connected with an ultrasonic welder and dried under reduced pressure at 150 ° C. to produce a positive electrode.

(4) Preparation Procedure of Electrolytic Solution A solvent was prepared by mixing ethylene carbonate and diethyl carbonate from which water was sufficiently removed at a volume ratio of 3: 7.

A solution obtained by dissolving 1M (mol / liter) of lithium hexafluorophosphate (LiPF ₆ ) in the obtained solvent was used as an electrolytic solution.
(5) Separator A polyethylene microporous film having a thickness of 16 microns was used as a separator.

(6) Battery assembly The assembly was all performed in a dry atmosphere in which moisture having a dew point of -50 ° C or lower was controlled.
A separator is sandwiched between the negative electrode and the positive electrode prepared in the above operation, and the negative electrode / separator / positive electrode is inserted into a battery case in which a polyethylene / aluminum foil / nylon-structured aluminum laminate film is pocketed, and an electrolyte solution is injected into the electrode. The lead was taken out and heat sealed to produce a battery for evaluation of positive electrode capacity regulation. The outer side of the aluminum laminate film was a nylon film, and the inner side was a polyethylene film.

Example 17
(1) Preparation of main material of negative electrode layer Si-Sn-Cu alloy-carbon composite powder obtained in (1) of Reference Example 2, pseudo-spherical artificial graphite powder having an average particle size of 27 μm, conductive auxiliary material Graphite powder having an average particle diameter of 5 μm and a coal tar pitch MCP-350 (softening temperature 350 ° C., fixed carbon 88%, 1000 ° C., weight loss 16%) manufactured by JFE Chemical Co., Ltd. in a weight ratio of 74:10 : 5: 1 ratio, add isopropyl alcohol, mix with an agate vessel and ball using a planetary ball mill, dry the resulting mixture at 80 ° C, alloy-graphite-coal Tar pitch composite powder was obtained.

(2) Production of Negative Electrode The solid content of the N-methyl-2-pyrrolidone solution of alloy-graphite-coal tar pitch composite powder and polyamideimide obtained in (1) above is 89:11 by weight ratio. Then, N-methyl-2-pyrrolidone is added as a solvent, kneaded to prepare a slurry, and the obtained slurry is made into a copper foil having a 10-point average height Rz = 0.6 μm and a thickness of 15 μm. The coater was used for coating. Subsequently, it heat-processed for 30 minutes at 150 degreeC, and it dried under reduced pressure at 200 degreeC, and produced the electrode structure for negative electrodes with a density of 1.3 g / cm < ³ > of 20 micrometers of average thickness negative electrode layers.

The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.
A battery for evaluation was produced in the same manner as in Reference Example 2 below.

Example 18
(1) Preparation of main material of negative electrode layer Si-Sn-Cu alloy-carbon composite powder obtained in (1) of Reference Example 2, pseudo-spherical artificial graphite powder having an average particle size of 27 μm, conductive auxiliary material A graphite powder having an average particle size of 5 μm, a coal tar pitch MCP-350 manufactured by JFE Chemical Co., Ltd. (softening temperature 350 ° C., fixed carbon 88%, weight loss starting temperature 420 ° C., 1000 ° C. weight loss 16%) Each is mixed at a weight ratio of 74: 10: 5: 10, isopropyl alcohol is added, mixed with an agate vessel and ball using a planetary ball mill, and the resulting mixture is dried at 80 ° C. Thus, an alloy-coal tar pitch-graphite composite powder was obtained. The obtained composite powder was subjected to heat treatment at 550 ° C. for 1 hour under N 2 gas flow to carbonize the coal tar pitch to amorphous carbon to obtain an alloy-carbonized carbon tar pitch-graphite composite powder.

(2) Production of Negative Electrode The alloy-coal tartar pitch-graphite composite powder obtained in (1) above and the solid content of the N-methyl-2-pyrrolidone solution of polyamideimide were 89:11 in weight ratio. Then, N-methyl-2-pyrrolidone is added as a solvent, kneaded to prepare a slurry, and the obtained slurry is a 10-point average height Rz = 0.6 μm and a thickness of 15 μm copper. The foil was coated with a coater device. Subsequently, it heat-processed for 30 minutes at 150 degreeC, and it dried under reduced pressure at 200 degreeC, and produced the electrode structure for negative electrodes with a density of 1.3 g / cm < ³ > of 20 micrometers of average thickness negative electrode layers.

The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.
A battery for evaluation was produced in the same manner as in Reference Example 2 below.

Example 19
(1) Preparation of main material of negative electrode layer Si—Sn—Cu alloy-carbon composite powder obtained in (1) of Reference Example 2 (softening temperature 350 ° C., fixed carbon 88%, weight loss starting temperature Is a coal tar pitch MCP-350 manufactured by JFE Chemical Co., Ltd. and 3M fluorine-based aliphatic polymer ester surfactant Novec FC-4430, respectively. Mix at a ratio of 95: 5: 0.5, add acetone, mix in an agate vessel and a planetary ball mill using a ball, dry the resulting mixture at 50 ° C., and coat with coal tar pitch An alloy-carbon composite powder was obtained. The obtained alloy powder was heat-treated at 700 ° C. for 1 hour under an Ar gas flow to carbonize the coal tar pitch to obtain an amorphous carbon-coated alloy-carbon composite powder.

(2) Production of negative electrode Amorphous carbon-coated alloy-carbon composite powder, pseudo-spherical artificial graphite powder having an average particle size of 27 μm, and graphite powder having an average particle size of 5 μm of conductive auxiliary material obtained in (1) above Surfactant Novec FC-4430, a fluorine-based aliphatic polymer ester manufactured by 3M, was mixed in a weight ratio of 74: 10: 5: 0.1, respectively, and N-methyl-2- Pyrrolidone was added and further mixed. Next, the solid content of the polyamide-imide N-methyl-2-pyrrolidone solution was added to the amorphous carbon-coated alloy-carbon composite powder 74 in a weight ratio of 11, and kneaded to obtain a slurry. The slurry obtained was coated on a copper foil having a 10-point average height Rz = 0.6 μm and a thickness of 15 μm using a coater device. Subsequently, it heat-processed for 30 minutes at 150 degreeC, and it dried under reduced pressure at 200 degreeC, and produced the electrode structure for negative electrodes with a density of 1.3 g / cm < ³ > of 20 micrometers of average thickness negative electrode layers.

The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.
A battery for evaluation was produced in the same manner as in Reference Example 2 below.

Example 20
In the preparation of the negative electrode of (2) in Reference Example 2 above,
Si-Sn-Cu alloy-carbon composite powder obtained in (1) above, pseudo-spherical artificial graphite powder having an average particle diameter of 27 μm, graphite powder having an average particle diameter of 5 μm of conductive auxiliary material, fluorine system manufactured by 3M Company Surfactant Novec FC-4430, which is an aliphatic polymer ester, was mixed in a weight ratio of 74: 10: 5: 0.1, and N-methyl-2-pyrrolidone was added as a solvent. Mixed. Then, the solid content of the polyamide-imide N-methyl-2-pyrrolidone solution was added to the Si-Sn-Cu alloy-carbon composite powder 74 in a weight ratio of 11, and kneaded to prepare a slurry. The slurry obtained was coated on a copper foil having a 10-point average height Rz = 0.6 μm and a thickness of 15 μm using a coater device. Subsequently, it heat-processed for 30 minutes at 150 degreeC, and it dried under reduced pressure at 200 degreeC, and produced the electrode structure for negative electrodes with a density of 1.3 g / cm < ³ > of 20 micrometers of average thickness negative electrode layers.

The obtained electrode structure was cut into a predetermined size, and a nickel ribbon lead was connected to the electrode by spot welding to obtain a negative electrode.
Others were the same as in Reference Example 1, and a battery for evaluation was produced.

[Battery evaluation]
Based on the capacity of the positive electrode, charge to 4.2V at a constant current of 1C rate, and when the battery voltage reaches 4.2V, switch to 4.2V constant voltage charging and charge at constant current-constant voltage The test of discharging to a battery voltage of 2.5 V at a constant current of 1 C rate was repeated 100 times. In addition, a pause of 30 minutes was provided during the transition from charging to discharging and from discharging to charging. The 100th discharge amount with respect to the first discharge amount was evaluated as a capacity maintenance rate, and the capacity maintenance rate value of Reference Example 2 was normalized as 1.0 and evaluated. The evaluation results are summarized in Table 3.

  As described above, according to the present invention, it is possible to provide a lithium secondary battery having a high capacity, a high energy density, and a repeated life.

It is the schematic cross section of an example of the electrode structure of this invention, and explanatory drawing explaining the state at the time of charge. It is a schematic cross section of an example of the electrode structure of the present invention. It is a schematic cross section of an example of the electrode structure of the present invention. It is a schematic cross section of an example of the electrode structure of the present invention. It is the schematic cross section of an example of the electrode structure which compounded flat graphite, and the explanatory view explaining the state at the time of charge. It is a conceptual diagram which shows typically the cross section of one embodiment of the secondary battery (lithium secondary battery) of this invention. It is sectional drawing of a single layer type flat (coin type) battery. It is sectional drawing of a spiral type cylindrical battery. It is a schematic image figure of an example by which the metal powder particle and carbon particle of the electrode structure of this invention are connected by the connection material.

Explanation of symbols

100, 200, 300, 400, 500 Current collector 101, 201, 301, 401, 501 Si, Sn or their alloy particles 101 ′, 501 ′ Si, Sn or their alloy particles expanded by alloying with Li 102, 202, 302, 402, 503 Conductive auxiliary material particles 103, 203, 207, 303, 307, 403, 407, 410, 504 Binder 104, 204, 304, 404 Support material particles 105, 205, 305, 405 , 505 Main active material layer 106, 209, 309, 412, 506 Electrode structure 206, 406 Electroconductive particle 208, 408 Buffer layer 306, 409 Ion conductive / electroconductive particle 308, 411 Cover layer 413 Surface roughening Electric conductor 502 Flat conductive auxiliary material particles 601, 701, 803 Negative electrode 602, 70 , 606 battery jar 806 positive 603,702,807 ion conductor 604 negative terminal 605 positive terminal (cell housing)
704 Negative electrode cap 705 Positive electrode can 706, 810 Gasket 801 Negative electrode current collector 802 Negative electrode active material layer 804 Positive electrode current collector 805 Positive electrode active material layer 808 Negative electrode can (negative electrode terminal)
811 Insulating plate 812 Negative electrode lead 813 Positive electrode lead 814 Safety valve 901 Metal powder particle 902 Carbon particle 903 Binder

Claims (34)

Main active material layer and current collector comprising metal powder selected from silicon, tin, or an alloy containing any of these elements and capable of storing and releasing lithium by an electrochemical reaction and an organic polymer binder In an electrode structure composed of a body,
(A) In addition to the metal powder, the main active material layer includes at least a support material powder that supports electronic conduction of the main active material layer, and the shape of the powder of the support material is spherical, pseudo-spherical, or columnar. The average particle size is 0.3 to 1.35 times the average thickness of the main active material layer, and the support material is a transition metal oxide selected from graphite, TiO ₂ , MoO ₃ , and WO ₃ , Li and One or more selected from the group consisting of Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and metals selected from these alloys that do not form alloys electrochemically An electrode structure for a lithium secondary battery, characterized by being a material. Main active material layer and current collector comprising metal powder selected from silicon, tin, or an alloy containing any of these elements and capable of storing and releasing lithium by an electrochemical reaction and an organic polymer binder In an electrode structure composed of a body,
(A) In addition to the metal powder, the main active material layer includes at least a support material powder that supports electronic conduction of the main active material layer, and the shape of the powder of the support material is spherical, pseudo-spherical, or columnar. The average particle size is 0.3 to 1.35 times the thickness of the main active material layer, and the support material is a transition metal oxide selected from graphite, TiO ₂ , MoO ₃ , and WO ₃ , Li and electricity One or more materials selected from the group consisting of Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and metals selected from these alloys that do not form alloys chemically And
(B) An electron conductive buffer layer is provided between the current collector and the main active material layer of the electrode structure, and the buffer layer includes at least an organic polymer binder, a conductive polymer, Graphite, Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and a metal that does not form an alloy with Li selected from the group of these alloys, TiO ₂ , MoO ₃ , composed of particles of one or more materials selected from the group consisting of transition metal oxides selected from WO ₃ , wherein the material particles have an average particle size of 0.5 μm to 10 μm An electrode structure for a lithium secondary battery. Main active material layer and current collector comprising metal powder selected from silicon, tin, or an alloy containing any of these elements and capable of storing and releasing lithium by an electrochemical reaction and an organic polymer binder In an electrode structure composed of a body,
(A) In addition to the metal powder, the main active material layer includes at least a support material powder that supports electronic conduction of the main active material layer, and the shape of the powder of the support material is spherical, pseudo-spherical, or columnar. The average particle size is 0.3 to 1.35 times the thickness of the main active material layer, and the support material is a transition metal oxide selected from graphite, TiO ₂ , MoO ₃ , and WO ₃ , Li and electricity One or more materials selected from the group consisting of Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and metals selected from these alloys that do not form alloys chemically And
(C) A surface coating layer is provided on the surface of the main active material layer of the electrode structure, the surface coating layer has electron conductivity and ion permeability or ion conductivity, and the surface coating layer is at least From the group of organic polymer binders and conductive polymers, amorphous carbon, graphite, Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and alloys thereof A particle composed of one or more materials selected from the group consisting of transition metal oxides selected from metals selected from Li, TiO ₂ , MoO ₃ , and WO ₃ that do not electrochemically form an alloy with Li. An electrode structure for a lithium secondary battery, wherein the secondary particles have an average particle size of 0.5 μm to 10 μm. Main active material layer and current collector comprising metal powder selected from silicon, tin, or an alloy containing any of these elements and capable of storing and releasing lithium by an electrochemical reaction and an organic polymer binder In an electrode structure composed of a body,
(A) In addition to the metal powder, the main active material layer includes at least a support material powder that supports electronic conduction of the main active material layer, and the shape of the powder of the support material is spherical, pseudo-spherical, or columnar. The average particle size is 0.3 to 1.35 times the thickness of the main active material layer, and the support material is a transition metal oxide selected from graphite, TiO ₂ , MoO ₃ , and WO ₃ , Li and electricity One or more materials selected from the group consisting of Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and metals selected from these alloys that do not form alloys chemically And
(B) An electron conductive buffer layer is provided between the current collector and the main active material layer of the electrode structure, and the buffer layer includes at least an organic polymer binder, a conductive polymer, Graphite, Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and a metal that does not form an alloy with Li selected from the group of these alloys, TiO ₂ , MoO _3, WO ₃ is composed of particles of one or more materials selected from the group consisting of transition metal oxide selected from the mean particle size of the material particles is 0.5 ~ 10 m,
(C) A surface coating layer is provided on the surface of the main active material layer of the electrode structure, the surface coating layer has electron conductivity and ion permeability or ion conductivity, and the surface coating layer is at least From the group of organic polymer binders and conductive polymers, amorphous carbon, graphite, Cu, Ni, Co, Ti, Fe, Cr, Mo, W, Pd, Pt, Au, and alloys thereof A particle composed of one or more materials selected from the group consisting of transition metal oxides selected from metals selected from Li, TiO ₂ , MoO ₃ , and WO ₃ that do not electrochemically form an alloy with Li. An electrode structure for a lithium secondary battery, wherein the secondary particles have an average particle size of 0.5 μm to 10 μm.   The electrode structure for a lithium secondary battery according to any one of claims 1 to 4, wherein the support material is graphite.   The electrode structure for a lithium secondary battery according to claim 3 or 4, wherein the surface coating layer is formed of at least an organic polymer binder and graphite particles.   The electrode structure for a lithium secondary battery according to claim 2 or 4, wherein the binder of the main active material layer and the buffer layer is the same material.   The electrode structure for a lithium secondary battery according to claim 3 or 4, wherein the binder of the main active material layer and the surface coating layer is the same material.   The electrode structure for a lithium secondary battery according to claim 4, wherein the binder of the main active material layer, the buffer layer, and the surface coating layer is the same material.   The electrode structure for a lithium secondary battery according to any one of claims 1 to 9, wherein a conductive organic polymer is dispersed in the binder.   11. The electrode structure for a lithium secondary battery according to claim 1, wherein an average particle diameter of primary particles forming the metal powder particles of the main active material layer is 0.05 μm to 5 μm.   The electrode structure for a lithium secondary battery according to any one of claims 1 to 11, wherein the surface of the metal powder particles of the main active material layer is coated with a carbide of coal tar pitch.   The electrode structure for a lithium secondary battery according to any one of claims 1 to 12, wherein a ten-point average height Rz of the surface roughness of the current collector is 0.7 µm to 3 µm. 2. The metal powder and the support material powder are combined by a binder material having a function as a linkage for carrying out chemical bonding or electronic conduction between the metal powder and the support material powder. Electrode structure for lithium secondary battery.   A secondary battery comprising a negative electrode using the electrode structure according to any one of claims 1 to 14, a lithium ion conductor, and a positive electrode, and utilizing a lithium oxidation reaction and a lithium ion reduction reaction.   The secondary battery according to claim 15, wherein the support material powder in the main active material layer of the negative electrode has an expansion coefficient in the direction of the positive electrode facing after charging of 1.5 times or less.   The secondary battery according to claim 15, wherein the positive electrode material constituting the positive electrode is made of a lithium transition metal oxide, and the lithium transition metal oxide is coated with a carbide of coal tar pitch.   The lithium ion conductor comprises an electrolytic solution prepared by dissolving a lithium salt in a solvent, and a vinyl compound monomer is contained in the electrolytic solution when the secondary battery is assembled. Secondary battery.   Main active material consisting of metal powder capable of storing and releasing lithium by electrochemical reaction, hard carbon powder or graphite carbon powder, and organic polymer binder selected from silicon, tin, and their alloys In the electrode structure composed of a layer and a current collector, the metal powder and the carbon powder are combined by a binder material having a function as a binder for carrying out chemical bonding or electronic conduction between the metal powder and the carbon powder. An electrode structure for a lithium secondary battery.   20. The electrode structure for a lithium secondary battery according to claim 19, wherein the connecting material is coal tar pitch.   21. The electrode structure for a lithium secondary battery according to claim 20, wherein the coal tar pitch is contained in the main active material layer in an amount of 0.1 to 3% by weight.   The electrode structure for a lithium secondary battery according to claim 19, wherein the connecting material is amorphous carbon.   The electrode structure for a lithium secondary battery according to claim 22, wherein the amorphous carbon is a carbide of coal tar pitch.   The electrode structure for a lithium secondary battery according to claim 23, wherein the main active material layer contains 1 to 10% by weight of the amorphous carbon.   The electrode structure for a lithium secondary battery according to claim 19, wherein the connecting material is a nonionic fluorine-based surfactant having an ether bond or an ester bond.   26. The electrode structure for a lithium secondary battery according to claim 25, wherein the main active material layer contains 0.01 to 0.5% by weight of the nonionic fluorine-based surfactant.   27. A lithium secondary battery comprising a negative electrode, a lithium ion conductor, and a positive electrode using the electrode structure according to claim 19 to 26, and utilizing a lithium oxidation reaction and a lithium ion reduction reaction.   21. The method for manufacturing an electrode structure according to claim 20, wherein the metal powder and the carbon powder are mixed with 0.1 to 3% by weight of coal tar pitch, and the binding particles are mixed with the mixture particles obtained in the step. A method of producing an electrode structure for a lithium secondary battery, comprising at least a step of adding and mixing an agent, and applying the obtained mixture onto a plate-shaped metal current collector.   In the step of adding and mixing the binder, and applying the resulting mixture onto a plate-shaped metal current collector, the solvent of the binder is mixed when the particles and the binder are mixed. The method for producing an electrode structure for a lithium secondary battery according to claim 28, wherein addition and mixing are performed.   24. The method of manufacturing an electrode structure according to claim 23, wherein at least the metal and carbon powder are mixed with 1 to 10% by weight of coal tar pitch and subjected to heat treatment at 400 to 700 ° C. under an inert gas. At least a step of obtaining particles in which powder and carbon powder are combined, and a step of mixing the particles and the binder and applying the obtained mixture onto a plate-shaped metal current collector. A method for producing an electrode structure for a lithium secondary battery.   In the step of mixing the particles and the binder and applying the obtained mixture onto a plate-shaped metal current collector, the binder and the binder are mixed when the particles and the binder are mixed. 31. The method for producing an electrode structure for a lithium secondary battery according to claim 30, wherein the solvent is added and mixed.   The method for producing an electrode structure according to claim 25, wherein 0.1 to 0.5% by weight of the fluorosurfactant is mixed into the metal powder and carbon powder, and the product obtained in the step is mixed with the product. A method for producing an electrode structure for a lithium secondary battery, comprising at least a step of adding and mixing a binder and applying the obtained mixture particles on a plate-shaped metal current collector.   In the step of adding and mixing the binder, and applying the obtained mixture particles on a plate-shaped metal current collector, the solvent of the binder is mixed when the particles and the binder are mixed. The method for producing an electrode structure for a lithium secondary battery according to claim 32, wherein:   34. A lithium secondary battery, wherein at least a lithium ion conductor is formed between a negative electrode and a positive electrode using the electrode structure obtained by the manufacturing method according to any one of claims 28 to 33. Manufacturing method.

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