JP2004311428A - Electrode material for lithium secondary battery, electrode structure with the electrode material and secondary battery with the electrode structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode material for a lithium secondary battery, an electrode structure with the electrode material and a secondary battery with the electrode structure of which capacity is not much lowered by repeated charge and discharge, of which charge and discharge cycle life is improved. <P>SOLUTION: In powder particles, consisting of an alloy mainly consisting of silicone, of which mean particle diameter is from 0.02 to 5 μm, a material of which crystallite size of the alloy is equal to or more than 2 nm and equal to or less than 500 nm and intermetallics 107 including at least tin is dispersed in a silicone phase 106 is used as the electrode material 103 of the lithium secondary battery. Otherwise, in the powder particles, consisting of the alloy mainly consisting of silicone, of which mean particle diameter is from 0.02 to 5 μm, a material of which crystallite size of the alloy is equal to or more than 2 nm and equal to or less than 500 nm and one or more kinds of the intermetallics 107 including at least any of aluminum, zinc, indium, antimony, bismuth and lead are dispersed in the silicone phase 106. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrode material for a lithium secondary battery comprising a powder of particles containing silicon as a main component, an electrode structure having the electrode material, and a secondary battery having the electrode 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 and the like into electric energy. However, it is difficult to construct a new thermal power plant because a large amount of CO ₂ gas is emitted by combustion. ing. Therefore, as an effective use of power generated by generators such as thermal power plants, surplus nighttime power is stored in secondary batteries installed in ordinary households and used during daytime when power consumption is high. A so-called load leveling has been proposed.

In addition, in electric vehicle applications that do not emit substances related to air pollution including CO _x , NO _x , and hydrocarbons, development of secondary batteries with high energy density is expected. Furthermore, in the power supply application of portable devices such as a book-type personal computer, a video camera, a digital camera, a mobile phone, and a PDA (Personal Digital Assistant), there is an urgent need to develop a small, lightweight, and high-performance secondary battery.

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

  However, in this "lithium ion battery", the negative electrode composed of a carbon material can theoretically intercalate only a maximum of 1/6 lithium atoms per carbon atom. A secondary battery with a high energy density comparable to a primary battery cannot be realized.

  If, during charging, an attempt is made to intercalate a stoichiometric amount of lithium into the negative electrode made of carbon in a “lithium ion battery” or if the battery is charged under conditions of high current density, lithium metal is dendritic on the surface of the carbon negative electrode. It grows in a (dendritic) shape and may eventually lead to an internal short circuit between the negative electrode and the positive electrode due to repeated charge / discharge cycles. A "lithium-ion battery" exceeding the theoretical capacity of the graphite negative electrode has sufficient cycle life. Not been.

  On the other hand, a high-capacity lithium secondary battery using metallic lithium as a negative electrode has attracted attention as a secondary battery having a high energy density, but has not been put to practical use.

  The reason is that the charge / discharge cycle life is extremely short. The main cause of the extremely short charge / discharge cycle life is that metallic lithium reacts with impurities such as moisture in the electrolyte and organic solvents to form an insulating film, or the surface of the metallic lithium foil is not flat and the electric field concentrates It is considered that there is a point, and as a result, lithium metal grows in a dendrite shape due to repetition of charge / discharge, causing an internal short circuit between the negative electrode and the positive electrode to reach a life.

  A method of using a lithium alloy composed of lithium, aluminum, or the like for the negative electrode in order to suppress the progress of the reaction between lithium metal and water or an organic solvent in the electrolytic solution, which is a problem of a secondary battery using the above-described metal lithium anode. Has been proposed.

  However, in this case, since the lithium alloy is hard and cannot be wound in a spiral shape, a spiral cylindrical battery cannot be manufactured, the cycle life cannot be sufficiently extended, and the energy is comparable to that of a battery using metallic lithium for the negative electrode. At present, it has not been put to practical use in a wide range because of insufficient density and the like.

  By the way, in order to solve the above-mentioned problems, conventionally, as a secondary battery using a negative electrode for a lithium secondary battery made of silicon or tin, US Pat. No. 6,051,340, US Pat. No. 5,795,679, US Pat. No. 283627, Japanese Patent Application Laid-Open No. 2000-31681, and WO00 / 17949 have been proposed.

  Here, in U.S. Pat. No. 6,051,340, an electrode layer formed of a metal that alloys with lithium of silicon or tin and a metal that does not alloy with lithium of nickel or copper are formed on a current collector made of a metal material that does not alloy with lithium. A lithium secondary battery using the formed negative electrode has been proposed.

U.S. Pat. No. 5,795,679 discloses a lithium secondary battery using a negative electrode formed from an alloy powder of an element such as nickel or copper and an element such as tin. In U.S. Pat. No. 6,432,585, an electrode material layer has an average particle diameter of 0.5. Lithium secondary battery using a negative electrode having a particle size of silicon or tin of 35 to 60 μm in an amount of 35% by weight or more, a porosity of 0.10 to 0.86, and a density of 1.00 to 6.56 g / cm ³ Has been proposed.

  JP-A-11-283627 discloses a lithium secondary battery using a negative electrode having silicon or tin having an amorphous phase, and JP-A-2000-31681 discloses an amorphous tin having a non-stoichiometric composition. -A lithium secondary battery using a negative electrode composed of transition metal alloy particles is proposed. In WO00 / 17949, a lithium secondary battery using a negative electrode composed of non-stoichiometric amorphous silicon-transition metal alloy particles is proposed. ing.

  However, in the lithium secondary batteries according to the above proposals, the efficiency of the amount of electricity associated with the release of lithium with respect to the amount of electricity associated with the first lithium insertion has not been obtained to the same level as that of the graphite anode, and the efficiency has been further improved. Was expected. Further, since the electrode of the lithium secondary battery proposed above has a higher resistance than the graphite electrode, it has been desired to reduce the resistance.

  In Japanese Patent Application Laid-Open No. 2000-21587, a metal layer or a metalloid capable of forming a lithium alloy, particularly, a carbon layer is formed on the surface of silicon particles by a chemical vapor deposition method of thermal decomposition such as benzene to improve conductivity. Thus, a lithium secondary battery having a high capacity and a high charge / discharge efficiency has been proposed, by suppressing volume expansion upon alloying with lithium to prevent electrode destruction.

However, in this lithium secondary battery, while the theoretical storage capacity calculated from Li _4.4 Si as a compound of silicon and lithium is 4200 mAh / g, lithium insertion of an electric quantity exceeding 1000 mAh / g is performed. The electrode performance that does not allow desorption is not attained, and the development of a high-capacity and long-life negative electrode is desired.

  Therefore, the present invention has been made in view of the above circumstances, an electrode material for a lithium secondary battery having a small capacity reduction due to repeated charge and discharge, and an improved charge / discharge cycle life, and the electrode material. An object of the present invention is to provide an electrode structure having the above, and a secondary battery having the electrode structure.

  The present invention is an electrode material for a lithium secondary battery comprising particles of an alloy having silicon as a main component and having an average particle size of 0.02 μm to 5 μm, wherein the crystallite size of the alloy is 2 nm or more and 500 nm or less. And an intermetallic compound containing at least tin is dispersed in a silicon phase (first invention).

  The present invention also provides an electrode material for a lithium secondary battery comprising particles of an alloy having silicon as a main component and having an average particle size of 0.02 μm to 5 μm, wherein the crystallite size of the alloy is 2 nm or more and 500 nm or less. Wherein at least one intermetallic compound containing at least one of aluminum, zinc, indium, antimony, bismuth and lead is dispersed in the silicon phase (second invention). .

  As in the present invention, an alloy containing silicon as a main component and having an average particle size of 0.02 μm to 5 μm or less has a crystallite size of 2 nm or more and 500 nm or less, and an intermetallic compound containing at least tin in a silicon phase, or Is composed of an electrode material in which at least one kind of intermetallic compound containing at least one of aluminum, zinc, indium, antimony, bismuth and lead is dispersed, and this electrode structure is used as a negative electrode to form a lithium electrode. By configuring a secondary battery, a high-capacity secondary battery in which a decrease in capacity due to repeated charging and discharging is small and in which a charge / discharge cycle life is improved can be manufactured.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  The present inventors have prepared a fine powder in which tin or copper has been added to silicon and the average particle diameter of alloyed particles containing silicon element of 50% by weight or more is 0.1 μm or more and 2.5 μm or less. It has been found that a high-capacity lithium secondary battery can be manufactured by using the same.

  And this time, an intermetallic compound containing tin or one or more intermetallic compounds containing any of aluminum, zinc, indium, antimony, bismuth, and lead are dispersed in a silicon phase having a crystallite size of 2 nm or more and 500 nm or less. The present invention has been found that, in the electrode material characterized in that the charge / discharge cycle is repeated, the capacity is not reduced by repeated charge / discharge.

  FIG. 1 is a schematic sectional view of particles of an electrode material constituting an electrode structure according to the present invention. In FIG. 1, reference numeral 103 denotes particles of an electrode material (active material) containing silicon as a main component according to the present invention. is there. Here, the average particle diameter of the electrode material particles 103 is 0.02 μm to 5 μm or less, and the electrode material particles 103 are formed of a silicon phase 106 and tin or aluminum, zinc, indium, antimony, bismuth, or lead. It is composed of an intermetallic compound 107 containing the selected element.

  That is, in the electrode material 103 of the present invention, an intermetallic compound 107 containing tin or an element selected from aluminum, zinc, indium, antimony, bismuth, and lead is contained in a silicon phase 106 having a crystallite size of 2 nm or more and 500 nm or less. Wherein the intermetallic compound 107 containing is dispersed. Here, not only the intermetallic compound 107, but also tin or an element selected from aluminum, zinc, indium, antimony, bismuth, and lead may be present as a simple metal.

  In this specification, the state in which “the intermetallic compound 107 is dispersed in the silicon phase 106” means that the powder particles are formed in a segregated state in which the powder particles are separated into the silicon phase 106 and the intermetallic compound 107. Rather, it means that the main component of the powder particles is silicon, and the intermetallic compound 107 is mixed therein. Such a state can be observed with a transmission electron microscope or a selected area electron beam diffraction.

Here, as an element forming an intermetallic compound with tin, copper, nickel, cobalt, iron, manganese, vanadium, molybdenum, niobium, tantalum, titanium, zirconia, yttrium, lanthanum, selenium, magnesium, and silver are preferable, among which Copper, nickel and cobalt are preferred. These elements tin and _{Cu 41 Sn 11, Cu 10 Sn} 3, Cu 5 Sn 4, Cu 5 Sn, Cu 3 Sn, Ni 3 Sn 4, Ni 3 Sn 2, Ni 3 Sn, Co 3 Sn 2, CoSn _{2, CoSn, Fe 5 Sn 3} , Fe 3 Sn 2, FeSn 2, FeSn, Mn 3 Sn, Mn 2 Sn, MnSn 2, Sn 3 V 2, SnV 3, Mo 3 Sn, Mo 2 Sn 3, MoSn 2, _{NbSn 2, Nb 6 Sn 5,} Nb 3 Sn, SnTa 3, Sn 3 Ta 2, SnTi 2, SnTi 3, Sn 3 Ti 5, Sn 5 Ti 6, SnZr 4, Sn 2 Zr, Sn 3 Zr 5, Sn 2 _{Y, Sn 3 Y, Sn 3} Y 5, Sn 4 Y 5, Sn 10 Y 11, LaSn, LaSn 3, La 2 Sn 3, La 3 Sn, La 3 _{Sn 5, La 5 Sn 3,} La 5 Sn 4, La 11 Sn 10, Ce 3 Sn, Ce 5 Sn 3, Ce 5 Sn 4, Ce 11 Sn 10, Ce 3 Sn 5, Ce 3 Sn 7, Ce 2 Sn ₅ , intermetallic compounds such as CeSn ₃ , Mg ₂ Sn, Ag ₃ Sn, and Ag ₇ Sn.

  By the way, when silicon is used as an electrode material, the volume change during the insertion / desorption reaction of lithium into silicon accompanying charging / discharging is large, so that the crystal structure of silicon collapses and particles are pulverized to charge and discharge. become unable.

  Thus, the present inventors have found that the cycle life can be improved by using amorphous silicon or silicon alloy fine powder, but this time, the present invention further includes tin in the silicon phase. By dispersing an intermetallic compound or an intermetallic compound containing an element selected from aluminum, zinc, indium, antimony, bismuth, and lead, lithium can be uniformly inserted into the silicon phase and cycle life can be improved. I found it.

Taking tin as an example of this, the potential E1 (Li / Li ⁺ ) of the electrochemical lithium oxidation / reduction reaction (1) with respect to tin is equal to the potential E2 of the oxidation / reduction reaction (2) with silicon. It is more noble than (Li / Li ⁺ ).
(1) Sn + xLi → Li _x Sn E1 (Li / Li ⁺ )
(2) Si + xLi → Li _x Si E2 (Li / Li ⁺ )
E1 (Li / Li ⁺ )> E2 (Li / Li ⁺ )

  Here, since the lithium insertion reaction accompanying charging occurs from the noble potential, it is considered that lithium insertion occurs first in tin and then in silicon. Therefore, by uniformly dispersing tin in the silicon phase, the insertion reaction of lithium into the silicon phase also occurs uniformly, and the collapse of the crystal structure of silicon can be suppressed by more uniformly incorporating lithium into the silicon phase. ,it is conceivable that.

  By the way, as a means for producing an alloy powder of silicon and tin, a method of mixing and melting and then alloying by an atomizing treatment, that is, a method using a so-called gas atomizing method or a water atomizing method is industrially simple. However, since the melting point of silicon is 1412 ° C., and the melting point of tin is 231.9 ° C., which is a large difference between the melting points, the silicon phase and the tin phase are easily formed in a segregated state.

  As a means for suppressing this, it is effective to use an intermetallic compound containing tin as shown in the first invention.

Specifically, when producing an alloy, together with tin, to form an intermetallic compound with tin, copper, nickel, cobalt, iron, manganese, vanadium, molybdenum, niobium, tantalum, titanium, zirconia, yttrium, lanthanum, A method of adding at least one element of selenium, magnesium, and silver is effective.

  Here, since the melting point of these intermetallic compounds is higher than the melting point of tin, the difference in melting point with silicon can be reduced, and the silicon phase and the tin alloy phase can be uniformly dispersed. In addition, by forming an intermetallic compound, an effect of suppressing a volume change of tin when lithium is taken in can be expected.

  In addition, elements of aluminum, zinc, indium, antimony, bismuth, and lead can also electrochemically insert / desorb Li, and like tin, the potential of the oxidation / reduction reaction of Li is more noble than silicon. . Furthermore, their melting points are aluminum (660 ° C.), zinc (419.5 ° C.), indium (156.4 ° C.), antimony (630.5 ° C.), bismuth (271 ° C.), and lead (327.4 ° C.). And lower than silicon. Then, as shown in the second invention, by forming an intermetallic compound containing any of these elements, the difference in melting point from silicon can be reduced and uniform dispersion can be achieved.

As these intermetallic _{compounds, AlCu, AlCu 2, AlCu 3} , Al 2 Cu, Al 2 Cu 3, Al 2 Cu 7, Al 3 Cu 7, Al 4 Cu 5, CuZn, CuZn 3, CuZn 4, _{Cu 5 Zn 8, Cu 2 In} , Cu 4 In, Cu 7 In 3, Cu 11 In 9, Cu 2 Sb, Cu 3 Sb, Cu 4 Sb, Cu 5 Sb, Cu 10 Sb 3, biNi, Bi 3 Ni, Bi ₃ Pb ₇ , Pb ₃ Zr ₅ , and the like.

  In addition, the content of silicon in the alloy is preferably 50 wt% or more in order to exhibit high power storage performance as a negative electrode material of a lithium secondary battery. Further, the average particle size of the primary particles of the silicon alloy of the present invention is from 0.02 to 5.5 so that the lithium insertion and desorption reaction electrochemically occurs uniformly and quickly as a negative electrode material of a lithium secondary battery. It is preferably in the range of 0 μm, more preferably in the range of 0.05 to 1.0 μm. In addition, in this specification, an "average particle size" means an average primary particle size (average particle size in the state where it does not aggregate).

  Here, if the average particle diameter is too small, handling becomes difficult and the contact area between the particles when an electrode is formed increases, and the contact resistance increases. In this case, assembling the primary particles to enlarge the particles facilitates handling and leads to a reduction in resistance.

  Further, in order to obtain a battery having a long cycle life, the crystal structure of the pulverized fine powder preferably contains an amorphous phase. Furthermore, since the fine powder of the negative electrode material produced by the method for producing a negative electrode material of a lithium secondary battery of the present invention contains an amorphous phase, volume expansion during alloying with lithium can be reduced.

  Also, when the proportion of the amorphous phase is increased, the peak of the sharp X-ray diffraction chart which is crystalline has a broader half width of the peak, and becomes broader. The half-value width of the main peak of the X-ray diffraction chart of the diffraction intensity with respect to 2θ is preferably 0.1 ° or more, more preferably 0.2 ° or more.

  The crystallite size of the negative electrode material powder (powder of particles mainly composed of silicon) prepared according to the present invention, particularly the crystallite size before charging / discharging the electrode structure (unused state) is 2 nm. The thickness is preferably in the range of 2 to 50 nm, more preferably in the range of 2 to 50 nm, and more preferably in the range of 2 to 30 nm. By using such fine crystal grains, the electrochemical reaction at the time of charge and discharge can be made smoother, and the charge capacity can be improved. In addition, it is possible to suppress the distortion caused by the inflow and outflow of lithium during charging and discharging, and to prolong the cycle life.

  In the present invention, the crystallite size of the particles is determined from the half-value width and the diffraction angle of the peak of the X-ray diffraction curve using CuKα as the radiation source, using the following Scherrer's formula.

Lc = 0.94λ / (βcosθ) (Scherrer's formula)
Lc: crystallite size λ: wavelength of X-ray beam β: half width of peak (radian)
θ: Bragg angle of diffraction line

On the other hand, as a means for producing the electrode material of the present invention,
(A) a method of mixing and melting silicon, tin or aluminum, zinc, indium, antimony, bismuth, lead, transition metal and the like and then alloying by atomizing (gas atomizing method, water atomizing method, etc.),
(B) a method of pulverizing an ingot of silicon alloy produced by mixing and melting silicon, tin or aluminum, zinc, indium, antimony, bismuth, lead, transition metal and the like;
(C) a method of alloying while pulverizing and mixing silicon powder, tin or aluminum, zinc, indium, antimony, bismuth, lead powder, transition metal powder and the like under an inert gas (mechanical alloying method);
(D) a method using a volatile chloride (or another halide), an oxide, or the like to generate from a gas phase by plasma, electron beam, laser, or induction heating.

  In addition, by mechanically pulverizing these alloy powders, at least one or more of intermetallic compounds containing tin uniformly in the silicon phase, or any one of aluminum, zinc, indium, antimony, bismuth, and lead are further pulverized. Can be dispersed.

  Here, as the mechanical pulverizer, a ball mill such as a planetary mill, a vibrating ball mill, a conical mill, and a tube mill, and a media mill such as an attritor type, a sand grinder type, an aniler mill type, and a tower mill type can be used. It is preferable to use zirconia, stainless steel, or steel as the material of the ball as the grinding media.

  The pulverization may be performed by either a wet method or a dry method. In the wet pulverization, pulverization is performed in a solvent or pulverization is performed by adding a certain amount of a solvent. In such a wet pulverization, water or an organic solvent such as alcohol or hexane can be used. Specific examples of the alcohol include methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, isopropyl alcohol, 1-butyl alcohol, and 2-butyl alcohol.

  FIG. 2 shows a schematic cross-sectional structure of the electrode structure of the present invention. In FIG. 2A, reference numeral 102 denotes an electrode structure. The electrode structure 102 includes an electrode material layer 101 and a current collector 100. The electrode material layer 101 is formed as shown in FIG. As shown, it is composed of particles (active material) 103 containing silicon as a main component, a conductive auxiliary material 104 and a binder 105. Although the electrode material layer 101 is provided only on one surface of the current collector 100 in FIG. 2, depending on the form of the battery, the electrode material layer 101 may be formed on both surfaces of the current collector 100. Good.

  Here, the content of the conductive auxiliary material 104 is preferably 5% by weight or more and 40% by weight or less, more preferably 10% by weight or more and 30% by weight or less. The content of the binder 105 is preferably 2% by weight or more and 20% by weight or less, more preferably 5% by weight or more and 15% by weight or less. The content of the particles (powder) 103 containing silicon as a main component contained in the electrode material layer 101 is preferably in a range of 40% by weight to 93% by weight.

  In addition, as the conductive auxiliary material 104, a carbon material such as amorphous carbon such as acetylene black or Ketjen black, graphite structure carbon, nickel, copper, silver, titanium, platinum, aluminum, cobalt, iron, chromium, or the like is used. However, graphite is particularly preferred. As the shape of the conductive auxiliary material, preferably, a shape selected from a sphere, a flake, a filament, a fiber, a spike, a needle and the like can be adopted. Furthermore, by employing powders of two or more different shapes, the packing density at the time of forming the electrode material layer can be increased and the impedance of the electrode structure 102 can be reduced.

  Examples of the material of the binder 105 include water-soluble polymers such as polyvinyl alcohol, water-soluble ethylene-vinyl alcohol copolymer, polyvinyl butyral, polyethylene glycol, carboxymethyl cellulose sodium, and hydroxyethyl cellulose, polyvinylidene fluoride, and vinylidene fluoride-hexafluoropropylene. Examples include fluororesins such as polymers, polyolefins such as polyethylene and polypropylene, styrene-butadiene rubber, polyamideimide, polyimide, and polyamic acid (polyamide precursor).

  Among them, when polyvinyl alcohol and carboxymethylcellulose sodium are used together, or when polyamide imide or polyamic acid (polyamide precursor) is used, the strength of the electrode is increased, and an electrode having excellent charge / discharge cycle characteristics can be produced.

  In addition, since the current collector 100 efficiently supplies the current consumed in the electrode reaction at the time of charging or collects the current generated at the time of discharging, particularly, the current When applied to the negative electrode of a battery, as a material for forming the current collector 100, a material having high electric conductivity and inert to a battery reaction is desirable. Preferred 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 100 is plate-like, and the “plate-like” is not specified in the practical range of the thickness, and is called a “foil” having a thickness of about 100 μm or less. Embodied forms. In addition, a plate-shaped member such as a mesh, a sponge, or a fiber, a punched metal, an expanded metal, or the like may be used.

  Next, a procedure for manufacturing the electrode structure 102 will be described.

  First, a conductive auxiliary material powder and a binder 105 are mixed with the silicon alloy powder of the present invention, and a solvent for the binder 105 is appropriately added and kneaded to prepare a paste. Next, the prepared paste is applied to the current collector 100, dried to form the electrode material layer 101, and then subjected to a press treatment to adjust the thickness and density of the electrode material layer 101 to form the electrode structure 102. I do.

  As the above-mentioned coating method, for example, a coater coating method and a screen printing method can be applied. In addition, the above-mentioned main material, conductive auxiliary material 104 and binder 105 are added without adding a solvent, or only the above-mentioned negative electrode material and conductive auxiliary material 104 are added onto the current collector without mixing binder 105. The electrode material layer 101 can be formed by pressing.

Here, if the density of the electrode material layer 101 is too high, the expansion at the time of insertion of lithium increases, and peeling from the current collector 100 occurs. If the density is too low, the resistance of the electrode increases, so that the charging / discharging efficiency decreases and the voltage drop at the time of battery discharge increases. Therefore, the density of the electrode material layer 101 of the present invention is more it is preferably in the range of 0.8 to 2.0 g / cm ^3, in the range of 0.9~1.5g / cm ³ preferable.

  Note that the electrode structure 102 formed using only the silicon alloy particles of the present invention without using the conductive auxiliary material 104 or the binder 105 is collected by a method such as sputtering, electron beam evaporation, or cluster ion beam evaporation. It can be manufactured by forming the electrode material layer 101 directly on the electric body 100.

  However, if the thickness of the electrode material layer 101 is increased, peeling is likely to occur at the interface with the current collector 100, so that it is not suitable for forming a thick electrode structure 102. In order to prevent peeling at the interface, a current collector 100 is provided with a metal layer, an oxide layer, or a nitride layer on the order of nanometers to form irregularities on the current collector 100, thereby improving the adhesion of the interface. Preferably, it is improved. As a more specific oxide layer or nitride layer, a silicon or metal oxide layer or nitride layer is preferably used.

  Incidentally, 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 features, and utilizes a lithium oxidation reaction and a lithium ion reduction reaction.

  FIG. 3 is a diagram showing a basic configuration of such a lithium secondary battery of the present invention. In FIG. 3, 201 denotes a negative electrode using the electrode structure of the present invention, 202 denotes an ion conductor, and 203 denotes a positive electrode. , 204 is a negative electrode terminal, 205 is a positive electrode terminal, and 206 is a battery case (housing).

  Here, in the secondary battery, an ion conductor 202 is laminated between the negative electrode 201 and the positive electrode 203 to form an electrode group, and in a dry air or dry inert gas atmosphere where the dew point is sufficiently controlled, After the electrode group is inserted into the battery case, the electrodes 201 and 203 are connected to the electrode terminals 204 and 205, and the battery case is sealed.

  In the case where a material in which an electrolytic solution is held in a microporous plastic film is used as the ion conductor 202, a microporous plastic film is sandwiched between the negative electrode 201 and the positive electrode 203 as a separator for preventing short circuit. After forming the electrode group, it is inserted into a battery case, the electrodes 201 and 203 are connected to the electrode terminals 204 and 205, and an electrolyte is injected before the battery case is sealed to assemble the battery.

  A lithium secondary battery using the electrode structure made of the electrode material of the present invention as a negative electrode has high charge / discharge efficiency, capacity, and energy density due to the beneficial effects of the negative electrode.

  Here, the positive electrode 203 serving as a counter electrode of the lithium secondary battery using the above-described electrode structure of the present invention as a negative electrode is at least a lithium ion source and is made of a positive electrode material serving as a lithium ion host material, and is preferably lithium. It is composed of a current collector and a layer formed from a positive electrode material serving as an ion host material. Further, the layer formed from the positive electrode material is preferably made of a material in which a positive electrode material serving as a host material of lithium ions and a binder, and in some cases, a conductive auxiliary material are added thereto.

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

  When the shape of the positive electrode active material is a powder, a positive electrode is manufactured by using a binder or by sintering or vapor deposition to form a positive electrode active material layer on a current collector. When the conductivity of the positive electrode active material powder is low, it is necessary to appropriately mix a conductive auxiliary material in the same manner as in the formation of the active material layer of the electrode structure. As the conductive auxiliary material and the binder, those used for the above-described electrode structure 102 of the present invention can be similarly used.

  Here, as the current collector material used for the positive electrode, aluminum, titanium, nickel, and platinum, which are materials having high electric conductivity and inert to a battery reaction, are preferable. Specifically, nickel, stainless steel, Titanium and aluminum are preferred, and aluminum is more preferred because of its low cost and high electrical conductivity. The shape of the current collector is a plate shape, but the “plate shape” is not specified in the practical range of the thickness, and is called a “foil” having a thickness of about 100 μm or less. Also encompasses forms. In addition, a plate-shaped member such as a mesh, a sponge, or a fiber, a punched metal, an expanded metal, or the like may be used.

In addition, the ion conductor 202 of the lithium secondary battery of the present invention has a separator holding an electrolytic solution (an electrolytic solution prepared by dissolving an electrolyte in a solvent), a solid electrolyte, and a polymer gel or the like. A lithium ion conductor such as a solidified electrolyte, a composite of a polymer gel and a solid electrolyte, or the like can be used. Here, the conductivity of the ion conductor 202 as a value at 25 ° C. is preferably 1 × 10 ⁻³ S / cm or more, more preferably 5 × 10 ⁻³ S / cm or more.

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 mixed salts thereof. It is desirable that the salt is sufficiently dehydrated and deoxidized by heating under reduced pressure.

  Further, as a solvent for the electrolyte, for example, 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, dimethylsulfide, dimethylsulfoxide, methyl formate, 3-methyl-2-oxidazolidinone, 2-methyltetrahydrofuran, 3-propylsidone, sulfur dioxide, phosphoryl chloride, thionyl chloride, Sulfuryl chloride or a mixture thereof can be used.

  The solvent is, for example, dehydrated with activated alumina, molecular sieve, phosphorus pentoxide, calcium chloride, or the like, or, depending on the solvent, is also subjected to impurity removal and dehydration by distillation in the presence of an alkali metal in an inert gas. Is good.

  In order to prevent leakage of the electrolyte, it is preferable to use a solid electrolyte or a solidified electrolyte. Examples of the solid electrolyte include glass such as an oxide including a lithium element, a silicon element, an oxygen element, a phosphorus element, and a sulfur element, and a polymer complex of an organic polymer having an ether structure. As the solidified electrolyte, those obtained by gelling the electrolytic solution with a gelling agent and solidifying are preferable.

  As the gelling agent, it is desirable to use a polymer which absorbs the solvent of the electrolytic solution and swells, or a porous material having a large liquid absorption such as silica gel. Further, as the polymer, polyethylene oxide, polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, vinylidene fluoride-hexafluoropropylene copolymer and the like are used. Further, the polymer is more preferably one having a crosslinked structure.

  Note that the ion conductor 202 constituting a separator that plays a role in preventing a short circuit between the negative electrode 201 and the positive electrode 203 in the secondary battery may have a role of holding an electrolytic solution. It is necessary to have a large number and to be insoluble and stable in the electrolytic solution.

  Therefore, as the ion conductor 202 (separator), for example, a material having a micropore structure or a nonwoven fabric such as glass, polyolefin such as polypropylene or polyethylene, or a fluororesin is preferably used. Further, a metal oxide film having fine pores or a resin film in which a metal oxide is compounded can be used.

  Next, the shape and structure of the secondary battery will be described.

  Specific shapes of the secondary battery of the present invention include, for example, a flat shape, a cylindrical shape, a rectangular parallelepiped shape, and a sheet shape. In addition, examples of the structure of the battery include a single-layer type, a multilayer type, and a spiral type. Among them, a spiral cylindrical battery is characterized in that the electrode area can be increased by winding a separator between the negative electrode and the positive electrode, and a large current can flow during charging and discharging. Further, a rectangular parallelepiped or sheet type battery has a feature that a storage space of a device configured to store a plurality of batteries can be effectively used.

  Next, the shape and structure of the battery will be described in more detail with reference to FIGS. FIG. 4 is a cross-sectional view of a single-layer flat battery (coin type), and FIG. 5 is a cross-sectional view of a spiral cylindrical battery. The lithium secondary battery having these shapes has basically the same configuration as that of FIG. 3 and includes a negative electrode, a positive electrode, an ion conductor, a battery housing, and an output terminal.

  4 and 5, reference numerals 301 and 403 denote negative electrodes, reference numerals 303 and 406 denote positive electrodes, reference numerals 304 and 408 denote negative electrode caps or negative cans as negative electrode terminals, reference numerals 305 and 409 denote positive electrode cans or positive electrode caps as positive electrode terminals, and reference numerals 302 and 407 Is an ion conductor, 306 and 410 are gaskets, 401 is a negative electrode current collector, 404 is a positive electrode current collector, 411 is an insulating plate, 412 is a negative electrode lead, 413 is a positive electrode lead, and 414 is a safety valve.

  Here, in the flat-type (coin-type) secondary battery shown in FIG. 4, a positive electrode 303 including a positive electrode material layer and a negative electrode 301 including a negative electrode material layer are formed, for example, by an ion formed by a separator holding at least an electrolytic solution. The laminate is stacked via a conductor 302. The laminate is accommodated from the positive electrode side in a positive electrode can 305 as a positive electrode terminal, and the negative electrode side is covered with a negative electrode cap 304 as a negative electrode terminal. Then, a gasket 306 is arranged at another portion in the positive electrode can.

  In the spiral cylindrical secondary battery shown in FIG. 5, a positive electrode 406 having a positive electrode (material) layer 405 formed on a positive electrode current collector 404 and a negative electrode (material) formed on a negative electrode current collector 401 The negative electrode 403 having the layer 402 is opposed, for example, via an ion conductor 407 formed of at least a separator holding an electrolytic solution, and forms a multilayer structure having a cylindrical structure wound in multiple layers.

  The laminate having the cylindrical structure is accommodated in a negative electrode can 408 as a negative electrode terminal. In addition, a positive electrode cap 409 as a positive electrode terminal is provided on the opening side of the negative electrode can 408, and a gasket 410 is disposed in another part in the negative electrode can. The laminated body of electrodes having a cylindrical structure is separated from the positive electrode cap side via an insulating plate 411.

  The positive electrode 406 is connected to a positive electrode cap 409 via a positive electrode lead 413. The negative electrode 403 is connected to a negative electrode can 408 via a negative electrode lead 412. A safety valve 414 for adjusting the internal pressure inside the battery is provided on the positive electrode cap side. As described above, for the active material layer of the negative electrode 401 and the active material layer 402 of the negative electrode 403, the layer made of the above-described negative electrode material fine powder of the present invention is used.

Next, an example of a method of assembling the battery shown in FIGS. 4 and 5 will be described.
(1) The separator is assembled into the positive electrode can 305 or the negative electrode can 408 with the ion conductors 302 and 407 as separators interposed between the negative electrodes 301 and 403 and the molded positive electrodes 303 and 406.
(2) After injecting the electrolytic solution, the negative electrode cap 304 or the positive electrode cap 409 and the gaskets 306 and 410 are assembled.
(3) The above (2) is swaged.

  Thereby, the battery is completed. The above-described preparation of the lithium battery material and assembly of the battery are desirably performed in dry air from which moisture is sufficiently removed or in a dry inert gas.

  Next, members constituting such a secondary battery will be described.

  As a material of the gaskets 306 and 410, for example, a fluorine resin, a polyolefin resin, a polyamide resin, a polysulfone resin, and various rubbers can be used. In addition, as a method for sealing the battery, a method such as glass sealing tube, adhesive, welding, soldering, or the like is used in addition to “caulking” using a gasket as shown in FIGS. As the material of the insulating plate 411 in FIG. 4, various organic resin materials and ceramics are used.

  The outer can of the battery includes a battery positive or negative electrode can 305, 408 and a negative or positive electrode cap 304, 409. As a material for the outer can, stainless steel is preferably used. As other materials for the outer can, aluminum alloy, titanium-clad stainless steel, copper-clad stainless steel, nickel-plated steel plate and the like are often used.

  Since the positive electrode can 305 in FIG. 4 and the negative electrode can 408 in FIG. 5 also serve as a battery housing (case) and terminals, the above stainless steel is preferable. However, when the positive electrode can 305 or the negative electrode can 408 does not double as a battery housing and a terminal, besides stainless steel, use metal such as zinc, plastic such as polypropylene, or a composite material of metal or glass fiber and plastic. Can be.

  As the safety valve 414 provided in the lithium secondary battery as a safety measure when the internal pressure of the battery increases, for example, rubber, a spring, a metal ball, a burst foil, or the like can be used.

  Hereinafter, the present invention will be described in more detail by way of examples.

(Preparation of electrode material)
First, an example of preparing a negative electrode material will be described.

(Example 1)
An alloy was prepared by melting and mixing 65% by weight of Si, 30% by weight of Sn, and 5% by weight of Cu, and a Si-Sn-Cu alloy powder having an average particle size of 10 µm was prepared by a water atomizing method. Next, the prepared alloy powder was pulverized by a bead mill (that is, a ball mill using relatively small beads as a pulverizing medium) to obtain a fine powder of a Si—Sn—Cu alloy. The pulverization was performed using zirconia beads in isopropyl alcohol.

  Next, an electrode material of a Si-Sn-Cu alloy fine powder which was treated for 2 hours using a silicon nitride ball in an argon gas atmosphere in a high energy planetary ball mill was obtained.

(Example 2)
In the above-mentioned Example 1, a Si-Zn-Cu alloy fine powder was prepared in the same manner as in Example 1 except that an alloy having a composition of 70% by weight of Si, 25% by weight of Zn, and 5% by weight of Cu was prepared by a gas atomization method using nitrogen gas. A powdered electrode material was obtained.

(Example 3)
In Example 1, the same operation as in Example 1 was performed except that an alloy having a composition of 50% by weight of Si, 40% by weight of Sn, and 10% by weight of Co was prepared by a water atomizing method. An electrode material was obtained.

(Example 4)
In Example 1, the same operation as in Example 1 was carried out except that an alloy having a composition of 85% by weight of Si, 10% by weight of Sn, and 5% by weight of Ni was prepared by a water atomizing method. An electrode material was obtained.

(Reference Example 1)
An electrode material of a Si—Sn—Cu alloy fine powder which was not subjected to the high energy planetary ball mill treatment in Example 1 was obtained.

(Reference Example 2)
An electrode material of a Si-Zn-Cu alloy fine powder which was not subjected to the high energy planetary ball mill treatment in Example 2 was obtained.

(Reference Example 3)
An electrode material of a Si—Sn—Co alloy fine powder which was not subjected to the high energy planetary ball mill treatment in Example 3 was obtained.

(Reference Example 4)
An electrode material of a Si-Sn-Ni alloy fine powder which was not subjected to the high energy planetary ball mill treatment in Example 4 was obtained.

  Next, the results of analyzing the electrode materials obtained in Examples 1 to 4 and Reference Examples 1 to 4 will be described.

  The electrode material of the Si alloy was analyzed from the viewpoints of an average particle diameter, a crystallite size, an intermetallic compound of Sn and Zn, and an element distribution in the alloy, which are considered to affect the performance of the negative electrode of the lithium secondary battery.

  Here, the average particle diameter was determined by a laser diffraction / scattering type particle size distribution analyzer, and further confirmed by observation with a scanning electron microscope (SEM). The crystallite size was calculated from the Scherrer's equation using the half width of the X-ray diffraction peak, and the detection of Sn and Zn intermetallic compounds was examined by TEM with selected area electron diffraction.

  The distribution of elements in the alloy was examined by TEM observation based on uneven distribution of density in the alloy particles. When the elements in the alloy are less unevenly distributed and uniformly dispersed, the image is observed as an image with less shading in the alloy particles, and the element mapping by EDXS analysis combined with TEM shows that the unevenness of the element distribution in the particles is small. Less observed.

  Using the electrode material produced in Example 1, the particle size distribution was measured with a laser diffraction / scattering type particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.). As a result, the median diameter was found to be 0.28 μm. Was. FIG. 6 is a photograph of the electrode material obtained from the SEM observation. From the same figure, it was found that the electrode material (negative electrode material) was uniform particles of 0.5 μm or less.

  Further, X-ray diffraction measurement was performed to obtain a profile shown in FIG. The crystallite size calculated from the Scherrer equation using the half width of the peak at 28 ° ± 1, which is the main peak of silicon, was 11.1 nm.

  Further, electron diffraction was performed in a 150 nm-diameter limited visual field region by TEM observation. FIG. 8 summarizes the results. Table 1 summarizes the results of calculating the d value for the diffraction pattern of the ring in FIG.

Then, from the table 1, from the d value of the JCPDS card number in d-values and _Cu 6 Sn ₅ that is calculated from electron diffraction results of material prepared in Example 1 is well approximated, the _Cu 6 Sn ₅ Turned out to exist.

  In addition, Examples 2 to 4 were examined in the same manner, and the average particle diameter, crystallite size, and observed intermetallic compounds of the electrode materials manufactured in Examples 1 to 4 were summarized in Table 2.

  From Table 2, it was found that the average particle diameter of the Si alloys prepared in Examples 1 to 4 was 0.24 to 0.49 μm, and the crystallite size was 10.5 to 11.7 nm. It was also found that a Sn intermetallic compound or a Zn intermetallic compound was present.

  Next, the element distribution in the alloy was examined using the electrode materials produced in Example 1 and Reference Example 1. 9 and 10 show photographs obtained by TEM observation of the electrode materials manufactured in Example 1 and Reference Example 1. FIG. 11 and 12 show the results of element mapping by EDXS analysis.

From these results, it was found that the light-colored portion was the Si phase, and the dark portions were the Sn phase and the Sn ₆ Cu ₅ phase. From FIG. 9, it was found that the electrode material manufactured in Example 1 had a small difference in shading, and the Sn phase and the Sn ₆ Cu ₅ phase were uniformly dispersed in the Si phase. On the other hand, from FIG. 10, it was confirmed that the electrode material produced in Reference Example 1 had a large uneven distribution of density in the alloy particles, and the Si phase and the Sn or Sn ₆ Cu ₅ phase were unevenly distributed in the particles.

  Similar observation results were obtained in Example 2 and Reference Example 2, Example 3 and Reference Example 3, and Example 4 and Reference Example 4.

  Next, an electrode structure was manufactured using the fine powders of various silicon alloys obtained by the above-described procedure as described below, and the performance of lithium insertion / desorption of the electrode structure was evaluated.

  First, 66.5% by weight of the fine powder of various silicon alloys obtained by the above-described procedure and flat graphite powder (specifically, a substantially disc having a diameter of about 5 μm and a thickness of about 5 μm) as a conductive auxiliary material 10.0% by weight of graphite powder), 6.0% by weight of graphite powder (substantially spherical, having an average particle size of 0.5 to 1.0 μm), and acetylene black (substantially spherical, 4.0 wt% of an average particle size of 4 × 10 −2 μm), 10.5 wt% of polyvinyl alcohol as a binder and 3.0 wt% of sodium carboxymethylcellulose were mixed, and water was added. And kneaded to prepare a paste.

  Next, the paste thus prepared is applied on a 15 μm-thick electric field copper foil (a copper foil produced electrochemically) by a coater, dried, and the thickness is adjusted by a roll press. The electrode structure of the active material layer was manufactured.

  Then, the electrode structure was cut into a size of 2.5 cm × 2.5 cm, and a copper tab was welded to form a silicon electrode.

[Evaluation procedure of lithium insertion / desorption amount]
Next, a lithium electrode was fabricated by pressing a 100 μm-thick lithium metal foil on a copper foil. Next, 1 M (mol / l) of a salt of LiPF ₆ was dissolved in an organic solvent obtained by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 3: 7 to prepare an electrolyte solution.

  Then, the electrolytic solution was impregnated into a porous polyethylene film having a thickness of 25 μm, and the silicon electrode described above was disposed on one surface of the film, and the lithium electrode described above was disposed on the other surface. To sandwich the polyethylene film. Next, in order to obtain flatness, it was sandwiched between glass plates from both sides, and further covered with an aluminum laminate film to prepare an evaluation cell.

  The aluminum laminated film used was a three-layer film in which the outermost layer was a nylon film, the middle layer was an aluminum foil having a thickness of 20 μm, and the inner layer was a polyethylene film. Note that the lead terminal portion of each electrode was sealed without being laminated by fusing.

  Then, in order to evaluate the function of the electrode structure as a negative electrode, a lithium insertion / desorption cycle test (charge / discharge cycle test) was performed.

That is, the above-described cell for evaluation was connected to a charging / discharging device with the lithium electrode serving as the anode and the silicon electrode serving as the cathode. First, the current density was 0.112 mA / cm ² (70 mA per gram of the active material layer of the silicon electrode, That is, the evaluation cell is discharged at 70 mA / g of the electrode layer to insert lithium into the silicon electrode layer, and then charged at a current density of 0.32 mA / cm ² (200 mA / g of the electrode layer). Then, lithium was desorbed from the silicon layer, and the weight of the silicon electrode layer or the quantity of electricity associated with the insertion and desorption of lithium per silicon powder or silicon alloy powder was evaluated in the voltage range of 0 to 1.2 V.

  FIG. 13 is a view showing the results of lithium insertion / desorption cycle tests of the electrode structures of Examples 1 to 4 and Reference Examples 1 to 4. In the figure, the horizontal axis represents the number of cycles, and the vertical axis represents the amount of desorbed Li.

  As shown in FIG. 13, in the electrodes of Reference Examples 1 to 4 in which the intermetallic compound of Sn or Zn is not uniformly dispersed in the Si phase, the amount of desorbed Li decreases when the cycle is repeated. However, it does not decrease in the electrodes of the present invention in which the intermetallic compound of Sn or Zn is uniformly dispersed in the Si phase (Examples 1 to 4). From the above, it was found that the cycle life of the silicon alloy electrode manufactured in this example was prolonged.

  Next, a secondary battery was manufactured as Example 5 of the present invention.

(Example 5)
In this example, an electrode structure in which electrode layers were provided on both surfaces of a current collector using the negative electrode material of the present invention was manufactured, and the manufactured electrode structure was used as a negative electrode. No. 18650 (diameter 18 mmφ × height 65 mm) lithium secondary battery was manufactured.

(1) Production of Negative Electrode 403 A negative electrode 403 was produced using the electrode materials of Examples 1 to 4 in the following procedure.

First, 66.5% by weight of the fine powder of various silicon alloys obtained by the above-described procedure and flat graphite powder (specifically, a substantially disc having a diameter of about 5 μm and a thickness of about 5 μm) as a conductive auxiliary material 10.0% by weight of graphite powder), 6.0% by weight of graphite powder (substantially spherical, having an average particle size of 0.5 to 1.0 μm), and acetylene black (substantially spherical, After mixing 4.0% by weight of an average particle size of 4 × 10 ⁻² μm) and 13.5% by weight of a binder, a paste is prepared by adding N-methyl-2-pyrrolidone. did.

  In addition, as a binder, polyamideimide was used for the electrode materials of Examples 1 and 2, and polyamic acid (polyamide precursor) was used for the electrode materials of Examples 3 and 4.

  Next, the paste thus prepared is applied on a 15 μm-thick electric field copper foil (a copper foil produced electrochemically) by a coater, dried, and the thickness is adjusted by a roll press. The electrode structure of the active material layer was manufactured.

  The electrode structure provided with the electrode layers on both surfaces of the current collector was cut into a predetermined size by the above procedure, and a lead of a nickel ribbon was connected to the electrode by spot welding to obtain a negative electrode 403.

(2) Preparation of positive electrode 406 [1] Lithium citrate and cobalt nitrate were mixed at a molar ratio of 1: 3, and an aqueous solution in which citric acid was added and dissolved in ion-exchanged water was sprayed into an air stream at 200 ° C. Thus, a fine powder of a lithium-cobalt oxide precursor was prepared.
[2] The precursor of the lithium-cobalt oxide obtained in the above [1] was further heat-treated at 850 ° C in an oxygen stream.
[3] After mixing 3% by weight of graphite powder and 5% by weight of polyvinylidene fluoride powder with the lithium-cobalt oxide prepared in [2] above, N-methyl-2-pyrrolidone was added to prepare a paste. .
[4] After applying and drying the paste obtained in the above [3] on both surfaces of the current collector 404 made of aluminum foil having a thickness of 20 μm, the thickness of one side of the positive electrode active material layer is adjusted to 90 μm by a roll press. did. Further, an aluminum lead was connected with an ultrasonic welding machine, and dried under reduced pressure at 150 ° C. to produce a positive electrode 406.

(3) Preparation Procedure of Electrolyte Solution [1] A solvent was prepared by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 3: 7 from which water had been sufficiently removed.
[2] A solution prepared by dissolving lithium tetrafluoroborate (LiBF ₄ ) at 1 M (mol / L) in the solvent obtained in [1] above was used as an electrolytic solution.

(4) Separator 407
A 25 micron thick polyethylene microporous film was used as the separator.

(5) Assembling of Battery Assembling was all performed under a dry atmosphere in which moisture at a dew point of −50 ° C. or less was controlled.

  A separator 407 was sandwiched between the negative electrode 403 and the positive electrode 406, wound spirally so as to form a separator / positive electrode / separator / negative electrode / separator, and inserted into a stainless steel negative electrode can 408.

  Next, the negative electrode lead 412 was connected to the bottom of the negative electrode can 408 by spot welding. A neck was formed on the upper part of the negative electrode can by a necking device, and a positive electrode lead 413 was welded to a positive electrode cap 409 with a gasket 410 made of polypropylene by a spot welding machine.

[3] Next, after injecting the electrolytic solution, the positive electrode cap was covered, and the positive electrode cap and the negative electrode can were caulked with a caulking machine and sealed to produce a battery.

  This battery was a battery with a positive electrode capacity regulation in which the capacity of the negative electrode was larger than that of the positive electrode.

(6) Evaluation Each battery was charged and discharged, and the discharge capacity was measured.

  As a result, the discharge capacity of each of the lithium secondary batteries using the electrode structures formed from the electrode materials of Examples 1 to 4 as the negative electrode exceeded 2800 mAh. Also, the discharge capacity at the 100th cycle was maintained at 75% or more of the initial capacity.

FIG. 2 is a schematic cross-sectional view of particles of an electrode material constituting the electrode structure according to the present invention. The conceptual diagram which shows typically the cross section of one Embodiment of the electrode structure which consists of a negative electrode material of the lithium secondary battery which concerns on this invention. FIG. 1 is a conceptual diagram schematically showing a cross section of one embodiment of a secondary battery (lithium secondary battery) of the present invention. FIG. 3 is a cross-sectional view of a single-layer flat (coin-shaped) battery. FIG. 2 is a cross-sectional view of a spiral cylindrical battery. FIG. 2 is a photograph of the electrode material manufactured in Example 1 of the present invention observed with a scanning electron microscope. The figure which shows the X-ray diffraction profile of the electrode material produced in Example 1 of this invention. FIG. 3 is a view showing a selected area electron diffraction image of the electrode material manufactured in Example 1 of the present invention. The figure which shows the image observed by the transmission electron microscope of the electrode material produced in Example 1 of this invention. The figure which shows the image observed by the transmission electron microscope of the electrode material produced in the reference example 1 of this invention. The figure which shows the result of the element mapping by EDXS analysis of the electrode material produced in Example 1 of this invention. The figure which shows the result of the element mapping by EDXS analysis of the electrode material produced in the reference example 1 of this invention. The figure which shows the lithium desorption and the insertion desorption cycle test result of the electrode produced in Examples 1-4 of this invention, and Reference Examples 1-4.

Explanation of reference numerals

Reference Signs List 101 electrode material layer 102 electrode structure 103 negative electrode material fine powder 104 conductive auxiliary material 105 binder 106 silicon phase 107 intermetallic compound 201, 301, 403 negative electrode 203, 303, 406 positive electrode 202, 302, 407 ion conductor 204 negative electrode Terminal 205 Positive terminal 206 Battery case (battery housing)
304 Negative electrode cap 305 Positive electrode can 306, 410 Gasket 401 Negative current collector 402 Negative electrode material layer 404 Positive current collector 405 Positive electrode material layer 408 Negative electrode can (negative electrode terminal)
409 Positive electrode cap (positive electrode terminal)
411 Insulating plate 412 Negative lead 413 Positive lead 414 Safety valve

Claims (9)

An electrode material for a lithium secondary battery comprising particles of an alloy having a mean particle size of silicon as a main component of 0.02 μm to 5 μm or less,
An electrode material for a lithium secondary battery, wherein the crystallite size of the alloy is 2 nm or more and 500 nm or less, and an intermetallic compound containing at least tin is dispersed in a silicon phase.   The intermetallic compound containing tin has at least one element of copper, nickel, cobalt, iron, manganese, vanadium, molybdenum, niobium, tantalum, zirconia, yttrium, lanthanum, selenium, and magnesium. The electrode material for a lithium secondary battery according to claim 1.   The lithium secondary according to claim 1, wherein the alloy containing silicon as a main component has at least one or more simple metals selected from tin, aluminum, zinc, indium, antimony, bismuth, and lead. Electrode material for batteries. An electrode material for a lithium secondary battery comprising particles of an alloy having a mean particle size of silicon as a main component of 0.02 μm to 5 μm or less,
The alloy has a crystallite size of 2 nm or more and 500 nm or less, and at least one kind of intermetallic compound containing at least one of aluminum, zinc, indium, antimony, bismuth, and lead is dispersed in a silicon phase. Characteristic electrode material for lithium secondary batteries.   5. The lithium secondary battery according to claim 4, wherein the alloy containing silicon as a main component has at least one kind of simple metal selected from tin, aluminum, zinc, indium, antimony, bismuth, and lead. Electrode material.   The electrode material for a lithium secondary battery according to any one of claims 1 to 5, wherein the content of silicon in the alloy is 50 wt% or more and 90 wt% or less.   An electrode structure comprising the electrode material according to claim 1, a conductive auxiliary material, a binder, and a current collector.   The electrode structure according to claim 7, wherein the conductive auxiliary material is a carbon material. A secondary battery comprising a negative electrode, an electrolyte, and a positive electrode using the electrode structure according to claim 7, and utilizing an oxidation reaction of lithium and a reduction reaction of lithium ions.

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