JP2008311209A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an anode in which an anode mixture layer containing an anode active substance and a binder is formed on an anode current collector and provide a nonaqueous electrolyte secondary battery which has a high capacity and excellent cycle characteristics. <P>SOLUTION: The nonaqueous electrolyte secondary battery is provided with a cathode 12, and anode 11 in which an anode mixture layer containing an anode active substance and a binder is formed on an anode current collector, and a nonaqueous electrolyte solution 14. The above anode active substance contains compound alloy powder containing tin, cobalt, carbon and graphite powder, and a porosity of the anode mixture layer formed on the anode current collector is within a range of 5-20 vol.%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, and in particular, a negative electrode mixture layer including a negative electrode active material and a binder is formed on a negative electrode current collector. Further, the present invention is characterized in that a non-aqueous electrolyte secondary battery having a high capacity and excellent cycle characteristics can be obtained by improving the negative electrode.

  In recent years, non-aqueous electrolyte secondary batteries that use non-aqueous electrolyte and charge and discharge by moving lithium ions between the positive and negative electrodes have been used as power sources for portable electronic devices and power storage. Has been.

  In such a nonaqueous electrolyte secondary battery, a graphite material is widely used as a negative electrode active material in the negative electrode.

  Here, in the case of a graphite material, the discharge potential is flat and the lithium ions are inserted and desorbed between the graphite crystal layers to be charged / discharged. There is an advantage that the volume change is small.

  On the other hand, in recent years, there has been a demand for a non-aqueous electrolyte secondary battery with a higher capacity in order to cope with the multifunctional and high performance of portable electronic devices and the like, but the capacity of the above graphite material is not always sufficient. However, there is a problem that it is not possible to sufficiently meet the above demand.

  For this reason, in recent years, the use of a material that forms an alloy with lithium, such as Si, Zn, Pb, Sn, Ge, and Al, as a high-capacity negative electrode active material has been studied.

  However, these materials that form an alloy with lithium have a large volume change due to insertion and extraction of lithium, and when repeated charging and discharging are performed, the particle structure is destroyed and refined, thereby collecting current inside the negative electrode. As a result, there was a problem that the capacity was significantly reduced.

  For this reason, conventionally, as disclosed in Patent Document 1, a material that forms an alloy with lithium, such as Si, Pb, Sn, Ge, and Al, which has a large volume change due to insertion and extraction of lithium, and Sc, Ti , V and other alloy powders using a mechanically alloyed negative electrode active material, and as disclosed in Patent Document 2, Si, Pb, Al that occlude / release lithium And the like, and an alloy containing a first metal such as the above and a second metal that stabilizes the shape change of the first metal at the time of occlusion / release of lithium is proposed as a negative electrode active material. Yes.

  However, even when such a negative electrode active material is used, the volume change of the alloy accompanying charging / discharging is large, and when charging / discharging is repeated, the capacity still decreases greatly.

  In addition, in the past, for the purpose of ensuring a sufficient space for the volume change during charge and discharge, as shown in Patent Document 3, a negative electrode using a metal or alloy that occludes / releases lithium as a negative electrode active material In the negative electrode having a negative electrode mixture layer containing a tin-containing alloy powder as shown in Patent Document 4 or 50% to 90% by volume, the negative electrode mixture layer has a porosity of 25 to 65 volumes. % Have been proposed.

  On the other hand, in order to obtain a high-capacity electrode, not only a negative electrode active material alloyed with lithium, which is a high-capacity material, is used, but also the utilization rate of the material used for this negative electrode active material is increased, and the reversible capacity in the battery is increased. It is necessary to raise.

  Therefore, by forming a composite alloy with cobalt and carbon together with tin alloyed with lithium, the utilization rate of tin can be increased, and carbon in the composite alloy occludes and releases lithium to charge and discharge, The reversible capacity of the battery can be increased. In particular, when highly conductive graphite is used for the carbon, the internal resistance in the negative electrode mixture layer is reduced, the utilization of the composite alloy is improved, and the graphite has a reversible capacity per unit weight. When graphite of 330 mAh / g or more is used, the capacity of the negative electrode can be increased, the initial charge / discharge efficiency of the negative electrode can be improved, and the capacity of the battery can be increased.

However, when such a composite alloy containing graphite is used for the negative electrode active material, if the porosity in the negative electrode is increased as shown in Patent Documents 3 and 4 above, the capacity per unit volume in the negative electrode decreases. As a result, a high-capacity non-aqueous electrolyte secondary battery cannot be obtained, and the contact points between the negative electrode active materials are reduced due to expansion and contraction of the negative electrode active material. There is a problem that the resistance increases and the cycle characteristics of the nonaqueous electrolyte secondary battery deteriorate.
Japanese Patent No. 3624417 JP 2006-1000024 A JP 2002-367602 A Japanese Patent No. 3726958

  An object of the present invention is to solve various problems as described above in a non-aqueous electrolyte secondary battery, and a negative electrode mixture layer including a negative electrode active material and a binder is formed on a negative electrode current collector. It is an object of the present invention to improve the negative electrode so that a non-aqueous electrolyte secondary battery having a high capacity and excellent cycle characteristics can be obtained.

  In order to solve the above-mentioned problems, the present invention comprises a positive electrode, a negative electrode in which a negative electrode mixture layer containing a negative electrode active material and a binder is formed on a negative electrode current collector, and a non-aqueous electrolyte. In the non-aqueous electrolyte secondary battery, the negative electrode active material includes a composite alloy powder containing tin, cobalt, and carbon and a graphite powder, and the negative electrode mixture layer formed on the negative electrode current collector The porosity was adjusted to be in the range of 5 to 20% by volume.

  Here, the porosity is the ratio of the volume of the void to the apparent volume of the negative electrode mixture layer. This porosity is measured directly by mercury porosimetry or the like, and the volume of the negative electrode mixture layer is calculated by measuring the true density and weight of the negative electrode mixture and subtracting this from the apparent volume. And the ratio of the void volume to the apparent volume can be obtained as the void ratio. The porosity does not include the volume of the negative electrode current collector.

  In the non-aqueous electrolyte secondary battery according to the present invention, since the negative electrode active material including the composite alloy powder containing tin, cobalt, and carbon and the graphite powder is used as described above, the tin contained in the composite alloy powder is reduced. A high capacity is obtained by alloying with lithium, and the utilization rate of the tin is improved by cobalt and carbon contained in the composite alloy powder. Moreover, since the graphite powder is contained in the negative electrode active material, the conductivity of the negative electrode is improved by the graphite powder.

  In the nonaqueous electrolyte secondary battery according to the present invention, when the negative electrode mixture layer containing the negative electrode active material and the binder is formed on the negative electrode current collector, the negative electrode mixture layer has a porosity of 5 to 5. Since the volume is in the range of 20% by volume, even if the negative electrode active material expands and contracts due to charge / discharge, the contact points between the negative electrode active materials are suppressed from decreasing, and the conductive network in the negative electrode is appropriately maintained. As a result, the internal resistance of the negative electrode is prevented from increasing due to charge / discharge.

  Here, the graphite powder used for the negative electrode active material expands anisotropically during charge and discharge, and is oriented in the negative electrode when compressed after application, and therefore tends to expand particularly in the vertical direction during charge and discharge. For this reason, the negative electrode active material does not expand so that the individual negative electrode active material particles fill the voids during charging, but the entire negative electrode mixture layer forming the conductive network is in contact with the negative electrode current collector. It also expands vertically. For this reason, when the porosity of the negative electrode mixture layer is increased as shown in the above-mentioned patent document, the conductive network is destroyed by the volume shrinkage of the negative electrode active material particles during discharge, and the charge / discharge efficiency is reduced. By setting the porosity of the negative electrode mixture layer to 20% by volume or less as in the invention, good charge / discharge cycle characteristics can be obtained.

  In addition, by making the porosity of the negative electrode mixture layer 20% by volume or less, the thickness of the negative electrode can be reduced, and the stress caused by the volume change of the electrode body due to the expansion of the negative electrode active material in the battery container is relieved. Even when a space is provided, a high-capacity nonaqueous electrolyte secondary battery can be obtained. In the conventional battery, when a non-aqueous electrolyte secondary battery having the same capacity is manufactured, the space in the battery container cannot be increased, so that the stress generated by the volume change of the electrode body is increased. The charge / discharge cycle characteristics of the water electrolyte secondary battery may be deteriorated.

  As a result, in the nonaqueous electrolyte secondary battery according to the present invention, high capacity is obtained, and deterioration of the negative electrode due to charge / discharge is suppressed, and excellent cycle characteristics can be obtained.

  Next, an embodiment of the nonaqueous electrolyte secondary battery according to the embodiment of the present invention will be specifically described. In addition, the nonaqueous electrolyte secondary battery in this invention is not limited to what was shown to the following embodiment, In the range which does not change the summary, it can implement suitably.

  In the non-aqueous electrolyte secondary battery of the present invention, the composite containing tin, cobalt, and carbon in the negative electrode in which the negative electrode mixture layer including the negative electrode active material and the binder is formed on the negative electrode current collector as described above. A negative electrode active material containing an alloy powder and graphite powder is used, and the porosity of the negative electrode mixture layer formed on the negative electrode current collector is in the range of 5 to 20% by volume.

  Here, as the graphite powder used for the negative electrode active material, the conductivity of the negative electrode is increased to reduce its internal resistance, the utilization rate of the composite alloy powder is increased and the initial charge / discharge efficiency is increased. In order to increase the capacitance, the lattice spacing d002 measured by the X-ray diffraction method is 0.337 nm or less, the crystallite size Lc in the c-axis direction is 30 nm or more, and the 50% particle size (median diameter) D50 is 5 to 5. It is preferable to use graphite powder in the range of 35 μm.

  Moreover, in the composite alloy powder containing tin, cobalt and carbon used for the negative electrode active material, if the particle diameter becomes too small, the contact surface between the particles cannot be increased, and the particles contact each other during discharge. The number of points decreases and the conductivity of the negative electrode decreases. On the other hand, if the particle size becomes too large, the ratio of the particle size to the thickness of the negative electrode mixture layer increases, and the composite alloy powder is uniformly distributed in the negative electrode mixture layer. Therefore, it is preferable to use a composite alloy powder having a 50% particle diameter (median diameter) D50 in the range of 5 to 35 μm, and more preferably. The composite alloy powder having the D50 in the range of 10 to 30 μm is used.

  Moreover, as said composite alloy powder, it is preferable to use what has the ratio of a carbon atom in the range of 40-80 atomic%. When carbon atoms are contained in an amount of 40 atomic% or more, tin, cobalt, and carbon are easily compounded, and the structure of the composite alloy particles is prevented from changing even after repeated charge and discharge. The conductivity in the composite alloy is also improved, and the utilization rate of tin is improved. On the other hand, when the proportion of carbon atoms exceeds 80 atomic%, the proportion of tin in the composite alloy is reduced, resulting in a high capacity. This is because the battery cannot be obtained.

  Moreover, in order to improve the cycling characteristics in said composite alloy powder, it is preferable to use the one in which the ratio of tin to the total amount of tin and cobalt is in the range of 45 to 55 atomic%.

  In addition, a uniform charge / discharge reaction is performed in the above composite alloy, and when the charge / discharge is repeated, the structure of the composite alloy particles is suppressed from changing, so that even better cycle characteristics can be obtained. In order to obtain a desirable alloy state by sufficiently reducing the crystal grains, the X-ray diffraction using Cu—Kα rays as the above composite alloy powder has a peak position 2θ of the main peak of 40 ° to It is preferable to use one having a SnCo phase in a composite alloy having a range of 45 ° and a half-value width of 0.7 ° or more.

  In addition to the tin, cobalt, and carbon, the composite alloy powder can contain other elements, and the composite alloy can be increased in its composite capacity so as not to reduce the capacity of the composite alloy. In order to further reduce the crystal grain size and improve the cycle characteristics, 2 to 20 atomic% of one or more elements selected from titanium, indium, iron, chromium, molybdenum, zirconium and oxygen are used. It is preferable to make it contain in the range.

  Further, in order to uniformly combine tin, cobalt, and carbon in the composite alloy powder, and to produce composite alloy particles having small crystal grains, it is preferable to perform a mechanical milling process using a ball mill, an attritor, or the like. .

  In obtaining a negative electrode active material containing the above graphite powder and composite alloy powder, if the proportion of the graphite powder in the negative electrode active material is small, it becomes difficult to improve the conductivity in the negative electrode, and at the time of charge / discharge On the other hand, it is difficult to sufficiently suppress the expansion and contraction of the negative electrode active material in the negative electrode active material. The battery cannot be obtained. For this reason, as said negative electrode active material, it is preferable to use the thing whose ratio of the graphite powder with respect to the total amount of said graphite powder and composite alloy powder is the range of 20-60 mass%, More preferably, graphite powder The ratio is 30 to 50% by mass.

  Further, when forming the negative electrode mixture layer containing the negative electrode active material and the binder on the negative electrode current collector, if the amount of the binder in the negative electrode mixture layer is small, the adhesion between the negative electrode active materials and the negative electrode The adhesion between the active material and the negative electrode current collector is reduced, and the negative electrode active material is easily separated from the negative electrode current collector. On the other hand, if the amount of the binder in the negative electrode mixture layer is too large, the conductivity in the negative electrode is reduced. And the porosity of the negative electrode mixture layer becomes difficult to be 20% by volume or less. For this reason, it is preferable to make the quantity of the binder in a negative mix layer into the range of 0.4-2 mass%.

  Moreover, as a binder in a negative mix layer, it is preferable to use an emulsion type binder. When using an emulsion type binder, the area of the binder covering the surface of the negative electrode active material can be reduced without reducing the adhesion between the negative electrode active materials and the adhesion between the negative electrode active material and the negative electrode current collector. it can. As a result, the area where the negative electrode active material is in contact with the non-aqueous electrolyte and the contact area between the negative electrode active materials can be increased, and efficient charge and discharge can be performed, improving initial characteristics and cycle characteristics. Is done.

  Further, when an emulsion type binder is used, the adhesion between the negative electrode active materials and the adhesion between the negative electrode active material and the negative electrode current collector can be improved even in a small amount as compared with the solution type binder. At the same time, as the amount of the binder decreases, the above-described effect is obtained. Therefore, when an emulsion type binder is used as the binder in the negative electrode mixture layer, the amount of the binder in the negative electrode mixture layer is set to 0. It is preferable to make it into the range of 4-1 mass%.

  Here, examples of the emulsion type binder include fluoro rubber, ethylene-propylene-diene terpolymer (EPDM), styrene-butadiene rubber (SBR), polyethylene, polybutadiene, polytetrafluoroethylene (PTFE), and polyvinyl alcohol. A high molecular compound such as (PVA) can be used.

  In addition, since emulsion type binders generally have low viscosity, when this emulsion type binder is mixed with a negative electrode active material to produce a negative electrode mixture slurry, a thickener is used to stabilize the negative electrode mixture slurry. Preferably, carboxymethyl cellulose sodium salt can be used as the thickener.

In the nonaqueous electrolyte secondary battery of the present invention, a commonly used positive electrode active material can be used as the positive electrode active material used for the positive electrode. For example, lithium cobalt complex oxides such as LiCoO _2, lithium-nickel composite oxides such as _{LiNiO 2, LiMn 2 O 4,} LiMnO lithium-manganese composite oxides such as _{2, LiNi 1-x Co x} O 2 (0 <X <1) and other lithium / nickel / cobalt composite oxides, LiMn _1-x Co _x O ₂ (0 <x <1) and other lithium / manganese / cobalt composite oxides, LiN _x Co _y Mn _z O ₂ (x + y + z = 1 ) lithium-nickel-cobalt-manganese composite oxides such _{as, LiNi x Co y Al z O} 2 (x + y + z = 1) containing lithium transition metal oxide of the lithium-nickel-cobalt-aluminum composite oxides such as can be used goods and manganese oxides such as MnO _2, metal oxides vanadium oxides such as V ₂ O ₅ and, other oxides and sulfides

  Further, as the nonaqueous electrolyte solution in the nonaqueous electrolyte secondary battery of the present invention, a solution obtained by dissolving a solute in a nonaqueous solvent generally used in a nonaqueous electrolyte secondary battery can be used.

  Examples of the non-aqueous solvent include a mixed solvent of a cyclic carbonate such as ethylene carbonate, propylene carbonate, and butylene carbonate and a chain carbonate such as dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate, and cyclic carbonate and 1 , 2-dimethoxyethane, 1,2-diethoxyethane, and other mixed solvents with ether solvents can be used.

Examples of the solute include LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C _{4 F 9 SO 2), LiC} (CF 3 SO 2) 3, LiC (C 2 F 5 SO 2) 3, LiAsF 6, LiClO 4, Li 2 B 10 Cl 10, Li 2 B 12 Cl 12 and, of these A mixture or the like can be used.

  Next, the nonaqueous electrolyte secondary battery according to the present invention will be specifically described with reference to examples, and in the nonaqueous electrolyte secondary battery according to this example, cycle characteristics and initial charge / discharge efficiency are improved. This will be clarified with a comparative example.

Example 1
In Example 1, in preparing the negative electrode, first, a mixture of tin, cobalt, titanium, and indium at an atomic ratio of 45: 45: 9: 1 was melted, and this was cooled at a cooling rate of 10 by a gas atomization method. ^An alloy containing these elements was prepared by rapid cooling at ³ ° C./sec.

  And after making said alloy into the ratio of 78 weight part and carbon material acetylene black 22 weight part, and performing these mechanical alloying processes using a planetary ball mill in argon atmosphere for 15 hours, composite alloy powder was obtained. The composite alloy powder was taken out into the atmosphere and passed through a sieve having an opening of 150 μm to remove coarse particles, thereby obtaining a composite alloy powder used for the negative electrode active material.

  Here, this composite alloy powder was subjected to X-ray diffraction using an X-ray diffractometer (Rigaku Corporation: RINT2000 / PC) using a Cu-Kα tube as an X-ray source, and the results are shown in FIG.

  As a result, as shown in FIG. 1, a main peak corresponding to the SnCo (002) plane appears at a position of 2θ = 42.4 °, and its half-value width was measured using the application of the X-ray diffractometer. As a result, the half width was 0.84 °. Further, as shown in FIG. 1, the peak corresponding to the SnCo (101) plane is at the position of 2θ = 28.8 °, and the peak corresponding to the SnCo (110) plane is at the position of 2θ = 34.0 °. A peak corresponding to the (201) plane appeared at a position of 2θ = 44.9 °.

  Further, as a result of elemental analysis of the above composite alloy powder using a fluorescent X-ray analyzer attached to a scanning electron microscope, 12.5 atomic% of tin and cobalt were present in the composite alloy powder. 11.6 atomic%, carbon 64.2 atomic%, titanium 2.2 atomic%, indium 0.2 atomic%, iron 4.6 atomic%, chromium 1.2 atomic%, oxygen 3. It was contained at 5 atomic%.

  Further, as a result of measuring the particle diameter of the above composite alloy powder with a laser diffraction particle size distribution measuring apparatus, the 50% particle diameter (median diameter) D50 of this composite alloy powder was 6 μm, and 10 was measured from the small diameter side. The% particle size D10 was 1 μm, and the 90% particle size D90 was 16 μm.

Further, when the true density of the composite alloy powder was measured with a dry density measuring apparatus, the true density of the composite alloy powder was 4.98 g / cm ³ .

  On the other hand, as the graphite powder used for the negative electrode active material, the lattice spacing d002 measured by the X-ray diffraction method is 0.336 nm, the crystallite size Lc in the c-axis direction is 40 nm, and the 50% particle size (median diameter) D50. The scale-like artificial graphite powder having a diameter of 20 μm was used.

Further, when the true density of the artificial graphite powder was measured by a dry density measuring device, the true density of the artificial graphite powder was 2.26 g / cm ³ .

And in producing a negative electrode, 98.4 weight part of negative electrode active materials which mixed said composite alloy powder and artificial graphite powder by the weight ratio of 6: 4, and the true density which is a binder are 1.78 g / cm. 1.6 parts by weight of polyvinylidene fluoride (PVdF) ³ and N-methyl 2-pyrrolidone as a solvent were kneaded to prepare a negative electrode mixture slurry. Next, this negative electrode mixture slurry was applied onto a current collector made of an electrolytic copper foil having a thickness of 10 μm, and after heating and drying at 120 ° C., this was rolled by a roller press, A negative electrode mixture layer was formed thereon, and this was cut into a size of 2 cm × 2 cm to produce a negative electrode.

Then, the filling density of the negative electrode mixture layer in this negative electrode is obtained, and from the true density (3.32 g / cm ³ ) of the negative electrode mixture calculated from the true density of the above composite alloy powder, artificial graphite powder and binder, As a result of obtaining the porosity of the negative electrode mixture layer by the following formula, the porosity of the negative electrode mixture layer was 14% by volume.

  Porosity (volume%) = (1−filling density ÷ true density of negative electrode mixture) × 100

(Example 2)
In Example 2, in the production of the negative electrode in Example 1 described above, only the rolling conditions by the roller press were changed, and a negative electrode in which the porosity of the negative electrode mixture layer was 19% by volume was produced.

(Comparative Example 1)
In Comparative Example 1, in the production of the negative electrode in Example 1 described above, only the rolling conditions by the roller press were changed, and a negative electrode in which the porosity of the negative electrode mixture layer was 29% by volume was produced.

  And the three-electrode type test cell 10 shown in FIG. 2 was produced using each negative electrode of Examples 1 and 2 and Comparative Example 1 produced as described above.

Here, in the above-described three-electrode test cell 10, each of the above negative electrodes is used as the working electrode 11, metallic lithium is used for each of the counter electrode 12 and the reference electrode 13 that are positive electrodes, and the non-aqueous electrolyte solution 14 is In this non-aqueous electrolyte solution 14, a solution obtained by dissolving lithium hexafluorophosphate LiPF ₆ at a ratio of 1 mol / l in a mixed solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 3: 7 is used. The working electrode 11, the counter electrode 12, and the reference electrode 13 were immersed in the above.

Each of the three-electrode test cells 10 using the negative electrodes of Examples 1 and 2 and Comparative Example 1 as the working electrode 11 has a potential of the working electrode 11 with respect to the reference electrode 13 at a constant current of 0.1 mA / cm ^2. After charging to 0 V, discharging was performed at a constant current of 0.1 mA / cm ² until the potential of the working electrode 11 with respect to the reference electrode 13 became 2 V, and charge and discharge in the first cycle was performed, then 0.5 mA / after the potential of the working electrode 11 with respect to the reference electrode 13 at a constant current of cm ² was charged until to 0V, and the discharge until the potential of the working electrode 11 with respect to the reference electrode 13 at a constant current of 0.5 mA / cm ² is 2V Then, charge / discharge of the second cycle was performed.

Then, the third cycle and later, after the potential of the working electrode 11 with respect to the reference electrode 13 at a constant current of 0.5 mA / cm ² was charged until to 0V, and with respect to the reference electrode 13 at a constant current of 0.5 mA / cm ² Discharge until the potential of the working electrode 11 reaches 1 V, measure the discharge capacity Q3 of the third cycle and the discharge capacity Q7 of the seventh cycle, and the ratio of the discharge capacity Q7 of the seventh cycle to the discharge capacity Q3 of the third cycle Asked.

  As the cycle characteristic index, the above ratio when the negative electrode of Example 1 was used was set to 100, and the cycle characteristic index when each negative electrode of Examples 1, 2 and Comparative Example 1 was used is shown in Table 1 below. Indicated.

  As is clear from this result, when the negative electrodes of Examples 1 and 2 in which the porosity of the negative electrode mixture layer was 20% by volume or less were used, the porosity of the negative electrode mixture layer exceeded 20% by volume. Compared with the case where the negative electrode of Comparative Example 1 was used, the cycle characteristics were greatly improved.

(Example 3)
In Example 3, the composite alloy powder produced in the same manner as in Example 1 was passed through a sieve having an opening of 20 μm, and the composite alloy powder remaining on the sieve was used. Otherwise, the same as in Example 1 above Thus, the negative electrode of Example 3 was produced.

  Here, the particle diameter of the above composite alloy powder was measured in the same manner as in Example 1. As a result, the 50% particle diameter (median diameter) D50 of this composite alloy powder was 16 μm and measured from the small diameter side. The 10% particle diameter D10 was 5 μm, and the 90% particle diameter D90 was 20 μm.

  Moreover, as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 3, the porosity was 15 volume%.

Example 4
In Example 4, the composite alloy powder produced in the same manner as in Example 1 was dispersed in water, passed through a sieve having an opening of 10 μm, and the composite alloy powder remaining on the sieve was dried by heating at 100 ° C. under vacuum. A negative electrode of Example 4 was produced in the same manner as in Example 1 except that the composite alloy powder was used.

  Here, the particle diameter of the above composite alloy powder was measured in the same manner as in Example 1. As a result, the 50% particle diameter (median diameter) D50 of this composite alloy powder was 13 μm and measured from the small diameter side. The 10% particle diameter D10 was 4 μm and the 90% particle diameter D90 was 17 μm.

  Moreover, as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 4, the porosity was 16 volume%.

(Example 5)
In Example 5, the composite alloy powder produced in the same manner as in Example 1 was passed through a sieve having an opening of 20 μm, and the composite alloy powder that passed through the sieve was used. Other than that, the same as in Example 1 above Thus, the negative electrode of Example 5 was produced.

  Here, the particle diameter of the above composite alloy powder was measured in the same manner as in Example 1. As a result, the 50% particle diameter (median diameter) D50 of this composite alloy powder was 5 μm, and measured from the small diameter side. The 10% particle diameter D10 was 1 μm, and the 90% particle diameter D90 was 12 μm.

  Moreover, as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 5, the porosity was 16 volume%.

  And using each negative electrode of Examples 3-5 produced as mentioned above, it carried out similarly to the said case, and produced the three-electrode-type test cell 10 shown in FIG.

  Each of the three-electrode test cells 10 was charged and discharged in the same manner as in Example 1 above, and the ratio of the discharge capacity Q7 in the seventh cycle to the discharge capacity Q3 in the third cycle was determined. The above ratio in the case of using the negative electrode 1 was set to 100, and the cycle characteristic index in the case of using the negative electrodes of Examples 3 to 5 was calculated. The results are shown in Table 2 below.

  As a result, when the negative electrodes of Examples 3 and 4 using the composite alloy powder having a 50% particle diameter (median diameter) D50 of 10 μm or more were used, the 50% particle diameter (median diameter) D50 was less than 10 μm. The cycle characteristics were improved as compared with the case of using the negative electrodes of Examples 1 and 5 using the composite alloy powder obtained.

(Example 6)
In Example 6, as graphite powder, the lattice spacing d002 measured by the X-ray diffraction method was 0.336 nm, the crystallite size Lc in the c-axis direction was 40 nm, and the 50% particle size (median diameter) D50 was 25 μm. A scale-like artificial graphite powder was used, and this artificial graphite powder was mixed with a composite alloy powder having a 50% particle size (median diameter) D50 of 6 μm as in Example 1 in a weight ratio of 5: 5. A negative electrode of Example 6 was produced in the same manner as in Example 1 except that the negative electrode active material mixed as described above was used.

  And as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 6, the porosity was 11 volume%.

(Example 7)
In Example 7, the artificial graphite powder used in Example 6 above and the composite alloy powder having the same 50% particle size (median diameter) D50 of 6 μm as in Example 1 in a weight ratio of 3: 7. A negative electrode of Example 7 was produced in the same manner as in Example 1 except that the negative electrode active material mixed as described above was used.

  And as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 7, the porosity was 17 volume%.

(Example 8)
In Example 8, the artificial graphite powder used in Example 6 above and the composite alloy powder having the same 50% particle size (median diameter) D50 of 6 μm as in Example 1 in a weight ratio of 2: 8. A negative electrode of Example 8 was produced in the same manner as in Example 1 except that the negative electrode active material mixed as described above was used.

  And as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 8, the porosity was 19 volume%.

Example 9
In Example 9, the artificial graphite powder used in Example 6 above and the composite alloy powder having the same 50% particle size (median diameter) D50 of 6 μm as in Example 1 in a weight ratio of 1: 9. A negative electrode of Example 9 was prepared in the same manner as in Example 1 except that the negative electrode active material mixed as described above was used.

  And as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 9, the porosity was 19 volume%.

(Comparative Example 2)
In Comparative Example 2, the composite graphite powder having the same 50% particle size (median diameter) D50 of 6 μm as in Example 1 was used as the negative electrode active material without using the artificial graphite powder, and the others were as described above. In the same manner as in Example 1, a negative electrode of Comparative Example 2 was produced.

  And as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this comparative example 2, the porosity was 28 volume%.

  And using each negative electrode of Examples 6-9 produced as mentioned above and the comparative example 2, it carried out similarly to the said case, and produced the 3 electrode type test cell 10 shown in FIG.

  Each of the three-electrode test cells 10 is charged / discharged in the same manner as in Example 1 to determine the initial discharge capacity in the first cycle, and the seventh cycle relative to the discharge capacity Q3 in the third cycle. The ratio of the discharge capacity Q7 was calculated, and the cycle characteristic index when each of the negative electrodes of Examples 6 to 9 and Comparative Example 2 was used was calculated with the above ratio when the negative electrode of Example 8 was used as 100, These results are shown in Table 3 below.

  As a result, when the negative electrodes of Examples 6 to 9 using the negative electrode active material in which the graphite powder and the composite alloy powder were mixed, only the composite alloy powder was mixed with the negative electrode active material without mixing the graphite powder. Compared with the case where the negative electrode of Comparative Example 1 used for the substance was used, the cycle characteristics were greatly improved.

  Further, when the negative electrodes of Examples 6 to 8 in which the amount of graphite powder in the negative electrode active material was 20% by mass or more were used, the example in which the amount of graphite powder in the negative electrode active material was less than 20% by mass. Compared with the case where the negative electrode of 9 was used, the cycle characteristics were further improved.

  In addition, when comparing the initial discharge capacity, when the negative electrode of Example 6 in which the amount of graphite powder in the negative electrode active material was 50% by mass, the initial discharge capacity was slightly reduced, but only the composite alloy powder When using the negative electrodes of Examples 7 to 9 in which the amount of graphite powder in the negative electrode active material was 30% by mass or less, there was little difference from the case of using the negative electrode of Comparative Example 1 using The initial discharge capacity was higher than when the negative electrode of Comparative Example 1 was used. This is considered to be because the utilization rate of the composite alloy powder was improved by adding the graphite powder.

(Example 10)
In Example 10, the same negative electrode active material as in Example 1 above was used, and 98.4 parts by weight of this negative electrode active material, a styrene-butadiene rubber having an emulsion type binder and a true density of 0.91 g / cm ³ ( SBR) is 0.8 parts by weight in terms of solid content, and the true density as a thickener is 1.35 g / cm ³ carboxymethylcellulose sodium salt (CMC) at a ratio of 0.8 parts by weight, and these are solvents. A negative electrode mixture slurry was prepared by kneading water. Next, this negative electrode mixture slurry was applied onto a current collector made of an electrolytic copper foil having a thickness of 10 μm, and after heating and drying at 120 ° C., this was rolled by a roller press, A negative electrode mixture layer was formed thereon, and this was cut into a size of 2 cm × 2 cm to produce a negative electrode of Example 10.

  And as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 10, the porosity was 16 volume%.

(Example 11)
In Example 11, 98.8 parts by weight of the negative electrode active material in Example 10 above, 0.8 parts by weight of styrene-butadiene rubber (SBR), which is an emulsion type binder, in terms of solid content, and a thickener The negative electrode of Example 11 was produced in the same manner as in Example 10 except that the carboxymethylcellulose sodium salt (CMC) was 0.4 parts by weight.

  And as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 11, the porosity was 15 volume%.

(Example 12)
In Example 12, 99.2 parts by weight of the negative electrode active material in Example 10 above, 0.4 parts by weight of styrene-butadiene rubber (SBR), which is an emulsion type binder, in terms of solid content, and a thickener The negative electrode of Example 12 was produced in the same manner as in Example 10 except that the carboxymethylcellulose sodium salt (CMC) was 0.4 parts by weight.

  And as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 12, the porosity was 15 volume%.

(Example 13)
In Example 13, 97.5 parts by weight of the negative electrode active material in Example 10 above, 1.5 parts by weight of styrene-butadiene rubber (SBR), which is an emulsion type binder, in terms of solid content, and a thickener The negative electrode of Example 13 was produced in the same manner as in Example 10 except that the amount of carboxymethylcellulose sodium salt (CMC) was 1.0 parts by weight.

  And as a result of calculating | requiring the porosity of the negative mix layer in the negative electrode of this Example 13, the porosity was 20 volume%.

  And using each negative electrode of Examples 10-13 produced as mentioned above, it carried out similarly to the said case, and produced the 3 electrode type test cell 10 shown in FIG.

  And each 3 electrode type test cell 10 using the negative electrode of said Examples 10-13 and Example 1 was charged / discharged similarly to the case of said Example 1, and in each 3 electrode type test cell 10, The ratio of the discharge capacity of the first cycle to the charge capacity of the first cycle (initial charge / discharge efficiency) is determined, and the ratio of the discharge capacity Q7 of the seventh cycle to the discharge capacity Q3 of the third cycle is determined. The cycle characteristic index when each negative electrode of Examples 10 to 13 was used was calculated with the above ratio when the negative electrode was used as 100, and the results are shown in Table 4 below.

  As a result, while using the emulsion type binder styrene-butadiene rubber (SBR) as a binder in the negative electrode mixture layer, the negative electrodes of Examples 10 to 13 containing carboxymethyl cellulose sodium salt as a thickener were added. When used, the initial charge / discharge efficiency was improved as compared with the case where the negative electrode of Example 1 using polyvinylidene fluoride (PVdF) as the binder was used.

  In particular, when the negative electrode of Examples 10 to 12 is used with the amount of styrene-butadiene rubber (SBR), which is an emulsion-type binder, in the negative electrode mixture layer being 1% by mass or less, the initial charge / discharge efficiency is further improved. In addition, the cycle characteristics were improved.

It is the figure which showed the X-ray-diffraction measurement result of the composite alloy powder manufactured in Example 1 of this invention. It is a schematic explanatory drawing of the 3 electrode type test cell which used each negative electrode of Examples 1-13 of this invention and Comparative Examples 1 and 2 for a working electrode.

Explanation of symbols

10 Three-electrode test cell 11 Working electrode (negative electrode)
12 Counter electrode (positive electrode)
13 Reference electrode 14 Non-aqueous electrolyte

Claims (13)

  In a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode in which a negative electrode mixture layer including a negative electrode active material and a binder is formed on a negative electrode current collector, and a nonaqueous electrolyte solution, the negative electrode active material includes: In addition, the composite alloy powder containing tin, cobalt and carbon and the graphite powder, and the porosity of the negative electrode mixture layer formed on the negative electrode current collector is in the range of 5 to 20% by volume. Non-aqueous electrolyte secondary battery characterized.   2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the graphite powder used for the negative electrode active material has a lattice spacing d002 of 0.337 nm or less measured by an X-ray diffraction method and a crystallite size in the c-axis direction. A non-aqueous electrolyte secondary battery having a thickness Lc of 30 nm or more and a 50% particle diameter (median diameter) D50 in the range of 5 to 35 μm.   3. The nonaqueous electrolyte secondary battery according to claim 1, wherein a 50% particle size (median diameter) D50 of the composite alloy powder used for the negative electrode active material is in the range of 5 to 35 μm. Non-aqueous electrolyte secondary battery.   4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the ratio of the graphite powder to the total amount of the graphite powder and the composite alloy powder used for the negative electrode active material is 20 to 60 mass. % Nonaqueous electrolyte secondary battery.   The nonaqueous electrolyte secondary battery according to claim 4, wherein the ratio of the graphite powder to the total amount of the graphite powder and the composite alloy powder used for the negative electrode active material is in the range of 30 to 50 mass%. Non-aqueous electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the composite alloy powder used for the negative electrode active material has a carbon atom ratio in a range of 40 to 80 atomic%. A non-aqueous electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the composite alloy powder used for the negative electrode active material has a ratio of tin to 45 to 55 atomic% with respect to a total amount of tin and cobalt. The nonaqueous electrolyte secondary battery according to claim 1, wherein the nonaqueous electrolyte secondary battery is in a range of   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein the composite alloy powder used for the negative electrode active material has a peak position of a main peak in X-ray diffraction using Cu-Kα rays. A non-aqueous electrolyte secondary battery characterized in that 2θ is in the range of 40 ° to 45 ° and the half-value width thereof is 0.7 ° or more.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 8, wherein the composite alloy powder used for the negative electrode active material has a SnCo phase. battery.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 9, wherein the amount of the binder in the negative electrode mixture layer is in the range of 0.4 to 2% by mass. Water electrolyte secondary battery.   11. The non-aqueous electrolyte secondary battery according to claim 1, wherein the binder in the negative electrode mixture layer is an emulsion-type binder. 11.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 11, wherein the binder in the negative electrode mixture layer is styrene-butadiene rubber.   13. The non-aqueous electrolyte secondary battery according to claim 11, wherein a thickener carboxymethyl cellulose is contained in the negative electrode mixture layer. 14.

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