JP5216973B2 - Non-aqueous secondary battery and non-aqueous secondary battery system - Google Patents

Description

  The present invention relates to a non-aqueous secondary battery and a non-aqueous secondary battery system including the non-aqueous secondary battery and a charging circuit thereof.

  Non-aqueous secondary batteries are widely used as power sources for portable devices such as mobile phones and notebook personal computers because of their high energy density. As mobile devices become more sophisticated, non-aqueous secondary batteries are required to have higher output and longer life, and ensuring safety is also an important issue. In addition, non-aqueous secondary batteries used for power supplies such as power tools are charged and discharged with a large current, so the temperature of the battery tends to rise. There is a need to prevent degradation.

  From the viewpoint of extending the life of the battery, the use of lithium titanium oxide for the negative electrode has been studied, and a battery using lithium cobalt oxide, lithium nickel oxide or lithium manganese oxide for the positive electrode (Patent Document) 1) a battery using a lithium oxide having a layer structure and containing substantially the same ratio of nickel and cobalt (Patent Document 2), a battery using a spinel structure lithium manganese oxide (Patent Document 3), etc. Has been proposed.

JP 10-27626 A Japanese Patent Laid-Open No. 2005-142047 JP-A-10-27609

  However, in the nonaqueous secondary battery described in Patent Document 1, the ratio of the practical amount of the negative electrode active material to the actual capacity of the positive electrode active material is 0.5 or less, and before the potential on the positive electrode side increases, The capacity ratio between the positive electrode and the negative electrode is set so that the potential drops. For this reason, the potential of the positive electrode hardly changes even at the end of charging, and when the end of charging is determined by a change in the voltage of the battery, the determination is made substantially only by a change in the potential of the negative electrode. Such a battery can solve problems such as decomposition of the electrolytic solution due to the potential increase of the positive electrode, but it is necessary to set the ratio of the negative electrode active material low, so that a battery suitable for high output should be configured. I can't.

  In addition, in the non-aqueous secondary battery described in Patent Document 2, the shape of the charge / discharge curve of the negative electrode becomes completely flat in all regions, and the shape of the charge / discharge curve of the positive electrode is The battery is designed to correspond to the voltage of the battery as it is. From the 60% charged state to the 100% charged state, the potential of the positive electrode rises linearly and slowly with the progress of charging, the change in the positive electrode potential at the end of charging is small, and the time during which the positive electrode is held at a certain level or higher. Therefore, problems such as decomposition of the electrolyte during the charging process are likely to occur.

  Further, in the non-aqueous secondary battery described in Patent Document 3, a change in the potential of the electrode during charging is not considered, and satisfactory charge / discharge cycle characteristics are not necessarily obtained.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-aqueous secondary battery having excellent safety, high output, and long life.

  The non-aqueous secondary battery of the present invention that has achieved the above object is a lithium-titanium composite oxide having a spinel structure or a ramsdellite structure as an active material, a negative electrode containing a conductive additive, and a lithium-containing composite having a spinel structure. A nonaqueous secondary battery having a positive electrode using an oxide as an active material and a nonaqueous electrolyte, wherein the negative electrode active material has an average particle size of primary particles of 1 μm or less, and the negative electrode conductive additive. Includes at least one of carbon particles having a particle diameter of 0.1 μm or less, fibrous carbon having a fiber length of 1 μm or more, and flaky carbon having a particle diameter of 1 μm or more, and the positive electrode active material comprises: The average particle size of the primary particles is 3 μm or less, and the capacity ratio of the negative electrode to the capacity of the positive electrode is set to 0.92 to 1.2.

  The non-aqueous secondary battery system of the present invention includes the non-aqueous secondary battery of the present invention and a charge / discharge circuit, and the current value in charging of the non-aqueous secondary battery is 1 C with respect to the rated capacity of the battery. The above is maintained.

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous secondary battery system which can utilize the characteristic of the non-aqueous secondary battery excellent in safety | security, a high output and a long lifetime, and the said non-aqueous secondary battery can be provided.

  In the non-aqueous secondary battery of the present invention, a lithium titanium composite oxide having a spinel structure or a ramsdellite structure is used as an active material, and a negative electrode containing a conductive assistant and a lithium-containing composite oxide having a spinel structure are used as an active material. Combined with a positive electrode, the average particle diameter of primary particles of the negative electrode active material is 1 μm or less, carbon particles having a particle diameter of 0.1 μm or less, and fibers having a fiber length of 1 μm or more as a conductive aid for the negative electrode At least one kind of scaly carbon having a particle diameter of 1 μm or more, an average particle diameter of primary particles of the positive electrode active material of 3 μm or less, and a capacity ratio of the negative electrode to a capacity of the positive electrode, It is characterized by being 0.92-1.2.

  In the present invention, a lithium titanium composite oxide having a spinel crystal structure or a ramsdellite crystal structure is used as the negative electrode active material. The lithium titanium composite oxide has high thermal stability, and lithium dendrite hardly occurs in a battery having a negative electrode using such a negative electrode active material. Therefore, it is possible to ensure the reliability and safety of the battery even if the charging current value is increased.

As the lithium-titanium composite oxide having a spinel crystal structure, an oxide represented by a composition such as Li ₄ Ti ₅ O ₁₂ or LiTi ₂ O ₄ can be used, and in particular, Li ₄ Ti ₅ O ₁₂ is representative. Those having a defective spinel structure are preferably used.

In addition, as the lithium titanium composite oxide having a ramsdellite type crystal structure, oxides typified by compositions such as Li ₂ Ti ₃ O ₇ and Li ₄ Ti ₅ O ₁₂ can be used, and in particular, Li ₂ Ti What is represented by ₃ O ₇ is preferably used. In the case of this Li ₂ Ti ₃ O ₇ , the d value of the main peak by the X-ray diffraction method using Cu as a target is 0.445 nm, 0.269 nm, 0.224 nm, and 0.177 nm (each ± 0.0002 nm). Preferably there is.

  In any of the lithium titanium composite oxides, some of the constituent elements may be substituted with other elements, such as Ca, Mg, Sr, Sc, Zr, V, Nb, W, Cr, Mo, Mn, Elements such as Fe, Co, Ni, Cu, Zn, Al, Si, Ga, Ge, and Sn can be substituted elements. The amount of substitution is preferably 10 mol% or less of the element to be substituted.

  The negative electrode active material is preferably composed only of the lithium titanium composite oxide having the above-described crystal structure, but a negative electrode active material other than the lithium titanium composite oxide can coexist. Examples of such a negative electrode active material include carbon-based materials such as graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, mesocarbon microbeads (MCMB), and carbon fibers; And a simple element of an element that can be alloyed with lithium, such as Si, Sn, Ge, Bi, Sb, and In, an alloy thereof, or an oxide thereof. In addition, it is preferable that lithium lithium complex oxide which has the said crystal structure is 80 mass% or more in all the negative electrode active materials.

  In the present invention, the average particle diameter of the primary particles of the negative electrode active material is 1 μm or less. This is because if the primary particle size of the negative electrode active material is too large, the rapid charge / discharge characteristics of the battery are lowered, making it difficult to construct a high output battery. From the viewpoint of rapid charge / discharge characteristics, the average particle diameter of the primary particles of the negative electrode active material is preferably 0.5 μm or less. However, if the primary particle diameter of the negative electrode active material is too small, it may be difficult to disperse the negative electrode active material in the negative electrode mixture layer, and the density of the negative electrode mixture layer may be reduced or the conductivity of the negative electrode may be reduced. Therefore, the average particle diameter is preferably 0.01 μm or more, and more preferably 0.05 μm or more.

  The primary particles of the negative electrode active material may be aggregated to form secondary particles, and the negative electrode active material may be a mixture of primary particles and secondary particles.

  In the present invention, the conductive aid for the negative electrode is at least one of carbon particles having a particle diameter of 0.1 μm or less, fibrous carbon having a fiber length of 1 μm or more, and flaky carbon having a particle diameter of 1 μm or more. Use seeds. By using carbon particles having a particle size of 0.1 μm or less, the contact area between the particle surface of the negative electrode active material and the conductive additive can be increased, the current collection effect can be enhanced, and a high output battery can be configured. . Further, by using at least one kind of fibrous carbon having a fiber length of 1 μm or more and scale-like carbon having a particle diameter of 1 μm or more, the conductivity can be enhanced over the entire inside of the electrode, and the electrode at high-speed charging The internal resistance is reduced, and the battery life can be extended.

  As the carbon particles having a particle diameter of 0.1 μm or less, carbon black such as acetylene black and ketjen black, pulverized graphite, and the like can be used. In addition, as the fibrous carbon having a fiber length of 1 μm or more, vapor grown carbon fiber, carbon nanotube, or the like can be used. Furthermore, the scaly carbon having a particle diameter of 1 μm or more is desirably graphite particles from the viewpoint of conductivity, and scaly graphite particles are preferably used.

  Among the conductive assistants for the negative electrode, the fibrous carbon having a fiber length of 1 μm or more and the scaly carbon having a particle diameter of 1 μm or more are preferably those shorter (smaller) than the thickness of the negative electrode mixture layer. More preferably, the length and particle size are up to about 20 μm.

  The content of the negative electrode is preferably 30 wt% or less when the total with the active material is 100 in order to ensure the capacity of the negative electrode, and is preferably 5 wt% in order to ensure conductivity. . Among the conductive assistants, the content of carbon particles having a particle diameter of 0.1 μm or less is preferably 4 to 20 wt%, fibrous carbon having a fiber length of 1 μm or more, and a particle diameter of 1 μm or more. The scaly carbon content is preferably 1 to 10 wt%.

  On the other hand, in the present invention, a lithium-containing composite oxide having a spinel structure is used as the positive electrode active material. The lithium-containing composite oxide has high thermal stability, and it is possible to ensure the reliability and safety of the battery even when the charging current value is increased. In addition, since the potential change at the end of charging is large and charging can proceed while maintaining the potential of the active material at a low potential until the state is close to full charging, the time during which the active material is at a high potential during the charging period And the reaction such as decomposition of the electrolytic solution by the positive electrode active material can be suppressed.

Examples of the lithium-containing composite oxide having the spinel structure include spinel manganese composite oxides represented by compositions such as LiMn ₂ O ₄ and LiNi _0.5 Mn _1.5 O ₄ , and some of the elements thereof as other elements. For example, a spinel structure substituted with an element such as Ca, Mg, Sr, Sc, Zr, V, Nb, W, Cr, Mo, Fe, Co, Ni, Cu, Zn, Al, Si, Ga, Ge, or Sn. Lithium manganese composite oxide can be used. These positive electrode active materials have a feature that they show a significant voltage change at the end of charging.

The positive electrode active material is preferably composed only of the lithium-containing composite oxide having the above spinel structure, but a positive electrode active material other than the lithium-containing composite oxide can also coexist. As such a positive electrode active material, lithium having a layered structure represented by Li _{1 + x} MO ₂ (−0.1 <x <0.1, M: Co, Ni, Mn, Al, Mg, Zr, Ti, etc.) Examples thereof include transition metal oxides and olivine type compounds represented by LiMPO ₄ (M: Co, Ni, Mn, Fe, etc.). Specific examples of the lithium-containing transition metal oxide having a layered structure include LiCoO ₂ and LiNi _1-x Co _xy Al _y O ₂ (0.1 ≦ x ≦ 0.3, 0.01 ≦ y ≦ 0. 2) and other oxides containing at least Co, Ni and Mn (LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6 O ₂ , LiNi _{3 / 5} Mn _1/5 Co _1/5 O ₂ etc.). In addition, it is preferable that the lithium containing complex oxide which has the said spinel structure in all the positive electrode active materials is 80 mass% or more.

  In order to improve rapid charge / discharge characteristics and constitute a high-power battery, the average particle diameter of primary particles of the positive electrode active material is preferably 3 μm or less, more preferably 1 μm or less, and Particularly preferably, it is 8 μm or less. However, if the primary particle size of the positive electrode active material is too small, it is difficult to disperse the positive electrode active material in the positive electrode mixture layer, and the density of the positive electrode mixture layer and the conductivity of the positive electrode may decrease. Therefore, the average particle diameter is preferably 0.01 μm or more, and more preferably 0.05 μm or more.

  The primary particles of the positive electrode active material may be aggregated to form secondary particles, and the positive electrode active material may be a mixture of primary particles and secondary particles.

  The primary particle diameter of the negative electrode active material and the primary particle diameter of the positive electrode active material may be obtained by measuring the number of particles dispersed in water using a laser diffraction particle size distribution analyzer or the like. . However, when the particle size is very small or when secondary particles are formed, the average value may be obtained from the particle size observed with an electron microscope.

  The negative electrode is produced by forming a negative electrode mixture layer containing a binder or the like on the current collector in addition to the negative electrode active material and the conductive additive. As the binder, a fluorine resin such as polyvinylidene fluoride (PVDF) is used.

  The thickness of the negative electrode mixture layer (when the negative electrode mixture layer is formed on both sides of the negative electrode, the thickness per one surface. The same applies to the thickness of the negative electrode mixture layer). For this purpose, it is preferably 50 μm or less, and more preferably 40 μm or less. However, if the negative electrode mixture layer is too thin, the amount of the active material may decrease and the battery capacity may be reduced. Therefore, the thickness of the negative electrode mixture layer is preferably 15 μm or more, and preferably 20 μm or more. Is more preferable.

  The negative electrode can be composed only of the negative electrode mixture layer, but when a current collector is used, a foil composed of a metal such as copper, nickel, or an alloy thereof, punching metal, net, expanded metal, etc. May be used. In the case where the negative electrode active material is composed of only the lithium titanium composite oxide having the above-described crystal structure, and charging / discharging is performed in a range where the potential of the negative electrode is 1.0 V or higher, a collector composed of aluminum or an alloy thereof is used. An electric body can also be used. The thickness of the negative electrode current collector is preferably 30 μm or less, and more preferably 5 μm or more.

  The positive electrode is produced, for example, by forming, on the current collector, a positive electrode mixture layer containing a binder and a conductive additive added as necessary in addition to the positive electrode active material. As the conductive auxiliary agent, a carbon material similar to the negative electrode conductive auxiliary agent such as carbon black can be used, and as the binder, a fluorine resin such as polyvinylidene fluoride (PVDF) is used.

  The thickness of the positive electrode mixture layer (when the positive electrode mixture layer is formed on both surfaces of the positive electrode, the thickness per one surface. The same applies to the thickness of the positive electrode mixture layer). For this purpose, it is preferably 50 μm or less, and more preferably 40 μm or less. However, if the positive electrode mixture layer is too thin, the amount of active material may decrease and the battery capacity may be reduced. Therefore, the thickness of the positive electrode mixture layer is preferably 15 μm or more, and more preferably 20 μm or more. Is more preferable.

  The positive electrode can be composed only of the positive electrode mixture layer, but when using a current collector, a foil, punching metal, net, expanded metal, or the like made of a metal such as aluminum or aluminum alloy is used. Good. The thickness of the positive electrode current collector is preferably 30 μm or less, and more preferably 10 μm or more.

  The non-aqueous secondary battery of the present invention is configured by combining the negative electrode and the positive electrode, and the ratio of the negative electrode capacity to the positive electrode capacity (negative electrode capacity / positive electrode capacity) is 0.92-1. The capacity of each electrode is adjusted to be 2. By making the capacity ratio of the positive electrode and the negative electrode within the above range, the characteristics of the positive electrode active material exhibiting a significant potential change at the end of charging are reflected in the charging of the battery, and the non-aqueous secondary whose voltage increases greatly at the end of charging. A battery can be constructed. For example, with respect to the rated capacity of the battery, the potential of the positive electrode in the 100% charged state (charged with the amount of electricity corresponding to the rated capacity) is charged with 90% charged state (90% of the rated capacity). The battery can be configured so as to be 0.2 V or more higher than the potential in the (state). Thus, the potential of the positive electrode is kept low until the charging proceeds near the end, so that a reaction such as decomposition of the electrolytic solution can be suppressed. Furthermore, since the voltage of the battery greatly increases at the end of charging due to the potential change of the positive electrode, it is possible to accurately detect the completion time of charging, and it is possible to suppress deterioration in battery characteristics due to overcharging.

  Note that the lithium-titanium composite oxide having the spinel crystal structure or the ramsdellite crystal structure, which is a negative electrode active material, also shows a significant potential change at the end of charging, similar to the positive electrode active material (the potential greatly decreases). ) Because it is an active material, by adjusting the capacity ratio to a value close to 1, the voltage change of the battery at the end of charging reflects the potential change of the negative electrode in addition to the potential change of the positive electrode. A battery that exhibits a large voltage rise can be constructed. For this reason, the capacity ratio is preferably 1.15 or less, more preferably 1.1 or less, on the other hand, preferably 0.97 or more, more preferably 0.985 or more. preferable.

  When the capacity ratio is smaller than 0.92, the battery is completely negative electrode regulated, and the characteristics of the positive electrode active material are not reflected in the battery voltage. In addition, when charge control is performed using battery voltage, the potential of the negative electrode is too low when fully charged, which may cause side reactions such as lithium deposition on the negative electrode. On the other hand, when the capacity ratio is larger than 1.2, the capacity per volume of the electrode is reduced, and it becomes difficult to construct a high-power battery.

  The capacity of the positive electrode is a capacity between 3.0V and 4.5V with respect to Li, and the capacity of the negative electrode is a capacity between 2.5V and 1.0V with respect to Li. Each means a capacity that can be actually charged and discharged within the battery excluding the reverse load capacity.

  The non-aqueous secondary battery of the present invention is configured, for example, by enclosing the above-described negative electrode and positive electrode and an electrolytic solution in an outer package according to a conventional method. As for the form of the battery, similarly to a conventionally known non-aqueous secondary battery, a cylindrical battery using a cylindrical (cylindrical or rectangular) outer can, or a flat (round or square flat in a plan view) A flat battery using a shape) outer can, and a soft package battery using a metal-deposited laminated film as an outer package. The outer can can be made of steel or aluminum.

As the electrolytic solution (nonaqueous electrolytic solution), for example, a solution in which a lithium salt is dissolved in an organic solvent is used. The lithium salt is not particularly limited as long as it dissociates in a solvent to form Li ⁺ ions and hardly causes side reactions such as decomposition in a voltage range used as a battery. For example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ and other inorganic lithium salts, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), LiN (RfOSO ₂ ) ₂ [where Rf is a fluoroalkyl group] and the like can be used. .

  The organic solvent is not particularly limited as long as it dissolves the lithium salt and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, chain esters such as methyl propionate, cyclic esters such as γ-butyrolactone, Chain ethers such as dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme, cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran, nitriles such as acetonitrile, propionitrile and methoxypropionitrile And sulfites such as ethylene glycol sulfite. These may be used as a mixture of two or more. Kill. In order to obtain a battery with better characteristics, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate. In addition, vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, cyclohexyl benzene, biphenyl, fluorobenzene, t are used for the purpose of improving safety, charge / discharge cycleability, and high-temperature storage properties of these electrolytes. -Additives such as butylbenzene can be added as appropriate.

  The concentration of the lithium salt in the electrolytic solution is preferably 0.5 to 1.5 mol / l, and more preferably 0.9 to 1.25 mol / l.

  The non-aqueous secondary battery of this invention can comprise a non-aqueous secondary battery system by combining with a charging / discharging circuit. As the charge / discharge circuit, a circuit generally used for a non-aqueous secondary battery can be used. Charging is a circuit capable of performing constant current charging, constant current-constant voltage charging, pulse charging, and discharging. A circuit capable of performing constant current discharge, pulse discharge, or the like may be used. In order to take advantage of the characteristics of the non-aqueous secondary battery of the present invention, it is desirable to set the charging conditions so that the current value in charging can be maintained at 1 C or more with respect to the rated capacity of the battery. That is, from the start to the end of charging, the charging current is maintained at 1 C or more, so that the charging time can be shortened and the time for the positive electrode potential to be high can be shortened, and the electrolytic solution is decomposed. This reaction can be suppressed. On the other hand, since the voltage of the battery greatly increases at the end of charging, it is possible to accurately control the termination of charging, and it is possible to prevent deterioration in characteristics due to overcharging, which is problematic when the charging current is increased. In order to shorten the charging time, it is desirable to set the charging conditions so that the charging current value is 5 C or more during at least a part of the charging. In order to simplify the circuit, it is desirable to use constant current charging. However, in the non-aqueous secondary battery of the present invention, even if constant current charging is performed at a current value of 5 C or more, high safety and excellent performance are achieved. Cycle life can be maintained.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
(Production of negative electrode)
The average particle diameter of primary particles is 0.1 μm, Li ₄ Ti ₅ O ₁₂ having a spinel crystal structure: 75 parts by weight, and acetylene black having an average particle diameter of 0.05 μm as a conductive auxiliary agent: 10 parts by weight Then, flaky graphite having a particle diameter of about 10 μm: 5 parts by weight and PVDF as a binder: 10 parts by weight were mixed so as to be uniform using N-methylpyrrolidone as a solvent to prepare a negative electrode mixture-containing paste. . This negative electrode mixture-containing paste was applied on both sides of a 15 μm-thick aluminum foil serving as a current collector so that the coating weight was 5 mg / cm ² on one side in terms of the weight after drying. Then, the thickness of the negative electrode mixture layer was adjusted so that the total thickness was 75 μm, and was cut so as to have a width of 45 mm, thereby preparing a negative electrode having a length of 72 mm and a width of 45 mm. Further, a tab was welded to the exposed portion of the aluminum foil of the negative electrode to form a lead portion.

[Production of positive electrode]
The average particle diameter of primary particles is 0.05 μm, LiMn ₂ O ₄ having a spinel crystal structure: 75 parts by weight, and acetylene black having an average particle diameter of 0.05 μm as a conductive assistant: 10 parts by weight, particle diameter Was mixed with 5 parts by weight of scaly graphite having a particle size of about 7 μm and 10 parts by weight of PVDF as a binder, using N-methylpyrrolidone as a solvent, to prepare a positive electrode mixture-containing paste. This positive electrode mixture-containing paste was applied on both sides of a 15 μm-thick aluminum foil serving as a current collector so that the coating weight was 7 mg / cm ² on one side in terms of the weight after drying. The thickness of the positive electrode mixture layer was adjusted so that the total thickness became 75 μm, and the positive electrode mixture layer was cut to a width of 43 mm to produce a positive electrode having a length of 70 mm and a width of 43 mm. Further, a tab was welded to the exposed portion of the aluminum foil of the positive electrode to form a lead portion.

[Assembling the battery]
The negative electrode and the positive electrode obtained as described above were laminated through a PET nonwoven fabric separator having a thickness of 30 μm to produce a laminated electrode body. In addition, LiPF ₆ was dissolved at a concentration of 1.0 mol / l in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2 to prepare a non-aqueous electrolyte. The laminated electrode body was sealed together with the non-aqueous electrolyte in an exterior body made of an aluminum laminate film to produce a non-aqueous secondary battery.

(Measurement of electrode capacity)
The capacity | capacitance of the negative electrode and the positive electrode was calculated | required with the following method. A negative electrode was produced under the same conditions as the negative electrode of Example 1 except that the negative electrode mixture-containing paste was applied only to one side of the current collector, and a cell was constructed using the above electrolyte with Li metal as a counter electrode. The negative electrode of this cell was charged at a current density of 20 mA per gram of the negative electrode active material until the potential with respect to Li was 1.0 V, and then discharged at the same current density until 2.5 V. The capacity was measured. In addition, the cell was configured in the same manner for the positive electrode of Example 1, and charged at a current density of 20 mA per 1 g of the positive electrode active material until the potential with respect to Li was 4.5 V, and thereafter, 3.0 V. The capacity when discharging at the same current density was measured. From the above measurement, the capacity of the negative electrode and the positive electrode of Example 1 was 18.7 mAh for the negative electrode and 18.2 mAh for the positive electrode on one side of the electrode, and the capacity ratio of the negative electrode to the positive electrode capacity was 1.03.

(Example 2)
A nonaqueous secondary battery was produced in the same manner as in Example 1 except that LiMn ₂ O ₄ having an average primary particle size of 0.5 μm was used as the positive electrode active material. The capacity ratio of the negative electrode to the capacity of the positive electrode of this battery was 0.99.

(Example 3)
A nonaqueous secondary battery was produced in the same manner as in Example 1 except that Li ₄ Ti ₅ O ₁₂ having an average primary particle diameter of 0.4 μm was used as the negative electrode active material. The capacity ratio of the negative electrode to the capacity of the positive electrode of this battery was 1.05.

Example 4
A non-aqueous secondary battery was produced in the same manner as in Example 1 except that a polyethylene microporous film having a thickness of 20 μm was used as the separator. The capacity ratio of the negative electrode to the capacity of the positive electrode of this battery was 1.03.

(Example 5)
Example 1 except that the conductive auxiliary for the negative electrode and the positive electrode was replaced with two types of Ketjen black having an average particle diameter of 0.04 μm: 10 parts by weight and carbon nanotubes having a fiber length of about 3 μm: 5 parts by weight. A non-aqueous secondary battery was produced in the same manner as described above.

(Example 6)
The conductive aid for the negative electrode and the positive electrode was replaced with two types: Ketjen black having an average particle size of 0.04 μm: 10 parts by weight and VGCF (vapor-grown carbon fiber) having a fiber length of about 15 μm: 5 parts by weight. A nonaqueous secondary battery was produced in the same manner as in Example 1 except for the above.

(Comparative Example 1)
The same as in Example 2 except that LiCoO ₂ having an average primary particle size of 0.5 μm was used as the positive electrode active material, and the coating weight on one side of the mixture layer was 6 mg / cm ² after drying. Thus, a non-aqueous secondary battery was produced. The capacity ratio of the negative electrode to the capacity of the positive electrode of this battery was 0.98.

(Comparative Example 2)
A nonaqueous secondary battery was produced in the same manner as in Example 2 except that Li ₄ Ti ₅ O ₁₂ having an average primary particle size of 4.0 μm was used as the negative electrode active material. The capacity ratio of the negative electrode to the capacity of the positive electrode of this battery was 0.99.

(Comparative Example 3)
A nonaqueous secondary battery was produced in the same manner as in Example 1 except that LiMn ₂ O ₄ having an average primary particle size of 4.0 μm was used as the positive electrode active material. The capacity ratio of the negative electrode to the capacity of the positive electrode of this battery was 0.94.

(Comparative Example 4)
A nonaqueous secondary battery was produced in the same manner as in Example 2, except that the coating amount of the negative electrode mixture layer was reduced so that the negative electrode capacity ratio to the positive electrode capacity was 0.9.

(Comparative Example 5)
A nonaqueous secondary battery was produced in the same manner as in Example 2 except that the coating amount of the negative electrode mixture layer was increased so that the negative electrode capacity ratio to the positive electrode capacity was 1.3.

(Comparative Example 6)
A nonaqueous secondary battery was produced in the same manner as in Example 1 except that the conductive aid used for the negative electrode and the positive electrode was changed to 15 parts by weight of ketjen black having an average particle size of 0.04 μm.

(Comparative Example 7)
A non-aqueous secondary battery was produced in the same manner as in Example 1 except that VGCF (vapor-grown carbon fiber) having an average fiber length of 15 μm: 15 parts by weight was used as the conductive additive used for the negative electrode and the positive electrode.

  About the non-aqueous secondary battery of Examples 1-7 and Comparative Examples 1-6, it charges by constant current charge to 2.9V by the electric current value (10C) which can charge the capacity | capacitance of a cell in 6 minutes, and with the same electric current value The cycle for discharging to 1.0 V was repeated 1000 times, and the ratio (capacity maintenance ratio) between the discharge capacity at the 1000th cycle and the discharge capacity at the 1st cycle was measured. Table 1 shows the configuration of the electrodes, and Table 2 shows the measurement results.

  In the nonaqueous secondary battery of the present invention, a negative electrode using a lithium titanium composite oxide having a spinel structure or a ramsdellite structure as an active material and a positive electrode using a lithium-containing composite oxide having a spinel structure as an active material are combined, An average particle diameter of primary particles of the negative electrode active material is 1 μm or less, and carbon particles having a particle diameter of 0.1 μm or less, fibrous carbon having a fiber length of 1 μm or more, and a particle diameter as a conductive auxiliary for the negative electrode At least one type of scaly carbon having a particle size of 1 μm or more, the average particle diameter of primary particles of the positive electrode active material is 3 μm or less, and the capacity ratio of the negative electrode to the capacity of the positive electrode is 0.92-1. As a result, it was possible to suppress the capacity deterioration accompanying the cycle even in the charge / discharge cycle at a high output of 10C. In addition, even when a separator having a large pore diameter and easily forming lithium dendrites, such as a nonwoven fabric separator, was used, no behavior leading to a decrease in safety was observed.

On the other hand, in Comparative Example 1 in which the positive electrode active material is LiCoO ₂ , since the time during which the positive electrode is at a high potential near the end of charging is longer than that of the battery of the present invention, a reaction such as decomposition of the electrolyte proceeds, and the cycle At the same time, the capacity dropped significantly.

  Further, in Comparative Example 2 in which the average particle diameter of the primary particles of the negative electrode active material exceeded 1 μm, the negative electrode could not cope with rapid charge / discharge, and the capacity decreased with the cycle.

  Further, in Comparative Example 3 in which the average particle diameter of the primary particles of the positive electrode active material exceeded 3 μm, the positive electrode could not cope with rapid charge / discharge, and the capacity decreased with the cycle.

  Furthermore, in Comparative Examples 4 and 5 in which the capacity ratio of the negative electrode to the positive electrode capacity deviated from the range of 0.92 to 1.2, the voltage change of the battery at the end of charging was smaller than that of the battery of the present invention. Since the charging of the positive electrode or the negative electrode proceeds deeper than the battery of the invention, the deterioration of the electrode was promoted and the capacity was reduced.

  Further, Comparative Example 6 in which neither fibrous carbon having a fiber length of 1 μm or more and flaky carbon having a particle diameter of 1 μm or more is included as a conductive additive for the negative electrode, and carbon having a particle diameter of 0.1 μm or less. In Comparative Example 7 in which particles were not included as a conductive additive for the negative electrode, the capacity decreased with the cycle because of poor current collection and non-uniform charge / discharge reaction in the negative electrode.

Claims (5)

A non-aqueous electrolyte comprising a lithium titanium composite oxide having a spinel structure or a ramsdellite structure as an active material, a negative electrode containing a conductive additive, a positive electrode using a lithium-containing composite oxide having a spinel structure as an active material, and a non-aqueous electrolyte. A water secondary battery,
The negative electrode active material has an average primary particle size of 1 μm or less,
The conductive auxiliary agent for the negative electrode includes at least one of carbon particles having a particle diameter of 0.1 μm or less, fibrous carbon having a fiber length of 1 μm or more, and flaky carbon having a particle diameter of 1 μm or more,
The positive electrode active material has an average primary particle size of 3 μm or less,
The nonaqueous secondary battery, wherein a capacity ratio of the negative electrode to a capacity of the positive electrode is set to 0.92 to 1.2.   The non-aqueous secondary battery according to claim 1, wherein the carbon particles having a particle diameter of 0.1 μm or less are ketjen black or acetylene black.   The non-aqueous secondary battery according to claim 1 and a charge / discharge circuit are provided, and a current value in charging of the non-aqueous secondary battery is maintained at 1 C or more with respect to a rated capacity of the battery. Non-aqueous secondary battery system.   The nonaqueous secondary battery system according to claim 3, wherein the nonaqueous secondary battery system includes a charging condition in which the current value is at least 5 C or more.   The non-aqueous secondary battery system according to claim 3 or 4, wherein the charging is constant current charging.