JP6187293B2 - Method for producing non-aqueous secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous secondary battery manufacturing method for manufacturing a non-aqueous secondary battery that can be used at a high voltage.

  In recent years, along with the development of portable electronic devices such as mobile phones and notebook computers, and the practical application of electric vehicles, secondary batteries with small and light weight and high capacity are required. As a high-capacity secondary battery that meets this demand, a non-aqueous secondary battery using a lithium composite metal oxide as a positive electrode material and a carbon-based material as a negative electrode material has been developed.

Examples of the lithium composite metal oxide used as the positive electrode active material include LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ and Li _1.0 Ni _0.5 Co _0.2 Mn _0.3 O _2. Can be mentioned.

  By the way, although the general voltage upper limit of a non-aqueous secondary battery is 4.2V, charging to the voltage exceeding 4.2V is examined (refer patent document 4). There is a concern that such high-voltage charging may cause an excessive load on the positive electrode, damage the structure of the positive electrode active material, and increase resistance or decrease cycle characteristics.

  In a non-aqueous secondary battery, in order to improve charge / discharge cycle characteristics, it has been proposed to perform initial charge / discharge (conditioning treatment) under a predetermined condition. For example, Patent Document 1 proposes to perform the first charge / discharge at 35 to 80 ° C. In Patent Document 2, it is proposed that the initial charging conditions are a charging voltage of 4.2 to 4.75 V and a charging time of 10 to 20 minutes. Patent Document 3 proposes that when the electrolyte solution contains LiBOB, the charging treatment is performed until the film of the oxidative decomposition product of the BOB anion belongs to the high voltage range formed on the surface of the positive electrode active material.

JP 2012-230779 A JP 2009-238433 A JP 2009-252489 A JP 2012-160435 A

  However, even if the first charge / discharge is performed under the conditions disclosed in the above-mentioned patent document, structural damage of the positive electrode active material occurs when the battery is used under a high voltage, and the cycle characteristics can be improved. Can not.

  Therefore, the present inventor has eagerly studied the conditions of the first charge / discharge in order to develop a non-aqueous secondary battery that is excellent in cycle characteristics even when used under a high voltage.

  This invention is made | formed in view of this situation, and makes it a subject to provide the manufacturing method of the non-aqueous secondary battery for manufacturing the non-aqueous secondary battery excellent in cycling characteristics.

  The method for producing a non-aqueous secondary battery of the present invention accommodates a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, a non-aqueous electrolyte, the positive electrode, the negative electrode, and the non-aqueous electrolyte. The first charge is performed on the non-aqueous secondary battery assembly (hereinafter referred to as “battery assembly”) having a case so that the voltage of the battery assembly reaches a range of the rated voltage to 4.2 V or less. The aging process is started in less than 12 hours after the initial charging process and the initial charging process are performed. In the aging process, the battery assembly is held in a high temperature environment of 40 ° C. or more and 65 ° C. or less for a predetermined time. Charge / discharge in which the battery assembly subjected to the high temperature holding step and the aging treatment is charged until the voltage of the battery assembly reaches a range exceeding 4.2 V, and then subjected to a conditioning process for discharging. Process It is characterized in.

  In the present invention, since the aging process and the conditioning process are performed under predetermined conditions as described above, a non-aqueous secondary battery having excellent cycle characteristics can be manufactured.

  Embodiments of the present invention will be described in detail.

  The manufacturing method of the non-aqueous secondary battery of this invention has an initial charge process, a high temperature holding process, and a charging / discharging process in the assembly (battery assembly) of a non-aqueous secondary battery. Since the initial charging step, the high temperature holding step, and the charge / discharge step are performed before actual use of the non-aqueous secondary battery, the non-aqueous secondary battery manufacturing method of the present invention is a pre-treatment method for a non-aqueous secondary battery. Can also be grasped. In this specification, a battery that performs a charging process, a high temperature holding process, and a charge / discharge process is referred to as a battery assembly, and a battery that is manufactured by performing these processes is referred to as a non-aqueous secondary battery.

  In general, in the battery assembly, impurities such as a raw material of the positive electrode active material, unbaked residue, and oxide remain on the surface of the positive electrode. For this reason, battery reactions occur locally in the positive electrode, and the crystal structure of the positive electrode active material is destroyed. It leads to deterioration of the positive electrode active material, and the cycle characteristics are lowered.

  Therefore, in the present invention, after the initial charge is performed, the battery assembly is held at a high temperature in the high temperature holding step to decompose and remove impurities remaining on the surface of the positive electrode before the actual use, The surface state is to react uniformly.

  Then, it becomes a more stable surface state by performing a conditioning process to a battery assembly under a high voltage in a charge / discharge process. Uses a high voltage to reduce resistance and improve cycle characteristics.

  If only the conditioning process is performed, an excessive load is applied to the positive electrode during the conditioning process, the reactivity becomes non-uniform, the crystal structure is broken locally, and the resistance is increased. When the initial charge and the conditioning process are performed, the resistance can be lowered as compared with the case where only the conditioning process is performed, but the cycle characteristics tend to be slightly decreased. By performing the initial charging, aging treatment, and conditioning treatment, the resistance can be further lowered and the cycle characteristics can be improved.

  As will be described later, the non-aqueous secondary battery assembly (battery assembly) includes a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, a non-aqueous electrolyte, and a case containing these. Have This battery assembly is subjected to an initial charge process, a high temperature holding process, and a charge / discharge process. Each process will be described in detail below.

(1) Initial charging step In the initial charging step, initial charging is performed on the battery assembly so that the voltage (battery voltage) of the battery assembly reaches a range of the rated voltage to 4.2V. The initial charging is preferably started within 20 hours from the time when the positive electrode of the battery assembly and the electrolytic solution come into contact with each other. If the start of the first charge is too late, the negative electrode current collector foil may be dissolved.

  In the initial charging of the battery assembly, a charger is used so that the voltage of the battery assembly, that is, the potential difference between the positive electrode and the negative electrode reaches a range of the rated voltage or more and 4.2 V or less. When the voltage of the battery assembly exceeds 4.2 V, a high voltage is applied to the positive electrode, and an excessive load is applied to the positive electrode. In this case, the battery reaction of the positive electrode active material becomes non-uniform, which causes local crystal structure destruction, which may increase resistance and decrease cycle characteristics.

  The lower limit of the voltage range for the initial charge of the battery assembly is, for example, the rated voltage of the non-aqueous secondary battery. When the voltage for the initial charge of the battery assembly is less than the rated voltage, there is a risk that the resistance and cycle characteristics may deteriorate due to insufficient voltage.

  The rated voltage refers to the upper limit value of the voltage at which the non-aqueous secondary battery can be used stably. The rated voltage of the non-aqueous secondary battery is often 4.2 V or less. For example, the rated voltages in the case of various combinations of positive and negative electrodes are listed below as examples.

  In the initial charging step, the applied voltage applied to the battery assembly needs to be higher than the battery voltage charged and reached by the battery assembly. The applied voltage is preferably 4.2 V or less. When the applied voltage exceeds 4.2 V, an excessive load is applied to the positive electrode active material during the initial charge, and the cycle characteristics during actual use may be deteriorated. The lower limit of the applied voltage applied to the battery assembly is preferably the rated voltage of the non-aqueous secondary battery. It is preferable that the voltage (potential difference between the positive electrode and the negative electrode) of the battery assembly is made to reach the rated voltage or more and 4.2 V or less by setting the applied voltage applied to the battery assembly to the rated voltage or more and 4.2 V or less.

  The charge rate in the first charge is preferably 0.05 C or more and 2 C or less, and more preferably 0.1 C or more and 1 C or less. When the charging rate is excessive, the load on the positive electrode active material at the time of the first charge is large, and the structure of the positive electrode active material may be defective. If the charge rate is too low, the initial charge takes time. Regarding the charging rate, “C” refers to the speed at which the entire capacity of the battery is charged, that is, the charging rate. For example, 1C with respect to the charge rate can be represented by a current value at which the battery is fully charged (SOC 100%) in one hour.

  Although the temperature of the battery assembly at the time of performing the initial charge is not particularly limited, it is preferable that the temperature is equal to or lower than the temperature in the next high temperature holding step. This is because if the initial charge is performed at a temperature higher than the temperature in the high temperature holding step, defects may occur in the crystal structure of the positive electrode active material.

  The time spent for the first charge is preferably 0.5 hours or more and 20 hours or less, and preferably 1 hour or more and 10 hours or less. In this case, the resistance of the battery can be reduced. If the initial charge is too short, the predetermined voltage will not be reached and sufficient conditioning will not be achieved, and cycle characteristics may be degraded.If it is too long, the active material will be exposed to a high voltage for a long time. This can cause damage and reduce cycle characteristics.

  The temperature of the atmosphere in which the battery assembly is initially charged is preferably 0 ° C. or higher and 60 ° C. or lower, and more preferably 20 ° C. or higher and 40 ° C. or lower. If the temperature is too low, lithium may deposit on the negative electrode and break through the separator to cause a short circuit. If it is too high, cycle characteristics may be deteriorated due to active material damage.

(2) High temperature holding process In the high temperature holding process, the aging process is started in less than 12 hours after the initial charging process, and the battery assembly is held in a high temperature environment of 40 ° C. or higher and 65 ° C. or lower for a predetermined time in the aging process. To do. The reason why the aging treatment is started in less than 12 hours after the initial charging step is performed is to promote uniform film formation at a high temperature.

  The aging process is a process for holding the battery assembly at 40 to 65 ° C. for a predetermined time. When the battery assembly is held at 40 to 65 ° C., charge / discharge cycle characteristics are reliably improved by performing a predetermined conditioning process thereafter. When the holding temperature of the battery assembly in the aging treatment is less than 40 ° C., the aging property is insufficient and the cycle characteristics may be deteriorated. When the holding temperature exceeds 65 ° C., the resistance of the non-aqueous secondary battery increases even if the conditioning process is performed thereafter, and the cycle characteristics may be deteriorated.

  The holding time of the battery assembly in the aging process in a high temperature environment is preferably 10 hours or more and less than 72 hours. When the holding time is 72 hours or more, the discharge capacity may be reduced. If it is less than 10 hours, aging is insufficient and the resistance and cycle characteristics may be deteriorated.

  The aging process may be performed without separating the battery assembly from the charger and applying a voltage to the battery assembly. When the aging treatment is performed while applying a voltage, a large load is applied to the positive electrode active material, the crystal structure may be damaged, and the cycle characteristics may be deteriorated.

(3) Charging / discharging process The battery assembly that has been subjected to the aging treatment is charged until the battery assembly reaches a voltage (battery voltage) exceeding 4.2 V, and then a conditioning process is performed for discharging.

  The battery assembly is charged using a charger until the voltage of the battery assembly (battery voltage) reaches a range exceeding 4.2V. That is, charging is performed until the potential difference between the positive electrode and the negative electrode of the battery assembly reaches a range exceeding 4.2V. This is to stabilize the battery performance in a high voltage state during use. If the battery voltage of the battery assembly is less than 4.2 V, the battery performance may become unstable when using a high voltage.

  In the conditioning process, charging of the battery assembly is preferably performed until the potential difference between the positive electrode and the negative electrode is not more than the maximum operating voltage in the actual operating voltage of the non-aqueous secondary battery. If the battery assembly is charged until it reaches a voltage exceeding the maximum operating voltage, which is the maximum of the operating voltage, the crystal structure of the positive electrode active material is destroyed, the resistance increases, and the cycle characteristics are improved. May decrease.

  The maximum operating voltage is the maximum voltage among the planned operating voltages, for example, a voltage higher than the voltage of the plateau part (flat part) of the charging curve, or the positive active material The voltage is higher than the average charging voltage. Various batteries are set to stop the application of voltage when a predetermined voltage is reached during discharging. This end voltage can be grasped as the maximum operating voltage.

  It is preferable to perform the charging of the conditioning process in the charge / discharge process until the voltage of the battery assembly reaches 4.2V or more and 4.6V or less. If it exceeds 4.6 V, the crystal structure of the positive electrode active material may be destroyed during the charging of the conditioning treatment, and the capacity may be reduced.

  In order for the battery assembly to reach a voltage (battery voltage) exceeding 4.2V, the applied voltage applied to the battery assembly needs to be a voltage exceeding 4.2V. Preferably, the applied voltage is more than 4.2V and not more than 4.6V. When an excessively high voltage is applied, structural destruction of the positive electrode active material occurs, and the cycle characteristics may be deteriorated.

  The charging rate in the conditioning process is preferably 0.1 C or more and 2 C or less, and more preferably 0.2 C or more and 1 C or less. When the charge rate is excessive, Li may be excessively deposited on the negative electrode, which may break through the separator and cause a short circuit. If the charging rate is too low, charging takes time. The charging rate in the conditioning process is synonymous with the charging rate in the initial charging process.

  The discharge rate in the conditioning treatment is preferably from 0.1 C to 2 C, and more preferably from 0.2 C to 1 C. When the discharge rate is excessive, the battery reaction becomes non-uniform, which may cause local deterioration. When the discharge rate is too low, it takes time to discharge. Regarding the discharge rate, “C” refers to the speed at which the entire capacity of the battery is discharged, that is, the discharge rate. For example, 1 C with respect to the discharge rate can be represented by a current value at which the battery is discharged (SOC 0%) in one hour.

  The discharge in the conditioning process is preferably performed until the voltage of the battery assembly (battery voltage) reaches the rated voltage or less, and further, the discharge is preferably performed until it reaches 2.5 V or more and 3.0 V or less. .

  The conditioning process may be performed once or more and not more than 5 times for both charging and discharging. Although depending on the type of non-aqueous secondary battery, many batteries will stabilize while charging and discharging are repeated up to 5 times, so even if charging and discharging over 5 times is repeated, further effects can be expected. Can not.

  It is good to hold | maintain for the predetermined time in the state which maintained the charge state between charge and discharge. This is because the battery assembly that has been charged and heated is allowed to cool and stabilize. The holding time is preferably 1 hour or more and 5 hours or less. During the holding in the state where the charged state is maintained, the constant voltage may be applied by connecting to the charger, or the voltage may not be applied by disconnecting from the charger. In order to stabilize the battery assembly, it is preferable that no voltage is applied.

  The conditioning treatment is preferably performed in an atmosphere of 0 ° C. or higher and 65 ° C. or lower, and more preferably performed in an atmosphere of 10 ° C. or higher and 40 ° C. or lower. When the conditioning treatment is performed in an excessively high temperature atmosphere, the crystal structure of the positive electrode active material is destroyed to increase the resistance, and the cycle characteristics may be deteriorated. When the atmospheric temperature of the conditioning treatment is excessively low, Li may deposit on the negative electrode, which may break through the separator and cause a short circuit.

(Non-aqueous secondary battery assembly)
An assembly of a non-aqueous secondary battery (battery assembly) includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and a case. The positive electrode has a positive electrode active material that can occlude and release metal ions. The positive electrode has a current collector and a positive electrode active material layer bound to the surface of the current collector.

  The positive electrode active material may be a positive electrode active material that can occlude and release metal ions such as lithium ions. The positive electrode active material capable of occluding and releasing lithium ions may have a lithium metal composite oxide and / or a polyanionic compound.

The lithium metal composite oxide preferably has a spinel structure. The lithium metal composite oxide having a spinel structure has a general formula: Li _x (A _y Mn _2-y ) O ₄ (A is Ca, Mg, S, Si, Na, K, Al, P, Ga, Ge) It is preferable that at least one element selected and at least one metal element selected from transition metal elements, 0 <x ≦ 2.2, 0 <y ≦ 1). The transition metal element that can constitute A in the general formula is, for example, at least one element selected from Fe, Cr, Cu, Zn, Zr, Ti, V, Mo, Nb, W, La, Ni, and Co. There should be. Specific examples of the lithium metal composite oxide may be at least one selected from LiMn ₂ O _4, Li ₂ Mn ₂ O _4, and LiNi _0.5 Mn _1.5 O ₄ .

The lithium metal composite oxide may have a layered rock salt structure in addition to the spinel structure. A lithium metal composite oxide having a layered rock salt structure is also referred to as a layered compound. The lithium metal composite oxide having a layered rock salt structure has a general formula: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1.2, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Ni, Co And at least one element, 1.7 ≦ f ≦ 2.1), and Li ₂ MnO ₃ . The ratio of b: c: d in the general formula is 0.5: 0.2: 0.3, 1/3: 1/3: 1/3, 0.75: 0.10: 0.15. 0: 0: 1, 1: 0: 0, and 0: 1: 0.

That is, as specific examples of lithium metal composite oxide having a layered rock salt structure, LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _{0 .5} Mn _0.5 O ₂ , LiNi _0.75 Co _0.1 Mn _0.15 O ₂ , LiMnO ₂ , LiNiO ₂ , and LiCoO ₂ may be at least one kind.

The positive electrode active material may include a solid solution composed of a mixture of a lithium metal composite oxide having a layered rock salt structure and spinel such as LiMn ₂ O ₄ and Li ₂ Mn ₂ O ₄ . there is a Li ₂ MnO ₃ -LiMo _2.

The polyanionic compound is preferably, for example, a polyanionic compound containing lithium. The polyanionic compound containing lithium is LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (wherein M is selected from at least one of Co, Ni, Mn, and Fe). Can be mentioned.

  Any metal oxide used as the positive electrode active material may have the above composition formula as a basic composition, and a metal element included in the basic composition may be replaced with another metal element, and Mg, etc. Other metal elements may be added to the basic composition to form a metal oxide.

The non-aqueous secondary battery manufactured by the non-aqueous secondary battery manufacturing method of the present invention can be used at a high voltage (for example, a voltage exceeding 4.2 V). In order to use at a high voltage, the potential at which the positive electrode active material can react should exceed 4.2 V on the basis of the Li ⁺ / Li electrode.

Among the various positive electrode active materials described above, the lithium metal composite oxide and / or the polyanion-based material preferably react in a region exceeding 4.2 V on the basis of the Li ⁺ / Li electrode.

Examples of the lithium metal composite oxide and polyanion compound that can react at a potential exceeding 4.2 V on the basis of the Li ⁺ / Li electrode include LiNi _0.5 Mn _1.5 O ₄ (spinel), LiCoPO ₄ (polyanion), Li ₂ CoPO ₄ F (polyanion), Li ₂ MnO ₃ —LiMO ₂ (wherein M is selected from at least one of Co, Ni, Mn, and Fe) (solid solution system having a layered rock salt structure), Li ₂ MnSiO ₄ (polyanion) and the like are exemplified, but not limited thereto.

Further, the lithium metal composite oxide and the polyanion compound may react in a region of 4.2 V or less on the basis of the Li ⁺ / Li electrode. As such a lithium metal composite oxide, for example, among those having a layered rock salt structure, LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , at least one selected from LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.75 Co _0.1 Mn _0.15 O ₂ , LiMnO ₂ , LiNiO ₂ , and LiCoO _2, but is not limited thereto. Not.

  The positive electrode active materials and batteries using them are classified into the types shown in Table 2 to describe the characteristics.

  Lithium metal composite oxides include a solid solution type and a two-phase coexistence type. The solid solution type is a case where the reaction of the active material passes through the solid solution, and as the discharge proceeds, the positive electrode potential gradually decreases, and as the charging proceeds, the potential gradually increases. In the two-phase coexistence type, when the active material is discharged, the second phase appears, the two phases coexist, there is a region where the positive electrode potential does not decrease even if the discharge proceeds, and there is a region where the potential does not increase even when the charging proceeds. is there.

In a battery using a solid solution type 4V class active material (LiCoO ₂ or the like), when the maximum use potential (Li / Li ⁺ standard) of the positive electrode active material is 5 V, the average discharge voltage and the capacity are slightly improved. However, in general, the active material itself may deteriorate due to the high potential.

In a battery using a two-phase coexistence type 4V class active material (LMn ₂ O ₄ or the like), when the maximum use potential (Li / Li ⁺ standard) is 5 V, the average discharge voltage and the capacity are hardly changed. However, since the high potential resistance of the active material itself is generally high, the maximum usable potential (Li / Li ⁺ standard) can be increased to 5V.

In a battery using a two-phase coexistence type 5V class active material (such as LiNi _0.5 Mn _1.5 O ₄ ), the capacity decreases when the maximum working potential (Li / Li ⁺ standard) is 4 V, and when the voltage is 5 V Capacity appears.

  The lithium metal composite oxide used as the positive electrode active material only needs to have the above composition formula as a basic composition, and can be used in which the metal element contained in the basic composition is replaced with another metal element, such as Mg. Other metal elements may be added to the basic composition to form a metal oxide.

  The current collector of the positive electrode is not particularly limited as long as it is a metal that can withstand a potential suitable for the active material to be used. The current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharging or charging of a non-aqueous secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel, etc. Metal materials can be exemplified. When the potential of the positive electrode is 4 V or higher with respect to lithium, it is preferable to employ aluminum as the current collector. The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector.

  The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm.

  The positive electrode active material layer includes a positive electrode active material and, if necessary, a binder and / or a conductive aid.

  The binder serves to bind the active material and the conductive additive to the surface of the current collector.

  Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins. be able to.

  Moreover, you may employ | adopt the polymer which has a hydrophilic group as a binder. Examples of the hydrophilic group of the polymer having a hydrophilic group include a phosphate group such as a carboxyl group, a sulfo group, a silanol group, an amino group, a hydroxyl group, and a phosphate group. Among them, a polymer containing a carboxyl group in the molecule such as polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polymethacrylic acid, or a polymer containing a sulfo group such as poly (p-styrenesulfonic acid) is preferable.

  A polymer containing many carboxyl groups and / or sulfo groups such as polyacrylic acid or a copolymer of acrylic acid and vinyl sulfonic acid becomes water-soluble. Therefore, the polymer having a hydrophilic group is preferably a water-soluble polymer, and a polymer containing a plurality of carboxyl groups and / or sulfo groups in one molecule is preferable.

  A polymer containing a carboxyl group in the molecule can be produced by, for example, a method of polymerizing an acid monomer or adding a carboxyl group to the polymer. Acid monomers include acrylic acid, methacrylic acid, vinyl benzoic acid, crotonic acid, pentenoic acid, angelic acid, tiglic acid, etc., acid monomers having one carboxyl group in the molecule, itaconic acid, mesaconic acid, citraconic acid, fumaric acid , Maleic acid, 2-pentenedioic acid, methylene succinic acid, allyl malonic acid, isopropylidene succinic acid, 2,4-hexadiene diacid, acetylenedicarboxylic acid, etc., acid monomers having two or more carboxyl groups in the molecule Is done. A copolymer obtained by polymerizing two or more kinds of monomers selected from these may be used.

  For example, a polymer composed of a copolymer of acrylic acid and itaconic acid as described in JP-A-2013-065493, and containing an acid anhydride group formed by condensation of carboxyl groups in the molecule It is also preferable to use as a binder. The structure derived from a highly acidic monomer having two or more carboxyl groups in one molecule is believed to facilitate trapping of metal ions such as lithium ions before the electrolytic solution decomposition reaction occurs during charging. Furthermore, the acidity is not excessively increased because there are more carboxyl groups and the acidity is higher than polyacrylic acid and polymethacrylic acid, and a predetermined amount of the carboxyl groups are changed to acid anhydride groups. Therefore, a secondary battery having a negative electrode formed using this binder has improved initial efficiency and improved input / output characteristics.

  The blending ratio of the binder in the negative electrode active material layer is preferably a mass ratio of negative electrode active material: binder = 1: 0.005 to 1: 0.5. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  The conductive assistant is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be any chemically inert electronic high conductor, such as carbon black, graphite, acetylene black, ketjen black (registered trademark), vapor grown carbon fiber (Vapor Grown Carbon). Fiber: VGCF) and various metal particles are exemplified. These conductive assistants can be added to the active material layer alone or in combination of two or more.

  The blending ratio of the binder in the positive electrode active material layer is preferably a mass ratio of positive electrode active material: binder = 1: 0.05 to 1: 0.5. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  The negative electrode used for the non-aqueous secondary battery of the present invention has a current collector and a negative electrode active material layer bound to the surface of the current collector.

As the negative electrode active material, a material that can occlude and release metal ions such as lithium ions can be used. Therefore, there is no particular limitation as long as it is a simple substance, alloy, or compound that can occlude and release metal ions such as lithium ions. For example, as a negative electrode active material, Li, group 14 elements such as carbon, silicon, germanium and tin, group 13 elements such as aluminum and indium, group 12 elements such as zinc and cadmium, group 15 elements such as antimony and bismuth, magnesium , Alkaline earth metals such as calcium, and group 11 elements such as silver and gold may be employed alone. When silicon or the like is used for the negative electrode active material, a silicon atom reacts with a plurality of lithiums, so that it becomes a high-capacity active material. However, there is a problem that volume expansion and contraction due to insertion and extraction of lithium becomes significant. In order to reduce the fear, it is also preferable to employ an alloy or compound in which another element such as a transition metal is combined with a simple substance such as silicon as the negative electrode active material. Specific examples of the alloy or compound include tin-based materials such as Ag-Sn alloy, Cu-Sn alloy, Co-Sn alloy, carbon-based materials such as various graphites, SiO _x (disproportionated to silicon simple substance and silicon dioxide). Examples thereof include silicon-based materials such as 0.3 ≦ x ≦ 1.6), silicon alone, or composites obtained by combining silicon-based materials and carbon-based materials. In addition, as the negative electrode active material, oxides such as Nb ₂ O ₅ , TiO ₂ , Li ₄ Ti ₅ O ₁₂ , WO ₂ , MoO ₂ , Fe ₂ O ₃ , or Li _3-x M _x N (M = A nitride represented by (Co, Ni, Cu) may be employed. One or more of these materials can be used as the negative electrode active material.

The potential (Li / Li ⁺ standard) of the negative electrode active material is, for example, 0.1 to 0.2 V in the case of carbon such as graphite, 0.1 to 1.0 V in the case of silicon, and LTO (Li ₄ Ti ₅ O ₁₂ ). In the case of 1 to 2V. In order to allow the non-aqueous secondary battery to be used at a high voltage, the negative electrode active material and the positive electrode active material are combined, and the voltage that is the potential difference between the positive electrode active material and the negative electrode active material is 4.2 V. It is better to make it higher than that.

  Here, the nonaqueous secondary battery in which the positive electrode active material and the negative electrode active material are materials capable of inserting and extracting lithium ions is referred to as a lithium ion secondary battery. Especially, the non-aqueous secondary battery whose negative electrode active material is Li is also called a lithium secondary battery.

  The negative electrode has a current collector and a negative electrode active material layer bound to the surface of the current collector. As the negative electrode current collector, for example, the one described for the positive electrode current collector can be adopted.

  The negative electrode active material layer includes a negative electrode active material and, if necessary, a binder and / or a conductive aid.

  The negative electrode current collector is not particularly limited as long as it is a metal that can withstand a potential suitable for the active material to be used, and for example, the one described for the positive electrode current collector can be adopted. As the negative electrode binder and the conductive additive, those described for the positive electrode can be adopted.

  As a method for forming the active material layer on the surface of the current collector, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used. An active material may be applied to the surface of the electric body. Specifically, an active material layer-forming composition containing an active material and, if necessary, a binder and a conductive aid is prepared, and an appropriate solvent is added to the composition to make a paste, and then the collection is performed. After applying to the surface of the electric body, it is dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.

  A separator is used in the non-aqueous secondary battery as necessary. The separator separates the positive electrode and the negative electrode and allows metal ions such as lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes. As separators, natural resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramide (Aromatic polyamide), polyester, polyacrylonitrile, etc., polysaccharides such as cellulose, amylose, fibroin, keratin, lignin, suberin, etc. Examples thereof include porous bodies, nonwoven fabrics, and woven fabrics using one or more electrically insulating materials such as polymers and ceramics. The separator may have a multilayer structure. Since the electrolytic solution has a slightly high viscosity and a high polarity, a membrane in which a polar solvent such as water can easily penetrate is preferable. Specifically, a film in which a polar solvent such as water soaks into 90% or more of the existing voids is more preferable.

  A separator is sandwiched between the positive electrode and the negative electrode as necessary to form an electrode body. The electrode body may be either a stacked type in which the positive electrode, the separator and the negative electrode are stacked, or a wound type in which the positive electrode, the separator and the negative electrode are sandwiched. After connecting between the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal connected to the outside using a current collecting lead or the like, an electrolyte is added to the electrode body to add a non-aqueous secondary battery It is good to do. Moreover, the non-aqueous secondary battery of this invention should just be charged / discharged in the electric potential range suitable for the kind of active material contained in an electrode.

  The shape of the case of the nonaqueous secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be employed. The case may be formed of a metal such as aluminum, for example.

  The non-aqueous secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from a non-aqueous secondary battery for all or a part of its power source. For example, the vehicle may be an electric vehicle or a hybrid vehicle. When a non-aqueous secondary battery is mounted on a vehicle, a plurality of non-aqueous secondary batteries may be connected in series to form an assembled battery. Examples of the non-aqueous secondary battery include various home electric appliances, office equipment, industrial equipment, and the like driven by batteries, such as personal computers and mobile communication devices, in addition to vehicles. Further, the non-aqueous secondary battery of the present invention includes a wind power generation, solar power generation, hydroelectric power generation and other power system power storage device and power smoothing device, power for ships and / or auxiliary power supply sources, aircraft, Power supply for spacecraft and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as a power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in the charging station for electric vehicles.

  As mentioned above, although embodiment of electrolyte solution was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Lithium ion secondary batteries of batteries 1 to 11 were produced as follows, and a cycle evaluation test of each battery was performed.

(Battery 1)
First, graphite powder (carbon, negative electrode active material, Li ⁺ / Li electrode reference potential of 0.1 to 0.2 V), 1 part by weight of acetylene black as a conductive assistant, and as a binder, 1 part by mass of styrene-butadiene rubber (SBR) and 1 part by mass of carboxymethylcellulose (CMC) were mixed, and this mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a slurry. This slurry was applied to a copper foil having a thickness of 20 μm as a negative electrode current collector so as to form a film using a doctor blade, and the current collector coated with the slurry was dried and pressed. Heated with a vacuum drier for a time, cut into a predetermined shape (rectangular shape of 26 mm × 31 mm), and made a negative electrode having a thickness of about 45 μm.

Next, 94 parts by mass of a lithium / nickel composite oxide LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (reactive potential 3.6 V based on Li ⁺ / Li electrode) as a positive electrode active material, 3 parts by mass of acetylene black as an auxiliary agent and 3 parts by mass of polyvinylidene fluoride (PVDF) as a binder are mixed to form a slurry, and this slurry is applied to a 20 μm aluminum foil as a current collector using a doctor blade, The current collector coated with the slurry is dried and pressed, and the bonded product is heated in a vacuum dryer at 120 ° C. for 6 hours, cut into a predetermined shape (rectangular shape of 25 mm × 30 mm), and a positive electrode having a thickness of about 50 μm and did. A polypropylene porous membrane as a separator was sandwiched between the positive electrode and the negative electrode. A plurality of electrode bodies composed of the positive electrode, the separator, and the negative electrode were stacked. The periphery of the two aluminum films was sealed by heat-welding except for a part to make a bag shape. The laminated electrode body was put in a bag-shaped aluminum film, and an electrolyte was injected and vacuum sealed. The electrolytic solution is obtained by dissolving LiPF ₆ as an electrolyte in an organic solvent. The organic solvent was prepared by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at a blending ratio of EC / DEC = 3: 7 (mass ratio). The concentration of LiPF ₆ in the electrolytic solution was 1 mol / L. Thus, a battery 1 (battery assembly) was obtained.

(Battery 2)
The battery assembly (Battery 1) was subjected to a conditioning treatment (charging / discharging process) within 20 hours after injection of the electrolyte. The conditioning treatment was performed at an ambient temperature of 25 ° C. In the conditioning process, a charger with a charge rate of 1C and CCCV (constant current constant voltage) is connected to the battery assembly, and the voltage is maintained after the battery assembly voltage (battery voltage) reaches 4.5V. And charged for 3 hours. The battery assembly with the battery voltage of 4.5V was disconnected from the charger and held for 3 hours without applying voltage. Next, the positive electrode and the negative electrode of the battery assembly were connected and discharged at a discharge rate of 1C until the battery voltage reached 3V. Thereafter, the battery 2 was degassed and vacuum-sealed again.

(Battery 3)
About the battery assembly (battery 1), the first charge was performed within 20 hours after the electrolyte injection (first charge step). The initial charge was performed in an atmosphere at room temperature (25 ° C.). In the initial charge, the battery assembly is connected to a charger with a charge rate of 0.8 C and a CCCV (constant current constant voltage) voltage until the battery voltage reaches 3.9 V and the total charge time reaches 4 hours. Was charged. Immediately after the completion of the first charge, the battery assembly was disconnected from the charger. The total charging time refers to the time from the start of charging to the end of the initial charging.

  After the initial charge, a conditioning process was performed in the same manner as the battery 2 (charge / discharge process). Thereafter, the battery 3 was degassed and vacuum sealed again.

(Battery 4)
About the battery assembly (battery 1), the first charge (initial charge process), the aging process (high temperature holding process), and the conditioning process (charge / discharge process) were performed.

  Within 20 hours after the electrolyte injection, the initial charge was performed in the same manner as the battery 3 (initial charge step). Within 1 hour after the completion of the first charge, the battery assembly was transferred to a constant temperature bath at 50 ° C., and aging treatment was started. The battery assembly was held in a thermostat at 50 ° C. for 20 hours for aging treatment (high temperature holding treatment). After holding the battery assembly in a 50 ° C. thermostat for 20 hours, the battery assembly is transferred to a 25 ° C. thermostat and left in the 25 ° C. thermostat for 3 hours or more to adjust the temperature of the battery assembly to 25. C.

  After the temperature of the battery assembly was 25 ° C., the conditioning treatment (charging / discharging process) was performed in the same manner as the battery 2.

(Battery 5)
About the battery assembly (battery 1), the first charge (initial charge process), the aging process (high temperature holding process), and the conditioning process (charge / discharge process) were performed. The aging treatment is the same as that of the battery 4 except that the holding time of the battery assembly in the 50 ° C. thermostat is 72 hours.

(Battery 6)
About the battery assembly (battery 1), the first charge (initial charge process) and the conditioning process (charge / discharge process) were performed. In the initial charge, the battery assembly was connected to a charger with a charge rate of 0.8 C and a CCCV (constant current constant voltage), and the battery voltage of the battery assembly was charged until it reached 4.2V. Others are the same as the battery 3.

(Battery 7)
About the battery assembly (battery 1), the first charge (initial charge process), the aging process (high temperature holding process), and the conditioning process (charge / discharge process) were performed. Others are the same as the battery 4.

(Battery 8)
About the battery assembly (battery 1), the first charge (initial charge process), the aging process (high temperature holding process), and the conditioning process (charge / discharge process) were performed. In the initial charge, the battery assembly was connected to a charger with a charge rate of 0.8 C and a CCCV (constant current constant voltage), and the battery voltage of the battery assembly was charged until it reached 4.2V. Others are the same as the battery 5.

(Battery 9)
About the battery assembly (battery 1), the first charge (initial charge process) and the conditioning process (charge / discharge process) were performed. In the initial charge, the battery assembly was connected to a charger having a charge rate of 0.8 C and a CCCV (constant current constant voltage), and the battery voltage of the battery assembly was charged until it reached 4.5V. Others are the same as the battery 3.

(Battery 10)
About the battery assembly (battery 1), the initial charge was performed in the same manner as the battery 9 within 20 hours after the electrolyte injection (initial charge step). In the initial charge, the battery assembly was connected to a charger having a charge rate of 0.8 C and a CCCV (constant current constant voltage), and the battery voltage of the battery assembly was charged until it reached 4.5V. Others are the same as the battery 4.

(Battery 11)
About the battery assembly (battery 1), the first charge (initial charge process), the aging process (high temperature holding process), and the conditioning process (charge / discharge process) were performed. In the initial charge, the battery assembly was connected to a charger having a charge rate of 0.8 C and a CCCV (constant current constant voltage), and the battery voltage of the battery assembly was charged until it reached 4.5V. Others are the same as the battery 5.

  The production methods of the batteries 1 to 11 are summarized in Table 1.

<Battery performance evaluation>
A charge / discharge (cycle) test and a resistance test of the batteries 1 to 11 were performed. In the charge / discharge test, the charging under the condition of the charging rate 1C and the discharging under the condition of the discharging rate 1C were repeated 200 times. From the results of the charge / discharge test, the initial discharge capacity, the discharge capacity after 200 cycles, and the capacity maintenance rate after 200 cycles were determined. The capacity retention rate (X) after 200 cycles was determined by the following formula (A). This capacity retention ratio represents the cycle characteristics of the battery.

X (%) = 100 × (discharge capacity after 200 cycles) / initial discharge capacity (A)
The discharge DC resistance was measured from the voltage drop when the voltage was maintained at 3.6 V and discharged at a 3C rate. The test results are shown in Table 4.

  As shown in Table 4, the batteries 4, 5, 7, and 8 had higher capacity retention rates than the batteries 1 to 3, 6, and 9 to 11. The battery 2 that had been subjected only to the conditioning treatment had improved cycle characteristics compared to the battery 1 that had not been subjected to the conditioning treatment, but on the other hand, the discharge DC resistance was higher. The battery 3 subjected to the initial charge and conditioning process and the battery 4 subjected to the initial charge, aging process and conditioning process had lower resistance than the battery 1 not subjected to these processes.

  The batteries 4, 7, and 10 have a shorter retention time of the aging process than the batteries 5, 8, and 11. Batteries 4, 7, and 10 have lower resistance and higher initial discharge capacity and higher cycle characteristics than batteries 5, 8, and 11.

  Comparing the batteries 4, 7, 10, the capacity retention rate of the battery 10 was lower than that of the batteries 4, 7. From this, it was found that when the voltage of the first charge exceeds 4.2 V, the cycle characteristics deteriorate.

  In the batteries 2 to 11, the temperature of the first charge was normal temperature, but when the first charge was performed at a low temperature of 0 ° C. and a high temperature of 65 ° C., a problem of abnormal charging occurred. In batteries 4, 5, 7, 8, 10, and 11, the aging process started within 1 hour after the initial charge, but when the aging process was started after 12 hours or more had elapsed, the cycle characteristics were degraded. . In the batteries 4, 5, 7, 8, 10, and 11, when the aging temperature was 50 ° C., the resistance increased and the cycle characteristics deteriorated when the temperature was 0 ° C. or 65 ° C. Further, in the case where the retention time of the aging process is a short time of 0.5 hour, the result is equal to the case where the aging process is not performed.

Claims (6)

Non-aqueous secondary battery assembly comprising a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, a non-aqueous electrolyte, and a case containing the positive electrode, the negative electrode, and the non-aqueous electrolyte (Hereinafter referred to as “battery assembly”), an initial charging step of performing initial charging so that the voltage of the battery assembly reaches a range of not less than the rated voltage and not more than 4.2 V;
A high temperature holding step of starting an aging process in less than 12 hours after performing the initial charging step, and holding the battery assembly in a high temperature environment of 40 ° C. or higher and 50 ° C. or lower for a predetermined time in the aging process;
The battery assembly that has been subjected to the aging treatment is charged until a voltage of the battery assembly reaches a range exceeding 4.2 V, and then a charging / discharging step of performing a conditioning process for discharging. And
The holding time in the high temperature environment of the battery assembly in the aging treatment is 10 hours or more and less than 72 hours,
A method for producing a non-aqueous secondary battery, wherein no charge / discharge treatment is performed between the initial charge step and the aging treatment (however, the non-aqueous electrolyte includes ethylene sulfite, propylene sulfite, and propane). Including at least one additive (A) selected from the group consisting of sultone and at least one additive (B) selected from the group consisting of maleic anhydride, vinylene carbonate, vinyl ethylene carbonate, and LiBF ₄ (Excluding methods for manufacturing non-aqueous secondary batteries.)   The method for manufacturing a non-aqueous secondary battery according to claim 1, wherein a charging rate of the first charging in the first charging step is 0.1 C or more and 1 C or less. The charge of the conditioning process of the said charging / discharging process is performed until the voltage of the said battery assembly reaches over 4.2V and the range of 4.6V or less, The non-aqueous secondary battery of Claim 1 or 2 Production method. The method for manufacturing a non-aqueous secondary battery according to any one of claims 1 to 3 , wherein a charging rate of the conditioning process in the charge / discharge process is 0.1 C or more and 2 C or less. The manufacturing method of the non-aqueous secondary battery according to any one of claims 1 to 4 , wherein an atmosphere in which the conditioning treatment is performed is less than 40 ° C. The said positive electrode active material is a manufacturing method of the non-aqueous secondary battery of any one of Claims 1-5 which has 1 or more types chosen from the group of lithium metal complex oxide and a polyanion type compound.