JP6125719B1 - Charging system and method for charging non-aqueous electrolyte battery - Google Patents

Abstract

According to the embodiment, a charging system including a secondary battery unit and a charging control unit is provided. The secondary battery part includes a positive electrode active material containing an Fe-containing phosphate compound having an olivine structure and a negative electrode active material containing a titanium composite oxide. The charging control unit performs constant voltage charging after constant current charging so that the secondary battery unit satisfies the following expression (1). 0.1V.ltoreq.VCC-VCCV.ltoreq.0.5V (1) where VCC is a voltage reached at constant current charging (V) and VCCV is a closed circuit voltage at constant voltage charging (V).

Description

  Embodiments relate to a charging system and a charging method for a nonaqueous electrolyte battery.

  Non-aqueous electrolyte batteries that are charged and discharged by moving lithium ions between the negative electrode and the positive electrode are actively studied as high energy density batteries.

  This non-aqueous electrolyte battery is expected to be used as a medium- and large-sized power source in addition to being used as a power source for small electronic devices. In such medium and large-sized applications, life characteristics and high safety are required.

  Lithium transition metal composite oxide is used for the positive electrode active material of the nonaqueous electrolyte battery. Co, Mn, Ni, or the like is used as the transition metal of the oxide. In recent years, studies on olivine type compounds such as spinel type lithium manganate, olivine type lithium iron phosphate, and olivine type lithium manganese phosphate as active cathode materials that are inexpensive and highly safe have been actively conducted.

  Since the compound having an olivine structure has low electron conductivity, it is difficult to obtain good charge / discharge characteristics. Among these, it has been difficult for a nonaqueous electrolyte battery containing lithium manganese phosphate as a positive electrode active material to achieve good charge / discharge characteristics.

JP 2011-124166 A

  The subject of embodiment is providing the manufacturing method of the charging system and nonaqueous electrolyte battery with which lifetime performance was improved.

  According to the embodiment, a charging system including a secondary battery unit and a charging control unit is provided. The secondary battery unit includes a non-aqueous electrolyte battery including a positive electrode including a positive electrode active material including a Fe-containing phosphate compound having an olivine structure, a negative electrode including a negative electrode active material including a titanium composite oxide, and a non-aqueous electrolyte. Including. The charging control unit performs constant voltage charging after constant current charging so that the secondary battery unit satisfies the following expression (1).

0.1V ≦ V _CC −V _CCV ≦ 0.5V (1)
However, V _CC is an ultimate voltage (V) in constant current charging, and V _CCV is a closed circuit voltage (V) in constant voltage charging.

Moreover, according to other embodiment, the charging method of a nonaqueous electrolyte battery is provided. The nonaqueous electrolyte battery includes a positive electrode including a positive electrode active material including an Fe-containing phosphate compound having an olivine structure, a negative electrode including a negative electrode active material including a titanium composite oxide, and a nonaqueous electrolyte. The charging method includes subjecting the nonaqueous electrolyte battery to constant current charging up to the ultimate voltage V _CC (V) and subjecting the nonaqueous electrolyte battery to constant voltage charging at the voltage V _CCV (V). The ultimate voltage V _CC (V) and the voltage V _CCV (V) satisfy the following expression (1).

0.1V ≦ V _CC −V _CCV ≦ 0.5V (1)

It is an example of the flowchart which shows the constant current constant voltage charge by the charging system of 1st Embodiment. The graph which shows the time-dependent change of the cell voltage in the constant current constant voltage charge by the charging system of 1st Embodiment. The graph which shows the change over time of the cell voltage in the constant current constant voltage charge by a reference example. It is a block diagram which shows an example of the charging system of 1st Embodiment. It is sectional drawing which shows an example of the nonaqueous electrolyte battery contained in the charging system of 1st Embodiment. It is an expanded sectional view of the A section of FIG. It is a perspective view which shows the other example of the nonaqueous electrolyte battery contained in the charging system of 1st Embodiment. It is an expanded sectional view of the B section of FIG.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
According to the first embodiment, a non-aqueous solution including a positive electrode including a positive electrode active material including a Fe-containing phosphate compound having an olivine structure, a negative electrode including a negative electrode active material including a titanium composite oxide, and a non-aqueous electrolyte. A charging system including a secondary battery unit including an electrolyte battery is provided.

  An example of the Fe-containing phosphate compound having an olivine structure is lithium manganese phosphate. Fe-containing phosphate compounds having an olivine structure such as lithium manganese phosphate are difficult to be charged. Therefore, in a nonaqueous electrolyte battery including a positive electrode active material containing an Fe-containing phosphate compound having an olivine structure, it is desirable to increase the overvoltage during charging. However, it has been found that when constant voltage charging is performed with an overvoltage applied to the battery, oxidative decomposition of the nonaqueous electrolyte occurs and the deterioration of the positive electrode is accelerated.

  According to the charging system of the embodiment, the constant voltage charging (constant voltage: CV) is performed after the constant current charging (constant current: CC) so that the secondary battery unit including the nonaqueous electrolyte battery satisfies the following expression (1). Since the charging control unit to be applied is included, the lifetime performance of the system can be improved.

0.1V ≦ V _CC −V _CCV ≦ 0.5V (1)
However, V _CC is an ultimate voltage (V) in constant current charging, and V _CCV is a closed circuit voltage (CCV) (V) in constant voltage charging.

If the voltage difference represented by V _CC −V _CCV is less than 0.1 V, the progress of constant voltage charging performed after constant current charging is slowed down, and the total time required for constant current constant voltage charging is increased. Inferior. On the other hand, when the voltage difference exceeds 0.5 V, the overvoltage applied to the battery after constant current charging is increased and the oxidative decomposition of the nonaqueous electrolyte proceeds. As a result, the resistance of the positive electrode increases, and the charge / discharge cycle life of the battery decreases.

When the voltage difference is 0.1 V or more and 0.5 V or less, constant voltage charging can be promoted by applying an overvoltage to the battery after constant current charging. Moreover, since constant voltage charging is 0.1 to 0.5 V lower than the ultimate voltage in constant current charging, oxidative decomposition of the nonaqueous electrolyte during constant voltage charging can be suppressed. Therefore, it is possible to suppress the increase in resistance of the positive electrode by suppressing the oxidative decomposition of the nonaqueous electrolyte while shortening the charging time. As a result, since the charge / discharge cycle life of the battery can be improved, the life performance of the charging system can be improved. A more preferable range of the voltage difference represented by V _CC −V _CCV is 0.2V ≦ V _CC −V _CCV ≦ 0.3V.

A flow of constant current and constant voltage charging by the charging control unit is shown in FIG. In step 21, the secondary battery unit is charged with a constant current with a current I _cc (C). Here, 1C is a value corresponding to a current value (A) that can discharge the nonaqueous electrolyte battery in one hour.

The constant voltage charging is performed until the voltage of the secondary battery unit reaches the ultimate voltage V _CC (V) (step 22). Next, the process proceeds to constant voltage charging (step 23). The closed circuit voltage (V) during constant voltage charging is set to V _CCV (V). V _CC (V) and V _CCV (V) satisfy the above-described expression (1). When the current value converges to the set value (step 24), the constant voltage charging is terminated.

FIG. 2 shows the relationship between the cell voltage and the charging time in the constant current and constant voltage charging by the charging control unit. The cell voltage that is the vertical axis of the graph of FIG. 2 is the voltage of the unit cell of the nonaqueous electrolyte battery. As shown in FIG. 2, when the constant voltage charging is terminated at the ultimate voltage V _CC (V), the slope of the voltage increase at the end of the constant voltage charging becomes large. Thereafter, the voltage is lowered to V _CCV (V) to shift to constant voltage charging. By performing constant voltage charging up to the ultimate voltage V _CC (V), the constant voltage charging time required to reach a predetermined SOC (State of charge) can be shortened.

In contrast, in the case of the reference example does not perform the constant current constant voltage charging by the charging control unit, as shown in FIG. 3, up to V ₂ is V _{1 (V)} voltage above a voltage charged theoretically After performing constant current charging, constant voltage charging is performed at a voltage of V ₂ (V). According to this method, in order to avoid the acceleration of oxidative decomposition of the nonaqueous electrolyte, since it is impossible to increase the V ₂ to perform the constant voltage charging, the charging time required to reach the predetermined SOC becomes longer, Productivity is inferior. Further increasing the V ₂ to shorten the charging time, since a large overvoltage is applied over a long period of time, since the oxidative decomposition of the nonaqueous electrolyte is accelerated, it is difficult achieve both productivity and deterioration prevention.

The ultimate voltage V _CC (V) is desirably a value equal to or higher than the theoretical voltage (V) of the nonaqueous electrolyte battery. LiMn _1-xy Fe _x A _y PO ₄ (0 <x ≦ 0.3, 0 ≦ y ≦ 0.1, A is Mg, Ca, Al, Ti, Zn) And a non-aqueous electrolyte battery in which the negative electrode active material is a spinel type lithium titanium oxide which is a kind of titanium composite oxide. Working potential of the positive electrode containing _{LiMn 1-x-y Fe x} A y PO 4 is 4.1V (vs.Li/Li ^+). The operating potential of the negative electrode containing titanium composite oxide is around 1.5 V (vs. Li ^/ Li ⁺ ), and the operating potential of the negative electrode containing spinel type lithium titanium oxide is 1.55 V (vs. Li ^/ Li ⁺ ). is there. Thus, the theoretical voltage of the nonaqueous electrolyte battery for the 2.55V, _{V CC} and _{V ccv} if conventional Considering the suppression of oxidative decomposition of the nonaqueous electrolyte about 2.6V is preferred. However, considering both productivity and suppression of oxidative decomposition of the nonaqueous electrolyte as in the embodiment, the ultimate voltage V _CC (V) is set to approximately 2.7 V or more and 3.2 V, and the closed circuit voltage V _CCV is 2.6 V. It is preferable to set it as the range below 3.1V. A more preferable range of the reached voltage V _CC (V) is a range of 2.7 to 3.1 V.

When the current value during constant current charging is I _CC (C), it is desirable that the current value I _CC (C) satisfies the following formula (2).

0.2C ≦ I _CC ≦ 30C (2)
By setting it as such a range, both shortening of charge time and suppression of a deterioration of a positive electrode active material are achieved.

  The form of the secondary battery part including the nonaqueous electrolyte battery is not particularly limited, and may be either a single cell or an assembled battery in which a plurality of unit cells are electrically connected. The method for electrically connecting the unit cells in the assembled battery is not particularly limited, and examples include serial, parallel, and combinations of series and parallel.

  When the secondary battery unit is an assembled battery in which a plurality of unit cells are connected in series, it is desirable that the charge control unit performs constant voltage charging after constant current charging so as to satisfy the following expression (3). Thereby, the lifetime performance of a charging system can be improved.

0.1nV ≦ V _CC −V _CCV ≦ 0.5nV (3)
Here, n is the number of unit cells included in the assembled battery.

  The form of the charging system is not particularly limited, and may be a battery pack in which the secondary battery unit and the charging control unit are housed in the housing, or the charging control unit is incorporated in the in-vehicle microcontroller and the charging control unit is incorporated. It is also possible to form a charging system by electrically connecting the secondary battery units. In addition, the charging system can be used for various applications, for example, for stationary or in-vehicle use, specifically, a stationary power source, a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, etc. Can be mentioned.

  An example of the charging system is shown in FIG. The charging system shown in FIG. 4 includes a secondary battery unit 25 and a battery management circuit 26. The secondary battery unit 25 includes an assembled battery in which a plurality of nonaqueous electrolyte battery unit cells 10 are connected in series. The battery management circuit 26 functions as a charge control unit. The battery management circuit 26 is electrically connected to each non-aqueous electrolyte battery unit cell 10 by a wiring 28. The secondary battery unit 25 of the charging system having such a configuration is electrically connected to the charger 27 by the wiring 29.

  The structure of the nonaqueous electrolyte battery is not particularly limited, and can have a flat shape, a square shape, a cylindrical shape, a coin shape, a button shape, or the like. An example of a flat type non-aqueous electrolyte battery is shown in FIGS.

  As shown in FIGS. 5 and 6, the flat wound electrode group 1 is accommodated in a bag-shaped exterior member 2 made of a laminate film in which a metal layer is interposed between two resin films. The flat wound electrode group 1 is formed by winding a laminate in which the negative electrode 3, the separator 4, the positive electrode 5, and the separator 4 are laminated in this order from the outside, and then press-molding the laminate. As shown in FIG. 6, the outermost negative electrode 3 has a configuration in which a negative electrode layer 3b containing a negative electrode active material is formed on one surface on the inner surface side of the negative electrode current collector 3a. The negative electrode layer 3b is formed on both surfaces of 3a. The positive electrode 5 is configured by forming a positive electrode layer 5b on both surfaces of a positive electrode current collector 5a.

  In the vicinity of the outer peripheral end of the wound electrode group 1, the negative electrode terminal 6 is connected to the negative electrode current collector 3 a of the outermost negative electrode 3, and the positive electrode terminal 7 is connected to the positive electrode current collector 5 a of the inner positive electrode 5. The negative electrode terminal 6 and the positive electrode terminal 7 are extended to the outside from the opening of the bag-shaped exterior member 2. For example, the liquid nonaqueous electrolyte is injected from the opening of the bag-shaped exterior member 2. The wound electrode group 1 and the liquid nonaqueous electrolyte are completely sealed by heat-sealing the opening of the bag-shaped exterior member 2. When heat-sealing, the negative electrode terminal 6 and the positive electrode terminal 7 are sandwiched by the bag-shaped exterior member 2 at this opening.

  As shown in FIGS. 7 and 8, the laminated electrode group 11 is housed in an exterior member 12 made of a laminate film in which a metal layer is interposed between two resin films. As shown in FIG. 8, the stacked electrode group 11 has a structure in which positive electrodes 13 and negative electrodes 14 are alternately stacked with separators 15 interposed therebetween. There are a plurality of positive electrodes 13, each including a current collector 13 a and a positive electrode layer 13 b supported on both surfaces of the current collector 13 a. There are a plurality of negative electrodes 14, each of which includes a current collector 14a and a negative electrode layer 14b supported on both surfaces of the current collector 14a. One end of the current collector 14 a of each negative electrode 14 protrudes from the positive electrode 13. One end of the current collector 14 a protruding is electrically connected to the strip-shaped negative terminal 16. The tip of the strip-shaped negative electrode terminal 16 is drawn out from the exterior member 12 to the outside. Although not shown, one end of the current collector 13 a of the positive electrode 13 protrudes from the negative electrode 14. One end of the positive electrode 13a protruding from the negative electrode 14 is located on the opposite side to the one end of the current collector 14a protruding. The projecting end of the current collector 13 a is electrically connected to the belt-like positive electrode terminal 17. The tip of the strip-like positive electrode terminal 17 is located on the opposite side of the negative electrode terminal 16 and is drawn out from the side of the exterior member 12 to the outside.

  Hereinafter, the negative electrode, the positive electrode, the nonaqueous electrolyte, the separator, the exterior member, the positive electrode terminal, and the negative electrode terminal used in the nonaqueous electrolyte battery will be described in detail.

(Negative electrode)
The negative electrode includes a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode active material-containing layer includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material-containing layer is formed on one side or both sides of the negative electrode current collector.

The negative electrode active material includes a titanium composite oxide. Examples of the titanium composite oxide that can be used as the negative electrode active material include spinel lithium titanate (for example, the general formula Li _{4/3 + x} Ti _5/3 O ₄ (0 ≦ x ≦ 1.1)), single Oblique type titanium composite oxide (for example, monoclinic β-type Li _x TiO ₂ (0 ≦ x, more preferably 0 ≦ x ≦ 1)), anatase type titanium composite oxide (for example, anatase type titanium dioxide) and Ramsdelide type lithium titanate (for example, Li _{2 + x} Ti ₃ O ₇ (−1 ≦ x ≦ 3)) or general formula Ti _1-x M _{x + y} Nb _2-y O _7-δ (0 ≦ x <1, 0 ≦ y <1, and M includes at least one selected from Mg, Fe, Ni, Co, W, Ta and Mo), and a general formula Li _{2 + v} Na _{2 -w} M1 _x Ti _6-yz Nb _y M2 _z O _{14 + δ} (0 ≦ v ≦ 4, 0 <w <2, 0 ≦ x <2, 0 <y ≦ 6, 0 ≦ z <3, -0.5 ≦ δ ≦ 0.5, M1 is selected from Cs, K, Sr, Ba, Ca At least one, and M2 includes at least one selected from Zr, Sn, V, Ta, Mo, W, Fe, Co, Mn, and Al). Examples thereof include titanium-containing oxides. Among them, spinel-structured lithium titanate is preferable because it has excellent life performance and quick charge performance, that is, so-called cycle performance and rate performance. In addition, a niobium composite oxide may be further included. For _{example, Nb 2 O 5, Nb 12} O 29, and the like. Moreover, the negative electrode active material can exist as particles in the negative electrode active material-containing layer.

  The compounding ratio of the negative electrode active material, the conductive agent and the binder is such that the negative electrode active material is 70% by mass to 96% by mass, the negative electrode conductive agent is 2% by mass to 28% by mass, and the binder is 2% by mass to 28% by mass. It is preferable that it is the range of the mass% or less. If the conductive agent is less than 2% by mass, the current collecting performance of the negative electrode active material-containing layer may be reduced, and the large current characteristics of the nonaqueous electrolyte battery may be reduced. On the other hand, if the binder is less than 2% by mass, the binding property between the negative electrode active material-containing layer and the negative electrode current collector is lowered, and the cycle characteristics may be lowered. On the other hand, from the viewpoint of increasing the capacity, the conductive agent and the binder are each preferably 28% by mass or less.

  The negative electrode current collector is either an aluminum foil that is electrochemically stable in a potential range nobler than 1.0 V or an aluminum alloy foil containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. Preferably it is formed.

  The negative electrode can be produced, for example, by the following method. First, a negative electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one side or both sides of the negative electrode current collector. Next, the applied slurry is dried to form a negative electrode active material-containing layer. Thereafter, the current collector and the negative electrode active material-containing layer are pressed. Alternatively, the negative electrode active material, the conductive agent, and the binder can be formed into a pellet and used as the negative electrode active material-containing layer. By forming this pellet on the negative electrode current collector, a negative electrode can be produced.

(Positive electrode)
The positive electrode includes a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer includes particles of the positive electrode active material, and may include a conductive agent and a binder as necessary. The positive electrode active material-containing layer is formed on one side or both sides of the positive electrode current collector.
The positive electrode active material includes an Fe-containing phosphate compound having an olivine structure. Examples of Fe-containing phosphate compounds with olivine structure include LiMn _1-xy Fe _x A _y PO ₄ (0 <x ≦ 0.3, 0 ≦ y ≦ 0.1, A is composed of Mg, Ca, Al, Ti, Zn and Zr At least one element selected from the group). This is because the phosphoric acid compound represented by LiMn _1-xy Fe _x A _y PO ₄ is excellent in safety and can realize a positive electrode having a high potential. More preferable ranges of x and y are 0.05 ≦ x ≦ 0.2 and 0.05 ≦ y ≦ 0.1.

The content of phosphoric acid compound represented by _{LiMn 1-xy Fe x A y} PO 4 in the positive electrode active material is desirably 70 wt% or more. Further preferred is that the cathode active material consists essentially of phosphoric acid compounds represented by _{LiMn 1-xy Fe x A y} PO 4.

The positive electrode active material is present in the positive electrode in the form of particles. Phosphoric acid compounds represented by _{LiMn 1-xy Fe x A y} PO 4 may be a single primary particles may be secondary particles formed by aggregation of primary particles alone of the primary particles and secondary particles Both of them may be included.

  Further, the positive electrode active material may include an Fe-containing phosphate compound having an olivine structure and another positive electrode active material. Other positive electrode active materials include lithium-containing oxides.

Examples of the lithium-containing oxide include lithium manganese composite oxide (for example, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxide (for example, Li _x NiO ₂ ), lithium cobalt composite oxide ( For example, Li _x CoO _2), lithium nickel cobalt composite oxide _{(e.g., LiNi 1-y Co y O} 2), lithium manganese cobalt composite oxide _{(e.g., Li x Mn y Co 1-} y O 2), lithium nickel cobalt-manganese composite oxide _{(e.g., LiNi 1-yz Co y Mn} z O 2), lithium-nickel-cobalt-aluminum composite oxide _{(e.g., LiNi 1-yz Co y Al} z O 2) are included. In the above, 0 <x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ z ≦ 1 are preferable.

Among them, lithium manganese composite oxide (Li _x Mn ₂ O ₄ ), lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel cobalt composite oxide (Li _x Ni _1-y Co _y O ₂ ), lithium manganese cobalt composite oxide _{(Li x Mn y Co 1-} y O 2), lithium-nickel-cobalt-manganese composite oxide (e.g., _{LiNi 1-yz Co y Mn z} O 2) is preferred. In the above, 0 <x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ z ≦ 1 are preferable.

  Examples of the conductive agent include carbon materials such as acetylene black, carbon black, graphite, carbon nanofiber, and carbon nanotube. These carbon materials may be used alone or a plurality of carbon materials may be used.

  The binder binds the active material, the conductive agent, and the current collector. Examples of the binder include cellulose such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, acrylic resin, carboxymethyl cellulose (CMC), and the like. . The type of the binder can be one type or two or more types.

  The positive electrode active material, the conductive agent, and the binder in the positive electrode layer should be blended at a ratio of 80% by mass to 95% by mass, 3% by mass to 18% by mass, and 2% by mass to 17% by mass, respectively. Is preferred. The conductive agent can exert a sufficient effect by adjusting the amount to 3% by mass or more. By making the amount of the conductive agent 18% by mass or less, the decomposition of the nonaqueous electrolyte on the surface of the conductive agent under high temperature storage can be reduced. Sufficient electrode strength can be obtained by setting the binder to an amount of 2% by mass or more. The amount of the binder, which is an insulating material in the positive electrode, can be reduced by setting the amount of the binder to 17% by mass or less. As a result, the internal resistance can be reduced.

  The current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si.

  The positive electrode can be produced, for example, by the following method. First, a slurry is prepared by suspending particles of a positive electrode active material, a conductive agent, and a binder in a solvent. This slurry is applied to one side or both sides of the current collector. Next, the applied slurry is dried to form a positive electrode active material-containing layer. Thereafter, the current collector and the positive electrode active material-containing layer are pressed.

(Nonaqueous electrolyte)
As the non-aqueous electrolyte, a liquid non-aqueous electrolyte or a gel non-aqueous electrolyte can be used. The liquid non-aqueous electrolyte is prepared by dissolving the electrolyte in an organic solvent. The concentration of the electrolyte is preferably in the range of 0.5 to 2.5 mol / l. The gel-like nonaqueous electrolyte is prepared by combining a liquid electrolyte and a polymer material. The liquid non-aqueous electrolyte is also referred to as a non-aqueous electrolyte.

Examples of electrolytes include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), trifluoromethanesulfone Lithium salts such as lithium acid (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ] are included. These electrolytes can be used alone or in combination of two or more. The electrolyte preferably contains LiPF ₆ .

  Examples of organic solvents include: cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC); diethyl carbonate (DEC), dimethyl carbonate Chain carbonates such as (dimethyl carbonate; DMC), methyl ethyl carbonate (MEC); Tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), Dioxolane (DOX) ); Cyclic ethers such as dimethoxyethane (DME), chain ethers such as diethoxyethane (DEE); gamma-butyrolactone (GBL), α-methyl γ-butyrolactone (alpha- methyl gamma-butyrolactone (MBL), acetonitrile (acetonitrile; AN), and sulfolane : SL) is included. These organic solvents can be used alone or in combination of two or more.

  Examples of more preferable organic solvents include two or more selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC). And a mixed solvent containing γ-butyrolactone (GBL). By using such a mixed solvent, a nonaqueous electrolyte battery having excellent low-temperature performance can be obtained.

  Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyetheylene oxide (PEO).

(Separator)
As the separator, for example, a porous film formed from a material such as polyethylene (PE), polypropylene (polypropylene; PP), cellulose, and polyvinylidene fluoride (PVdF), a synthetic resin nonwoven fabric, or the like is used. be able to. Among these, a porous film containing polyethylene or polypropylene is preferable from the viewpoint of improving safety because it can be melted at a constant temperature to interrupt the current.

(Exterior material)
As the exterior member, a laminated film bag-like container or a metal container is used.

  Examples of the shape include a flat type, a square type, a cylindrical type, a coin type, a button type, a sheet type, and a laminated type. Of course, in addition to a small battery mounted on a portable electronic device or the like, a large battery mounted on a two-wheel or four-wheel automobile or the like may be used.

  As the laminate film, a multilayer film in which a metal layer is interposed between resin films is used. The metal layer is preferably an aluminum foil or an aluminum alloy foil for weight reduction. For the resin film, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) can be used. The laminate film can be formed into the shape of an exterior member by sealing by heat sealing. The laminate film preferably has a thickness of 0.2 mm or less.

  The metallic container can be formed from aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc and silicon. On the other hand, the content of transition metals such as iron, copper, nickel and chromium is preferably 100 ppm or less. Thereby, it becomes possible to dramatically improve long-term reliability and heat dissipation in a high temperature environment. The metal container preferably has a thickness of 0.5 mm or less, and more preferably has a thickness of 0.2 mm or less.

(Negative terminal)
The negative electrode terminal is formed of a material that is electrically stable and has electrical conductivity in a range where the potential with respect to lithium metal is 1 V (vs. Li ^/ Li ⁺ ) or more and 3 V (vs. Li ^/ Li ⁺ ) or less. The negative electrode terminal is preferably formed from aluminum or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The negative electrode terminal is preferably formed from the same material as the negative electrode current collector in order to reduce the contact resistance with the negative electrode current collector.

(Positive terminal)
The positive electrode terminal is made of a material that is electrically stable and has electrical conductivity in the range where the potential with respect to lithium metal is 3 V (vs. Li ^/ Li ⁺ ) or more and 4.5 V (vs. Li ^/ Li ⁺ ) or less. The The positive electrode terminal is preferably formed from aluminum or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal is preferably formed of the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

According to the charging system of the first embodiment described above, the secondary battery unit including the positive electrode including the Fe-containing phosphate compound having the olivine structure and the negative electrode including the titanium composite oxide, and the secondary battery unit (1 ) Constant current constant voltage charging while suppressing deterioration of the positive electrode because it includes a charge control unit that performs constant voltage charging after constant current charging so as to satisfy the equation (0.1 V ≦ V _CC −V _CCV ≦ 0.5 V) Can be shortened. As a result, it is possible to realize a charging system capable of rapid charging and having excellent life performance.
(Second Embodiment)
According to the second embodiment, a method for charging a nonaqueous electrolyte battery is provided. The nonaqueous electrolyte battery includes a positive electrode including a positive electrode active material including an Fe-containing phosphate compound having an olivine structure, a negative electrode including a negative electrode active material including a titanium composite oxide, and a nonaqueous electrolyte. This charging method includes subjecting the nonaqueous electrolyte battery to constant current charging up to the ultimate voltage V _CC (V) and subjecting the nonaqueous electrolyte battery to constant voltage charging at the voltage V _CCV (V). The ultimate voltage V _CC (V) and the voltage V _CCV (V) satisfy the following expression (1).

0.1V ≦ V _CC −V _CCV ≦ 0.5V (1)
The charging method of the second embodiment can be performed using, for example, the charging system of the first embodiment. The nonaqueous electrolyte battery may be a single cell or an assembled battery in which unit cells are electrically connected. Examples of the non-aqueous electrolyte battery include the same ones as described in the first embodiment.

  According to the charging method of the second embodiment, it is possible to reduce the time required for constant current and constant voltage charging while suppressing deterioration of the positive electrode of the nonaqueous electrolyte battery. As a result, it is possible to realize a charging method capable of rapid charging and capable of improving the life performance of the nonaqueous electrolyte battery.

Examples will be described below, but the present invention is not limited to the examples described below unless the gist of the present invention is exceeded.
Example 1
Preparation of positive electrode First, 90% by weight of LiMn _0.85 Fe _0.1 Mg _0.05 PO ₄ particles as a positive electrode active material, 5% by weight of acetylene black as a conductive agent, and 5% by weight of polyvinylidene fluoride (PVdF) as a binder are N-methylpyrrolidone. (NMP) and mixed to form a slurry, and this slurry was applied to both sides of a current collector made of aluminum foil having a thickness of 15 μm, then dried and pressed to form a positive electrode having an electrode density of 2.0 g / cm ³ Was made.

Production of negative electrode
A slurry was prepared by adding 90% by weight of Li ₄ Ti ₅ O ₁₂ powder, ₅ % by weight of acetylene black and 5% by weight of polyvinylidene fluoride (PVdF) to N-methylpyrrolidone (NMP) and mixing them. This slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm, dried, and pressed to prepare a negative electrode having an electrode density of 2.0 g / cm ³ .

Production of Electrode Group After a positive electrode, a separator made of a polyethylene porous film having a thickness of 25 μm, a negative electrode and a separator were laminated in this order, they were wound in a spiral shape. This was heated and pressed at 90 ° C. to produce a flat electrode group having a width of 30 mm and a thickness of 3.0 mm. The obtained electrode group was housed in a pack made of a laminate film and vacuum dried at 80 ° C. for 24 hours. The laminate film is formed by forming a polypropylene layer on both sides of an aluminum foil having a thickness of 40 μm, and the overall thickness is 0.1 mm.

Preparation of liquid non-aqueous electrolyte Propylene carbonate (PC) and ethyl methyl carbonate (MEC) were mixed at a volume ratio of 1: 2 to obtain a mixed solvent. A liquid nonaqueous electrolyte was prepared by dissolving 1 M of LiPF ₆ as an electrolyte in this mixed solvent.

Production of Nonaqueous Electrolyte Secondary Battery A liquid nonaqueous electrolyte was injected into a laminate film pack containing an electrode group. Thereafter, the pack was completely sealed by heat sealing to produce a non-aqueous electrolyte secondary battery having a structure shown in FIG. 5 and having a width of 35 mm, a thickness of 3.2 mm, and a height of 65 mm.

  The produced cell was incorporated in the charging system shown in FIG. The number of batteries used in the charging system was one, and a battery management circuit was electrically connected to this battery. Next, a 1C discharge cycle was performed in a 45 ° C. environment. Discharge was performed by constant current discharge, and the final discharge voltage was 1.5V. Charging was performed as follows.

In the charging method, the current value I _CC during CC charging was set to 2C, and the ultimate voltage V _CC during CC charging was set to 2.7 V. The voltage V _CCV during CV charging was 2.6 V. That is, charging was performed with V _CC −V _CCV being 0.1 V.
(Example 2)
The charging current value I _CC was set to 2 C, V _CC was set to 2.9 V, V _CCV was set to 2.6 V, and charging was performed with V _CC −V _{CCV set} to 0.3 V.
(Example 3)
The charging current value I _CC was 2 C, V _CC was 3.1 V, V _CCV was 2.6 V, and charging was performed with V _CC −V _CCV being 0.5 V.
Example 4
The total weight of the positive electrode active material is 90% by weight, the weight ratio of LiMn _0.85 Fe _0.1 Mg _0.05 PO ₄ particles and LiCoO ₂ particles is 70:30, 5% by weight of acetylene black as a conductive agent and polyvinylidene fluoride (PVdF) as a binder. ) 5% by weight was added to N-methylpyrrolidone (NMP) and mixed to form a slurry. This slurry was applied to both sides of a current collector made of aluminum foil having a thickness of 15 μm, then dried and pressed to form an electrode. The method was the same as Example 1 except that a positive electrode having a density of 2.0 g / cm ³ was produced.
(Example 5)
The total weight of the positive electrode active material is 90% by weight, and the weight ratio of LiMn _0.85 Fe _0.1 Mg _0.05 PO ₄ particles and LiNi _0.33 Co _0.33 Mn _0.33 O ₂ particles is 70:30, 5% by weight of acetylene black as a conductive agent and a binder. As a slurry, 5% by weight of polyvinylidene fluoride (PVdF) is added to N-methylpyrrolidone (NMP) to form a slurry, and this slurry is applied to both sides of a current collector made of aluminum foil having a thickness of 15 μm, and then dried. The method was the same as in Example 1, except that a positive electrode having an electrode density of 2.0 g / cm ³ was produced by pressing.
(Example 6)
The total weight of the positive electrode active material is 90% by weight, LiMn _0.85 Fe _0.1 Mg _0.05 PO ₄ particles and LiNi _0.6 Co _0.2 Mn _0.2 O ₂ particles are in a weight ratio of 70:30, 5% by weight of acetylene black as a conductive agent and a binder. As a slurry, 5% by weight of polyvinylidene fluoride (PVdF) is added to N-methylpyrrolidone (NMP) to form a slurry, and this slurry is applied to both sides of a current collector made of aluminum foil having a thickness of 15 μm, and then dried. The method was the same as in Example 1, except that a positive electrode having an electrode density of 2.0 g / cm ³ was produced by pressing.
(Example 7)
The total weight of the positive electrode active material is 90% by weight, the weight ratio of LiMn _0.85 Fe _0.1 Mg _0.05 PO ₄ particles and LiCoO ₂ particles is 90:10, 5% by weight of acetylene black as a conductive agent and polyvinylidene fluoride (PVdF) as a binder. ) 5% by weight was added to N-methylpyrrolidone (NMP) and mixed to form a slurry. This slurry was applied to both sides of a current collector made of aluminum foil having a thickness of 15 μm, then dried and pressed to form an electrode. The method was the same as Example 1 except that a positive electrode having a density of 2.0 g / cm ³ was produced.
(Example 8)
The total weight of the positive electrode active material is 90% by weight, the weight ratio of LiMn _0.85 Fe _0.1 Mg _0.05 PO ₄ particles and LiCoO ₂ particles is 50:50, 5% by weight of acetylene black as a conductive agent and polyvinylidene fluoride (PVdF) as a binder. ) 5% by weight was added to N-methylpyrrolidone (NMP) and mixed to form a slurry. This slurry was applied to both sides of a current collector made of aluminum foil having a thickness of 15 μm, then dried and pressed to form an electrode. The method was the same as Example 1 except that a positive electrode having a density of 2.0 g / cm ³ was produced.
Example 9
90% by weight of monoclinic β-type titanium composite oxide (monoclinic β-type TiO ₂ ) powder, 5% by weight of acetylene black and 5% by weight of polyvinylidene fluoride (PVdF) are added to N-methylpyrrolidone (NMP). And mixed to prepare a slurry. This slurry was applied to both surfaces of a current collector made of aluminum foil having a thickness of 15 μm, dried, and then pressed to produce a negative electrode having an electrode density of 2.0 g / cm ³ , and a charging current value I _CC of 2 The method was the same as in Example 1 except that C and V _CC were set at 2.9 V, V _CCV was set at 2.8 V, and V _CC −V _CCV was set at 0.1 V.
(Example 10)
A slurry was prepared by adding 90% by weight of TiNb ₂ O ₇ powder, 5% by weight of acetylene black and 5% by weight of polyvinylidene fluoride (PVdF) to N-methylpyrrolidone (NMP) and mixing them. This slurry was applied to both sides of a current collector made of aluminum foil having a thickness of 15 μm, dried, and then pressed to produce a negative electrode having an electrode density of 2.6 g / cm ³ , and a charging current value I _CC of 2 The method was the same as in Example 1 except that C and V _CC were set at 2.9 V, V _CCV was set at 2.8 V, and V _CC −V _CCV was set at 0.1 V.
(Example 11)
The total weight of the negative electrode active material is 90% by weight, and the weight ratio of Li ₄ Ti ₅ O ₁₂ and monoclinic β-type titanium composite oxide (monoclinic β-type TiO ₂ ) powder is 50:50, and acetylene black 5 A slurry was prepared by adding wt% and 5 wt% of polyvinylidene fluoride (PVdF) to N-methylpyrrolidone (NMP) and mixing. This slurry was applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm, dried, and then pressed to produce a negative electrode having an electrode density of 2.0 g / cm ³ . It was a method.
(Example 12)
The total weight of the negative electrode active material is 90% by weight, and the weight ratio of Li ₄ Ti ₅ O ₁₂ and monoclinic β-type titanium composite oxide (monoclinic β-type TiO ₂ ) powder is 50:50, and acetylene black 5 A slurry was prepared by adding wt% and 5 wt% of polyvinylidene fluoride (PVdF) to N-methylpyrrolidone (NMP) and mixing. This slurry was applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm, dried, and then pressed to produce a negative electrode having an electrode density of 2.0 g / cm ³ . It was a method.
(Comparative Example 1)
In the charging method, the current value I _CC during CC charging was 2C, and the ultimate voltage V _CC during CC charging was 3.2 V. The voltage V _CCV during CV charging was 2.6 V. That is, the same method as in Example 1 was used except that charging was performed with V _CC −V _CCV being 0.6 V.
(Comparative Example 2)
In the charging method, the current value I _CC during CC charging was set to 2C, and the ultimate voltage V _CC during CC charging was set to 2.68 V. The voltage V _CCV during CV charging was 2.6 V. That is, the same method as in Example 1 was used except that charging was performed with V _CC −V _CCV being 0.08 V.
(Comparative Example 3)
A slurry was prepared by adding 90% by weight of graphite powder, 5% by weight of acetylene black and 5% by weight of polyvinylidene fluoride (PVdF) to N-methylpyrrolidone (NMP) and mixing them. This slurry was applied to both sides of a current collector made of copper foil having a thickness of 15 μm, dried, and pressed to prepare a negative electrode having an electrode density of 1.5 g / cm ³ . _Same as Example 1 except that charging was performed with a discharge end voltage of 2.5 V, a charging current value I _CC of 2 C, V _CC of 4.3 V, V _CCV of 4.2 V, and V _CC −V _CCV of 0.1 V. The method was

Table 1 shows capacity retention rates at 200 cycles with the charge systems of Examples 1 to 12 and Comparative Examples 1 to 3 subjected to charge / discharge cycles at 45 ° C., with the discharge capacity at the first cycle as a reference. The charging in each cycle was performed by setting the voltage difference (V _CC −V _CCV ) described in each of the example and the comparative example. The discharge was 1 C, and a constant current discharge was performed up to a discharge end voltage of 1.5 V. However, for Comparative Example 3, the final discharge voltage was 2.5V.

  As is clear from Table 1, the charging systems of Examples 1 to 12 have a capacity retention rate after 200 cycles superior to that of Comparative Examples 1 and 3. Although the charging system of Comparative Example 2 had a capacity retention rate after 200 cycles higher than that of the example, the time required for charging was 3 hours. On the other hand, in the charging systems of Examples 1 to 12, the time required for charging was in the range of 50 minutes to 2 hours. Therefore, it can be said that the charging systems of Examples 1 to 12 are superior in quick charging performance as compared with Comparative Example 2.

According to the charging system of the above embodiment and the examples, the secondary battery part including the positive electrode including the Fe-containing phosphate compound having the olivine structure and the negative electrode including the titanium composite oxide, and the secondary battery part (1 ) Constant current constant voltage charging while suppressing deterioration of the positive electrode because it includes a charge control unit that performs constant voltage charging after constant current charging so as to satisfy the equation (0.1 V ≦ V _CC −V _CCV ≦ 0.5 V) Can be shortened. As a result, it is possible to realize a charging system capable of rapid charging and having excellent life performance.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, In the category of the summary of the invention as described in a claim, it can change variously. In addition, the present invention can be variously modified without departing from the scope of the invention in the implementation stage. Furthermore, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment.

  DESCRIPTION OF SYMBOLS 1,11 ... Electrode group, 2,12 ... Exterior member, 3,14 ... Negative electrode, 4,15 ... Separator, 5,13 ... Positive electrode, 6,16 ... Negative electrode terminal, 7, 17 ... Positive electrode terminal, 10 ... Non-water Electrolyte battery, 25 ... assembled battery, 26 ... battery management circuit, 27 ... charger, 28, 29 ... wiring.

Claims (7)

A secondary battery unit including a non-aqueous electrolyte battery including a positive electrode including a positive electrode active material including a Fe-containing phosphate compound having an olivine structure, a negative electrode including a negative electrode active material including a titanium composite oxide, and a non-aqueous electrolyte; ,
A charging system including a charging control unit that performs constant voltage charging after constant current charging so that the secondary battery unit satisfies the following expression (1).
0.1V ≦ V _CC −V _CCV ≦ 0.5V (1)
However, the V _CC is an ultimate voltage (V) in the constant current charge, and the V _CCV is a closed circuit voltage (V) in the constant voltage charge. The charging system according to claim 1, wherein the following equation (2) is satisfied when the current value during the constant current charging is I _CC (C).
0.2C ≦ I _CC ≦ 30C (2) The Fe-containing phosphate compound having an olivine structure _{LiMn 1-xy Fe x A y} PO 4 (0 <x ≦ 0.3, 0 ≦ y ≦ 0.1, A is Mg, Ca, Al, Ti, from the group consisting of Zn and Zr The charging system according to claim 1 or 2, represented by at least one element selected. The positive active content of the _{LiMn 1-xy Fe x A y} PO 4 in the material is 70 wt% or more, charging system according to claim 3.   The titanium composite oxide includes at least one selected from the group consisting of a spinel type lithium titanium composite oxide, a monoclinic β-type titanium composite oxide, and a niobium titanium composite oxide. The charging system according to item 1. The secondary battery unit includes an assembled battery in which n (n ≧ 2) non-aqueous electrolyte batteries are connected in series,
The charging system according to any one of claims 1 to 5, wherein the charging control unit performs constant voltage charging after constant current charging so that the secondary battery unit satisfies the following expression (3).
0.1nV ≦ V _CC −V _CCV ≦ 0.5nV (3)
However, the V _CC is an ultimate voltage (V) in the constant current charge, and the V _CCV is a closed circuit voltage (V) in the constant voltage charge. A method for charging a non-aqueous electrolyte battery comprising a positive electrode including a positive electrode active material including an Fe-containing phosphate compound having an olivine structure, a negative electrode including a negative electrode active material including a titanium composite oxide, and a non-aqueous electrolyte,
Subjecting the non-aqueous electrolyte battery to constant current charging up to an ultimate voltage V _CC (V);
A non-aqueous electrolyte comprising charging the non-aqueous electrolyte battery at a constant voltage V _CCV (V), wherein the ultimate voltage V _CC (V) and the voltage V _CCV (V) satisfy the following formula (1): How to charge the battery.
0.1V ≦ V _CC −V _CCV ≦ 0.5V (1)

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