JP2009283276A - Lithium secondary battery manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery manufacturing method preventing a reduction in battery capacity due to deposition of lithium to increase a service life and to stably ensure a high output. <P>SOLUTION: The lithium secondary battery manufacturing method includes the steps of preparing a lithium secondary battery in which an electrode body having a positive electrode active substance containing positive electrode and a negative electrode active substance containing negative electrode and a lithium ion containing electrolyte are contained in a battery case, performing a charging process on the prepared lithium secondary battery at a temperature within a room temperature range until a predetermined voltage value is obtained, retaining the lithium secondary battery for 12 to 80 hours at a temperature within the room temperature range or within a temperature range lower than the room temperature after the charging process and retaining the lithium secondary battery at least for 6 hours at a high temperature ranging from 40°C to 65°C after the retaining process performed at the temperature within the room temperature range or within the temperature range lower than the room temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a lithium secondary battery, and more particularly to a method for manufacturing a lithium secondary battery suitable for mounting on a vehicle.

  In recent years, lithium secondary batteries, nickel metal hydride batteries, and other secondary batteries have become increasingly important as power sources for mounting on vehicles or as power sources for personal computers and portable terminals. In particular, a lithium ion battery that is lightweight and obtains a high energy density is expected to be preferably used as a high-output power source mounted on a vehicle.

Generally, a lithium ion battery includes a positive electrode containing a lithium-containing oxide (typically a lithium-containing transition metal oxide such as lithium nickelate (LiNiO ₂ )) as a positive electrode active material, and a carbon-based material such as graphite. It is constructed | assembled by accommodating the electrode body provided with the negative electrode which contains as a negative electrode active material, and the non-aqueous liquid electrolyte containing lithium ion in a battery case.

After the construction of such a battery, typically, an initial charge / discharge process (conditioning process) under a predetermined condition is performed in order to adjust the battery to a state where it can actually be used. In addition, for the purpose of, for example, selecting a battery with a large initial battery capacity drop (initial deterioration) that can correspond to the amount of self-discharge and stabilizing battery performance such as output characteristics, the environment is not subjected to the above-described conditioning process. Then, an aging treatment for holding (leaving) the lithium ion battery is performed. As such an aging treatment, for example, in Patent Document 1, the battery is held at a predetermined temperature while monitoring the change with time of the negative electrode potential of the constructed lithium ion battery. Moreover, in patent document 2, after performing initial charge with respect to the constructed lithium ion battery, it hold | maintains for one week-one month.
JP 2002-298925 A JP 2006-79857 A

  By the way, when a lithium secondary battery (typically a lithium ion battery) is mounted on a vehicle such as an automobile as a high output power source, the lithium secondary battery is charged and discharged with a large current of, for example, several tens of amperes (A) or more. It is desirable to be implemented rapidly at (high rate). However, in the conventional lithium secondary battery, the negative electrode potential decreases due to high-rate charging and falls below the lithium deposition potential (oxidation-reduction potential), and some of the lithium ions transferred between the positive and negative electrodes are, for example, carbon-based materials, etc. There is a possibility that the battery capacity (charge capacity) may be reduced by being reduced and deposited as lithium on the negative electrode surface. Even in the lithium secondary battery subjected to the aging treatment according to Patent Documents 1 and 2, lithium may be deposited on the negative electrode when high-rate charge / discharge is performed. In addition, as a cause that lithium can be deposited on the negative electrode, for example, it is generated on the surface of the negative electrode to inactivate and stabilize the surface, and lithium ions can be easily inserted into and removed from the negative electrode material (carbon-based material). The formation of SEI (Solid Electrolyte Interface) that can be made smooth and smooth is insufficient, or the SEI is not formed homogeneously.

  Accordingly, the present invention has been made in view of the problems of the above-described lithium secondary battery capable of high-rate charging / discharging, and its main object is a method for producing a lithium secondary battery, which is a battery formed by lithium deposition. It is an object of the present invention to provide a method for manufacturing a lithium secondary battery that can prevent a decrease in capacity, realize a long life, and can stably ensure a high output.

  A method for manufacturing a lithium secondary battery provided by the present invention to achieve the above object includes the following steps. That is, this method is prepared by preparing a lithium secondary battery in which an electrode body including a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material and an electrolyte including lithium ions are accommodated in a battery case. The lithium secondary battery is charged to a predetermined voltage value under a room temperature range, and after the charging process, the lithium secondary battery is placed in a room temperature range or lower temperature range for 12 hours to Holding for 80 hours, and holding the lithium secondary battery for at least 6 hours under a high temperature range of 40 ° C. to 65 ° C. after the holding treatment under the room temperature range or lower temperature range, Include.

  That is, the manufacturing method includes a “preparation step” for preparing a lithium secondary battery, a “charging process step” for performing the battery in a room temperature range, and a temperature range for the lithium secondary battery in a room temperature range or lower. A “room temperature holding treatment step” that is held under, and a “high temperature holding treatment step” that holds the lithium secondary battery in the high temperature range.

  According to such a manufacturing method, for the prepared (typically constructed) lithium secondary battery, the charging process under a room temperature range and the high temperature holding process for holding under a high temperature range of 40 ° C. to 65 ° C. Introduced “room temperature holding treatment” for holding for 12 to 80 hours under the temperature range of room temperature or lower (typically with the voltage value at the end of the charging process maintained) To do. Accordingly, SEI can be uniformly formed on the negative electrode of the lithium secondary battery during the room temperature holding process. For this reason, in such a lithium secondary battery, even after the cycle test is performed, lithium deposition on the negative electrode is suppressed, battery capacity reduction is prevented, and good cycle characteristics can be provided. For example, after the above high-temperature holding treatment, the battery capacity after 900 cycles of charge / discharge treatment for 0.1 seconds at a current value of 165 A under a temperature condition of −15 ° C. is about 90 before the charge / discharge treatment. % Or more can be maintained.

  Further, in the course of the charging process and the room temperature holding process, the electrolyte or the like housed in the battery case is decomposed (typically by a reduction reaction) to generate a decomposition product, and the decomposition product is lithium between the positive and negative electrodes. It can be adsorbed and deposited on the surface of the positive electrode as a resistance substance that prevents the transfer (insertion and desorption) of ions. However, the resistance substance can be removed from the positive electrode by performing the high temperature holding treatment. Therefore, in the lithium secondary battery manufactured by such a method, the reduction of the battery capacity can be prevented by suppressing lithium precipitation, and good cycle characteristics can be provided, and the insertion / extraction of lithium ions between the positive and negative electrodes can be performed efficiently. It is possible to provide high output characteristics that can ensure high output (discharge output).

  In this specification, the term “lithium secondary battery” refers to a secondary in which charge and discharge are realized by using lithium ions as electrolyte ions and transferring charges (transfer of lithium ions) associated with lithium ions between the positive and negative electrodes. A battery. A secondary battery generally referred to as a lithium ion battery is a typical example included in the lithium secondary battery in this specification.

  Further, in this specification, the “room temperature region” refers to a temperature region that is typically room temperature, and the room temperature conforms to the temperature class 15 defined in JIS Z 8703-1983, and is 20 ° C. ± 15 It shall refer to ° C. (for example, 10 ° C. to 30 ° C., preferably 20 ° C. to 30 ° C.).

  As another aspect, the manufacturing method disclosed herein can be provided as a method for adjusting the prepared (typically constructed) lithium secondary battery. That is, the adjustment method includes preparing a lithium secondary battery in which an electrode body including a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material and an electrolyte including lithium ions are accommodated in a battery case, The lithium secondary battery is charged to a predetermined voltage value under a room temperature range, and after the charging process, the lithium secondary battery is charged at a room temperature range or lower temperature range for 12 hours to 80 hours. Holding for a period of time, and holding the lithium secondary battery under a high temperature range of 40 ° C. to 65 ° C. for at least 6 hours after the holding treatment under the temperature range of room temperature or lower.

  As a preferred embodiment of the production method disclosed herein, the holding treatment under the room temperature range or lower temperature range is performed for 40 hours to 60 hours. According to such a method, in the lithium secondary battery obtained by the method, it is possible to prevent a decrease in battery capacity at a higher level and to obtain a high and stable output. For example, the battery capacity after performing 900 cycles of charge / discharge treatment for 0.1 seconds at a current value of 165A under the temperature condition of −15 ° C. after the high temperature holding treatment is about 92% or more before the charge / discharge treatment is performed. Can be maintained. In addition, the lithium secondary battery of this aspect is charged under a temperature condition of 30 ° C. until the SOC (state of charge) reaches 60% of full charge (or the rated capacity of the battery). When discharging from a voltage value (eg, 3.73 V) to 3.0 V within 10 seconds, the output can be as high as about 585 W or more.

  Moreover, as another preferable aspect of the manufacturing method disclosed herein, the charging process ends when the voltage value of the lithium secondary battery reaches within a range of 3.3V to 4.2V. More preferably, it exists in the range of 3.9V-4.1V. According to this aspect, initial deterioration can be appropriately advanced with respect to the lithium secondary battery to be processed, and battery performance can be effectively stabilized. That is, by performing the charging process in such a voltage range, the effect as a so-called aging process can be realized to the maximum. Further, the voltage value at the end of the charging process, that is, the state where the voltage value is kept within the above range (or in a state where the voltage value is slightly lower than the voltage value due to self-discharge etc.) shifts to the subsequent room temperature holding process. By doing so, the effect of the room temperature holding treatment is further enhanced, and a more uniform SEI can be formed on the negative electrode.

  As another preferred embodiment of the production method disclosed herein, the holding treatment under the high temperature range is performed for 6 hours to 24 hours. According to this aspect, by holding the lithium secondary battery in the high temperature range of 40 ° C. to 65 ° C. within the above time range, the effect of removing the resistance substance that can be adsorbed (deposited) on the positive electrode is enhanced, and The effect as a so-called aging process is further enhanced. Moreover, the above-mentioned effect (especially the aging treatment effect) can be achieved at an early stage by maintaining the temperature under the high temperature range as compared with maintaining at a room temperature range or lower temperature range.

  As another preferable aspect of the production method disclosed herein, the electrolyte is a non-aqueous electrolyte. The non-aqueous electrolyte is typically a non-aqueous liquid electrolyte, which is a non-aqueous solvent electrolyte in which a lithium salt is dissolved as a supporting salt in a non-aqueous solvent. According to this aspect, even if the solvent is partially decomposed as in the aqueous electrolyte, the degree is smaller than that in the aqueous electrolyte, and the non-aqueous solvent is partially decomposed (typically by a reduction reaction). Thus, a suitable SEI that can easily and smoothly insert and desorb lithium ions can be formed on the negative electrode. In addition, a preferable non-aqueous solvent can be appropriately selected depending on the combination of the negative electrode material and the electrolyte that facilitate the formation of the SEI. Examples of such a non-aqueous solvent include ethylene carbonate (EC), EC and diethyl carbonate (DEC), or a mixed solvent of EC and dimethyl carbonate (DMC).

  Furthermore, this invention provides the lithium secondary battery obtained by employ | adopting the manufacturing method disclosed here. That is, this lithium secondary battery is a lithium secondary battery obtained by any of the manufacturing methods disclosed herein. In such a battery, the battery capacity after performing 900 cycles of charge / discharge treatment for 0.1 seconds at a current value of 165 A under the temperature condition of −15 ° C. after the high temperature holding treatment is about 90% before the charge / discharge treatment is carried out. It is maintained as described above, and high durability (long life) can be realized with good cycle characteristics. In addition, such a battery can stably supply a high output with good output characteristics.

  Further, according to the present invention, the lithium secondary battery disclosed herein or the lithium secondary battery manufactured by any of the manufacturing methods disclosed herein suppresses lithium deposition even when high-rate charge / discharge is performed. Thus, the battery capacity can be prevented from being reduced, the life can be extended, and good (high) output characteristics can be provided. Therefore, it can be suitably used as a power source for a motor (electric motor) mounted on a vehicle. Therefore, according to the present invention, a vehicle (for example, an automobile) provided with such a lithium secondary battery is provided.

  Hereinafter, preferred embodiments of the present invention will be described. Matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, the configuration and construction procedure of the lithium secondary battery, the general technology relating to the construction of the battery, etc.) It can be understood as a design matter of a person skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  A method for manufacturing a lithium secondary battery disclosed herein includes constructing or preparing a lithium secondary battery, charging the prepared lithium secondary battery to a predetermined voltage value under a room temperature range, and then room temperature. This is a method in which the lithium secondary battery is held (for example, left) for a predetermined time under a region, and further maintained for a predetermined time under a high temperature region after the time has elapsed. The method and technique disclosed herein are preferably applied to a lithium secondary battery having a configuration in which an electrode body including a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material and an electrolyte including lithium ions are accommodated in a battery case. To get. In addition, such a lithium secondary battery may be any battery as long as it uses lithium ions as electrolyte ions and can be charged / discharged by the movement of charges accompanying the lithium ions between the positive and negative electrodes. The type of is not particularly limited. For example, the battery case may have a rectangular parallelepiped shape, a flat shape, a cylindrical shape, or the like.

As the positive electrode active material, a material capable of inserting and desorbing (inserting and desorbing) lithium ions is used, and a material conventionally used for a lithium secondary battery (for example, an oxide having a layered structure or an oxide having a spinel structure). One or more of these can be used without particular limitation. Preferable examples include lithium-nickel based composite oxides (oxides containing lithium and nickel as constituent metal elements, in which a part of nickel sites is replaced with other metal elements such as cobalt and aluminum). Lithium-containing transition metal oxides (lithium-containing, typically LiNiO ₂ ), lithium-cobalt complex oxides (typically LiCoO ₂ ), lithium-manganese complex oxides (typically LiMn ₂ O ₄ ) Composite oxide). Further, an olivine type lithium phosphate represented by the general formula LiMPO ₄ (M is at least one element of Co, Ni, Mn, and Fe; for example, LiFePO ₄ , LiMnPO ₄ ) is used as the positive electrode active material. Also good.

  The technology disclosed herein is a lithium secondary battery constructed using a positive electrode including such a positive electrode active material and a negative electrode including a negative electrode active material described later, and a voltage between both electrodes (inter-terminal voltage) is approximately. It can be preferably applied to a lithium secondary battery (typically a lithium ion battery) used in the range of 3V to 4.2V.

  The positive electrode typically has a configuration in which a layer containing a positive electrode active material as a main component (positive electrode active material layer) is held (applied) to a positive electrode current collector. As the positive electrode current collector, a metal conductive member having good conductivity is preferably used. In particular, it is preferable to use a positive electrode current collector made of aluminum (Al) or an alloy containing aluminum as a main component (aluminum alloy). For example, an aluminum foil having a thickness of about 5 μm to 30 μm (preferably 10 μm to 30 μm) is used as the positive electrode collector. It can be preferably used as an electric body. Since the shape of the positive electrode current collector can vary depending on the shape of the lithium secondary battery constructed using the obtained positive electrode, there is no particular limitation, rod shape, plate shape, sheet shape, foil shape, mesh shape And various other forms. The current collectors of various shapes may be produced by any conventionally known method in the field of lithium secondary batteries, and do not characterize the present invention. The technology disclosed herein can be preferably applied to a lithium secondary battery including a positive electrode in a form in which a positive electrode active material layer is held on, for example, a sheet-shaped or foil-shaped current collector. As a preferable embodiment of such a lithium secondary battery, a lithium secondary battery including a wound electrode body can be given.

  In the positive electrode active material layer, for example, a paste or slurry composition (positive electrode active material composition) in which the positive electrode active material is dispersed in a suitable solvent is applied to the positive electrode current collector, and the composition is dried. Can be preferably produced. In applying such a composition to a positive electrode current collector (preferably in a foil shape or a sheet shape), a technique similar to a conventionally known method can be appropriately employed. For example, a predetermined amount of the composition may be applied in a layered manner on the surface (one side or both sides) of the current collector using an appropriate application device. Further, as the solvent (dispersion medium), any of water, organic solvents, and mixed solvents thereof can be used.

  In addition to the positive electrode active material and the solvent, the positive electrode active material composition requires one or more materials that can be blended in a composition used for forming a positive electrode active material layer in a general lithium secondary battery. Depending on the content. Examples of such materials include various carbon blacks, conductive materials such as nickel, and / or polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene copolymer (SBR), carboxymethyl cellulose (CMC). And a binder made of a polymer material such as a viscosity adjusting material (typically a thickening material). Moreover, about the compounding ratio of the component of this positive electrode active material composition, what is necessary is just the same compounding ratio as the composition used for formation of the positive electrode active material layer in the conventional lithium secondary battery, and it does not specifically limit.

  On the other hand, as the negative electrode active material, materials capable of inserting and removing lithium ions (preferably in the form of particles) are used, and various materials conventionally used in lithium secondary batteries are used without particular limitation. Can do. Suitable negative electrode active materials in the technology disclosed herein include graphite carbon such as natural graphite and highly oriented graphite (HOPG), carbon-based materials such as amorphous carbon, lithium-containing transition metal oxides and transition metal nitrides, etc. Can be used. In order to realize a high voltage (high output) of the battery, a carbon-based material (carbon particles) such as graphite is preferable. Further, as the negative electrode active material (for example, carbon particles of graphite), for example, carbon particles having an average particle diameter of about 5 to 50 μm (preferably about 5 to 15 μm) are preferably used. Thus, carbon particles having a relatively small particle size have a large surface area per unit volume, and thus can be a negative electrode active material suitable for more rapid charge / discharge (for example, high power discharge). Therefore, the lithium secondary battery having such a negative electrode active material can be suitably used, for example, as a lithium secondary battery for vehicle mounting.

  The negative electrode in the technique disclosed herein typically has a configuration in which a layer (negative electrode active material layer) containing such a negative electrode active material as a main component is held (applied) to a negative electrode current collector. As the negative electrode current collector, a metal conductive member having good conductivity is preferably used. In particular, it is preferable to use a negative electrode current collector made of copper (Cu) or an alloy mainly composed of copper (copper alloy). For example, a copper foil having a thickness of about 5 μm to 30 μm (preferably 10 μm to 30 μm) is used as the negative electrode current collector. It can be preferably used as an electric body. The shape of the negative electrode current collector is not particularly limited because it can vary depending on the shape of the lithium secondary battery constructed using the obtained negative electrode, as in the above-described positive electrode current collector. The technology disclosed herein is, for example, a lithium secondary battery including a negative electrode in a form in which a negative electrode active material layer is held on a sheet-shaped or foil-shaped current collector (for example, a lithium secondary battery including a wound electrode body) ) Can be preferably applied.

  The negative electrode active material layer is, for example, applied (typically applied) a negative electrode current collector with a paste or slurry composition (negative electrode active material composition) in which the negative electrode active material is dispersed in an appropriate solvent, It can preferably be prepared by drying the composition. In applying such a composition to the negative electrode current collector (preferably in the form of a foil or sheet), a technique similar to a conventionally known method is used, as in the case of applying the positive electrode active material composition to the positive electrode current collector. It can be adopted as appropriate. As the solvent (dispersion medium for the negative electrode active material), any of water, organic solvents, and mixed solvents thereof can be used. For example, a negative electrode active material composition in which the solvent is an aqueous solvent (water or a mixed solvent mainly containing water) can be preferably employed.

  In addition to the negative electrode active material and the solvent, the negative electrode active material composition is one or more materials that can be blended in a composition used for forming a negative electrode active material layer in a general negative electrode for a lithium secondary battery. May be contained as necessary. Examples of such materials include binders and viscosity modifiers (thickeners). For example, the same polymer materials as those exemplified as materials that can be contained in the positive electrode active material composition can be suitably used. Moreover, about the compounding ratio of the component of this negative electrode active material composition, what is necessary is just the same compounding ratio as the composition used for formation of the negative electrode active material layer in the conventional lithium secondary battery, and it does not specifically limit.

The electrolyte in the technology disclosed herein is a non-aqueous electrolyte containing lithium ions (typically a non-aqueous liquid electrolyte), which is a non-aqueous solution in which a lithium salt is dissolved as a supporting salt in a non-aqueous solvent (organic solvent). For example, an electrolyte used in a general lithium secondary battery can be used. More preferably, the electrolyte has a high migration rate (conductivity) between the positive and negative electrodes of lithium ions in the electrolyte, and can easily and smoothly insert and desorb lithium ions at the positive and negative electrodes. In addition, SEI that can enable smooth insertion and removal of lithium ions from the negative electrode (negative electrode active material) can be formed from a decomposition product of an electrolyte that can be generated on the negative electrode side during charging and discharging of the lithium secondary battery. For this reason, it is preferable that this electrolyte can form suitable SEI on the surface of the negative electrode active material (for example, carbon-based material such as graphite). As the non-aqueous solvent constituting such an electrolyte, for example, one or more of ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate, etc. (for example, a mixture of EC and DEC) Or a mixed system of EC and DMC) can be preferably used. Moreover, as a lithium salt which is a supporting salt, for example, one or more of LiPF ₆ , LiClO ₄ , LiAsF ₆ , Li (CF ₃ SO ₂ ) ₂ N, LiBF ₃ , LiCF ₃ SO _{3 and the} like are used. Can do. For example, an electrolytic solution in which lithium hexafluorophosphate (LiPF ₆ ) as a supporting salt is contained in a mixed solvent containing EC and DMC at a mass ratio of 1: 1 at a concentration of about 1 M can be preferably used. .

  Hereinafter, with reference to the drawings, an embodiment of a method for manufacturing a lithium secondary battery according to the present invention and an embodiment of a lithium secondary battery manufactured by the method will be described as a prismatic lithium ion battery 10. This will be described as an example. FIG. 1 is a schematic overall perspective view of a lithium secondary battery (lithium ion battery 10) according to the present embodiment. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a graph showing the 900 cycle test evaluation results and output characteristic evaluation results in Examples 5 and 6 of Examples described later. FIG. 4 is a side view schematically showing a vehicle including the battery according to the present embodiment. It should be noted that the present invention is not intended to be limited to that described in the embodiment. In addition, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.

  As described above, the manufacturing method disclosed herein includes a “preparation step” of preparing a lithium secondary battery, a “charging process step” of charging the battery to a predetermined voltage value in a room temperature range, and a room temperature range or It includes a “room temperature holding treatment step” for holding for a predetermined time under a temperature range below that, and a “high temperature holding treatment step” for holding for a predetermined time under a high temperature range.

  In the preparation step, a lithium secondary battery is prepared (typically constructed) in which an electrode body including a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material and an electrolyte including lithium ions are accommodated in a battery case. To do. FIG. 1 and FIG. 2 show a lithium secondary battery according to the present embodiment, that is, a square-shaped lithium ion battery 10 to which the technology disclosed herein can be applied. As described above, a flat electrode body 30 including a positive electrode and a negative electrode is housed in a flat box-shaped battery case 11 corresponding to the shape of the electrode body 30 together with an electrolyte (not shown). For example, the lithium ion battery 10 can be constructed as follows.

  The battery case 11 includes a flat bottomed rectangular cylindrical casing 12 having an opening at one end, and a lid 13 attached to the opening to close the opening. As a material constituting the battery case 11, a metal material such as aluminum or steel is preferably used. Alternatively, it may be made of a resin material such as PPS (polyphenylene sulfide) or polyimide resin. For example, the battery case 11 in which the housing 12 and the lid 13 are both made of aluminum can be preferably used.

  The flat electrode body 30 according to the present embodiment is a wound electrode body (wound electrode body), and a long sheet-like positive electrode sheet and a negative electrode sheet are typically formed into two long sheets. And a separator (separator sheet), and wound in the longitudinal direction (typically wound in a substantially circular shape), and then the obtained wound body is crushed from the side surface direction and crushed. Thus, instead of a mode in which the laminate of sheets is rolled and then flattened, the laminate may be wound so as to have a flat shape (substantially oval, elliptical, etc.) from the beginning.

  Each of the positive electrode sheet and the negative electrode sheet has a configuration in which an active material layer is formed on a long sheet-like current collector. The active material layer is formed in a band-like region excluding one end in the width direction of the current collector (one end portion along the longitudinal direction), and the one end in the width direction is formed without forming the active material layer. The current collector is exposed to form a portion where no active material layer is formed. Each positive and negative electrode sheet and separator sheet are arranged so that the active material layers of both electrode sheets overlap, and the active material layer non-formation part of the positive electrode sheet and the active material layer non-formation part of the negative electrode sheet are arranged in the width direction of the separator. The positive and negative electrode sheets are laminated with their positions slightly shifted in the width direction so as to protrude from the one end and the other end, and these laminates are wound. As a result, at one end of the wound electrode body 30 in the winding axis direction, the active material layer non-formed portion of the positive electrode sheet is laminated and the wound core portion (that is, the active material layer and the separator of both electrode sheets are densely packed). The portion of the wound electrode body 30 that protrudes from the wound core portion protrudes outward from the wound core portion at the other end of the wound electrode body 30. One end of a positive terminal 14 and a negative terminal 16 for external connection is connected to each protruding portion. The other ends of the electrode terminals 14 and 16 are pulled out of the container 11 (lid 13).

  About the material and member itself which comprise the winding electrode body 30, the thing similar to the electrode body with which the conventional lithium ion battery is equipped as mentioned above can be used.

  As the separator, for example, a porous resin sheet (film) made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) can be suitably used. Such a porous resin sheet may have a single-layer structure or a multilayer structure of two or more layers (for example, a three-layer structure in which PE layers are laminated on both sides of a PP layer). For example, a porous separator sheet made of synthetic resin (for example, made of polyolefin such as polyethylene) having a thickness of about 5 μm to 30 μm can be preferably used. When a solid electrolyte or a gel electrolyte is used as the electrolyte, a generally used resin separator (for example, polypropylene) is not necessary (that is, in this case, the electrolyte itself is Can act as a separator).

  The electrode body 30 obtained as described above is accommodated in the casing 12 through the opening of the casing 12 of the battery case 11. Next, for example, an appropriate electrolyte is injected from a liquid injection port (not shown) formed in the battery case 11 (housing 12). Then, the lithium ion battery 10 is constructed by sealing the housing 12 with the lid 13.

  Next, in the charging process, the lithium ion battery 10 (lithium secondary battery) prepared (constructed) as described above is interposed between the positive electrode (positive electrode terminal 14) and the negative electrode (negative electrode terminal 16) of the battery. An external power supply is connected, and charging is performed up to a predetermined voltage value at room temperature.

  Here, the “room temperature region” refers to a temperature region that is typically normal temperature as described above, and refers to 20 ° C. ± 15 ° C. Here, in this charging process, the temperature to which the lithium ion battery 10 is exposed can be selected from, for example, a temperature range of 5 ° C. to 35 ° C., preferably 10 ° C. to 30 ° C., more preferably 20 ° C. to 30 degreeC is mentioned. In addition, the charging process according to the present embodiment is performed in a temperature range of 20 ° C. to 30 ° C., but the temperature in the charging process can be appropriately changed according to the environment that can actually be used. You may carry out under the temperature below 5 degreeC made into the low limit of the said room temperature area, ie, the temperature below a room temperature area.

  The predetermined voltage value is preferably a value within a range of 3.3V to 4.2V, and particularly preferably within a range of 3.9V to 4.1V. This voltage range can be indicated when the SOC of the lithium ion battery 10 is in the range of about 5% to 95% (preferably 70% to 90%) of the fully charged (or rated capacity of the battery). Range. When the charging process is performed with less than 5% SOC, the amount of charge to the lithium ion battery 10 is not sufficient, and the initial deterioration of the lithium ion battery 10 to be processed does not proceed appropriately. Further, if the charging process exceeds SOC 95%, the voltage value of the battery may rapidly increase when the battery is nearly fully charged, and the battery may be deteriorated. Further, the voltage value at the end of the charging can be appropriately set depending on the SOC value when the lithium ion battery 10 is held during the room temperature holding process after the charging process. About the charge rate of the said charge process, it may be the same as the conventionally well-known charge rate generally employable when carrying out the initial charge (or the first charge in a conditioning process) of the conventional lithium secondary battery (lithium ion battery). . For example, it is preferable to carry out at a charge rate (current value) of 1 / 3C or less (typically 1 / 20C to 1 / 3C) from the start of charge to at least SOC 20%. More preferably, it is 1 / 5C or less (typically 1 / 20C to 1 / 5C). Charging may be performed at such a charging rate until a voltage value within the above range is reached. Note that “C” with respect to the charging rate refers to the speed at which the entire capacity of the battery is charged, that is, the charging rate. For example, with respect to the charge rate, 1 C can be expressed as a current value at which the battery is fully charged (SOC 100%) in one hour.

  In the charging process, for example, a voltmeter is connected between the positive electrode terminal 14 and the negative electrode terminal 16 in the lithium ion battery 10, and the measured voltage value is monitored by the voltmeter, and a predetermined voltage value set in advance is measured. It suffices to end when it reaches.

  Next, in the room temperature holding treatment step, the lithium ion battery 10 charged to a predetermined voltage value (that is, up to a predetermined SOC (for example, SOC 80%)) by the charging process is placed under a room temperature range or lower temperature range. Hold (eg, leave).

  As described above, the room temperature range or lower temperature range is, for example, a temperature range of 20 ° C. ± 15 ° C. or lower, and may be a room temperature range similar to the above charging process, or a lower temperature range (for example, −30 ° C. to 5 ° C.).

  In the room temperature holding treatment step, the holding time (treatment time) of the lithium ion battery 10 to be treated is preferably 12 hours to 80 hours, more preferably 20 hours to 80 hours, and even more preferably 40 hours to 60 hours. It is. If the holding time is less than 12 hours, the holding time is too short, so that formation of homogeneous SEI at the negative electrode of the lithium ion battery 10 may be insufficient. In addition, when the holding time exceeds 80 hours, the decomposition of the electrolyte proceeds. In particular, the internal resistance of the battery becomes too large due to the decomposition product (resistive substance) of the electrolyte that can be adsorbed (deposited) on the positive electrode side. Output may be reduced and the output state may be unstable.

  In order to maintain the lithium ion battery 10 in the temperature range (that is, the room temperature range), the temperature in the room or the processing container in which the battery is processed, that is, the environmental temperature around the battery, should be adjusted to the temperature range. The temperature adjustment method is not particularly limited.

  In the course of the room temperature holding process, the SOC of the lithium ion battery 10 may be slightly lower than that at the end of the previous charging process or due to self-discharge or the like.

  Next, in the high temperature holding treatment step, the lithium ion battery 10 after the room temperature holding treatment is held under a high temperature range of 40 ° C to 65 ° C.

  In the high temperature holding treatment step, the holding temperature of the lithium ion battery 10 is preferably 40 ° C to 65 ° C. When the holding temperature is lower than 40 ° C., the effect of removing the resistance substance produced by the electrolyte decomposition product adsorbed (deposited) on the positive electrode is low. In addition, the effect of appropriately progressing the initial deterioration and the effect of stabilizing the output characteristics (so-called aging effect) are also low. On the other hand, when the holding temperature exceeds 65 ° C., the time required for obtaining the resistance substance removing effect or the aging effect (that is, the processing time) can be shortened, but there is a possibility of promoting further decomposition of the electrolyte.

  In the high temperature holding treatment step, the holding time of the lithium ion battery 10 is preferably at least 6 hours, and preferably 6 hours to 24 hours. When the holding time is less than 6 hours, the time required for removing the resistance substance is shortened, and thus the substance cannot be sufficiently removed. Further, since the lithium ion battery 10 is held under a high temperature range of 40 ° C. to 65 ° C., if it is held for a time within the above range, the effect of removing the resistance substance or the so-called aging effect is sufficiently achieved. , It may not be held for more than 24 hours. Further, the holding time is shortened as the holding temperature is high, and can be prolonged when the holding temperature is low. Therefore, the holding process may be performed by balancing the two. For example, the holding time is 45 ° C. The high temperature holding treatment for 10 hours is one of preferable processing conditions (holding conditions).

  In addition, the said holding | maintenance process may be performed continuously at the time of one process, or may be intermittently performed in two or more times. In the case of performing multiple times, the holding time for each time may be set so that the total holding time is within the above range (ie, 6 hours to 24 hours).

  As a method for holding the lithium ion battery 10 to be held in the above high temperature range, a conventionally known heating means can be preferably used. For example, a heat source (heating device) such as an infrared heater may be directly brought into contact with the battery 10 to heat the battery 10 to the high temperature range. Further, the battery 10 may be held by storing the battery 10 in a heating container such as a thermostatic device and maintaining (controlling) the inside of the container at a predetermined temperature within the above range.

  After completion of the high temperature holding process, the discharging process may be performed at the same rate as the charging process, and then the charging / discharging cycle may be repeated several times at the same rate as the charging process. Alternatively, the conditioning process may be performed at a rate different from the charge / discharge rate of the charge / discharge cycle.

  The atmosphere in the room temperature holding treatment step and the high temperature holding treatment step is not particularly limited. For example, an air atmosphere or an inert gas atmosphere such as nitrogen gas or argon can be preferably employed.

  Also in the process of the high temperature holding process, the SOC of the lithium ion battery 10 can be slightly lowered due to the state at the end of the previous charging process or due to self-discharge, as in the room temperature holding process.

  The following examples further illustrate the invention, but are not intended to limit the construction of the invention to those listed as such examples.

Whether the battery capacity (cycle characteristics) and output characteristics after the charge / discharge cycle were different or not was evaluated for the constructed lithium ion battery depending on the length of the holding time in the room temperature holding treatment step. The specific method is shown below.
<Example 1: Preparation of lithium ion battery>
A lithium ion battery was prepared (constructed) as a lithium secondary battery to be evaluated. That is, LiNiO ₂ as a positive electrode active material and polytetrafluoroethylene (PTFE) and carboxymethyl cellulose (CMC) as a thickener are used as a dispersion solvent so that the mass ratio thereof becomes 94: 5: 1. A paste-like positive electrode active material layer composition was prepared by adding to ion-exchanged water and mixing well. The obtained positive electrode active material layer composition was applied onto an aluminum foil having a length of 2 m, a width of 10 cm, and a thickness of 10 μm, and a roll press treatment was performed to form a positive electrode active material layer on the aluminum foil. A positive electrode sheet was produced.

  On the other hand, natural graphite as a negative electrode active material, styrene-butadiene copolymer (SBR) and carboxymethyl cellulose (CMC) as a thickener are used as dispersion solvents so that the mass ratio thereof becomes 98: 1: 1. Was added to ion-exchanged water and mixed well to prepare a paste-like negative electrode active material composition. The obtained negative electrode active material composition is applied onto a copper foil having a length of 2 m, a width of 10 cm, and a thickness of 10 μm, and a roll press treatment is performed to form a negative electrode active material layer on the copper foil. A negative electrode sheet was produced.

  The positive electrode sheet and the negative electrode sheet thus obtained are wound together with a separator sheet (two sheets) that is a porous film made of polypropylene having a length of 2 m, a width of 11 cm, and a thickness of 30 μm, and then crushed to be used for a lithium ion battery. A flat-shaped wound electrode body was produced.

The lead terminals of the positive and negative electrodes were welded to the wound electrode body thus produced and accommodated in a flat aluminum battery case (internal volume: about 100 mL) having a shape corresponding to the wound electrode body. In this case, 50 mL of an appropriate amount of electrolyte (nonaqueous electrolyte in which LiPF ₆ having a concentration of 1 M as a lithium salt was dissolved in a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) having a mass ratio of 1: 1). Poured and sealed. In this way, five identical lithium ion batteries were constructed.
<Example 2: Implementation of charging process>
Next, with respect to the five lithium ion batteries obtained as described above, a voltage value (voltage value between positive and negative terminals) at a charge rate of 1/5 C under a temperature condition of 25 ° C. (room temperature). ) Was charged from 0V to 4.0V.
<Example 3: Implementation of a room temperature holding treatment>
Next, under the temperature condition of 25 ° C. (room temperature), room temperature holding treatment was performed for each of the five lithium ion batteries with the following holding time. The lithium ion batteries thus obtained were designated as batteries (1) to (5).

  Batteries (1) and (2); room temperature holding time was 1.5 hours.

  Battery (3): The room temperature holding time was 24 hours.

  Battery (4): The room temperature retention time was 80 hours.

Battery (5): The room temperature retention time was 96 hours.
<Example 4: Implementation of high temperature holding treatment>
Each of the batteries (1) to (5) obtained as described above was subjected to a high-temperature holding treatment under a high-temperature condition of 45 ° C. and a holding time of 10 hours.
<Example 5: Evaluation of cycle characteristics>
A cycle test was performed on each of the batteries (1) to (5) according to the following procedure to evaluate the cycle characteristics.
I. Battery Capacity Measurement First, the batteries (1) to (5) were discharged to 3.0 V at the same discharge rate as in Example 2 under a temperature condition of 25 ° C.

Next, in order to evaluate the battery capacity of each of the batteries (1) to (5) before the cycle test, 25 constant current / constant voltage charging (CC / CV charging) at a current of 5.0 A and a voltage of 4.1 V was performed. This was carried out for 2 hours at 0 ° C. (After the voltage value reached 4.1 V, the voltage value was maintained and the current was attenuated). Next, after resting for 30 minutes, constant current discharge was performed at a current value of 1 A until the final voltage reached 3.0V. The discharge time required for the end voltage to reach 3.0 V was defined as “battery capacity [Ah] before the cycle test” of the battery.
II. 500 Cycle Test Next, each of the batteries (1) to (5) was charged for 0.1 second at a current value of −15 ° C. and 165 A, and then 0 at a current value of −15 ° C. and 165 A. . Discharge for 1 second was performed. This charging / discharging was made into 1 cycle (cycle), and 500-cycle charging / discharging process (500 cycle test) was implemented.

Next, the battery capacity was calculated | required with the measurement procedure similar to said I with respect to each of battery (1)-(5) after a cycle test implementation. The battery capacity thus obtained was defined as “battery capacity [Ah] after 500 cycle tests”.
III. 900 cycle test Further, 400 cycles of charge / discharge cycles under the same conditions as above were added to each of the batteries (1) to (5), and a total of 900 cycles of charge / discharge treatment (900 cycle test) was performed. .

  Again, for each of the batteries (1) to (5) after the cycle test, the battery capacity was determined by the same measurement procedure as in I above. The battery capacity thus obtained was defined as “battery capacity [Ah] after 900 cycle test”.

  The cycle test was performed twice. That is, cycle characteristics were evaluated by repeating the series of operations of Examples 1 to 5 twice. The results are shown in Table 1.

  Further, for each of the batteries (1) to (5), from the “battery capacity before the cycle test” and the “battery capacity after the 500 cycle test”, the battery capacity after the 500 cycle test is maintained. The rate (capacity maintenance rate) [%] was calculated. Further, from the “battery capacity before the cycle test” and the “battery capacity after the 900 cycle test”, the battery capacity maintenance rate (capacity maintenance rate) [%] after the 900 cycle test was calculated. The results of the battery capacity retention rates after the 500 cycle test and after the 900 cycle test are shown in Table 2 for each of the first and second cycle tests. Moreover, the result of the battery capacity maintenance rate after the 900 cycle test implemented 2nd time is shown in FIG. In addition, the vertical axis | shaft in FIG. 3 shows the capacity maintenance rate [%] after 2nd 900 cycle test implementation, and a horizontal axis | shaft shows room temperature retention processing time (retention time) [time].

<Example 6: Evaluation of output characteristics>
Output characteristics evaluation batteries (1) to (5) were newly constructed in the same procedure as in Examples 1 to 4 above. Subsequently, the test shown below was implemented as a test for evaluating the output characteristic of each battery (1)-(5). This test is to obtain the electric power [W] output when the battery is discharged to 3.0 V in 10 seconds after being charged to a voltage value of SOC 60% at a predetermined charging rate. Specifically, such a test was performed as follows.

  First, for each of the batteries (1) to (5) for which the high-temperature holding treatment in Example 4 was completed, the battery (1) was discharged at the same discharge rate as that in Example 2 under a temperature condition of 25 ° C. ) To (5) were discharged to 3.0V.

  Next, each of the batteries (1) to (5) is subjected to constant current-constant voltage charging at a charging rate of 2C under a temperature condition of 30 ° C., so that the SOC reaches 60% (about 3.73 V). Charged until Next, under a temperature condition of 30 ° C., each of these batteries (1) to (5) was discharged to 3.0 V at three power values of 350 W, 550 W and 650 W, and each power The time (required time) required to discharge to 3.0 V was measured. The correlation between the required time thus obtained and the power value was plotted, and the power value for 10 seconds (required time) was obtained for each battery by the plot.

  The respective power values (discharge output values [W]) of the batteries (1) to (5) obtained as described above are shown in Table 3 and FIG.

  As shown in Tables 1 to 3 and FIG. 3, when the room temperature holding treatment time (holding time) is short (for example, 1.5 hours), a high power value (discharge output) of about 585 [W] or more is obtained. As shown, good output characteristics were obtained, but on the contrary, the capacity retention rate of the battery after the 900 cycle test was about 82%, which was lower than 90%. On the other hand, in the case of room temperature holding treatment time of 20 hours or more, the capacity retention rate exceeded about 90%, and the output characteristics were good. On the other hand, when the room temperature holding treatment time exceeds 80 hours, the obtained battery has a good cycle characteristic in which the capacity retention rate exceeds about 92%, but the output characteristic deteriorates rapidly, for example, a room temperature of 96 hours. It was found that only an output (power value) of less than 580 [W] can be obtained in the holding processing time. Further, as shown in FIG. 3, it was found that when the room temperature holding treatment time is 40 hours to 60 hours, both the capacity retention ratio (cycle characteristics) and the output characteristics can be improved.

  As is clear from the above examples, according to the present invention, the prepared (constructed) lithium secondary battery is charged to a predetermined voltage value, and then is kept at a room temperature range or lower before being held at a high temperature range. Is maintained for a predetermined period of time, thereby preventing a decrease in battery capacity after the cycle test is performed and having favorable cycle characteristics, as well as producing a preferable lithium secondary battery that can ensure high output and also have favorable output characteristics. be able to. If the holding time under the room temperature range is, for example, 20 hours to 80 hours, for example, lithium deposition is suppressed even if high-rate charge / discharge of 5C or more is performed in an environment where lithium at −15 ° C. to 10 ° C. is likely to precipitate. It is possible to obtain a preferable lithium secondary battery. Therefore, according to the present invention, it is possible to provide a lithium secondary battery capable of achieving both good cycle characteristics and good output characteristics associated with the suppression of lithium deposition on a high level.

  Therefore, the lithium secondary battery of the present invention or the lithium secondary battery produced by the method of the present invention is particularly suitable as a vehicle-mounted power source mounted on a vehicle such as an automobile. For example, as shown in FIG. 4, a vehicle 1 including a lithium secondary battery 10 having the above-described configuration according to the present invention as a power source (typically an automobile, particularly a hybrid automobile, an electric automobile, a fuel cell automobile, etc. A motor vehicle equipped with a simple electric motor). In addition, the manufacturing method of this invention can be provided as an adjustment method which can adjust the prepared lithium secondary battery to the preferable battery provided with the above favorable characteristics as another side surface.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

It is a typical whole perspective view of the lithium secondary battery which concerns on this embodiment. It is the II-II sectional view taken on the line of FIG. It is the graph which showed the evaluation result of the 900 cycle test in Example 5 and Example 6 of an Example, and the evaluation result of output characteristics. It is a side view which shows typically the vehicle (automobile) provided with the lithium secondary battery which concerns on this embodiment.

Explanation of symbols

1 Vehicle 10 Lithium ion battery (lithium secondary battery)
DESCRIPTION OF SYMBOLS 11 Battery case 12 Case 13 Lid body 14 Positive electrode terminal 16 Negative electrode terminal 30 Electrode body

Claims (7)

A method for manufacturing a lithium secondary battery, comprising:
Preparing a lithium secondary battery in which an electrode body including a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material, and an electrolyte including lithium ions are accommodated in a battery case;
Charging the prepared lithium secondary battery to a predetermined voltage value under a room temperature range,
After the charging process, the lithium secondary battery is held for 12 hours to 80 hours under a room temperature range or lower temperature range, and after the holding process under the room temperature range or lower temperature range Holding the lithium secondary battery in a high temperature range of 40 ° C. to 65 ° C. for at least 6 hours,
A method for manufacturing a lithium secondary battery.   The manufacturing method according to claim 1, wherein the holding treatment in the room temperature range or lower temperature range is performed for 40 hours to 60 hours.   3. The manufacturing method according to claim 1, wherein the charging process is terminated when a voltage value of the lithium secondary battery reaches a range of 3.3 V to 4.2 V. 4.   The manufacturing method according to any one of claims 1 to 3, wherein the holding treatment under the high temperature region is performed for 6 hours to 24 hours.   The said electrolyte is a nonaqueous electrolyte, The manufacturing method as described in any one of Claims 1-4. A lithium secondary battery obtained by the production method according to any one of claims 1 to 5,
The battery capacity after 900 cycles of charge / discharge treatment for 0.1 seconds at a current value of 165A under a temperature condition of −15 ° C. after the holding treatment under the high temperature range is about 90 before the charge / discharge treatment is performed. A lithium secondary battery that is maintained at a level of at least%. A vehicle provided with the lithium secondary battery manufactured by the manufacturing method as described in any one of Claims 1-5, or the lithium secondary battery of Claim 6.

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