JP6863055B2 - Manufacturing method of non-aqueous electrolyte secondary battery - Google Patents

Description

The present disclosure relates to a method for manufacturing a non-aqueous electrolyte secondary battery.

Non-aqueous electrolyte solution As the solvent for the non-aqueous electrolyte solution used in the secondary battery, a cyclic carbonate such as ethylene carbonate (EC) generally having a high dielectric constant, and ethyl methyl carbonate (EMC) and dimethyl having a low viscosity are used. A chain carbonate such as carbonate (DMC) and diethyl carbonate (DEC) is mixed and used. EC has a function of forming an SEI (Solid Electrolyte Interface) film on a negative electrode to stabilize charging and discharging.

In Japanese Patent Application Laid-Open No. 2001-325988 (Patent Document 1), vinylene carbonate (VC), which is a film additive, is used in order to form a good SEI film on the negative electrode. Patent Document 1 further includes at least a step of charging at a potential at which the solvent is not reduced and decomposed in order to reduce and decompose the VC to form a VC film on the negative electrode while preventing the solvent from being reduced and decomposed. It is disclosed that the initial charging is performed by a charging step of one step or more. The term "initial charge" as used herein refers to the first charging of an uncharged non-aqueous electrolyte secondary battery (hereinafter, the non-aqueous electrolyte secondary battery is also abbreviated as "battery"). means.

Japanese Unexamined Patent Publication No. 2001-325988

On the other hand, it has been studied to use dimethoxyethane (hereinafter, also abbreviated as "DME") as a solvent for the non-aqueous electrolytic solution. Since DME has a low viscosity, it is expected to improve the electrical conductivity of the non-aqueous electrolyte solution. However, it is known that DME is co-inserted into the negative electrode and causes interlayer destruction of graphite, which is a negative electrode active material. If DME is used as the solvent for the non-aqueous electrolytic solution in the battery disclosed in Patent Document 1, there is a concern that the battery capacity may decrease due to the interlayer destruction of graphite. Furthermore, the battery resistance may increase due to the interlayer destruction of graphite.

An object of the present disclosure is to suppress a decrease in battery capacity in a method for manufacturing a battery using a non-aqueous electrolytic solution containing DME.

Hereinafter, the technical configuration and the mechanism of action of the present disclosure will be described. However, the mechanism of action of the present disclosure includes estimation. The correctness of the mechanism of action should not limit the scope of this disclosure.

The method for manufacturing a battery according to the present disclosure is a method for manufacturing a non-aqueous electrolyte secondary battery including a negative electrode and a non-aqueous electrolyte solution, which comprises a battery preparation step of preparing an uncharged non-aqueous electrolyte secondary battery. For an uncharged non-aqueous electrolyte secondary battery, a constant current is continuously applied at a predetermined current rate in a predetermined voltage step until the target voltage is reached in a range of at least 2.5V to 2.9V. It includes an initial charging step of performing constant voltage charging. The negative electrode contains a negative electrode mixture layer containing graphite, and the non-aqueous electrolytic solution contains 20% by volume or more of dimethoxyethane and 0.1 mol / L or more and 0.6 mol / L or less of 1,3-propanesulton. .. In addition, "C" is a unit of a current rate. “1C” indicates the current rate at which the SOC (Charge rate: State of Charge) reaches 0% to 100% after charging for 1 hour.

The co-insertion potential of DME contained in the non-aqueous electrolyte solution and the reduction potential of 1,3-propane sultone (hereinafter, also abbreviated as "PS") have close values. The "co-insertion potential of DME" in the present specification means the potential at which DME is co-inserted into graphite contained in the negative electrode mixture layer together with the supporting salt, and the "reduction potential of PS" is PS. Means the potential at which is reduced and decomposed. In the initial charge, in the range of 2.5V to 2.9V, constant current constant voltage charging is performed multiple times in a predetermined voltage step at a predetermined current rate until the target voltage is reached (hereinafter, constant current constant voltage charging). , Also abbreviated as "CCCV charging"), co-insertion of DME into graphite and reduction decomposition of PS occur almost at the same time, and a low-resistance mixed film consisting of DME and reduction-decomposition PS is applied to the negative electrode. It is thought that it will be formed. It is considered that the mixed coating suppresses the co-insertion of DME into graphite. In order to efficiently form the film, the non-aqueous electrolytic solution contains 20% by volume or more of DME and 0.1 mol / L or more and 0.6 mol / L or less of PS. Further, by repeatedly performing step charging and step discharging, at least a part of the DME co-inserted into the graphite contained in the negative electrode mixture layer is desorbed from the graphite, and the DME co-inserted into the graphite becomes the graphite. It is considered that it is possible to suppress the insertion into the inside. The term "step charging" in the present specification means a method of charging CCCV at a predetermined current rate in a predetermined voltage step, and "step discharge" means a constant current at a predetermined current rate in a predetermined voltage step. It means a method of performing constant voltage discharge (hereinafter, constant current constant voltage discharge is also abbreviated as "CCCV discharge"). It is expected that the synergistic effect of these effects will suppress the decrease in battery capacity. That is, there is provided a method for manufacturing a battery in which co-insertion of DME into the negative electrode is suppressed and a decrease in battery capacity is suppressed when a non-aqueous electrolytic solution containing DME is used.

It is a figure which shows the relationship between the CC current value and the battery voltage value in the initial charging process of Examples 1, 3 and Comparative Example 4. It is a figure which shows the relationship between the CC current value and the battery voltage value in the initial charging process of Example 2. FIG. It is a figure which shows the relationship between the CC current value and the battery voltage value in the initial charging process of Comparative Examples 1 and 2. It is a figure which shows the relationship between the CC current value and the battery voltage value in the initial charging process of the comparative example 3. FIG. It is a figure which shows the relationship between the CC current value and the battery voltage value in the initial charging process of the comparative example 5. FIG.

Hereinafter, embodiments of the present disclosure (hereinafter referred to as “the present embodiment”) will be described. However, the following description does not limit the scope of claims.

<Structure of non-aqueous electrolyte secondary battery>
The non-aqueous electrolytic solution secondary battery of the present disclosure can have a conventionally known configuration as long as it includes the negative electrode and the non-aqueous electrolytic solution described below. A conventionally known configuration includes, for example, a configuration in which an electrode group having a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode is provided, and the electrode group is arranged in a battery case together with a non-aqueous electrolytic solution. To say. The electrode group can be in a flatly wound form (wound electrode group).

<Manufacturing method of non-aqueous electrolyte secondary battery>
The method for producing a non-aqueous electrolyte secondary battery of the present disclosure includes a battery preparation step of preparing an uncharged non-aqueous electrolyte secondary battery and an uncharged non-aqueous electrolyte prepared in the battery preparation step. Initial charging of a secondary battery in a range of at least 2.5V to 2.9V, in which a constant current constant voltage charge is continuously performed a plurality of times at a predetermined current rate at a predetermined voltage step until the target voltage is reached. Includes steps. As long as these steps are included, other steps can be included. Further, the above two steps may further include a sub-step process.

<Negative electrode>
The negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on the main surface of the negative electrode current collector. The negative electrode current collector may be, for example, a copper (Cu) foil or the like. The negative electrode current collector may have a thickness of, for example, about 5 to 20 μm.

<< Negative electrode mixture layer >>
The negative electrode mixture layer contains a negative electrode active material and a binder. The negative electrode mixture layer may contain, for example, 95 to 99% by mass of the negative electrode active material and 1 to 5% by mass of the binder. The negative electrode mixture layer may have a thickness of, for example, about 50 to 150 μm.

(Negative electrode active material and binder)
The negative electrode active material contains at least graphite. That is, the negative electrode of the present disclosure includes a negative electrode mixture layer containing graphite. As the graphite, natural graphite such as lump graphite and scaly graphite, artificial graphite obtained by calcining a carbon precursor, or processed graphite such as pulverization, sieving, and pressing is used. be able to. Further, graphite may be coated with amorphous carbon. The negative electrode active material may contain an active material other than graphite, and may further contain, for example, silicon, silicon oxide, tin, tin oxide, and the like. Binders should not be particularly limited. The binder may be, for example, carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), or the like.

<Non-aqueous electrolyte>
The non-aqueous electrolyte contains a non-aqueous solvent, additives and supporting salts. The non-aqueous solvent contains at least DME and the additive contains at least PS. The non-aqueous electrolytic solution may contain only DME as the non-aqueous solvent, or may contain other non-aqueous solvent in addition to DME. As the other non-aqueous solvent, for example, cyclic or chain carbonates such as EC, EMC, DMC, and DEC may be used. The non-aqueous electrolyte solution may contain only PS as an additive, or may contain other additives in addition to PS. As other additives, for example, VC, cyclohexylbenzene (CHB) or the like may be used. The supporting salt may be, for example, a Li salt such as _{lithium hexafluorophosphate (LiPF 6} ) or lithium tetrafluoroborate (LiBF _4). The concentration of the Li salt may be, for example, about 0.5 to 2.0 mL / L.

The non-aqueous electrolytic solution contains at least 20% by volume or more of DME with respect to the total amount in the non-aqueous electrolytic solution. When the content of DME contained in the non-aqueous electrolytic solution is less than 20% by volume, improvement in electrical conductivity of the non-aqueous electrolytic solution may not be expected. The upper limit of the content of DME contained in the non-aqueous electrolytic solution is not particularly limited, but it is necessary to suppress co-insertion of DME into graphite as the content of DME contained in the non-aqueous electrolytic solution increases. May become difficult and the battery capacity may decrease. Therefore, the upper limit of the content of DME contained in the non-aqueous electrolytic solution may be, for example, 80% by volume or less, or 70% by volume or less, based on the total amount in the non-aqueous electrolytic solution. , 60% by volume or less, 50% by volume or less, 40% by volume or less, or 30% by volume or less.

The non-aqueous electrolyte solution contains PS having a concentration of 0.1 mol / L or more and 0.6 mol / L or less. That is, the non-aqueous electrolytic solution of the present disclosure contains 20% by volume or more of DME and 0.1 mol / L or more and 0.6 mol / L or less of PS. When the concentration of PS in the non-aqueous electrolytic solution is less than 0.1 mol / L, the absolute amount of PS contained in the non-aqueous electrolytic solution is small, so that it tends to be difficult to prepare a mixed film composed of DME and PS. There is. When the concentration of PS in the non-aqueous electrolytic solution exceeds 0.6 mol / L, the amount of DME contained in the non-aqueous electrolytic solution may be less than 20% by volume.

<Positive electrode>
The positive electrode includes a positive electrode current collector and a positive electrode mixture layer formed on the main surface of the positive electrode current collector. The positive electrode current collector may be, for example, an aluminum (Al) foil or the like. The positive electrode current collector may have a thickness of, for example, 10 to 30 μm.

<< Positive electrode mixture layer >>
The positive electrode mixture layer contains a positive electrode active material, a conductive material and a binder. The positive electrode mixture layer may contain, for example, 80 to 98% by weight of the positive electrode active material, 1 to 15% by weight of the conductive material, and 1 to 5% by weight of the binder. The positive electrode mixture layer may have a thickness of, for example, 100 to 200 μm.

(Positive electrode active material, conductive material and binder)
The positive electrode active material, the conductive material and the binder should not be particularly limited. The positive electrode active material may be, for example, LiCoO ₂ , LiNiO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM), LiMnO ₂ , LiMn ₂ O ₄ , LiFePO _4, or the like. The conductive material may be, for example, acetylene black (AB), furnace black, vapor-grown carbon fiber (VGCF), graphite or the like. The binder may be, for example, polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), or the like.

<Separator>
The separator is an electrically insulating porous membrane. The separator electrically separates the positive electrode and the negative electrode. The separator may have a thickness of, for example, 5 to 30 μm. The separator may be composed of, for example, a porous polyethylene (PE) film, a porous polypropylene (PP) film, or the like. The separator may include a multi-layer structure. For example, the separator may be composed of a porous PP film, a porous PE film, and a porous PP film laminated in this order. The separator may include a heat-resistant layer on its surface. The heat-resistant layer contains a heat-resistant material. Examples of the heat-resistant material include metal oxide particles such as alumina and a refractory resin such as polyimide.

<Electrode group>
The electrode body has a positive electrode, a negative electrode, and a separator provided between the positive electrode and the negative electrode. The electrode body may be, for example, a group of cylindrical electrodes.

<Battery case>
The battery case may be, for example, square (flat rectangular parallelepiped), cylindrical, or bag-shaped. For example, a metal such as aluminum (Al) or an Al alloy constitutes a battery case. However, as long as the battery case has a predetermined airtightness, for example, a composite material of metal and resin may form the battery case. Examples of the metal and resin composite material include an aluminum laminated film and the like. The battery case may include an external terminal, a liquid injection hole, a gas discharge valve, a current cutoff mechanism (CID), and the like.

<Battery preparation process>
In the battery preparation process, an uncharged battery is prepared. The battery preparation step includes, for example, a step of preparing a positive electrode, a step of preparing a negative electrode, a step of preparing a separator, and a positive electrode, a separator, a negative electrode, and a separator so that the positive electrode and the negative electrode face each other with the separator interposed therebetween. A step of manufacturing a cylindrical electrode group by laminating and further winding in a spiral shape, a step of storing the electrode group in a battery case, a step of injecting a non-aqueous electrolyte solution into a battery case, and a battery. It may include a step of sealing the case.

<Initial charging process>
In the initial charging step, the uncharged battery prepared in the battery preparing step is initially charged.

In the initial charging process, CCCV charging (step charging) is performed a plurality of times in a predetermined voltage step at a predetermined current rate until the target voltage is reached in the battery voltage range of at least 2.5V to 2.9V. Be told. As used herein, the "predetermined voltage step" is preferably a voltage of 0.05 to 0.2 V, and the "predetermined current rate" is a current rate of 0.01 to 0.3 C. Is desirable. Step charging in the battery voltage range of 2.5V to 2.9V may be performed at least once, but after the battery voltage reaches 2.9V in the initial charging step, step discharging is performed to reduce the battery voltage to 2.5V. After lowering to, step charging may be performed again. By performing step charging multiple times, the effect of desorbing at least a part of the DME co-inserted into the graphite contained in the negative electrode mixture layer from the graphite, and the DME co-inserted into the graphite are further inside the graphite. It is expected that the effect of suppressing insertion will be amplified.

The initial charge is preferably carried out at a reasonably low current rate. However, if the current rate is excessively low, it takes a long time for processing, so the current rate for initial charging is, for example, about 0.1 to 1.0 C. Further, after the initial charging step, the battery may be aged by allowing the battery to stand at a predetermined temperature for a predetermined period of time.

Hereinafter, examples of the present disclosure will be described. However, the following examples do not limit the scope of claims.

<Manufacturing of non-aqueous electrolyte secondary batteries>
<< Example 1 >>
1. 1. Manufacture of cathode The following materials were prepared.
Positive electrode active material: NCM
Conductive material: AB
Binder: PVdF
Solvent: N-methyl-2pyrrolidone (NMP)
Positive electrode current collector foil: Al foil (thickness 15 μm)

NCM, AB, PVdF and NMP were mixed by a planetary mixer. As a result, a paste-like positive electrode mixture (hereinafter, referred to as “positive electrode mixture paste”) was prepared. The solid content composition of the positive electrode mixture paste was "NCM: AB: PVdF = 93: 4: 3" in terms of mass ratio. The paste for the positive electrode mixture layer was applied to the surface of the positive electrode current collector and dried. As a result, a positive electrode mixture layer was formed. From the above, a positive electrode for a non-aqueous electrolyte secondary battery was formed. The positive electrode was rolled and cut into strips.

2. Manufacture of negative electrode The following materials were prepared.
Negative electrode active material: Amorphous coated natural graphite thickener: CMC
Binder: SBR
Solvent: Water Negative electrode current collector foil: Cu foil (thickness 10 μm)
Here, the "amorphous coated natural graphite" in the present specification means a natural graphite coated with amorphous carbon.

Amorphous coated spherical natural graphite, CMC, SBR and water are put into the stirring tank of the stirring device and stirred to form a paste-like negative electrode mixture (hereinafter, referred to as “negative electrode mixture paste”). Prepared. In the negative electrode mixture paste, the solid content was set to "amorphous coated natural graphite: CMC: SBR = 98: 1: 1" in terms of mass ratio. The paste for the negative electrode mixture layer was applied to the surface of the negative electrode current collector and dried. As a result, a negative electrode mixture layer was formed. As described above, the negative electrode for the non-aqueous electrolyte secondary battery was formed. The negative electrode was rolled and cut into strips.

3. 3. Preparation of non-aqueous electrolyte solution An electrolyte solution having the following composition was prepared.
Solvent composition: [EC: DMC: EMC: DME = 3: 1: 3: 3 (volume ratio)]
Supporting salt: LiPF ₆ (1.1 mol / L)
Additive: PS (0.28 mol / L)

4. Battery preparation step A band-shaped positive electrode, a band-shaped negative electrode, and a band-shaped separator (polyethylene porous membrane) were prepared. The positive electrode, the separator, the negative electrode, and the separator were laminated in this order. This formed a group of electrodes. Further, the positive electrode current collector plate, the electrode group, and the negative electrode current collector plate were laminated in this order, and the terminals were connected to the positive electrode current collector plate and the negative electrode current collector plate, respectively. The electrode group was housed in a battery case made of a laminated film. A non-aqueous electrolyte solution was injected into the battery case, and the battery case was sealed. From the above, the battery was assembled and the uncharged battery was prepared.

5. Initial Charging Step An uncharged battery was subjected to an initial charging step under the conditions shown in FIG. The conditions for the first CCCV charging are as follows.
CC current: 0.1C, CV voltage: 2.0V, termination current: 0.01C.

The battery charged to 2.0 V was step-charged until the battery voltage reached 3.0 V. The final current was similarly set to 0.01C. In the step charging, the voltage was set to 0.1 V and the current rate was set to 0.1 C. The same applies to the following step charging.

CCCV charging was performed on a battery charged to 3.0 V by step charging. The conditions for CCCV charging are as follows.
CC current: 0.7C, CV voltage: 4.1V, termination current: 0.01C.

From the above, the battery according to the present disclosure was obtained. The battery according to the present disclosure charged to 4.1 V was then aged at 60 ° C. for 1 day. From the above, the battery according to Example 1 shown in Table 1 was obtained. The battery has a laminated shape (width 60 mm, length 90 mm, thickness 2.5 mm). The battery is designed to have a capacity of 28 mAh in the voltage range of 3.0 to 4.1 V.

<Example 2>
As described below, the battery was manufactured in the same manner as in Example 1 except that the initial charging step was performed under the conditions shown in FIG.

The assembled uncharged battery was first charged with CCCV. The conditions for the first CCCV charging are as follows.
CC current: 0.1C, CV voltage: 2.5V, termination current: 0.01C.

The battery charged to 2.5 V was subjected to the first step charge until the battery voltage reached 2.9 V.

The battery charged to 2.9 V in the first step charge was subjected to the first step discharge until the battery voltage reached 2.5 V. In the step discharge, the voltage was set to 0.1 V and the current rate was set to 0.1 C. The same applies to the following step discharge.

The battery discharged to 2.5 V in the first step discharge was subjected to the second step charge until the battery voltage became 2.9 V.

The battery charged to 2.9 V in the second step charge was subjected to the second step discharge until the battery voltage reached 2.5 V.

The battery discharged to 2.5 V in the second step discharge was subjected to the third step charge until the battery voltage became 2.9 V.

CCCV charging was performed on the battery charged to 2.9V in the third step charging. The conditions for CCCV charging are as follows.
CC current: 0.7C, CV voltage: 4.1V, termination current: 0.01C.

<Example 3>
As shown in Table 1 below, the battery was manufactured by the same manufacturing method as in Example 1 except that the concentration of PS contained in the non-aqueous electrolyte solution was changed.

<Comparative example 1>
A battery was manufactured in the same manner as in Example 1 except that no additive was used and the assembled uncharged battery was subjected to the initial charging step under the conditions shown in FIG. .. The conditions for CCCV charging are as follows.
CC current: 0.7C, CV voltage: 4.1V, termination current: 0.01C.

<Comparative example 2>
A battery was manufactured in the same manner as in Example 1 except that the assembled uncharged battery was subjected to the initial charging step under the conditions shown in FIG. The conditions for CCCV charging are as follows.
CC current: 0.7C, CV voltage: 4.1V, termination current: 0.01C.

<Comparative example 3>
As shown in FIG. 4, the assembled uncharged battery is first charged with a current value of 0.1 C to a constant current until the battery voltage is charged to 3.4 V, and then charged to 3.4 V. A battery was manufactured in the same manner as in Example 1 except that the battery was charged with CCCV. The conditions for CCCV charging are as follows.
CC current: 0.7C, CV voltage: 4.1V, termination current: 0.01C.

<Comparative example 4>
As shown in Table 1 below, a battery was manufactured in the same manner as in Example 1 except that the additive was VC.

<Comparative example 5>
As described below, the battery was manufactured in the same manner as in Example 1 except that the initial charging step was performed under the conditions shown in FIG.

The assembled uncharged battery was charged for the first CCCV. The conditions for the first CCCV charging are as follows.
CC current: 0.1C, CV voltage: 2.9V, termination current: 0.01C.

The first CCCV discharge was performed on the battery charged to 2.9 V. The conditions for the first CCCV discharge are as follows.
CC current: 0.1C, CV voltage: 2.5V, termination current: 0.01C.

A second CCCV charge was performed on the battery discharged to 2.5 V under the same conditions as the first CCCV charge.

The second CCCV discharge was performed on the battery charged to 2.9 V under the same conditions as the first CCCV discharge.

The battery discharged to 2.5 V was charged for the third CCCV under the same conditions as the first CCCV charge.

The battery charged to 2.9 V was charged with CCCV for the fourth time. The conditions for the fourth CCCV charge are as follows.
CC current 0.7C, CV voltage 4.1V, termination current: 0.01C.

<Initial capacity measurement test>
CCCV discharge was performed on the batteries according to the Examples and Comparative Examples that had undergone the initial charging step under the following conditions, and the initial capacity [Ah] was measured. The results are shown in the "Initial Capacity" column of Table 1 below. In Table 1 below, the values shown in "Initial capacity" are relative evaluations of the battery capacities of the other Examples and Comparative Examples, with the initial capacity of Comparative Example 3 as 100%. The larger the initial capacity value, the larger the initial capacity of the battery.
CCCV discharge conditions: CC current value 0.7C, CV voltage 3.0V, termination current 0.01C.

<High temperature storage test>
The batteries according to the Examples and Comparative Examples that had undergone the initial capacity measurement test were charged with CCCV under the following conditions, and the SOC of the batteries was adjusted to 100% at 25 ° C. The batteries were stored for 7 days in a constant temperature bath set at 60 ° C. After 7 days, the battery was taken out and the capacity was measured after high temperature storage in the same manner as the initial capacity. The capacity retention rate after high temperature storage was calculated by dividing the capacity after high temperature storage by the initial capacity. The results are shown in the column of "Capacity retention rate after high temperature storage" in Table 1. The larger the value of the capacity retention rate after high temperature storage, the larger the battery capacity retention rate after the high temperature storage test.
CCCV charging conditions: CC current value 0.7C, CV voltage 4.1V, termination current 0.01C.

<Initial IV resistance measurement test>
An IV resistance measurement test was performed on the batteries according to each of the examples and comparative examples in the initial state. The batteries according to the Examples and Comparative Examples in the initial state were charged in an environment of a temperature of 25 ° C., and adjusted to a charged state of SOC 50%. Then, pulse charging was performed at 25 ° C. with a current of 5 C for 10 seconds, and the IV resistance value (mΩ) was calculated from the amount of voltage increase 10 seconds after the start of charging. The results are shown in Table 1 below. In Table 1 below, the values shown in "IV resistance" are relative evaluations of the IV resistance values of the other Examples and Comparative Examples, with the initial IV resistance value of Comparative Example 3 as 100%. The smaller the value, the smaller the initial IV resistance value.

<Result>
As shown in Table 1 above, Examples 1 to 3 were superior in initial capacity to Comparative Examples 1 to 5, and were also excellent in capacity retention after high temperature storage. Therefore, it is understood that when a non-aqueous electrolytic solution containing DME is used, a method for manufacturing a battery is provided in which co-insertion of DME into the negative electrode is suppressed and a decrease in battery capacity is suppressed. It was also confirmed that Examples 1 to 3 had a smaller initial IV resistance value than Comparative Examples 1 to 5.

From the comparison between Examples 1 to 3 and Comparative Examples 2, 3 and 5, it is assumed that a non-aqueous electrolytic solution containing 20% by volume or more of DME and 0.1 mol / L or more and 0.6 mol / L or less of PS was used. However, it was shown that the initial capacity and the capacity retention rate after high temperature storage are inferior to those of the examples unless step charging is performed in the range of 2.5 V to 2.9 V in the initial charging step. In Examples 1 to 3, since step charging is performed in the range of 2.5 V to 2.9 V, a part of the DME co-inserted into the graphite contained in the negative electrode mixture layer is desorbed from the graphite. At the same time, it is considered that the insertion of DME into the graphite is suppressed.

From the comparison between Examples 1 to 3 and Comparative Examples 1 and 4, it was shown that by using PS as an additive, a battery having an excellent initial capacity and a capacity retention rate after high temperature storage can be obtained. In addition, the initial IV resistance values of Examples 1 to 3 were also smaller than those of Comparative Examples 1 and 4. It is considered that by using PS as an additive, a low resistance mixed film composed of DME and PS was formed on the negative electrode, and the co-insertion of DME into graphite was suppressed by the mixed film.

The above embodiments and examples are exemplary in all respects and are not restrictive. The technical scope defined by the claims includes all changes within the meaning and scope equivalent to the claims.

Claims (1)

A method for manufacturing a non-aqueous electrolytic solution secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolytic solution.
Preparing the uncharged non-aqueous electrolyte secondary battery, the battery preparation process,
With respect to the uncharged non-aqueous electrolyte secondary battery, a constant current is continuously applied a plurality of times at a predetermined current rate in a predetermined voltage step until the target voltage is reached in a range of at least 2.5 V to 2.9 V. Including the initial charging process, which performs constant voltage charging
The positive electrode includes a positive electrode mixture layer containing a positive electrode active material and a conductive material, and contains a positive electrode mixture layer.
The positive electrode active material is at least one selected from _{LiCoO 2} , LiNiO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMnO ₂ , LiMn ₂ O ₄ and LiFePO _4.
The conductive material is at least one selected from acetylene black, furnace black, vapor-grown carbon fiber and graphite.
The negative electrode includes a negative electrode mixture layer containing graphite, and the negative electrode contains a negative electrode mixture layer.
The negative electrode mixture layer does not contain a conductive agent and does not contain a conductive agent.
The non-aqueous electrolytic solution contains 20% by volume or more of dimethoxyethane and 0.1 mol / L or more and 0.6 mol / L or less of 1,3-propane sultone.
A method for manufacturing a non-aqueous electrolyte secondary battery.

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