JP2018067455A - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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JP2018067455A
JP2018067455A JP2016205309A JP2016205309A JP2018067455A JP 2018067455 A JP2018067455 A JP 2018067455A JP 2016205309 A JP2016205309 A JP 2016205309A JP 2016205309 A JP2016205309 A JP 2016205309A JP 2018067455 A JP2018067455 A JP 2018067455A
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negative electrode
lithium ion
ion secondary
secondary battery
active material
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竜斗 坂本
Tatsuto Sakamoto
竜斗 坂本
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Toyota Motor Corp
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery using graphite as a negative electrode active material and having reduced resistance.SOLUTION: A lithium ion secondary battery 100 includes: a positive electrode; and a negative electrode. The negative electrode includes a negative electrode active material layer 64 containing a negative electrode active material. The negative electrode active material contains graphite having an azide group on its surface.SELECTED DRAWING: Figure 1

Description

本発明は、リチウムイオン二次電池に関する。   The present invention relates to a lithium ion secondary battery.

リチウムイオン二次電池は、既存の電池に比べて軽量かつエネルギー密度が高いことから、近年、パソコンや携帯端末等のいわゆるポータブル電源や車両駆動用電源として用いられている。リチウムイオン二次電池は、特に、電気自動車(EV)、ハイブリッド自動車(HV)、プラグインハイブリッド自動車(PHV)等の車両の駆動用高出力電源として今後ますます普及していくことが期待されている。   Lithium ion secondary batteries are lighter and have a higher energy density than existing batteries, and have recently been used as so-called portable power sources for vehicles and personal computers and power sources for driving vehicles. Lithium-ion secondary batteries are expected to become increasingly popular as high-output power sources for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). Yes.

リチウムイオン二次電池の一般的な構成は、正極と負極とを備え、当該負極は、負極活物質を含有する負極活物質層を備える。負極活物質の代表的な例としては、黒鉛が挙げられる。   A general configuration of a lithium ion secondary battery includes a positive electrode and a negative electrode, and the negative electrode includes a negative electrode active material layer containing a negative electrode active material. A typical example of the negative electrode active material is graphite.

リチウムイオン二次電池の負極活物質として黒鉛を用いた場合には、黒鉛表面において電解液の分解反応が起きて、電解液の分解ガスが発生するおそれがある。これに対し、黒鉛を非晶質炭素材料で被覆することにより、電解液の分解によるガス発生を抑制する技術が開発されている(例えば、特許文献1参照)。   When graphite is used as the negative electrode active material of the lithium ion secondary battery, the decomposition reaction of the electrolyte solution may occur on the graphite surface, and the decomposition gas of the electrolyte solution may be generated. On the other hand, the technique which suppresses the gas generation by decomposition | disassembly of electrolyte solution by coat | covering graphite with an amorphous carbon material is developed (for example, refer patent document 1).

特開2003−346796号公報JP 2003-346996 A

しかしながら本発明者が鋭意検討した結果、黒鉛を非晶質炭素材料で被覆することにより、電解液の分解によるガス発生を抑制することは可能であるが、その一方で、電池抵抗低減の面において改善の余地があることを見出した。   However, as a result of intensive studies by the present inventor, it is possible to suppress gas generation due to decomposition of the electrolytic solution by coating graphite with an amorphous carbon material, but on the other hand, in terms of reducing battery resistance I found that there was room for improvement.

そこで本発明の目的は、負極活物質として黒鉛が用いられているリチウムイオン二次電池において、抵抗が低減されたリチウムイオン二次電池を提供することにある。   Accordingly, an object of the present invention is to provide a lithium ion secondary battery with reduced resistance in a lithium ion secondary battery in which graphite is used as a negative electrode active material.

ここに開示されるリチウムイオン二次電池は、正極と、負極とを備える。前記負極は、負極活物質を含有する負極活物質層を備える。前記負極活物質は、表面にアジ基を有する黒鉛を含有する。
このような構成によれば、アジ基により効率良く電解液中のリチウムイオンを捕捉することができ、さらに、黒鉛へのリチウムイオンのインターカレーションを効率よく行なうことができる。すなわち、表面にアジ基を有する黒鉛をリチウムイオン二次電池の負極活物質に用いることにより、抵抗が低減されたリチウムイオン二次電池を提供することができる。
The lithium ion secondary battery disclosed herein includes a positive electrode and a negative electrode. The negative electrode includes a negative electrode active material layer containing a negative electrode active material. The negative electrode active material contains graphite having an azide group on the surface.
According to such a configuration, lithium ions in the electrolytic solution can be efficiently captured by the azide group, and further, intercalation of lithium ions into graphite can be performed efficiently. That is, by using graphite having an azide group on the surface as a negative electrode active material of a lithium ion secondary battery, a lithium ion secondary battery with reduced resistance can be provided.

本発明の一実施形態に係るリチウムイオン二次電池の内部構造を模式的に示す断面図である。It is sectional drawing which shows typically the internal structure of the lithium ion secondary battery which concerns on one Embodiment of this invention. 本発明の一実施形態に係るリチウムイオン二次電池の捲回電極体の構成を示す模式図である。It is a schematic diagram which shows the structure of the winding electrode body of the lithium ion secondary battery which concerns on one Embodiment of this invention. (a)アジ基を表面に有する黒鉛粒子を模式的に示す図であり、(b)当該黒鉛粒子において充電時のリチウムイオンの移動を模式的に示す図である。(A) It is a figure which shows typically the graphite particle which has an azide group on the surface, (b) It is a figure which shows typically the movement of the lithium ion at the time of charge in the said graphite particle. 実施例で作製した各リチウムイオン二次電池の評価結果を示すグラフである。It is a graph which shows the evaluation result of each lithium ion secondary battery produced in the Example.

以下、図面を参照しながら、本発明による実施の形態を説明する。なお、本明細書において特に言及している事項以外の事柄であって本発明の実施に必要な事柄(例えば、本発明を特徴付けないリチウムイオン二次電池の一般的な構成および製造プロセス)は、当該分野における従来技術に基づく当業者の設計事項として把握され得る。本発明は、本明細書に開示されている内容と当該分野における技術常識とに基づいて実施することができる。また、以下の図面においては、同じ作用を奏する部材・部位には同じ符号を付して説明している。また、各図における寸法関係(長さ、幅、厚さ等)は実際の寸法関係を反映するものではない。   Embodiments according to the present invention will be described below with reference to the drawings. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, a general configuration and manufacturing process of a lithium ion secondary battery that does not characterize the present invention) are as follows. Therefore, it can be grasped 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. Moreover, in the following drawings, the same code | symbol is attached | subjected and demonstrated to the member and site | part which show | plays the same effect | action. In addition, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.

なお、本明細書において「二次電池」とは、繰り返し充放電可能な蓄電デバイス一般をいい、いわゆる蓄電池ならびに電気二重層キャパシタ等の蓄電素子を包含する用語である。
また、本明細書において「リチウムイオン二次電池」とは、電荷担体としてリチウムイオンを利用し、正負極間におけるリチウムイオンに伴う電荷の移動により充放電が実現される二次電池をいう。
In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term including a power storage element such as a so-called storage battery and an electric double layer capacitor.
Further, in the present specification, the “lithium ion secondary battery” refers to a secondary battery that uses lithium ions as a charge carrier and is charged / discharged by movement of charges accompanying the lithium ions between the positive and negative electrodes.

以下、扁平形状の捲回電極体と扁平形状の電池ケースとを有する扁平角型のリチウムイオン二次電池を例にして、本発明について詳細に説明するが、本発明をかかる実施形態に記載されたものに限定することを意図したものではない。   Hereinafter, the present invention will be described in detail by taking a flat rectangular lithium ion secondary battery having a flat wound electrode body and a flat battery case as an example. However, the present invention is described in this embodiment. It is not intended to be limited to those.

図1に示すリチウムイオン二次電池100は、扁平形状の捲回電極体20と非水電解液(図示せず)とが扁平な角形の電池ケース(即ち外装容器)30に収容されることにより構築される密閉型のリチウムイオン二次電池100である。電池ケース30には外部接続用の正極端子42および負極端子44と、電池ケース30の内圧が所定レベル以上に上昇した場合に該内圧を開放するように設定された薄肉の安全弁36が設けられている。また、電池ケース30には、非水電解液を注入するための注入口(図示せず)が設けられている。正極端子42は、正極集電板42aと電気的に接続されている。負極端子44は、負極集電板44aと電気的に接続されている。電池ケース30の材質としては、例えば、アルミニウム等の軽量で熱伝導性の良い金属材料が用いられる。   The lithium ion secondary battery 100 shown in FIG. 1 has a flat wound electrode body 20 and a non-aqueous electrolyte (not shown) accommodated in a flat rectangular battery case (that is, an exterior container) 30. This is a sealed lithium ion secondary battery 100 to be constructed. The battery case 30 is provided with a positive terminal 42 and a negative terminal 44 for external connection, and a thin safety valve 36 set so as to release the internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. Yes. In addition, the battery case 30 is provided with an inlet (not shown) for injecting a non-aqueous electrolyte. The positive terminal 42 is electrically connected to the positive current collector 42a. The negative electrode terminal 44 is electrically connected to the negative electrode current collector plate 44a. As the material of the battery case 30, for example, a light metal material having good thermal conductivity such as aluminum is used.

捲回電極体20は、図1および図2に示すように、長尺状の正極集電体52の片面または両面(ここでは両面)に長手方向に沿って正極活物質層54が形成された正極シート50と、長尺状の負極集電体62の片面または両面(ここでは両面)に長手方向に沿って負極活物質層64が形成された負極シート60とが、2枚の長尺状のセパレータシート70を介して重ね合わされて長手方向に捲回された形態を有する。なお、捲回電極体20の捲回軸方向(上記長手方向に直交するシート幅方向をいう。)の両端から外方にはみ出すように形成された正極活物質層非形成部分52a(即ち、正極活物質層54が形成されずに正極集電体52が露出した部分)と負極活物質層非形成部分62a(即ち、負極活物質層64が形成されずに負極集電体62が露出した部分)には、それぞれ正極集電板42aおよび負極集電板44aが接合されている。   As shown in FIGS. 1 and 2, the wound electrode body 20 has a positive electrode active material layer 54 formed along the longitudinal direction on one side or both sides (here, both sides) of an elongated positive electrode current collector 52. The positive electrode sheet 50 and the negative electrode sheet 60 in which the negative electrode active material layer 64 is formed along the longitudinal direction on one side or both sides (here, both sides) of the long negative electrode current collector 62 are two long shapes. The separator sheet 70 is overlapped and wound in the longitudinal direction. The positive electrode active material layer non-forming portion 52a (that is, the positive electrode) formed so as to protrude outward from both ends in the winding axis direction of the wound electrode body 20 (referred to as the sheet width direction orthogonal to the longitudinal direction). The portion where the active material layer 54 is not formed and the positive electrode current collector 52 is exposed) and the negative electrode active material layer non-formed portion 62a (that is, the portion where the negative electrode active material layer 64 is not formed and the negative electrode current collector 62 is exposed). ) Are joined with a positive current collector 42a and a negative current collector 44a, respectively.

正極シート50を構成する正極集電体52としては、例えばアルミニウム箔等が挙げられる。正極活物質層54は、正極活物質を含む。正極活物質層54に含まれる正極活物質としては、例えばリチウム遷移金属酸化物(例、LiNi1/3Co1/3Mn1/3、LiNiO、LiCoO、LiFeO、LiMn、LiNi0.5Mn1.5等)、リチウム遷移金属リン酸化合物(例、LiFePO等)等が挙げられる。正極活物質層54は、活物質以外の成分、例えば導電材やバインダ等を含み得る。導電材としては、例えばアセチレンブラック(AB)等のカーボンブラックやその他(例、グラファイト等)の炭素材料を好適に使用し得る。バインダとしては、例えばポリフッ化ビニリデン(PVDF)等を使用し得る。 Examples of the positive electrode current collector 52 constituting the positive electrode sheet 50 include aluminum foil. The positive electrode active material layer 54 includes a positive electrode active material. Examples of the positive electrode active material included in the positive electrode active material layer 54 include lithium transition metal oxides (eg, LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiNiO 2 , LiCoO 2 , LiFeO 2 , LiMn 2 O). 4 , LiNi 0.5 Mn 1.5 O 4 etc.), lithium transition metal phosphate compounds (eg, LiFePO 4 etc.) and the like. The positive electrode active material layer 54 can include components other than the active material, such as a conductive material and a binder. As the conductive material, for example, carbon black such as acetylene black (AB) and other (eg, graphite) carbon materials can be suitably used. As the binder, for example, polyvinylidene fluoride (PVDF) can be used.

負極シート60を構成する負極集電体62としては、例えば銅箔等が挙げられる。負極活物質層64は負極活物質を含む。負極活物質層64に含まれる負極活物質には、表面にアジ基を有する黒鉛が少なくとも用いられる。負極活物質として表面にアジ基を有する黒鉛を用いることにより、リチウムイオン二次電池100の抵抗を低減することができる。その理由は、以下のように推測される。
図3に、表面にアジ基を有する黒鉛粒子80を模式的に示す。アジ基は、−Nで表される基であり、アジド基とも呼ばれることがある。このアジ基は、図3(a)に示されるように、−N=N=Nで表される構造および−N−N≡Nで表される構造の2つの構造が共鳴している構造にある。アジ基が−N=N=Nで表される構造にある場合には、アジ基の外側の窒素原子(すなわち、黒鉛粒子80から最も離れた窒素原子)に負の電荷があるために、充電時においては、図3(b)に示されるように、正の電荷を有するリチウムイオン(Li)を捕捉しやすい。そして、リチウムイオンを捕捉した−N=N=Nで表される構造のアジ基が−N−N≡Nで表される構造へ変移すると、黒鉛粒子80に最も近い窒素原子に負の電荷があるため、リチウムイオンは、黒鉛粒子80に最も近い窒素原子に移動しやすい。黒鉛粒子80に最も近い窒素原子にリチウムイオンが位置する場合には、リチウムイオンは、黒鉛粒子80にインターカレーションしやすい。したがって、黒鉛粒子80がその表面にアジ基を有する場合には、リチウムイオンのインターカレーションが起こりやすくなり、その結果、抵抗を低減することができる。
Examples of the negative electrode current collector 62 constituting the negative electrode sheet 60 include copper foil. The negative electrode active material layer 64 includes a negative electrode active material. As the negative electrode active material included in the negative electrode active material layer 64, at least graphite having an azide group on the surface is used. By using graphite having an azide group on the surface as the negative electrode active material, the resistance of the lithium ion secondary battery 100 can be reduced. The reason is presumed as follows.
FIG. 3 schematically shows graphite particles 80 having an azide group on the surface. The azide group is a group represented by —N 3 and may also be referred to as an azide group. The azide group, as shown in FIG. 3 (a), -N = N + = N - Structure and -N represented by - two structures having a structure represented by -N + ≡N resonates Is in the structure. Azide group -N = N + = N - when in the structure represented by the outer nitrogen atom of azide groups (i.e., farthest nitrogen atom graphite particles 80) due to the negative charge During charging, as shown in FIG. 3B, lithium ions (Li + ) having a positive charge are easily captured. Then, the lithium ions captured -N = N + = N - azide group having a structure represented by the -N - When transition to the structure represented by -N + ≡N, nearest nitrogen atom to graphite particles 80 Since there is a negative charge, lithium ions tend to move to the nitrogen atom closest to the graphite particles 80. When lithium ions are located at the nitrogen atom closest to the graphite particles 80, the lithium ions are likely to intercalate with the graphite particles 80. Therefore, when the graphite particle 80 has an azide group on the surface thereof, lithium ion intercalation easily occurs, and as a result, the resistance can be reduced.

表面にアジ基を有する黒鉛は、公知方法に従い作製することができる。例えば、黒鉛にプラズマ処理等の表面処理を施してその表面に水酸基等の官能基を導入し、次いで、当該官能基と、ジフェニルリン酸アジド(DPPA)、アジ化ナトリウム等のアジ化剤とを反応させることにより作製することができる。   Graphite having an azide group on the surface can be produced according to a known method. For example, graphite is subjected to a surface treatment such as plasma treatment, and a functional group such as a hydroxyl group is introduced to the surface, and then the functional group and an azilating agent such as diphenylphosphoric acid azide (DPPA) or sodium azide are used. It can produce by making it react.

なお、負極活物質層64は、本発明の効果を著しく損なわない範囲内において、負極活物質として、表面にアジ基を有する黒鉛以外の材料をさらに含んでいてもよい。このような材料の例としては、表面にアジ基を有しない黒鉛、ハードカーボン、ソフトカーボン等の炭素材料、リチウムチタン複合酸化物等の金属酸化物、スズ(Sn)やケイ素(Si)とリチウムの合金等が挙げられる。
負極活物質層64は、活物質以外の成分、例えばバインダや増粘剤等を含み得る。バインダとしては、例えばスチレンブタジエンラバー(SBR)、ポリフッ化ビニリデン(PVDF)等を使用し得る。増粘剤としては、例えばカルボキシメチルセルロース(CMC)等を使用し得る。
The negative electrode active material layer 64 may further include a material other than graphite having an azide group on the surface as a negative electrode active material within a range that does not significantly impair the effects of the present invention. Examples of such materials include carbon materials such as graphite, hard carbon, and soft carbon that do not have an azide group on the surface, metal oxides such as lithium titanium composite oxide, tin (Sn), silicon (Si), and lithium. And the like.
The negative electrode active material layer 64 can include components other than the active material, such as a binder and a thickener. As the binder, for example, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), or the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) can be used.

セパレータ70としては、例えばポリエチレン(PE)、ポリプロピレン(PP)、ポリエステル、セルロース、ポリアミド等の樹脂から成る多孔性シート(フィルム)が挙げられる。かかる多孔性シートは、単層構造であってもよく、二層以上の積層構造(例えば、PE層の両面にPP層が積層された三層構造)であってもよい。セパレータ70の表面には、耐熱層(HRL)が設けられていてもよい。   Examples of the separator 70 include a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat resistant layer (HRL) may be provided on the surface of the separator 70.

非水電解液は従来のリチウムイオン二次電池と同様のものを使用可能であり、典型的には有機溶媒(非水溶媒)中に、支持塩を含有させたものを用いることができる。非水溶媒としては、一般的なリチウムイオン二次電池の電解液に用いられる各種のカーボネート類、エーテル類、エステル類、ニトリル類、スルホン類、ラクトン類等の有機溶媒を、特に限定なく用いることができる。具体例として、エチレンカーボネート(EC)、プロピレンカーボネート(PC)、ジエチルカーボネート(DEC)、ジメチルカーボネート(DMC)、エチルメチルカーボネート(EMC)、モノフルオロエチレンカーボネート(MFEC)、ジフルオロエチレンカーボネート(DFEC)、モノフルオロメチルジフルオロメチルカーボネート(F−DMC)、トリフルオロジメチルカーボネート(TFDMC)等が例示される。このような非水溶媒は、1種を単独で、あるいは2種以上を適宜組み合わせて用いることができる。支持塩としては、例えば、LiPF、LiBF、LiClO等のリチウム塩(好ましくはLiPF)を好適に用いることができる。支持塩の濃度は、0.7mol/L以上1.3mol/L以下が好ましい。 The non-aqueous electrolyte can be the same as that of a conventional lithium ion secondary battery. Typically, a non-aqueous electrolyte containing a supporting salt in an organic solvent (non-aqueous solvent) can be used. As the non-aqueous solvent, various organic solvents such as carbonates, ethers, esters, nitriles, sulfones, lactones and the like used in electrolytes of general lithium ion secondary batteries are used without particular limitation. Can do. Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), Examples thereof include monofluoromethyl difluoromethyl carbonate (F-DMC) and trifluorodimethyl carbonate (TFDMC). Such a non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types as appropriate. As the supporting salt, for example, a lithium salt such as LiPF 6 , LiBF 4 , LiClO 4 (preferably LiPF 6 ) can be suitably used. The concentration of the supporting salt is preferably 0.7 mol / L or more and 1.3 mol / L or less.

なお、上記非水電解液は、本発明の効果を著しく損なわない限りにおいて、例えば、ビフェニル(BP)、シクロヘキシルベンゼン(CHB)等のガス発生剤;ホウ素原子および/またはリン原子を含むオキサラト錯体化合物、ビニレンカーボナート(VC)等の被膜形成剤;分散剤;増粘剤等の各種添加剤を含み得る。   In addition, the non-aqueous electrolyte is a gas generating agent such as biphenyl (BP) or cyclohexylbenzene (CHB); an oxalato complex compound containing a boron atom and / or a phosphorus atom, as long as the effects of the present invention are not significantly impaired. And film forming agents such as vinylene carbonate (VC); dispersants; various additives such as thickeners.

以上のようにして構成されるリチウムイオン二次電池100は、各種用途に利用可能である。好適な用途としては、電気自動車(EV)、ハイブリッド自動車(HV)、プラグインハイブリッド自動車(PHV)等の車両に搭載される駆動用電源が挙げられる。リチウムイオン二次電池100は、典型的には複数個を直列および/または並列に接続してなる組電池の形態でも使用され得る。   The lithium ion secondary battery 100 configured as described above can be used for various applications. Suitable applications include driving power sources mounted on vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). The lithium ion secondary battery 100 can also be used in the form of a battery pack typically formed by connecting a plurality of lithium ion secondary batteries 100 in series and / or in parallel.

なお、一例として扁平形状の捲回電極体20を備える角形のリチウムイオン二次電池100について説明した。しかしながら、リチウムイオン二次電池は、積層型電極体を備えるリチウムイオン二次電池として構成することもできる。また、リチウムイオン二次電池は、円筒形リチウムイオン二次電池として構成することもできる。   As an example, the rectangular lithium ion secondary battery 100 including the flat wound electrode body 20 has been described. However, the lithium ion secondary battery can also be configured as a lithium ion secondary battery including a stacked electrode body. The lithium ion secondary battery can also be configured as a cylindrical lithium ion secondary battery.

以下、本発明に関する実施例を説明するが、本発明をかかる実施例に示すものに限定することを意図したものではない。   EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<評価用リチウムイオン二次電池No.1の作製>
黒鉛を、東京ハイパワー製バリスティックコンデンサMB510ATを用いて15分間プラズマ処理(条件:300W、Ar/HO=8:2、80Pa)し、黒鉛の表面に水酸基を導入した。その後、得られた黒鉛を、ジメチルホルムアミド(DMF)中、濃度10wt%のアジ化剤(DPPA、NaN)で120℃で12時間処理して、表面にアジ基を有する黒鉛(以下、「アジ化黒鉛」ともいう)を得た。
得られたアジ化黒鉛(C)と、バインダとしてのSBRと、増粘剤としてのCMCとを、これら材料の質量比がC:SBR:CMC=98:1:1となるよう混練機に投入し、イオン交換水と共に混練して、負極作製用スラリーを調製した。このスラリーを厚み10μmの銅箔上に塗布し、乾燥した。これをプレスして所望の厚さに調整し、所定の幅に加工することによって負極シートを得た。
一方で、正極活物質としてのLiNi1/3Co1/3Mn1/3(LNCM)と、バインダとしてのPVDFと、導電材としてのABとを、これら材料の質量比がLNCM:PVDF:AB=89:8:3となるよう混練機に投入し、N−メチル−2−ピロリドン(NMP)と共に混練して、正極作製用スラリーを調製した。このスラリーを厚み15μmのアルミニウム箔上に塗布し、乾燥した。これをプレスして所望の厚さに調整し、所定の幅に加工することによって正極シートを得た。
セパレータとして、多孔質ポリオレフィンシートを用意した。
上記で作製した正極シートと負極シートとを、2枚のセパレータシートとともに積層し、捲回して電極体を作製し、これに正極端子および負極端子を接続した。次いで、これを電池ケースに収容し、非水電解液を注入した後気密に封止してNo.1の評価用リチウムイオン二次電池を得た。なお、非水電解液には、エチレンカーボネート(EC)とエチルメチルカーボネート(EMC)とジメチルカーボネート(DMC)とをEC:EMC:DMC=30:40:30の体積比で含む混合溶媒に、支持塩としてのLiPFを1.0mol/Lの濃度で溶解させたものを用いた。
<Evaluation lithium ion secondary battery No. Production of 1>
Graphite was subjected to plasma treatment for 15 minutes using a Tokyo High Power ballistic capacitor MB510AT (conditions: 300 W, Ar / H 2 O = 8: 2, 80 Pa) to introduce hydroxyl groups on the surface of the graphite. Thereafter, the obtained graphite was treated with azidating agent (DPPA, NaN 3 ) having a concentration of 10 wt% in dimethylformamide (DMF) at 120 ° C. for 12 hours to obtain graphite having an azide group on the surface (hereinafter referred to as “azimuth”). Also referred to as “graphite”.
The obtained graphite azide (C), SBR as a binder, and CMC as a thickener are charged into a kneader so that the mass ratio of these materials is C: SBR: CMC = 98: 1: 1. And knead | mixing with ion-exchange water prepared the slurry for negative electrode preparation. This slurry was applied onto a 10 μm thick copper foil and dried. This was pressed, adjusted to a desired thickness, and processed into a predetermined width to obtain a negative electrode sheet.
On the other hand, LiNi 1/3 Co 1/3 Mn 1/3 O 2 (LNCM) as the positive electrode active material, PVDF as the binder, and AB as the conductive material, the mass ratio of these materials is LNCM: PVDF : AB = 89: 8: 3 was charged into a kneader and kneaded with N-methyl-2-pyrrolidone (NMP) to prepare a slurry for preparing a positive electrode. This slurry was applied onto an aluminum foil having a thickness of 15 μm and dried. This was pressed, adjusted to a desired thickness, and processed into a predetermined width to obtain a positive electrode sheet.
A porous polyolefin sheet was prepared as a separator.
The positive electrode sheet and the negative electrode sheet prepared above were laminated together with two separator sheets, and wound to prepare an electrode body, to which a positive electrode terminal and a negative electrode terminal were connected. Next, this was housed in a battery case, and after injecting a non-aqueous electrolyte, it was hermetically sealed and No. 1 lithium ion secondary battery for evaluation was obtained. The non-aqueous electrolyte is supported by a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of EC: EMC: DMC = 30: 40: 30. of LiPF 6 as a salt were used as dissolved at a concentration of 1.0 mol / L.

<評価用リチウムイオン二次電池No.2の作製>
アジ化黒鉛を作製する際のプラズマ処理時間を30分に変更した以外は、上記No.1の評価用リチウムイオン二次電池と同様にして、アジ化黒鉛を作製した。
このアジ化黒鉛を用いた以外は、上記No.1の評価用リチウムイオン二次電池と同様にして、No.2の評価用リチウムイオン二次電池を作製した。
<Evaluation lithium ion secondary battery No. Production of 2>
Except for changing the plasma treatment time for producing azide graphite to 30 minutes, the above-mentioned No. 5 was used. In the same manner as in the evaluation 1 lithium ion secondary battery, graphite azide was produced.
Except for using this azide graphite, the above No. 1 was used. No. 1 in the same manner as the evaluation lithium ion secondary battery. 2 lithium ion secondary batteries for evaluation were produced.

<評価用リチウムイオン二次電池No.3の作製>
アジ化黒鉛を作製する際のプラズマ処理時間を1時間に変更した以外は、上記No.1の評価用リチウムイオン二次電池と同様にして、アジ化黒鉛を作製した。
このアジ化黒鉛を用いた以外は、上記No.1の評価用リチウムイオン二次電池と同様にして、No.3の評価用リチウムイオン二次電池を作製した。
<Evaluation lithium ion secondary battery No. 3 production>
Except for changing the plasma treatment time for producing azide graphite to 1 hour, the above-mentioned No. 1 was obtained. In the same manner as in the evaluation 1 lithium ion secondary battery, graphite azide was produced.
Except for using this azide graphite, the above No. 1 was used. No. 1 in the same manner as the evaluation lithium ion secondary battery. 3 evaluation lithium ion secondary batteries were produced.

<評価用リチウムイオン二次電池No.4の作製>
黒鉛をアジ化せずに、そのまま用いた以外は、上記No.1の評価用リチウムイオン二次電池と同様にして、No.4の評価用リチウムイオン二次電池を作製した。
<Evaluation lithium ion secondary battery No. 4 production>
Except that graphite was used as it was without being azide, the above No. 1 No. 1 in the same manner as the evaluation lithium ion secondary battery. No. 4 lithium ion secondary battery for evaluation was produced.

<IV抵抗評価>
各電池に対し、初期充電を施した。その後各電池を、25℃の温度下でSOC60%(State of Charge)の状態に調整し、1C,3C,5C,10Cの各レートでCC放電を行い、それぞれ放電開始から10秒間の電圧降下量を測定した。測定された電圧降下の値(V)を対応する電流値で除してIV抵抗を算出し、その平均値を求めた。その結果を図4に示す。
<IV resistance evaluation>
Each battery was initially charged. After that, each battery was adjusted to a state of SOC 60% (State of Charge) at a temperature of 25 ° C., and CC discharge was performed at each rate of 1C, 3C, 5C, and 10C. Was measured. The IV resistance was calculated by dividing the measured voltage drop value (V) by the corresponding current value, and the average value was obtained. The result is shown in FIG.

図4において、アジ化黒鉛を用いたNo.1〜No.3のリチウムイオン二次電池と、アジ化されていない黒鉛を用いたNo.4のリチウムイオン二次電池との比較より、アジ化黒鉛を用いることにより、電池抵抗が低減できることがわかる。また、No.1〜No.3のリチウムイオン二次電池の間の比較より、プラズマ処理の時間が長いほど、すなわち、黒鉛表面に導入されるアジ基の量が多いほど、電池抵抗の低減効果が高いが、本実施例の条件では、プラズマ処理時間が30分程度であれば、黒鉛の表面に十分な量のアジ基を導入できることがわかる。   In FIG. 4, No. using graphite azide. 1-No. No. 3 using a lithium ion secondary battery of No. 3 and graphite not azide. From comparison with the lithium ion secondary battery of No. 4, it can be seen that battery resistance can be reduced by using graphite azide. No. 1-No. 3 shows that the longer the plasma treatment time, that is, the greater the amount of azide groups introduced into the graphite surface, the higher the battery resistance reduction effect. Under the conditions, it can be seen that if the plasma treatment time is about 30 minutes, a sufficient amount of azide groups can be introduced into the surface of the graphite.

以上、本発明の具体例を詳細に説明したが、これらは例示にすぎず、請求の範囲を限定するものではない。請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。   As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

20 捲回電極体
30 電池ケース
36 安全弁
42 正極端子
42a 正極集電板
44 負極端子
44a 負極集電板
50 正極シート(正極)
52 正極集電体
52a 正極活物質層非形成部分
54 正極活物質層
60 負極シート(負極)
62 負極集電体
62a 負極活物質層非形成部分
64 負極活物質層
70 セパレータシート(セパレータ)
80 黒鉛粒子
100 リチウムイオン二次電池
20 wound electrode body 30 battery case 36 safety valve 42 positive electrode terminal 42a positive electrode current collector plate 44 negative electrode terminal 44a negative electrode current collector plate 50 positive electrode sheet (positive electrode)
52 Positive Current Collector 52a Positive Electrode Active Material Layer Non-Forming Portion 54 Positive Electrode Active Material Layer 60 Negative Electrode Sheet (Negative Electrode)
62 Negative electrode current collector 62a Negative electrode active material layer non-formed portion 64 Negative electrode active material layer 70 Separator sheet (separator)
80 Graphite particles 100 Lithium ion secondary battery

Claims (1)

正極と、負極とを備えるリチウムイオン二次電池であって、
前記負極は、負極活物質を含有する負極活物質層を備え、
前記負極活物質は、表面にアジ基を有する黒鉛を含有する、
リチウムイオン二次電池。
A lithium ion secondary battery comprising a positive electrode and a negative electrode,
The negative electrode includes a negative electrode active material layer containing a negative electrode active material,
The negative electrode active material contains graphite having an azide group on the surface,
Lithium ion secondary battery.
JP2016205309A 2016-10-19 2016-10-19 Lithium ion secondary battery Pending JP2018067455A (en)

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Citations (6)

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JP2014120287A (en) * 2012-12-14 2014-06-30 Showa Denko Kk Negative electrode material for lithium battery, method for producing the same, electrode and battery
JP2014139942A (en) * 2007-10-17 2014-07-31 Hitachi Chemical Co Ltd Carbon-coated graphite negative electrode material for lithium ion secondary battery, method for manufacturing the same, negative electrode for lithium ion secondary battery using the negative electrode material, and lithium ion secondary battery
JP2014157659A (en) * 2012-02-14 2014-08-28 Mitsubishi Chemicals Corp Active material for nonaqueous secondary battery negative electrode, negative electrode for nonaqueous secondary battery, and nonaqueous secondary battery
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JP2014139942A (en) * 2007-10-17 2014-07-31 Hitachi Chemical Co Ltd Carbon-coated graphite negative electrode material for lithium ion secondary battery, method for manufacturing the same, negative electrode for lithium ion secondary battery using the negative electrode material, and lithium ion secondary battery
JP2010118243A (en) * 2008-11-12 2010-05-27 Kansai Coke & Chem Co Ltd Anode material for lithium-ion secondary battery and method of manufacturing the same, and lithium-ion secondary battery using this anode material
JP2014157659A (en) * 2012-02-14 2014-08-28 Mitsubishi Chemicals Corp Active material for nonaqueous secondary battery negative electrode, negative electrode for nonaqueous secondary battery, and nonaqueous secondary battery
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