JP2007294198A - Lithium secondary battery and its manufacturing method - Google Patents

Lithium secondary battery and its manufacturing method Download PDF

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JP2007294198A
JP2007294198A JP2006119859A JP2006119859A JP2007294198A JP 2007294198 A JP2007294198 A JP 2007294198A JP 2006119859 A JP2006119859 A JP 2006119859A JP 2006119859 A JP2006119859 A JP 2006119859A JP 2007294198 A JP2007294198 A JP 2007294198A
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electrode
secondary battery
lithium secondary
pressure
separator
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Hideki Nakayama
英樹 中山
Yasuharu Onuma
康晴 大沼
Toshiya Nakamura
俊也 中村
Takashi Yabutani
剛史 薮谷
Hidekazu Yamanakajima
秀和 山中嶋
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Toyota Motor Corp
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    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL 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
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    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery excellent in characteristics, such as capacity, output, and resistance. <P>SOLUTION: In the lithium secondary battery having an electrode body formed by laminating a positive electrode and a negative electrode through a separator, pressure applied to the electrode body is a value or more, by which a noncontact area ratio between the electrode and the separator becomes 5% or less, and a value or less, by which a volume ratio of electrode breakage becomes 0.5% or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、容量、出力、抵抗等の特性に優れたリチウム二次電池に関するものである。   The present invention relates to a lithium secondary battery excellent in characteristics such as capacity, output, and resistance.

パソコン、ビデオカメラ、携帯電話等の小型化に伴い、情報関連機器、通信機器の分野では、これらの機器に用いる電源として、高エネルギー密度であるという理由から、リチウム二次電池が実用化され広く普及するに至っている。また一方で、自動車の分野においても、環境問題、資源問題から電気自動車の開発が急がれており、この電気自動車用の電源としても、リチウム二次電池が検討されている。   With the miniaturization of personal computers, video cameras, mobile phones, etc., in the fields of information-related equipment and communication equipment, lithium secondary batteries have been put into practical use because of their high energy density as the power source used for these equipment. It has become widespread. On the other hand, in the field of automobiles, the development of electric vehicles has been urgently caused by environmental problems and resource problems, and lithium secondary batteries have been studied as power sources for the electric vehicles.

容量、出力、抵抗等の特性に優れたリチウム二次電池を得るためには、正極と負極とをセパレータを介して積層した電極体に、適度な圧力（面圧）を加えることが重要となる。その理由は、後述するように、電極体に加える圧力が小さすぎると、正極および負極とセパレータとの間に空間が生じ、その空間により内部抵抗が増加する可能性があり、一方、電極体に加えられている圧力が大きすぎると、正極および負極に割れが生じる可能性があるからである。   In order to obtain a lithium secondary battery excellent in characteristics such as capacity, output, and resistance, it is important to apply an appropriate pressure (surface pressure) to an electrode body in which a positive electrode and a negative electrode are laminated via a separator. . The reason is that, as will be described later, if the pressure applied to the electrode body is too small, a space is created between the positive electrode and the negative electrode and the separator, and the internal resistance may increase due to the space. This is because if the applied pressure is too large, the positive electrode and the negative electrode may be cracked.

しかしながら、現在、電極体に加える圧力の決定方法は、経験則によるものが主流であり、明確な基準が存在しないというのが現状である。そのため、明確な基準（加圧管理範囲）を規定することが望まれている。   However, at present, the method of determining the pressure applied to the electrode body is mainly based on an empirical rule, and there is no clear standard at present. Therefore, it is desired to define a clear standard (pressurization control range).

また、本発明に直接関連する先行文献は、発見されていない。なお、特許文献１においては、電極体の形状による面圧の発生状況を捉え、電極体の形状係数（幅Ｈ、積層高さＴ、奥行Ｗ）を考慮した、角型二次電池の設計方法が開示されている。また、特許文献２においては、各二次電池に印加される面圧の均一化を目的とした、組電池が開示されている。
特開２００４−４７３３２公報 特開２００５−２５９５００公報 In addition, no prior literature directly related to the present invention has been found. In Patent Document 1, a method for designing a rectangular secondary battery that captures the state of occurrence of surface pressure due to the shape of the electrode body and considers the shape factor (width H, stacking height T, depth W) of the electrode body. Is disclosed. Patent Document 2 discloses an assembled battery for the purpose of equalizing the surface pressure applied to each secondary battery.
JP 2004-47332 A JP 2005-259500 A

本発明は、上記実情に鑑みてなされたものであり、容量、出力、抵抗等の特性に優れたリチウム二次電池を提供することを主目的とするものである。   The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a lithium secondary battery excellent in characteristics such as capacity, output, and resistance.

上記目的を達成するために、本発明においては、正極と負極とをセパレータを介して積層した電極体を有するリチウム二次電池であって、上記電極体に加えられている圧力が、電極−セパレータ非接触面積率が５％以下となる圧力以上、電極割れ体積率が０．５％以下となる圧力以下の範囲内の圧力であることを特徴とするリチウム二次電池を提供する。   In order to achieve the above object, in the present invention, a lithium secondary battery having an electrode body in which a positive electrode and a negative electrode are laminated via a separator, and the pressure applied to the electrode body is an electrode-separator. Provided is a lithium secondary battery characterized by having a pressure in a range of not less than a pressure at which a non-contact area ratio is 5% or less and not more than a pressure at which an electrode crack volume ratio is 0.5% or less.

本発明によれば、上記電極体が、最適な圧力（面圧）で加圧されていることから、容量、出力、抵抗等の特性に優れたリチウム二次電池とすることができる。   According to this invention, since the said electrode body is pressurized by the optimal pressure (surface pressure), it can be set as the lithium secondary battery excellent in characteristics, such as a capacity | capacitance, an output, and resistance.

また、上記発明においては、上記リチウム二次電池が、コイン型リチウム二次電池またはラミネート型リチウム二次電池であることが好ましい。汎用性に優れ、小型であっても大電流を取り出すことが可能なリチウム二次電池を得ることができるからである。   Moreover, in the said invention, it is preferable that the said lithium secondary battery is a coin-type lithium secondary battery or a laminate-type lithium secondary battery. This is because it is possible to obtain a lithium secondary battery that is excellent in versatility and that can extract a large current even if it is small.

また、本発明おいては、正極と負極とをセパレータを介して積層した電極体を加圧する加圧工程を有するリチウム二次電池の製造方法であって、上記加圧工程の際に、上記電極体に加えられる圧力が、電極−セパレータ非接触面積率が５％以下となる圧力以上、電極割れ体積率が０．５％以下となる圧力以下の範囲内の圧力であることを特徴とするリチウム二次電池の製造方法を提供する。   Further, in the present invention, there is provided a method for producing a lithium secondary battery having a pressurizing step of pressurizing an electrode body in which a positive electrode and a negative electrode are laminated via a separator, and the electrode is formed during the pressurizing step. Lithium characterized in that the pressure applied to the body is a pressure within a range of not less than the pressure at which the electrode-separator non-contact area ratio is 5% or less and not more than the pressure at which the electrode crack volume ratio is 0.5% or less. A method for manufacturing a secondary battery is provided.

本発明によれば、上記電極体を、最適な圧力（面圧）で加圧することにより、容量、出力、抵抗等の特性に優れたリチウム二次電池を得ることができる。   According to the present invention, a lithium secondary battery excellent in characteristics such as capacity, output, and resistance can be obtained by pressurizing the electrode body at an optimum pressure (surface pressure).

本発明においては、容量、出力、抵抗等の特性に優れたリチウム二次電池を提供することができるという効果を奏する。特に、小型であっても大電流を取り出すことが可能なリチウム二次電池を提供することができる。   In this invention, there exists an effect that the lithium secondary battery excellent in characteristics, such as a capacity | capacitance, an output, and resistance, can be provided. In particular, it is possible to provide a lithium secondary battery that can extract a large current even if it is small.

以下、本発明のリチウム二次電池およびその製造方法について説明する。   Hereinafter, the lithium secondary battery of the present invention and the manufacturing method thereof will be described.

Ａ．リチウム二次電池
まず、本発明のリチウム二次電池について説明する。本発明のリチウム二次電池は、正極と負極とをセパレータを介して積層した電極体を有するリチウム二次電池であって、上記電極体に加えられている圧力が、電極−セパレータ非接触面積率が５％以下となる圧力以上、電極割れ体積率が０．５％以下となる圧力以下の範囲内の圧力であることを特徴とするものである。 A. First, the lithium secondary battery of the present invention will be described. The lithium secondary battery of the present invention is a lithium secondary battery having an electrode body in which a positive electrode and a negative electrode are laminated via a separator, and the pressure applied to the electrode body is an electrode-separator non-contact area ratio. Is a pressure within a range of not less than 5% or less and not more than a pressure of electrode cracking volume ratio of 0.5% or less.

本発明によれば、上記電極体が、最適な圧力（面圧）で加圧されていることから、容量、出力、抵抗等の特性に優れたリチウム二次電池とすることができる。具体的には、上記電極体に加えられている圧力の範囲の上限および下限を、後述する電極−セパレータ非接触面積率および体積割れ体積率からそれぞれ規定することにより、容量等の特性に優れたリチウム二次電池とすることができるのである。特に、本発明においては、上記電極体に対して最適な圧力を加えることにより、小型であっても、大電流を得ることができるリチウム二次電池とすることができるという利点を有する。   According to this invention, since the said electrode body is pressurized by the optimal pressure (surface pressure), it can be set as the lithium secondary battery excellent in characteristics, such as a capacity | capacitance, an output, and resistance. Specifically, by defining the upper and lower limits of the pressure range applied to the electrode body from the electrode-separator non-contact area ratio and volume crack volume ratio, which will be described later, the characteristics such as capacity were excellent. It can be a lithium secondary battery. In particular, the present invention has an advantage that by applying an optimum pressure to the electrode body, a lithium secondary battery capable of obtaining a large current can be obtained even if it is small.

次に、本発明のリチウム二次電池について図面を用いて説明する。図１は、本発明のリチウム二次電池を説明する説明図である。図１に示すように、本発明のリチウム二次電池は、負極集電体１および負極層２からなる負極３と、正極層４および正極集電体５からなる正極６とをセパレータ７を介して積層した電極体８を有するリチウム二次電池であって、電極体８に加えられている圧力９が、特定の範囲内の圧力であることを特徴とするものである。
以下、本発明のリチウム二次電池について、構成ごとに説明する。 Next, the lithium secondary battery of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view illustrating a lithium secondary battery according to the present invention. As shown in FIG. 1, the lithium secondary battery of the present invention has a negative electrode 3 composed of a negative electrode current collector 1 and a negative electrode layer 2 and a positive electrode 6 composed of a positive electrode layer 4 and a positive electrode current collector 5 with a separator 7 interposed therebetween. A lithium secondary battery having a stacked electrode body 8 is characterized in that the pressure 9 applied to the electrode body 8 is a pressure within a specific range.
Hereinafter, the lithium secondary battery of this invention is demonstrated for every structure.

１．電極体
まず、本発明に用いられる電極体について説明する。本発明に用いられる電極体は、正極と負極とをセパレータを介して積層したものである。さらに、本発明においては、上記電極体に、特定の範囲内の圧力（面圧）が加えられている。本発明において、上記圧力範囲の下限は後述する「電極−セパレータ非接触面積率」により規定され、上記圧力範囲の上限は後述する「電極割れ体積率」により規定される。 1. Electrode Body First, the electrode body used in the present invention will be described. The electrode body used in the present invention is obtained by laminating a positive electrode and a negative electrode with a separator interposed therebetween. Furthermore, in the present invention, a pressure (surface pressure) within a specific range is applied to the electrode body. In the present invention, the lower limit of the pressure range is defined by “electrode-separator non-contact area ratio” described later, and the upper limit of the pressure range is defined by “electrode crack volume ratio” described later.

ここで、上記圧力範囲の決定方法について、図面を用いて説明する。図２は、面圧（Ｎ／ｍｍ２）と、電極−セパレータ非接触面積率（％）および電極割れ体積率（％）との関係を示すグラフである。なお、このグラフは後述する測定試験を行うことにより得られるものである。図２に示されるように、本発明においては、電極−セパレータ非接触面積（％）が所定の値（Ｘ）以下となる面圧（Ｘ´）を下限とし、一方、電極割れ体積率が所定の値（Ｙ）以下となる面圧（Ｙ´）を上限とし、その下限および上限から、上記圧力範囲を決定する。 Here, the determination method of the said pressure range is demonstrated using drawing. FIG. 2 is a graph showing the relationship between the surface pressure (N / mm 2 ), the electrode-separator non-contact area ratio (%), and the electrode crack volume ratio (%). This graph is obtained by conducting a measurement test described later. As shown in FIG. 2, in the present invention, the lower limit is the surface pressure (X ′) at which the electrode-separator non-contact area (%) is not more than a predetermined value (X), while the electrode crack volume ratio is predetermined. The surface pressure (Y ′) that is equal to or lower than the value (Y) is set as the upper limit, and the pressure range is determined from the lower limit and the upper limit.

本発明において、上記電極体に加えられる圧力の下限は、通常、電極−セパレータ非接触面積率が５％以下となる圧力以上であり、１％以下となる圧力以上であることが好ましく、０．１％以下となる圧力以上であることがより好ましい。一方、上記電極体に加えられる圧力の上限は、通常、体積割れ体積率が０．５％以下となる圧力以下であり、中でも０．３％以下となる圧力以下であることが好ましく、特に０．１％以下となる圧力以下であることがより好ましい。   In the present invention, the lower limit of the pressure applied to the electrode body is usually not less than the pressure at which the electrode-separator non-contact area ratio is 5% or less, preferably 1% or less. The pressure is more preferably 1% or less. On the other hand, the upper limit of the pressure applied to the electrode body is usually not more than the pressure at which the volumetric cracking volume ratio is 0.5% or less, preferably not more than 0.3% or less, particularly preferably 0 or less. More preferably, the pressure is 1% or less.

本発明において、電極−セパレータ非接触面積率（％）は、以下のように定義する。
電極−セパレータ非接触面積率（％）＝（電極−セパレータ非接触面積）／（電極面積）×１００ In the present invention, the electrode-separator non-contact area ratio (%) is defined as follows.
Electrode-separator non-contact area ratio (%) = (electrode-separator non-contact area) / (electrode area) × 100

電極−セパレータ非接触面積率は、上記の式から明らかなように、電極とセパレータとが接触していない面積の割合を示すものである。上述した図２に示したように、電極体に加えられる面圧が大きくなるほど、電極体はより密着した状態となり、電極−セパレータ非接触面積率は小さくなる。ここで、電極体に加えられる圧力が小さすぎる場合は、正極および負極とセパレータとの間に空間が生じ、その空間が内部抵抗増大の原因となる。本発明においては、電極−セパレータ非接触面積率を指標とし、その指標から電極体に加えられる圧力の下限を設定することにより、正極および負極とセパレータとの間に生じる空間に起因する内部抵抗増大を抑制することができ、容量、出力、抵抗等の特性に優れたリチウム二次電池を得ることができるのである。   The electrode-separator non-contact area ratio indicates the ratio of the area where the electrode and the separator are not in contact, as is apparent from the above formula. As shown in FIG. 2 described above, the greater the surface pressure applied to the electrode body, the closer the electrode body is, and the smaller the electrode-separator non-contact area ratio. Here, when the pressure applied to the electrode body is too small, a space is generated between the positive electrode, the negative electrode, and the separator, and this space causes an increase in internal resistance. In the present invention, the electrode-separator non-contact area ratio is used as an index, and the lower limit of the pressure applied to the electrode body is set from the index, thereby increasing the internal resistance due to the space generated between the positive electrode and the negative electrode and the separator. Therefore, it is possible to obtain a lithium secondary battery excellent in characteristics such as capacity, output, and resistance.

また、本発明において、電極−セパレータ非接触面積率（％）は、以下の測定試験により求める。すなわち、電極体に所定の圧力（面圧）を加えてなるリチウム二次電池（試験片）を作製し、そのリチウム二次電池に穴をあけて樹脂を注入し、固化して電池断面を切り出す。その後、電池断面を走査型電子顕微鏡（ＳＥＭ）にて観察し、正極および負極とセパレータとが密着してない部分を求める。さらに、電池断面を切り進め、電極とセパレータが密着していない部分の割合を測定し、電極面積全体に対する電極−セパレータ非接触面積を算出する。なお、リチウム二次電池に組付けずに、正極および負極とセパレータとの間に感圧紙を積層させた状態で、荷重をかけて感圧紙の荷重分布から非接触面積率を求めても良い。電極体に加える圧力（面圧）の大きさを変化させた複数のリチウム二次電池（試験片）を用いて同様の測定試験を行うことにより、図２に示すような電極−セパレータ非接触面積率の曲線が得られる。   In the present invention, the electrode-separator non-contact area ratio (%) is determined by the following measurement test. That is, a lithium secondary battery (test piece) is produced by applying a predetermined pressure (surface pressure) to the electrode body, a hole is made in the lithium secondary battery, a resin is injected, solidified, and a battery cross section is cut out. . Thereafter, the cross section of the battery is observed with a scanning electron microscope (SEM), and a portion where the positive electrode, the negative electrode, and the separator are not in close contact is obtained. Furthermore, the battery cross section is cut forward, the ratio of the portion where the electrode and the separator are not in close contact is measured, and the electrode-separator non-contact area relative to the entire electrode area is calculated. Note that the non-contact area ratio may be obtained from the load distribution of the pressure sensitive paper by applying a load in a state where the pressure sensitive paper is laminated between the positive electrode and the negative electrode and the separator without being assembled in the lithium secondary battery. The electrode-separator non-contact area as shown in FIG. 2 is obtained by performing the same measurement test using a plurality of lithium secondary batteries (test pieces) in which the pressure (surface pressure) applied to the electrode body is changed. A rate curve is obtained.

一方、本発明において電極割れ体積率（％）は、以下のように定義する。
電極割れ体積率（％）＝（電極内部割れ体積）／（電極体積）×１００ On the other hand, in the present invention, the electrode crack volume ratio (%) is defined as follows.
Electrode crack volume ratio (%) = (electrode internal crack volume) / (electrode volume) × 100

電極割れ体積率は、上記の式から明らかなように、電極内部に生じた割れの体積の割合を示すものである。上述した図２に示したように、電極体に加えられる面圧が大きくなるほど、電極体が過度に加圧された状態となり、電極割れ体積率は大きくなる。ここで、電極体に加えられる圧力が大きすぎる場合は、電極内部に多くの割れが生じ、リチウム二次電池の性能低下の原因となる。本発明においては、電極割れ体積率を指標とし、その指標から電極体に加えられる圧力の上限を設定することにより、電極割れによる性能低下を抑制することができ、容量、出力、抵抗等の特性に優れたリチウム二次電池を得ることができるのである。   The electrode crack volume ratio indicates the ratio of the volume of cracks generated inside the electrode, as is apparent from the above formula. As shown in FIG. 2 described above, as the surface pressure applied to the electrode body increases, the electrode body is excessively pressurized and the electrode crack volume ratio increases. Here, when the pressure applied to the electrode body is too large, many cracks are generated inside the electrode, which causes a decrease in performance of the lithium secondary battery. In the present invention, by setting the electrode crack volume ratio as an index, and setting the upper limit of the pressure applied to the electrode body from the index, performance degradation due to electrode cracking can be suppressed, and characteristics such as capacity, output, resistance, etc. Therefore, it is possible to obtain a lithium secondary battery excellent in the above.

また、本発明において、電極割れ体積率（％）は、以下の測定試験により求める。すなわち、リチウム二次電池に組付ける前の、正極および負極の細孔容積をＳＥＭ観察等により測定し、次に、リチウム二次電池を組付けた後の、正極および負極の細孔容積を同様に測定し、その後、組付け前後の細孔容積変化の差分から電極内部割れ体積を算出する。また、正極および負極の寸法から、正極および負極の体積（電極体積）を求める。なお、リチウム二次電池を組付けずに、正極および負極とセパレータとを積層させた状態で荷重をかけて、同様に細孔容積変化を測定し、電極割れ体積率を求めても良い。電極体に加える圧力（面圧）の大きさを変化させた複数のリチウム二次電池（試験片）を用いて同様の測定試験を行うことにより、図２に示すような電極割れ体積率の曲線が得られる。   In the present invention, the electrode crack volume ratio (%) is determined by the following measurement test. That is, the pore volume of the positive electrode and the negative electrode before being assembled to the lithium secondary battery is measured by SEM observation or the like, and then the pore volume of the positive electrode and the negative electrode after the lithium secondary battery is assembled is the same. After that, the electrode internal crack volume is calculated from the difference in pore volume change before and after assembly. Moreover, the volume (electrode volume) of a positive electrode and a negative electrode is calculated | required from the dimension of a positive electrode and a negative electrode. In addition, without assembling the lithium secondary battery, a load may be applied in a state where the positive electrode, the negative electrode, and the separator are stacked, and the pore volume change may be similarly measured to obtain the electrode crack volume ratio. By performing a similar measurement test using a plurality of lithium secondary batteries (test pieces) in which the pressure (surface pressure) applied to the electrode body is changed, a curve of the electrode crack volume ratio as shown in FIG. Is obtained.

また、上述した電極−セパレータ非接触面積率および電極割れ体積率から規定される、上記電極体に加えられる圧力の範囲としては、正極および負極の材料、厚み等により異なるものであるが、具体的には、０．０２Ｎ／ｍｍ２〜０．０４Ｎ／ｍｍ２程度である。 In addition, the range of pressure applied to the electrode body defined by the electrode-separator non-contact area ratio and the electrode crack volume ratio described above varies depending on the materials and thicknesses of the positive electrode and the negative electrode. in is a 0.02N / mm 2 ~0.04N / mm 2 about.

上記電極体の形状としては、電極体を上述した加圧範囲で加圧できるものであれば特に限定されるものではないが、例えば、平面構造および倦回構造等を挙げることができ、中でも平面構造が好ましい。小型のリチウム二次電池を得ることができるからである。また、本発明のリチウム二次電池は、上記平面構造の電極体を複数積層したものを有していても良い。   The shape of the electrode body is not particularly limited as long as the electrode body can be pressurized in the above-described pressurizing range, and examples thereof include a planar structure and a wound structure. A structure is preferred. This is because a small lithium secondary battery can be obtained. In addition, the lithium secondary battery of the present invention may have a stack of a plurality of electrode bodies having the above planar structure.

また、実際に得られたリチウム二次電池の電極体に加えられている圧力は、リチウム二次電池の寸法、電極体の厚さ、セパレータの厚さ、ウェーブワッシャのバネ定数、およびスペーサの厚さから測定することができる。   In addition, the pressure applied to the electrode body of the lithium secondary battery actually obtained depends on the dimensions of the lithium secondary battery, the thickness of the electrode body, the thickness of the separator, the spring constant of the wave washer, and the thickness of the spacer. It can be measured from this.

本発明に用いられる正極、負極およびセパレータについては、一般的なリチウム二次電池に用いられる部材と同様のものを用いることができ、特に限定されるものではない。
上記正極は、通常、正極活物質を含有する正極層と、正極集電体とを有する。上記正極活物質としては、例えばＬｉＭｎ２Ｏ４、ＬｉＣｏＯ４、ＬｉＮｉＯ２およびＬｉＦｅＰＯ４等を挙げることができる。また、上記正極集電体としては、例えばアルミニウム、ステンレス等の金属を板状に加工した箔等を挙げることができる。 About the positive electrode used for this invention, a negative electrode, and a separator, the thing similar to the member used for a general lithium secondary battery can be used, and it does not specifically limit.
The positive electrode usually has a positive electrode layer containing a positive electrode active material and a positive electrode current collector. Examples of the positive electrode active material include LiMn 2 O 4 , LiCoO 4 , LiNiO 2, and LiFePO 4 . Examples of the positive electrode current collector include foil obtained by processing a metal such as aluminum or stainless steel into a plate shape.

上記負極は、通常、負極活物質を含有する負極層と、負極集電体とを有する。上記負極活物質としては、例えば、結晶性の高い天然黒鉛や人造黒鉛等の炭素粒子、スズ化合物等の金属粒子、および導電性ポリマー等を挙げることができる。また、上記負極集電体としては、例えば銅、ニッケル等の金属を板状に加工した箔等を挙げることができる。   The negative electrode usually has a negative electrode layer containing a negative electrode active material and a negative electrode current collector. Examples of the negative electrode active material include carbon particles such as highly crystalline natural graphite and artificial graphite, metal particles such as a tin compound, and a conductive polymer. Examples of the negative electrode current collector include a foil obtained by processing a metal such as copper or nickel into a plate shape.

また、本発明においては、加圧による電極割れを防止するために、正極および負極の少なくとも一方が、圧力分散材を含有することが好ましい。上記圧力分散材としては、例えば、ポリアセチレン、ポリチオフェン等の導電性高分子等を挙げることができる。   In the present invention, it is preferable that at least one of the positive electrode and the negative electrode contains a pressure dispersion material in order to prevent electrode cracking due to pressurization. Examples of the pressure dispersion material include conductive polymers such as polyacetylene and polythiophene.

また、上記セパレータとしては、正極と負極とを分離し、電解液を保持する機能を有するものであれば特に限定されるものではないが、例えばポリエチレン、ポリプロピレン等の多孔膜等を挙げることができる。   The separator is not particularly limited as long as it has a function of separating the positive electrode and the negative electrode and retaining the electrolytic solution, and examples thereof include porous films such as polyethylene and polypropylene. .

２．その他の部材
本発明のリチウム二次電池は、上述した電極体の他に、通常、電解液、電池ケース、スペーサおよびウェーブワッシャ等を有する。これらの部材については、一般的なリチウム二次電池に用いられる部材と同様のものを用いることができ、特に限定されるものではない。 2. Other Members The lithium secondary battery of the present invention usually has an electrolytic solution, a battery case, a spacer, a wave washer and the like in addition to the electrode body described above. About these members, the thing similar to the member used for a general lithium secondary battery can be used, and it does not specifically limit.

上記電解液は、通常、電解質を有機溶媒に溶解してなるものである。上記電解質としては、例えば、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４およびＬｉＡｓＦ６等の無機リチウム塩；およびＬｉＣＦ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、等の有機リチウム塩等を挙げることができる。また、上記有機溶媒としては、例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、γ−ブチロラクトン、スルホラン、アセトニトリル、１，２−ジメトキシメタン、１，３−ジメトキシプロパン、ジエチルエーテル、テトラヒドロフラン、２−メチルテトラヒドロフラン、炭酸ジメチル、炭酸ジエチル、ジメチルカーボネートおよびエチルメチルカーボネート等を挙げることができる。 The electrolytic solution is usually obtained by dissolving an electrolyte in an organic solvent. Examples of the electrolyte include inorganic lithium salts such as LiPF 6 , LiBF 4 , LiClO 4, and LiAsF 6 ; and LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , and the like. Organic lithium salts and the like can be mentioned. Examples of the organic solvent include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, sulfolane, acetonitrile, 1,2-dimethoxymethane, 1,3-dimethoxypropane, diethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran. Dimethyl carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and the like.

３．リチウム二次電池
本発明のリチウム二次電池は、上述した電極体を有するものであれば、その形状は特に限定されるものではない。中でも、本発明のリチウム二次電池は、コイン型リチウム二次電池またはラミネート型リチウム二次電池であることが好ましい。汎用性に優れ、小型であっても大電流を取り出すことが可能なリチウム二次電池を得ることができるからである。 3. Lithium Secondary Battery The shape of the lithium secondary battery of the present invention is not particularly limited as long as it has the electrode body described above. Among these, the lithium secondary battery of the present invention is preferably a coin-type lithium secondary battery or a laminate-type lithium secondary battery. This is because it is possible to obtain a lithium secondary battery that is excellent in versatility and that can extract a large current even if it is small.

Ｂ．リチウム二次電池の製造方法
次に、本発明のリチウム二次電池の製造方法について説明する。本発明のリチウム二次電池の製造方法は、正極と負極とをセパレータを介して積層した電極体を加圧する加圧工程を有するリチウム二次電池の製造方法であって、上記加圧工程の際に、上記電極体に加えられる圧力が、電極−セパレータ非接触面積率が５％以下となる圧力以上、電極割れ体積率が０．５％以下となる圧力以下の範囲内の圧力であることを特徴とするものである。 B. Next, a method for producing a lithium secondary battery according to the present invention will be described. The method for producing a lithium secondary battery of the present invention is a method for producing a lithium secondary battery having a pressurizing step of pressurizing an electrode body in which a positive electrode and a negative electrode are laminated via a separator. In addition, the pressure applied to the electrode body is a pressure within a range not less than the pressure at which the electrode-separator non-contact area ratio is 5% or less and the pressure at which the electrode crack volume ratio is 0.5% or less. It is a feature.

本発明によれば、上記電極体を、最適な圧力（面圧）で加圧することにより、容量、出力、抵抗等の特性に優れたリチウム二次電池を得ることができる。具体的には、電極体に対して最適な圧力を加えることにより、加圧不足に起因する、電極とセパレータとの間に生じる空間による内部抵抗の増加を抑制でき、かつ、加圧過剰に起因する電極割れを防止することができる。
以下、本発明のリチウム二次電池の製造方法について、工程ごとに説明する。 According to the present invention, a lithium secondary battery excellent in characteristics such as capacity, output, and resistance can be obtained by pressurizing the electrode body at an optimum pressure (surface pressure). Specifically, by applying an optimum pressure to the electrode body, it is possible to suppress an increase in internal resistance due to a space between the electrode and the separator caused by insufficient pressurization, and due to excessive pressurization. Electrode cracking can be prevented.
Hereinafter, the manufacturing method of the lithium secondary battery of this invention is demonstrated for every process.

１．加圧工程
まず、本発明における加圧工程について説明する。本発明における加圧工程は、正極と負極とをセパレータを介して積層した電極体を加圧する工程である。さらに、本発明においては、加圧工程の際に、上記電極体に加えられる圧力が、上述した範囲内の圧力であることを特徴とする。なお、電極−セパレータ非接触面積率および電極割れ体積率の定義や好適な範囲等について、並びに、電極体に関する事項については、上記「Ａ．リチウム二次電池」に記載した内容と同様であるので、ここでの説明は省略する。 1. Pressurization Step First, the pressurization step in the present invention will be described. The pressurizing step in the present invention is a step of pressurizing an electrode body in which a positive electrode and a negative electrode are laminated via a separator. Furthermore, in the present invention, the pressure applied to the electrode body in the pressurizing step is a pressure within the above-described range. Note that the definition and preferred range of the electrode-separator non-contact area ratio and the electrode crack volume ratio, and the matters related to the electrode body are the same as the contents described in the above-mentioned “A. Lithium secondary battery”. Explanation here is omitted.

本発明における加圧工程は、通常、電池ケースの内部に電極体等を配置し、電解液等を添加した後に行われる。例えば、コイン型リチウム二次電池を作製する場合は、正極缶の内部に電極体、スペーサ、ウェーブワッシャ等を配置し、さらに、電解液を加えた後に負極缶を配置し、電極体の加圧を行う。また、ラミネート型リチウムのリチウム二次電池を作製する場合は、一方のラミネートフィルムの内部に、電極体等を配置し、さらに、電解液を加えた後に他方のラミネートフィルムを配置し、電極体の加圧を行う。また、加圧方法としては、一般的なリチウム二次電池と同様の方法を用いることができるので、ここでの説明は省略する。   The pressurizing step in the present invention is usually performed after an electrode body or the like is placed inside the battery case and an electrolytic solution or the like is added. For example, when producing a coin-type lithium secondary battery, an electrode body, a spacer, a wave washer, etc. are arranged inside the positive electrode can, and further, the negative electrode can is arranged after adding the electrolyte, and the electrode body is pressurized. I do. Further, when producing a lithium secondary battery of laminate type lithium, an electrode body or the like is disposed inside one laminate film, and the other laminate film is disposed after the addition of an electrolytic solution. Pressurize. Moreover, as a pressurization method, since the method similar to a general lithium secondary battery can be used, description here is abbreviate | omitted.

２．その他の工程
本発明のリチウム二次電池の製造方法は、上述した加圧工程の前に、正極を形成する正極形成工程や負極を形成する負極形成工程等を行っても良い。これらの工程については、一般的なリチウム二次電池の製造方法と同様であるので、ここでの説明は省略する。 2. Other Steps The method for producing a lithium secondary battery of the present invention may perform a positive electrode forming step for forming a positive electrode, a negative electrode forming step for forming a negative electrode, and the like before the pressurizing step described above. Since these steps are the same as those of a general method for manufacturing a lithium secondary battery, description thereof is omitted here.

なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は、例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。   The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

以下に実施例を示して本発明をさらに具体的に説明する。   Hereinafter, the present invention will be described in more detail with reference to examples.

［実施例］ [Example]

（正極の作製）
正極活物質としてリチウムニッケル酸化物、導電剤としてアセチレンブラック、結着剤としてポリテトラフルオロエチレンを用意し、正極活物質、導電剤および結着剤を重量比８５：１０：５で混合し、二軸撹拌機にて１時間撹拌した。このようにして得られたペーストをコータにて、正極集電体であるアルミ箔上に片面塗布した。次に、正極集電体であるアルミ箔上に目付量６．５１ｍｇ／ｃｍ２で片面塗布した。乾燥後、φ１６ｍｍに打抜き、その後、ロールプレス機に通し、線圧７４０ｋｇ／ｃｍの荷重をかけることにより、電極密度２．２０ｇ／ｃｍ３の正極を得た。 (Preparation of positive electrode)
Prepare lithium nickel oxide as the positive electrode active material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, and mix the positive electrode active material, the conductive agent and the binder in a weight ratio of 85: 10: 5. Stir for 1 hour with a shaft stirrer. The paste thus obtained was applied on one side by a coater onto an aluminum foil as a positive electrode current collector. Next, single-sided coating was applied at a basis weight of 6.51 mg / cm 2 on an aluminum foil as a positive electrode current collector. After drying, it was punched out to φ16 mm, then passed through a roll press machine, and a load with a linear pressure of 740 kg / cm 3 was applied to obtain a positive electrode with an electrode density of 2.20 g / cm 3 .

（負極の作製）
負極活物質として鱗片状グラファイト、結着剤としてポリテトラフルオロエチレンを用意し、正極活物質および導電剤を重量比９２．５：７．５で混合し、二軸撹拌機にて１時間撹拌した。このようにして得られたペーストをコータにて、負極集電体である銅箔上に目付量３．７４ｍｇ／ｃｍ２で片面塗布した。乾燥後、φ１９ｍｍに打抜き、その後、ロールプレス機に通し、線圧２５０ｋｇ／ｃｍの荷重をかけることにより、電極密度１．２５ｇ／ｃｍ３の負極を得た。 (Preparation of negative electrode)
Scalar graphite was prepared as the negative electrode active material, and polytetrafluoroethylene was prepared as the binder. The positive electrode active material and the conductive agent were mixed at a weight ratio of 92.5: 7.5, and the mixture was stirred for 1 hour with a biaxial stirrer. . The paste thus obtained was applied on one side with a coater onto a copper foil as a negative electrode current collector at a basis weight of 3.74 mg / cm 2 . After drying, it was punched out to φ19 mm, and then passed through a roll press machine, and a negative electrode with an electrode density of 1.25 g / cm 3 was obtained by applying a load of a linear pressure of 250 kg / cm 3 .

（試験片の作製）
電極−セパレータ非接触面積率および電極割れ体積率の測定を行うために、コイン型リチウム二次電池（試験片）を作製した。まず、正極缶に上述した正極を配置し、次に、電解液を含浸させたセパレータ（多孔性ポリエチレンフィルム）、負極、スペーサおよびウェーブワッシャを順に配置した。最後に、ウェーブワッシャの上から負極缶を被せ、加圧し封口することによって、コイン型リチウム二次電池（試験片）を得た。その後、スペーサの厚みを変えることにより、電極体に加えられる圧力を変化させたコイン型リチウム二次電池（試験片）を他に５個作製した。その後、上述した測定試験の方法に則り、電極−セパレータ非接触面積率および電極割れ体積率を測定した。得られた結果を図３に示す。この結果から、電極−セパレータ非接触面積率が５％以下となるのは、面圧０．０２Ｎ／ｍｍ２の時であった。同様に、電極割れ体積率が０．５％以下となるのは、面圧０．０４Ｎ／ｍｍ２の時であった。中でも、電極−セパレータ非接触面積率および電極割れ体積率が共に最小になるのは、面圧０．０３Ｎ／ｍｍ２の時であることが分かった。 (Preparation of test piece)
In order to measure the electrode-separator non-contact area ratio and the electrode crack volume ratio, a coin-type lithium secondary battery (test piece) was prepared. First, the positive electrode described above was placed in a positive electrode can, and then a separator (porous polyethylene film) impregnated with an electrolytic solution, a negative electrode, a spacer, and a wave washer were sequentially arranged. Finally, a negative electrode can was put on the wave washer, and the coin type lithium secondary battery (test piece) was obtained by pressurizing and sealing. Thereafter, five other coin-type lithium secondary batteries (test pieces) in which the pressure applied to the electrode body was changed by changing the thickness of the spacer were produced. Then, according to the measurement test method described above, the electrode-separator non-contact area ratio and the electrode crack volume ratio were measured. The obtained results are shown in FIG. From this result, the electrode-separator non-contact area ratio was 5% or less when the surface pressure was 0.02 N / mm 2 . Similarly, the electrode crack volume ratio was 0.5% or less when the surface pressure was 0.04 N / mm 2 . In particular, it was found that both the electrode-separator non-contact area ratio and the electrode crack volume ratio were minimized when the surface pressure was 0.03 N / mm 2 .

（評価）
上記のリチウム二次電池（試験片）について、電池容量および抵抗を測定した。電池容量は、上下限電圧を４．１Ｖ〜３．０Ｖとして、Ｃ／１０レートで３サイクル充放電を行い、３サイクル目の放電容量を評価した。抵抗は、充電状態を調整した電池にて充放電電流地をかえて電圧を測定することにより評価した。得られた結果を図４に示す。図４から明らかなように、電極−セパレータ非接触面積率および電極割れ体積率が共に最小になる、面圧０．０３Ｎ／ｍｍ２の時に、容量、出力、抵抗等の特性が最も優れたリチウム二次電池が得られた。 (Evaluation)
The battery capacity and resistance of the lithium secondary battery (test piece) were measured. As for the battery capacity, the upper and lower limit voltages were set to 4.1 V to 3.0 V, and charge / discharge was performed for 3 cycles at a C / 10 rate, and the discharge capacity at the third cycle was evaluated. The resistance was evaluated by measuring the voltage by changing the charging / discharging current location with a battery whose charge state was adjusted. The obtained results are shown in FIG. As is clear from FIG. 4, lithium having the most excellent characteristics such as capacity, output, resistance, etc. at a surface pressure of 0.03 N / mm 2 where the electrode-separator non-contact area ratio and electrode crack volume ratio are both minimized. A secondary battery was obtained.

本発明のリチウム二次電池を説明する説明図である。It is explanatory drawing explaining the lithium secondary battery of this invention. 面圧（Ｎ／ｍｍ２）と、電極−セパレータ非接触面積率（％）および電極割れ体積率（％）と、の関係を示すグラフである。It is a graph which shows the relationship between a surface pressure (N / mm < 2 >), an electrode-separator non-contact area ratio (%), and an electrode crack volume ratio (%). 実施例で得られたリチウム二次電池（試験片）の電極−セパレータ非接触面積率（％）および電極割れ体積率（％）を示すグラフである。It is a graph which shows the electrode-separator non-contact area ratio (%) and electrode crack volume ratio (%) of the lithium secondary battery (test piece) obtained in the Example. 実施例で得られたリチウム二次電池（試験片）の特性を示すグラフである。It is a graph which shows the characteristic of the lithium secondary battery (test piece) obtained in the Example.

符号の説明Explanation of symbols

１ … 負極集電体
２ … 負極層
３ … 負極
４ … 正極層
５ … 正極集電体
６ … 正極
７ … セパレータ
８ … 電極体
９ … 圧力 DESCRIPTION OF SYMBOLS 1 ... Negative electrode collector 2 ... Negative electrode layer 3 ... Negative electrode 4 ... Positive electrode layer 5 ... Positive electrode collector 6 ... Positive electrode 7 ... Separator 8 ... Electrode body 9 ... Pressure

Claims (3)

正極と負極とをセパレータを介して積層した電極体を有するリチウム二次電池であって、
前記電極体に加えられている圧力が、電極−セパレータ非接触面積率が５％以下となる圧力以上、電極割れ体積率が０．５％以下となる圧力以下の範囲内の圧力であることを特徴とするリチウム二次電池。 A lithium secondary battery having an electrode body in which a positive electrode and a negative electrode are laminated via a separator,
The pressure applied to the electrode body is not less than the pressure at which the electrode-separator non-contact area ratio is 5% or less and the pressure within the range of the pressure at which the electrode crack volume ratio is 0.5% or less. A featured lithium secondary battery. 前記リチウム二次電池が、コイン型リチウム二次電池またはラミネート型リチウム二次電池であることを特徴とする請求項１に記載のリチウム二次電池。   The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a coin-type lithium secondary battery or a laminate-type lithium secondary battery. 正極と負極とをセパレータを介して積層した電極体を加圧する加圧工程を有するリチウム二次電池の製造方法であって、
前記加圧工程の際に、前記電極体に加えられる圧力が、電極−セパレータ非接触面積率が５％以下となる圧力以上、電極割れ体積率が０．５％以下となる圧力以下の範囲内の圧力であることを特徴とするリチウム二次電池の製造方法。 A method for producing a lithium secondary battery comprising a pressurizing step of pressurizing an electrode body in which a positive electrode and a negative electrode are laminated via a separator,
The pressure applied to the electrode body during the pressurizing step is in a range of not less than the pressure at which the electrode-separator non-contact area ratio is 5% or less and not more than the pressure at which the electrode crack volume ratio is 0.5% or less. A method for producing a lithium secondary battery, wherein the pressure is
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010032492A (en) * 2008-07-02 2010-02-12 Toyota Motor Corp Pressure measuring device and thickness measuring device
JP2014120372A (en) * 2012-12-18 2014-06-30 Toyota Motor Corp All solid state battery and process of manufacturing the same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010032492A (en) * 2008-07-02 2010-02-12 Toyota Motor Corp Pressure measuring device and thickness measuring device
JP2014120372A (en) * 2012-12-18 2014-06-30 Toyota Motor Corp All solid state battery and process of manufacturing the same

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