JP2020013754A - Lithium ion battery - Google Patents

Lithium ion battery Download PDF

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JP2020013754A
JP2020013754A JP2018136874A JP2018136874A JP2020013754A JP 2020013754 A JP2020013754 A JP 2020013754A JP 2018136874 A JP2018136874 A JP 2018136874A JP 2018136874 A JP2018136874 A JP 2018136874A JP 2020013754 A JP2020013754 A JP 2020013754A
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active material
negative electrode
material layer
electrode active
lithium ion
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JP7145672B2 (en
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勇輔 中嶋
Yusuke Nakajima
勇輔 中嶋
大澤　康彦
Yasuhiko Osawa
康彦 大澤
雄樹 草地
Takeki Kusachi
雄樹 草地
佐藤　一
Hajime Sato
一 佐藤
赤間　弘
Hiroshi Akama
弘 赤間
堀江　英明
Hideaki Horie
英明 堀江
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Nissan Motor Co Ltd
Sanyo Chemical Industries Ltd
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Sanyo Chemical Industries Ltd
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Abstract

To provide an excellent endurance lithium ion battery capable of restraining deterioration of battery performance with no impact on a charge/discharge capacity per battery, even upon occurrence of a temporary micro short circuit in the lithium ion battery, without containing a gas generating agent.SOLUTION: In a lithium ion battery including at least a collector, a negative electrode active material layer, and a separator in this order, the negative electrode active material layer includes at least a first negative electrode active material layer, and a second negative electrode active material layer, the second negative electrode active material layer has a thickness of 1.5-50 μm, an amount of a silicon-based active material contained in the second negative electrode active material layer is 0.1-5 mg/cm, and a weight ratio of the silicon-based active material contained in the second negative electrode active material layer to a weight of the second negative electrode active material layer is larger than a weight ratio of the silicon-based active material contained in the first negative electrode active material layer to the first negative electrode active material layer.SELECTED DRAWING: None

Description

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

近年、環境保護のため、二酸化炭素排出量の低減が切に望まれている。自動車業界では、電気自動車（ＥＶ）やハイブリッド電気自動車（ＨＥＶ）の導入による二酸化炭素排出量の低減に期待が集まっており、これらの実用化の鍵を握るモータ駆動用二次電池の開発が鋭意行われている。二次電池としては、高エネルギー密度、高出力密度が達成できるリチウムイオン電池に注目が集まっている。 In recent years, reduction of carbon dioxide emission has been urgently required for environmental protection. The automobile industry is expected to reduce carbon dioxide emissions through the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs), and is keenly developing motor-driven secondary batteries that are key to their practical use. Is being done. As a secondary battery, attention is being paid to a lithium ion battery that can achieve high energy density and high output density.

リチウムイオン電池は、内的要因や外的要因によって、リチウムイオン電池内部に一時的に微小短絡が発生した場合、集電体表面から微小短絡部に向けて電流が流れるため、短絡部が極めて小さな短絡であっても、過電流や発熱が発生して電池性能が劣化する等、電池性能の耐久性に課題があった。 In the case of a lithium ion battery, when a short circuit occurs temporarily inside the lithium ion battery due to an internal factor or an external factor, an electric current flows from the surface of the current collector toward the minute short circuit, so that the short circuit is extremely small. Even with a short circuit, there is a problem in durability of battery performance, such as deterioration of battery performance due to overcurrent or heat generation.

特許文献１には、正極活物質層、電解質層及び負極活物質層からなる群より選択される少なくとも１層の表面又は内部に、ガス発生剤を含む非水電解質二次電池が開示されている。このような非水電解質二次電池では、ガス発生剤からガスが発生することにより、イオンの移動経路を狭めるか又は遮断して、イオンの移動量の低下や移動の停止が起こる。これにより、二次電池の内部抵抗が増加し、二次電池の稼動が抑制又は停止され、過電流や発熱を抑制することができる。 Patent Document 1 discloses a nonaqueous electrolyte secondary battery including a gas generating agent on the surface or inside of at least one layer selected from the group consisting of a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer. . In such a non-aqueous electrolyte secondary battery, the generation of gas from the gas generating agent narrows or cuts off the ion movement path, resulting in a decrease in the amount of ion movement or a stop of the movement. Thereby, the internal resistance of the secondary battery increases, the operation of the secondary battery is suppressed or stopped, and overcurrent and heat generation can be suppressed.

特開２００８−２２６８０７号公報JP 2008-226807 A

しかしながら、特許文献１に記載された発熱や過電流を抑制する機構では、電池の充放電に関与しないガス発生剤を含む必要がある。電池が充放電に関与しない構成を含むと電池１個あたりの充放電容量が減少してしまうため、特許文献１に記載された方法には未だ改善の余地があると言える。 However, the mechanism for suppressing heat generation and overcurrent described in Patent Literature 1 needs to include a gas generating agent that does not participate in charging and discharging of the battery. If the battery includes a configuration not involved in charge / discharge, the charge / discharge capacity per battery decreases, and thus the method described in Patent Document 1 still has room for improvement.

以上の状況を踏まえて、本発明は、ガス発生剤を含まずに、リチウムイオン電池内部に一時的に微小短絡が発生した場合であっても、電池あたりの充放電容量に影響を与えることなく、電池性能の劣化を抑制でき、耐久性に優れたリチウムイオン電池を得ることを目的とする。 Based on the above situation, the present invention does not include a gas generating agent, even if a small short circuit occurs temporarily inside the lithium ion battery, without affecting the charge / discharge capacity per battery Another object of the present invention is to obtain a lithium ion battery that can suppress deterioration of battery performance and has excellent durability.

本発明者らは、上記課題を解決するために鋭意検討した結果、本発明に想到した。
すなわち、本発明は、少なくとも集電体と、負極活物質層と、セパレータとをこの順で備えたリチウムイオン電池であって、上記負極活物質層は、少なくとも第一の負極活物質層と、第二の負極活物質層とを含み、上記第二の負極活物質層の膜厚が１．５〜５０μｍであり、上記第二の負極活物質層に含まれる珪素系活物質量が、０．１〜５ｍｇ／ｃｍ２であり、上記第二の負極活物質層に含まれる珪素系活物質の上記第二の負極活物質層の重量に対する重量割合が、上記第一の負極活物質層に含まれる珪素系活物質の上記第一の負極活物質層に対する重量割合よりも大きいことを特徴とするリチウムイオン電池である。 The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have arrived at the present invention.
That is, the present invention is a lithium ion battery including at least a current collector, a negative electrode active material layer, and a separator in this order, wherein the negative electrode active material layer has at least a first negative electrode active material layer, A second negative electrode active material layer, wherein the thickness of the second negative electrode active material layer is 1.5 to 50 μm, and the amount of the silicon-based active material contained in the second negative electrode active material layer is zero. 0.1 to 5 mg / cm 2 , and the weight ratio of the silicon-based active material contained in the second negative electrode active material layer to the weight of the second negative electrode active material layer is equal to that of the first negative electrode active material layer. A lithium ion battery, wherein the weight ratio of the silicon-based active material contained to the first negative electrode active material layer is larger than that of the first negative electrode active material layer.

本発明によると、内部に一時的に微小短絡が発生した場合であっても、電池性能の劣化を抑制でき、耐久性に優れたリチウムイオン電池を得ることができる。 ADVANTAGE OF THE INVENTION According to this invention, even when a micro short circuit occurs temporarily inside, deterioration of battery performance can be suppressed and a lithium ion battery excellent in durability can be obtained.

本発明のリチウムイオン電池は、少なくとも集電体と、負極活物質層と、セパレータとをこの順で備えたリチウムイオン電池であって、上記負極活物質層は、少なくとも第一の負極活物質層と、第二の負極活物質層とを含み、上記第二の負極活物質層の膜厚が１．５〜５０μｍであり、上記第二の負極活物質層に含まれる珪素系活物質量が、０．１〜５ｍｇ／ｃｍ２であり、上記第二の負極活物質層に含まれる珪素系活物質の上記第二の負極活物質層の重量に対する重量割合が、上記第一の負極活物質層に含まれる珪素系活物質の上記第一の負極活物質層の重量に対する重量割合よりも大きいことを特徴とする。 The lithium ion battery of the present invention is a lithium ion battery including at least a current collector, a negative electrode active material layer, and a separator in this order, wherein the negative electrode active material layer has at least a first negative electrode active material layer. And a second negative electrode active material layer, wherein the thickness of the second negative electrode active material layer is 1.5 to 50 μm, and the amount of the silicon-based active material contained in the second negative electrode active material layer is And the weight ratio of the silicon-based active material contained in the second negative electrode active material layer to the weight of the second negative electrode active material layer is 0.1 to 5 mg / cm 2. The weight ratio of the silicon-based active material contained in the layer to the weight of the first negative electrode active material layer is larger.

本発明のリチウムイオン電池では、少なくとも第一の負極活物質層と、第二の負極活物質層とを含み、第二の負極活物質層が所定の膜厚を有し、かつ、単位面積あたりに所定量の珪素系活物質を有する。
この第二の負極活物質層は、リチウムイオン電池内部に一時的に微小短絡が発生した場合に、以下の機構によって発熱や過電流を抑制すると考えられる。
リチウムイオン電池内部に一時的に微小短絡が発生すると、その熱により、第二の負極活物質層表面の固体電解質界面（ＳＥＩ）の分解反応が極めて速く進行する。それに伴って、微小短絡が発生した部位では、第二の負極活物質層表面での電解液の分解反応が起こってガスが発生する。発生したガスが発熱により膨張して、集電体と第一の負極活物質層との間、或いは、第一の負極活物質層とセパレータとの間に空間が生まれ、導電パスが切断される。
その結果、微小短絡が発生した部位に流れる電流が制限され、過電流や発熱が抑制されるので、電池性能の劣化を抑制でき、耐久性に優れたリチウムイオン電池を得ることができると考えられる。 In the lithium ion battery of the present invention, at least a first negative electrode active material layer, including a second negative electrode active material layer, the second negative electrode active material layer has a predetermined thickness, and per unit area Has a predetermined amount of a silicon-based active material.
This second negative electrode active material layer is considered to suppress heat generation and overcurrent by the following mechanism when a micro short circuit occurs temporarily inside the lithium ion battery.
When a micro short circuit occurs temporarily inside the lithium ion battery, the heat causes the decomposition reaction at the solid electrolyte interface (SEI) on the surface of the second negative electrode active material layer to proceed extremely quickly. Accordingly, a decomposition reaction of the electrolytic solution occurs on the surface of the second negative electrode active material layer at a portion where the micro short circuit occurs, and gas is generated. The generated gas expands due to heat generation, and a space is created between the current collector and the first negative electrode active material layer or between the first negative electrode active material layer and the separator, and the conductive path is cut. .
As a result, the current flowing to the portion where the micro short-circuit has occurred is limited, and overcurrent and heat generation are suppressed, so that deterioration of battery performance can be suppressed and a lithium-ion battery with excellent durability can be obtained. .

本発明のリチウムイオン電池は、少なくとも第一の負極活物質層と、第二の負極活物質層とを含む。
まずは、第一の負極活物質層について説明する。
第一の負極活物質層に含まれる珪素系活物質の第一の負極活物質層の重量に対する重量割合は、第二の負極活物質層に含まれる珪素系活物質の第二の負極活物質層の重量に対する重量割合よりも小さい。
また、第一の負極活物質層では、該第一の負極活物質層に含まれる珪素系活物質の含有量が、第一の負極活物質層の重量に対して４０重量％未満であることが好ましい。第一の負極活物質層に含まれる珪素系活物質の含有量は、電池容量と安全性の観点から、３０重量％以下がより好ましく、２０重量％以下であることがさらに好ましい。
なお、本明細書において、負極活物質層に含まれる珪素系活物質の含有量は、レーザーラマン顕微鏡［ナノフォトン株式会社製］等を用いて、層の断面を元素分析する等により特定することができる。 The lithium ion battery of the present invention includes at least a first negative electrode active material layer and a second negative electrode active material layer.
First, the first negative electrode active material layer will be described.
The weight ratio of the silicon-based active material contained in the first anode active material layer to the weight of the first anode active material layer is the second anode active material of the silicon-based active material contained in the second anode active material layer. Less than the weight ratio to the weight of the layer.
Further, in the first negative electrode active material layer, the content of the silicon-based active material contained in the first negative electrode active material layer is less than 40% by weight based on the weight of the first negative electrode active material layer. Is preferred. From the viewpoint of battery capacity and safety, the content of the silicon-based active material contained in the first negative electrode active material layer is more preferably 30% by weight or less, and further preferably 20% by weight or less.
Note that, in this specification, the content of the silicon-based active material contained in the negative electrode active material layer is specified by performing elemental analysis on the cross section of the layer using a laser Raman microscope [manufactured by Nanophoton Corporation] or the like. Can be.

第一の負極活物質層に含まれる負極活物質は、電池容量の観点から、炭素系活物質と珪素系活物質との混合物であってもよく、この場合、珪素系活物質の重量割合が、上記第一の負極活物質層の重量に対して２０重量％以下であってもよい。
また、第一の負極活物質層に含まれる負極活物質は、安全性の観点から、炭素系活物質からなるものであってもよい。 The negative electrode active material included in the first negative electrode active material layer may be a mixture of a carbon-based active material and a silicon-based active material from the viewpoint of battery capacity. In this case, the weight ratio of the silicon-based active material is The amount may be 20% by weight or less based on the weight of the first negative electrode active material layer.
Further, the negative electrode active material included in the first negative electrode active material layer may be made of a carbon-based active material from the viewpoint of safety.

第一の負極活物質層に含まれる炭素系活物質としては、炭素系材料［例えば黒鉛、難黒鉛化性炭素、アモルファス炭素、樹脂焼成体（例えばフェノール樹脂及びフラン樹脂等を焼成し炭素化したもの等）、コークス類（例えばピッチコークス、ニードルコークス及び石油コークス等）］、又は、導電性高分子（例えばポリアセチレン及びポリピロール等）、金属酸化物（チタン酸化物及びリチウム・チタン酸化物）及び金属合金（リチウム−スズ合金、リチウム−アルミニウム合金、アルミニウム−マンガン合金等）等と炭素系材料との混合物等が挙げられる。 Examples of the carbon-based active material contained in the first negative electrode active material layer include carbon-based materials [eg, graphite, non-graphitizable carbon, amorphous carbon, and resin fired bodies (eg, carbonized by firing a phenol resin, a furan resin, or the like). ), Cokes (eg, pitch coke, needle coke, petroleum coke, etc.)], or conductive polymers (eg, polyacetylene and polypyrrole), metal oxides (titanium oxide and lithium titanium oxide), and metals A mixture of an alloy (such as a lithium-tin alloy, a lithium-aluminum alloy, or an aluminum-manganese alloy) and a carbon-based material may be used.

炭素系活物質の数平均粒子径は、リチウムイオン電池用負極の電気特性の観点から、０．１〜５０μｍが好ましく、１５〜２０μｍであることがより好ましい。なお、炭素系活物質はリチウムイオンがドープされることで膨張するが、ここでいう数平均粒子径はリチウムイオンがドープされる前の数平均粒子径である。また、数平均粒子径は、マイクロトラック法（レーザー回折・散乱法）によって求めた粒度分布における積算値５０％での粒径（Ｄｖ５０）を意味する。マイクロトラック法とは、レーザー光を粒子に照射することによって得られる散乱光を利用して粒度分布を求める方法であり、日機装（株）製のマイクロトラック等を用いることができる。 The number average particle diameter of the carbon-based active material is preferably from 0.1 to 50 μm, more preferably from 15 to 20 μm, from the viewpoint of the electrical characteristics of the negative electrode for a lithium ion battery. The carbon-based active material expands when doped with lithium ions, and the number average particle diameter here is the number average particle diameter before the lithium ions are doped. The number average particle diameter means a particle diameter (Dv50) at an integrated value of 50% in a particle size distribution obtained by a microtrack method (laser diffraction / scattering method). The microtrack method is a method of obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light, and a microtrack manufactured by Nikkiso Co., Ltd. can be used.

第一の負極活物質層に含まれる珪素系活物質としては、例えば、酸化珪素（ＳｉＯｘ）、珪素−炭素（Ｓｉ−Ｃ）複合体、Ｓｉ−Ａｌ合金、Ｓｉ−Ｌｉ合金、Ｓｉ−Ｎｉ合金、Ｓｉ−Ｆｅ合金、Ｓｉ−Ｔｉ合金、Ｓｉ−Ｍｎ合金、Ｓｉ−Ｃｕ合金及びＳｉ−Ｓｎ合金からなる群から選択される少なくとも１種であることが好ましい。 The silicon-based active material contained in the first negative electrode active material layer, for example, silicon oxide (SiO x), silicon - carbon (Si-C) complex, Si-Al alloy, Si-Li alloy, Si-Ni Preferably, it is at least one selected from the group consisting of an alloy, a Si-Fe alloy, a Si-Ti alloy, a Si-Mn alloy, a Si-Cu alloy and a Si-Sn alloy.

第一の負極活物質層に含まれる炭素系活物質及び珪素系活物質（以下、負極活物質ともいう）は、その表面の少なくとも一部が高分子化合物を含む被覆層により被覆された被覆活物質であってもよい。
負極活物質の周囲が被覆層で被覆されていると、負極での体積変化が緩和され、膨張を抑制することができる。さらに、被覆活物質の非水系溶媒に対する濡れ性を向上させることができ、負極が有する被覆活物質に電解液を吸収させる工程に掛かる時間の短縮が可能になる。
なお、被覆層により被覆された負極活物質を被覆負極活物質ともいう。 The carbon-based active material and the silicon-based active material (hereinafter, also referred to as a negative electrode active material) contained in the first negative electrode active material layer have a coating activity in which at least a part of the surface is covered by a coating layer containing a polymer compound. It may be a substance.
When the periphery of the negative electrode active material is covered with the coating layer, a change in volume at the negative electrode is reduced, and expansion can be suppressed. Furthermore, the wettability of the coated active material with respect to the non-aqueous solvent can be improved, and the time required for the step of absorbing the electrolyte into the coated active material of the negative electrode can be reduced.
Note that the negative electrode active material covered with the coating layer is also referred to as a coated negative electrode active material.

被覆層を構成する高分子化合物としては、特開２０１７−０５４７０３号公報に非水系二次電池活物質被覆用樹脂として記載されたものを好適に用いることができる。 As the polymer compound constituting the coating layer, those described in JP-A-2017-054703 as a resin for coating a nonaqueous secondary battery active material can be suitably used.

本発明のリチウムイオン電池において負極活物質が被覆負極活物質を含む場合、被覆層は導電助剤を含むことが好ましい。
導電助剤としては、金属［ニッケル、アルミニウム、ステンレス（ＳＵＳ）、銀、銅及びチタン等］、カーボン［グラファイト及びカーボンブラック（アセチレンブラック、ケッチェンブラック、ファーネスブラック、チャンネルブラック、サーマルランプブラック等）等］、及びこれらの混合物等が挙げられるが、これらに限定されるわけではない。
これらの導電助剤は１種単独で用いてもよいし、２種以上併用してもよい。また、これらの合金又は金属酸化物を用いてもよい。電気的安定性の観点から、好ましくはアルミニウム、ステンレス、カーボン、銀、銅、チタン及びこれらの混合物であり、より好ましくは銀、アルミニウム、ステンレス及びカーボンであり、さらに好ましくはカーボンである。またこれらの導電助剤としては、粒子系セラミック材料や樹脂材料の周りに導電性材料（上記した導電助剤の材料のうち金属のもの）をめっき等でコーティングしたものでもよい。 When the negative electrode active material contains the coated negative electrode active material in the lithium ion battery of the present invention, the coating layer preferably contains a conductive auxiliary.
Examples of the conductive assistant include metals [nickel, aluminum, stainless steel (SUS), silver, copper and titanium, etc.], carbon [graphite and carbon black (acetylene black, Ketjen black, furnace black, channel black, thermal lamp black, etc.) And the like, and mixtures thereof, but are not limited thereto.
These conductive assistants may be used alone or in combination of two or more. Further, these alloys or metal oxides may be used. From the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, copper, titanium and mixtures thereof are preferred, silver, aluminum, stainless steel and carbon are more preferred, and carbon is more preferred. Further, as these conductive assistants, those obtained by coating a conductive material (a metal among the above-described conductive assistants) around a particle-based ceramic material or a resin material by plating or the like may be used.

導電助剤の平均粒子径は、特に限定されるものではないが、電池の電気特性の観点から、０．０１〜１０μｍであることが好ましく、０．０２〜５μｍであることがより好ましく、０．０３〜１μｍであることがさらに好ましい。なお、本明細書中において、「粒子径」とは、導電助剤の輪郭線上の任意の２点間の距離のうち、最大の距離Ｌを意味する。「平均粒子径」の値としては、走査型電子顕微鏡（ＳＥＭ）や透過型電子顕微鏡（ＴＥＭ）等の観察手段を用い、数〜数十視野中に観察される粒子の粒子径の平均値として算出される値を採用するものとする。 The average particle size of the conductive additive is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.02 to 5 μm, and more preferably 0 to 5 μm, from the viewpoint of electric characteristics of the battery. 0.03 to 1 μm is more preferable. In addition, in this specification, "particle diameter" means the largest distance L among the distances between any two points on the outline of the conductive additive. As the value of the “average particle diameter”, the average value of the particle diameter of particles observed in several to several tens of visual fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) is used. It is assumed that the calculated value is adopted.

導電助剤の形状（形態）は、粒子形態に限られず、粒子形態以外の形態であってもよく、カーボンナノチューブ等、いわゆるフィラー系導電助剤として実用化されている形態であってもよい。 The shape (form) of the conductive additive is not limited to the particle form, may be a form other than the particle form, and may be a form practically used as a so-called filler-based conductive aid such as a carbon nanotube.

導電助剤は、その形状が繊維状である導電性繊維であってもよい。
導電性繊維としては、ＰＡＮ系炭素繊維、ピッチ系炭素繊維等の炭素繊維、合成繊維の中に導電性のよい金属や黒鉛を均一に分散させてなる導電性繊維、ステンレス鋼のような金属を繊維化した金属繊維、有機物繊維の表面を金属で被覆した導電性繊維、有機物繊維の表面を、導電性物質を含む樹脂で被覆した導電性繊維等が挙げられる。これらの導電性繊維の中では炭素繊維が好ましい。また、グラフェンを練りこんだポリプロピレン樹脂を用いた合成繊維も好ましい。
導電助剤が導電性繊維である場合、その平均繊維径は０．１〜２０μｍであることが好ましい。 The conductive assistant may be a conductive fiber having a fibrous shape.
Examples of the conductive fiber include carbon fibers such as PAN-based carbon fiber and pitch-based carbon fiber, conductive fibers obtained by uniformly dispersing a highly conductive metal or graphite in synthetic fibers, and metals such as stainless steel. Examples include fibrous metal fibers, conductive fibers in which the surface of an organic fiber is coated with a metal, and conductive fibers in which the surface of an organic fiber is coated with a resin containing a conductive substance. Among these conductive fibers, carbon fibers are preferred. Further, a synthetic fiber using a polypropylene resin kneaded with graphene is also preferable.
When the conductive additive is a conductive fiber, the average fiber diameter is preferably 0.1 to 20 μm.

被覆層が導電助剤を含んでいる場合、被覆層に含まれる導電助剤の重量は、被覆用樹脂である高分子化合物と導電助剤との合計重量に対して１５〜７５重量％であることが好ましい。
被覆負極活物質が有する被覆層が導電助剤を含んでいる場合、予備充電後に負極活物質の表面にＳＥＩ膜が作製された場合であっても被覆層に含まれる導電助剤の効果によって活物質間の導通経路を維持することができ、ＳＥＩ膜の作製による抵抗上昇が抑制できるため好ましく、導電助剤の割合がこの範囲であると抵抗抑制が容易になり更に好ましい。 When the coating layer contains a conductive additive, the weight of the conductive additive contained in the coating layer is 15 to 75% by weight based on the total weight of the polymer compound as the coating resin and the conductive additive. Is preferred.
In the case where the coating layer of the coated negative electrode active material contains a conductive auxiliary, even if a SEI film is formed on the surface of the negative electrode active material after pre-charging, the active layer is activated by the effect of the conductive auxiliary contained in the coating layer. It is preferable because the conduction path between the substances can be maintained and the resistance increase due to the production of the SEI film can be suppressed. When the ratio of the conductive auxiliary agent is in this range, the resistance can be easily suppressed, and it is more preferable.

本発明のリチウムイオン電池では、第一の負極活物質層がリチウムイオン電池用電極バインダを含まない非結着体であることが好ましい。
第一の負極活物質層がリチウムイオン電池用電極バインダを含まないと、リチウムイオン電池用電極バインダによって、負極活物質の充放電時の膨張・収縮が制限されることがないので、負極活物質の自壊を抑制することができる。さらに、本発明のリチウムイオン電池を構成する第一の負極活物質層は、負極集電体表面がリチウムイオン電池用電極バインダにより固定されているわけではないため、負極活物質の充放電時の膨張・収縮によって第一の負極活物質層に亀裂が生じたり、剥離したりすることがない。そのため、サイクル特性の劣化を抑制することができる。
なお、本明細書においてリチウムイオン電池用電極バインダとしては、電極活物質同士及び電極活物質と集電体とを結着固定するために用いられる公知のリチウムイオン電池用電極バインダが挙げられ、デンプン、ポリフッ化ビニリデン、ポリビニルアルコール、カルボキシメチルセルロース、ポリビニルピロリドン、テトラフルオロエチレン、スチレン−ブタジエンゴム、ポリエチレン及びポリプロピレン等が挙げられる。これらの公知のリチウムイオン電池用電極バインダは、溶剤に溶解又は分散して用いられ、溶剤を揮発、留去して固体として析出することで電極活物質同士及び電極活物質と集電体とを結着固定する。 In the lithium ion battery of the present invention, it is preferable that the first negative electrode active material layer is a non-binding body that does not include an electrode binder for a lithium ion battery.
If the first negative electrode active material layer does not contain the lithium ion battery electrode binder, the lithium ion battery electrode binder does not limit the expansion and contraction of the negative electrode active material during charge and discharge, so that the negative electrode active material Self-destruction can be suppressed. Further, the first negative electrode active material layer constituting the lithium ion battery of the present invention, since the surface of the negative electrode current collector is not fixed by the lithium ion battery electrode binder, the charge and discharge of the negative electrode active material The first negative electrode active material layer does not crack or peel due to expansion and contraction. Therefore, deterioration of cycle characteristics can be suppressed.
In this specification, examples of the lithium ion battery electrode binder include a known lithium ion battery electrode binder used for binding and fixing the electrode active materials to each other and the electrode active material and the current collector. , Polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, styrene-butadiene rubber, polyethylene and polypropylene. These known lithium ion battery electrode binders are used by dissolving or dispersing in a solvent, evaporating and distilling off the solvent, and depositing as a solid to separate the electrode active materials and the electrode active material and the current collector. Secure and fix.

第一の負極活物質層の厚さは、電池容量の観点から、１００〜１５００μｍであることが好ましく、２００〜８００μｍであることがより好ましく、３００〜６００μｍであることがさらに好ましい。
また、第一の負極活物質層の厚さは、第一の負極活物質層に対して充電を行う前、又は、第一の負極活物質層を電極電位の値＋０．０５Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）以下まで放電した際の厚さとする。 The thickness of the first negative electrode active material layer is preferably from 100 to 1500 μm, more preferably from 200 to 800 μm, and still more preferably from 300 to 600 μm, from the viewpoint of battery capacity.
In addition, the thickness of the first negative electrode active material layer is determined before charging the first negative electrode active material layer or when the first negative electrode active material layer is charged with an electrode potential of +0.05 V (vs. Li). / Li + ).

続いて、第二の負極活物質層について説明する。
第二の負極活物質層は、集電体と負極活物質層とセパレータとをこの順で積層した構成において、集電体と第一の負極活物質層との間、又は、第一の負極活物質層とセパレータとの間に存在する層である。 Subsequently, the second negative electrode active material layer will be described.
The second negative electrode active material layer has a configuration in which a current collector, a negative electrode active material layer, and a separator are stacked in this order, between the current collector and the first negative electrode active material layer, or the first negative electrode. This is a layer existing between the active material layer and the separator.

第二の負極活物質層に含まれる珪素系活物質量は、０．１〜５ｍｇ／ｃｍ２である。
第二の負極活物質層に含まれる珪素系活物質量は、過電流や発熱を好適に抑制する観点から、０．２〜３ｍｇ／ｃｍ２であることが好ましく、０．２〜１ｍｇ／ｃｍ２であることがより好ましい。 The amount of the silicon-based active material contained in the second negative electrode active material layer is 0.1 to 5 mg / cm 2 .
The amount of the silicon-based active material contained in the second negative electrode active material layer is preferably from 0.2 to 3 mg / cm 2 , and more preferably from 0.2 to 1 mg / cm 2 from the viewpoint of appropriately suppressing overcurrent and heat generation. More preferably, it is 2 .

第二の負極活物質層は、膜厚が１．５〜５０μｍである。
第二の負極活物質層の膜厚が上記範囲であることで、過電流や発熱を抑制することができる。
第二の負極活物質層は、過電流や発熱を好適に抑制する観点から、膜厚が１．５〜３０μｍであることが好ましく、１．５〜１０μｍであることがより好ましい。 The second negative electrode active material layer has a thickness of 1.5 to 50 μm.
When the thickness of the second negative electrode active material layer is within the above range, overcurrent and heat generation can be suppressed.
The thickness of the second negative electrode active material layer is preferably from 1.5 to 30 μm, and more preferably from 1.5 to 10 μm, from the viewpoint of appropriately suppressing overcurrent and heat generation.

第二の負極活物質層に含まれる珪素系活物質の第二の負極活物質層の重量に対する重量割合が、第一の負極活物質層に含まれる珪素系活物質の第一の負極活物質層に対する重量割合よりも大きい。
第二の負極活物質層に含まれる珪素系活物質の含有量は、第二の負極活物質層の重量に対して４０重量％以上であることが好ましい。第二の負極活物質層に含まれる珪素系活物質の含有量は、過電流や発熱を好適に抑制する観点から、第二の負極活物質層の重量に対して４５重量％以上であることがより好ましく、５０重量％以上であることがさらに好ましい。
第二の負極活物質層に含まれる珪素系活物質の含有量の上限は特に限定されないが、例えば第二の負極活物質層の重量に対して８０重量％以下である。 The weight ratio of the silicon-based active material included in the second anode active material layer to the weight of the second anode active material layer is the first anode active material of the silicon-based active material included in the first anode active material layer. Greater than the weight ratio to the layer.
It is preferable that the content of the silicon-based active material contained in the second negative electrode active material layer is 40% by weight or more based on the weight of the second negative electrode active material layer. The content of the silicon-based active material contained in the second negative electrode active material layer is 45% by weight or more based on the weight of the second negative electrode active material layer from the viewpoint of appropriately suppressing overcurrent and heat generation. Is more preferable, and more preferably 50% by weight or more.
The upper limit of the content of the silicon-based active material contained in the second negative electrode active material layer is not particularly limited, but is, for example, 80% by weight or less based on the weight of the second negative electrode active material layer.

第二の負極活物質層に含まれる珪素系活物質としては、上述した第一の負極活物質層に含まれる珪素系活物質と同様のものを用いることができる。
なかでも、過電流や発熱を好適に抑制する観点から、酸化珪素及び珪素−炭素複合体が好ましい。
珪素−炭素複合体としては、炭素粒子の表面を珪素及び／又は炭化珪素で被覆したもの、珪素粒子又は酸化珪素粒子の表面を炭素及び／又は炭化珪素で被覆したもの並びに炭化珪素等が挙げられる。 As the silicon-based active material included in the second negative electrode active material layer, the same one as the silicon-based active material included in the above-described first negative electrode active material layer can be used.
Among them, silicon oxide and a silicon-carbon composite are preferred from the viewpoint of suitably suppressing overcurrent and heat generation.
Examples of the silicon-carbon composite include those obtained by coating the surfaces of carbon particles with silicon and / or silicon carbide, those obtained by coating the surfaces of silicon particles or silicon oxide particles with carbon and / or silicon carbide, and silicon carbide. .

第二の負極活物質層に含まれる珪素系活物質の体積平均粒子径は特に限定されないが、例えば０．０１〜１０μｍであることが好ましい。なお、珪素系活物質はリチウムイオンがドープされることで膨張するが、ここでいう体積平均粒子径は、リチウムイオンがドープされる前の珪素系活物質の粒子径を意味する。
体積平均粒子径は、マイクロトラック法（レーザー回折・散乱法）によって求めた粒度分布における積算値５０％での粒径（Ｄｖ５０）を意味する。マイクロトラック法とは、レーザー光を粒子に照射することによって得られる散乱光を利用して粒度分布を求める方法であり、測定には日機装（株）製のマイクロトラック等を用いることができる。 The volume average particle diameter of the silicon-based active material contained in the second negative electrode active material layer is not particularly limited, but is preferably, for example, 0.01 to 10 μm. The silicon-based active material expands when doped with lithium ions, and the volume average particle diameter referred to here means the particle diameter of the silicon-based active material before being doped with lithium ions.
The volume average particle diameter means a particle diameter (Dv50) at an integrated value of 50% in a particle size distribution obtained by a microtrack method (laser diffraction / scattering method). The microtrack method is a method of obtaining a particle size distribution using scattered light obtained by irradiating a particle with laser light, and a microtrack manufactured by Nikkiso Co., Ltd. can be used for the measurement.

第二の負極活物質層に含まれる珪素系活物質は、リチウムイオンがドープされていることが好ましい。
リチウムイオンがドープされた珪素系活物質は反応性が高いので、熱による第二の負極活物質層表面の固体電解質界面（ＳＥＩ）での分解反応がさらに速く進行し、上述した導電パスを切断し、過電流や発熱を抑制する機構を好適に構築することができる。
なお、本発明のリチウムイオン電池において第二の負極活物質層に含まれる珪素系活物質は、初回充電前はリチウムイオンがドープされていなくてもよいが、初回充電後は十分な量のリチウムイオンがドープされた状態となる。また、不可逆容量であっても、十分な量のリチウムイオンがドープされた状態となっている。 The silicon-based active material contained in the second negative electrode active material layer is preferably doped with lithium ions.
Since the silicon-based active material doped with lithium ions has high reactivity, the decomposition reaction at the solid electrolyte interface (SEI) on the surface of the second negative electrode active material layer due to heat proceeds more rapidly, and the above-described conductive path is cut. However, a mechanism for suppressing overcurrent and heat generation can be suitably constructed.
In the lithium ion battery of the present invention, the silicon-based active material contained in the second negative electrode active material layer may not be doped with lithium ions before the first charge, but after the first charge, a sufficient amount of lithium ions may be used. The ions are doped. In addition, even when the capacity is irreversible, a sufficient amount of lithium ions is doped.

本発明のリチウムイオン電池において第二の負極活物質層は、電池特性の観点から、導電助剤を含有することが好ましい。
導電助剤としては、上述した第一の負極活物質層に含まれる導電助剤と同様のものを用いることができ、同様のものが好ましい。 In the lithium ion battery of the present invention, the second negative electrode active material layer preferably contains a conductive additive from the viewpoint of battery characteristics.
As the conductive auxiliary, the same conductive auxiliary as that contained in the first negative electrode active material layer described above can be used, and the same is preferable.

第二の負極活物質層が導電助剤を含む場合、第二の負極活物質層の重量に対する導電助剤の重量の割合は、電池特性の観点から、５〜４０重量％であることが好ましく、７〜３０重量％であることがより好ましく、１０〜２０重量％であることがさらに好ましい。 When the second negative electrode active material layer contains a conductive auxiliary, the ratio of the weight of the conductive auxiliary to the weight of the second negative electrode active material layer is preferably 5 to 40% by weight from the viewpoint of battery characteristics. , More preferably 7 to 30% by weight, even more preferably 10 to 20% by weight.

本発明のリチウムイオン電池は、第三の負極活物質層を有していてもよい。
第三の負極活物質層は、第一の負極活物質層の第二の負極活物質層を有する面と、反対側の面上に有することが好ましい。第三の負極活物質層は、上述した第二の負極活物質層と同様の組成を有するものを好適に用いることができる。
この第三の負極活物質層も、第二の負極活物質層と同様の機構により、リチウムイオン電池内部に一時的に微小短絡が発生した場合に、発熱や過電流を抑制すると考えられる。 The lithium ion battery of the present invention may have a third negative electrode active material layer.
The third negative electrode active material layer is preferably provided on a surface of the first negative electrode active material layer opposite to the surface having the second negative electrode active material layer. As the third negative electrode active material layer, a material having the same composition as the above-described second negative electrode active material layer can be suitably used.
It is considered that the third negative electrode active material layer also suppresses heat generation and overcurrent when a minute short circuit occurs temporarily inside the lithium ion battery by the same mechanism as that of the second negative electrode active material layer.

なお、本発明のリチウムイオン電池が第三の負極活物質層を有する場合には、第二の負極活物質層及び第三の負極活物質層のそれぞれに含まれる珪素系活物質量が、０．１〜５ｍｇ／ｃｍ２であることが好ましい。
第三の負極活物質層に含まれる珪素系活物質量は、０．２〜３ｍｇ／ｃｍ２であることがより好ましく、０．２〜１ｍｇ／ｃｍ２であることがさらに好ましい。 When the lithium ion battery of the present invention has the third negative electrode active material layer, the amount of the silicon-based active material contained in each of the second negative electrode active material layer and the third negative electrode active material layer is 0. It is preferably 0.1 to 5 mg / cm 2 .
Silicon-based active material amount contained in the third negative electrode active material layer is more preferably 0.2~3mg / cm 2, further preferably 0.2 to 1 mg / cm 2.

第三の負極活物質層に含まれる珪素系活物質の第三の負極活物質層の重量に対する重量割合が、第一の負極活物質層に含まれる珪素系活物質の第一の負極活物質層に対する重量割合よりも大きいことが好ましい。
第三の負極活物質層に含まれる珪素系活物質の含有量は、過電流や発熱を好適に抑制する観点から、第三の負極活物質層の重量に対して４０重量％以上であることが好ましく、４５重量％以上であることがより好ましく、５０重量％以上であることがさらに好ましい。 The weight ratio of the silicon-based active material contained in the third anode active material layer to the weight of the third anode active material layer is the first anode active material of the silicon-based active material contained in the first anode active material layer. Preferably, it is greater than the weight ratio to the layer.
The content of the silicon-based active material contained in the third negative electrode active material layer is 40% by weight or more based on the weight of the third negative electrode active material layer from the viewpoint of appropriately suppressing overcurrent and heat generation. Is preferably 45% by weight or more, more preferably 50% by weight or more.

第三の負極活物質層は、過電流や発熱を好適に抑制する観点から、膜厚が１．５〜５０μｍであることが好ましく、１．５〜３０μｍであることがより好ましく、１．５〜１０μｍであることがさらに好ましい。 The third negative electrode active material layer preferably has a thickness of 1.5 to 50 μm, more preferably 1.5 to 30 μm, and more preferably 1.5 to 30 μm, from the viewpoint of appropriately suppressing overcurrent and heat generation. More preferably, it is 10 μm to 10 μm.

本発明のリチウムイオン電池は、集電体を備える。
集電体を構成する材料としては、銅、アルミニウム、チタン、ステンレス鋼、ニッケル及びこれらの合金等の金属材料等が挙げられる。なかでも、軽量化、耐食性、高導電性の観点から、好ましくは銅である。集電体としては、焼成炭素、導電性高分子及び導電性ガラス等からなる集電体であってもよく、導電剤と樹脂からなる樹脂集電体であってもよい。
集電体の形状は特に限定されず、上記の材料からなるシート状の集電体、及び、上記の材料で構成された微粒子からなる堆積層であってもよい。
集電体の厚さは、特に限定されないが、５０〜５００μｍであることが好ましい。 The lithium ion battery of the present invention includes a current collector.
Examples of the material forming the current collector include metal materials such as copper, aluminum, titanium, stainless steel, nickel, and alloys thereof. Among them, copper is preferable from the viewpoint of weight reduction, corrosion resistance, and high conductivity. The current collector may be a current collector made of fired carbon, a conductive polymer, a conductive glass, or the like, or may be a resin current collector made of a conductive agent and a resin.
The shape of the current collector is not particularly limited, and may be a sheet-shaped current collector made of the above material, or a deposited layer made of fine particles made of the above material.
The thickness of the current collector is not particularly limited, but is preferably 50 to 500 μm.

本発明のリチウムイオン電池において集電体は、樹脂集電体であることが好ましい。
樹脂集電体を構成する導電剤としては、上述した第一の負極活物質層に含まれる導電助剤と同様のものを好適に用いることができる。 In the lithium ion battery of the present invention, the current collector is preferably a resin current collector.
As the conductive agent constituting the resin current collector, the same conductive agent as the conductive auxiliary agent contained in the above-described first negative electrode active material layer can be suitably used.

樹脂集電体を構成する樹脂としては、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）、ポリメチルペンテン（ＰＭＰ）、ポリシクロオレフィン（ＰＣＯ）、ポリエチレンテレフタレート（ＰＥＴ）、ポリエーテルニトリル（ＰＥＮ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、スチレンブタジエンゴム（ＳＢＲ）、ポリアクリロニトリル（ＰＡＮ）、ポリメチルアクリレート（ＰＭＡ）、ポリメチルメタクリレート（ＰＭＭＡ）、ポリフッ化ビニリデン（ＰＶｄＦ）、エポキシ樹脂、シリコーン樹脂又はこれらの混合物等が挙げられる。
電気的安定性の観点から、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）、ポリメチルペンテン（ＰＭＰ）及びポリシクロオレフィン（ＰＣＯ）が好ましく、さらに好ましくはポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）及びポリメチルペンテン（ＰＭＰ）である。 Examples of the resin constituting the resin current collector include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyether nitrile (PEN), and polytetraethylene. Fluoroethylene (PTFE), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, silicone resin or a mixture thereof Is mentioned.
From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO) are preferred, and polyethylene (PE), polypropylene (PP) and polymethylpentene are more preferred. (PMP).

本発明のリチウムイオン電池においてリチウムイオン電池用負極は、例えば以下の方法により作製することができる。
上述した第二の負極活物質層に含有される珪素系活物質及び導電助剤を分散媒の重量に基づいて３０〜６０重量％の濃度で分散してスラリー化した分散液を、集電体の片面に塗布する。次いで、分散媒を乾燥又は濃縮することによって除去して、必要によりプレス機でプレスすることにより第二の負極活物質層を形成する。
その後、上述した第一の負極活物質層に含有される負極活物質及び導電助剤を分散媒の重量に基づいて３０〜６０重量％の濃度で分散してスラリー化した分散液を、得られた第二の負極活物質層の表面に塗布し、分散媒を乾燥又は濃縮することによって除去して、必要によりプレス機でプレスして第一の負極活物質層を形成することにより、リチウムイオン電池用負極を作製することができる。
また、集電体の片面に第一の負極活物質層を形成した後、得られた第一の負極活物質層の表面に第二の負極活物質層を形成してもよい。更に、集電体の片面に第二の負極活物質層を形成し、得られた第二の負極活物質層の表面に第一の負極活物質層を形成し、得られた第一の負極活物質層の表面にさらに第三の負極活物質層を第二の負極活物質層と同様の方法により形成してもよい。
また、アラミド不織布等の面上に、上述した方法により、第一〜第三の負極活物質層をそれぞれ形成し、アラミド不織布等を剥がした後、集電体や、後述するセパレータや、他の負極活物質層と重ね合わせ、必要によりプレス機でプレスして、リチウムイオン電池用負極を作製してもよい。
なお、上述したスラリーを塗布する際には、バーコーター等の公知の塗工装置を適宜用いることができる。 In the lithium ion battery of the present invention, the negative electrode for a lithium ion battery can be produced, for example, by the following method.
A current collector is prepared by dispersing the silicon-based active material and the conductive additive contained in the second negative electrode active material layer at a concentration of 30 to 60% by weight based on the weight of the dispersion medium to form a slurry. Apply to one side of Next, the dispersion medium is removed by drying or concentration, and if necessary, pressing is performed with a pressing machine to form a second negative electrode active material layer.
Thereafter, a dispersion in which the negative electrode active material and the conductive additive contained in the above-described first negative electrode active material layer are dispersed at a concentration of 30 to 60% by weight based on the weight of the dispersion medium to obtain a slurry is obtained. The first negative electrode active material layer is applied to the surface of the second negative electrode active material layer, and the dispersion medium is removed by drying or concentration, and if necessary, pressed with a press to form the first negative electrode active material layer. A negative electrode for a battery can be manufactured.
Further, after forming the first negative electrode active material layer on one surface of the current collector, a second negative electrode active material layer may be formed on the surface of the obtained first negative electrode active material layer. Further, a second negative electrode active material layer is formed on one surface of the current collector, and a first negative electrode active material layer is formed on the surface of the obtained second negative electrode active material layer. A third negative electrode active material layer may be further formed on the surface of the active material layer by a method similar to that of the second negative electrode active material layer.
Further, on the surface of the aramid nonwoven fabric or the like, the first to third negative electrode active material layers are formed by the above-described method, and after the aramid nonwoven fabric or the like is peeled off, a current collector, a separator described below, or another The negative electrode for a lithium ion battery may be manufactured by overlapping with the negative electrode active material layer and pressing with a press machine as necessary.
In applying the above-mentioned slurry, a known coating device such as a bar coater can be used as appropriate.

リチウムイオン電池用負極の製造に用いる分散媒としては、水及び溶剤を用いることができる。
分散媒のうち、水としては、イオン交換水及び超純水等が挙げられる。
分散媒のうち、溶剤としては、後述する電解液を構成する非水溶媒と同じものを用いることができる。これらの他にも、１−メチル−２−ピロリドン、ジメチルアセトアミド及びＮ，Ｎ−ジメチルアミノプロピルアミン等を用いることができる。 Water and a solvent can be used as a dispersion medium used for manufacturing a negative electrode for a lithium ion battery.
Among the dispersion media, examples of the water include ion-exchanged water and ultrapure water.
Among the dispersion media, the same solvent as the non-aqueous solvent constituting the electrolytic solution described later can be used as the solvent. Besides these, 1-methyl-2-pyrrolidone, dimethylacetamide, N, N-dimethylaminopropylamine and the like can be used.

本発明のリチウムイオン電池は、セパレータを備える。
セパレータとしては、ポリエチレン又はポリプロピレン製の多孔性フィルム、多孔性ポリエチレンフィルムと多孔性ポリプロピレンとの積層フィルム、合成繊維（ポリエステル繊維及びアラミド繊維等）又はガラス繊維等からなる不織布、及びそれらの表面にシリカ、アルミナ、チタニア等のセラミック微粒子を付着させたもの等の公知のリチウムイオン電池用のセパレータが挙げられる。
また、セパレータのリチウムイオン電池用負極を組み合わせる側の表面に、上述した方法で上述したスラリーを塗布することにより、第一、第二又は第三の負極活物質層を形成してもよい。 The lithium ion battery of the present invention includes a separator.
Examples of the separator include a porous film made of polyethylene or polypropylene, a laminated film of a porous polyethylene film and porous polypropylene, a nonwoven fabric made of synthetic fibers (such as polyester fibers and aramid fibers) or glass fibers, and silica on the surface thereof. And known separators for lithium ion batteries, such as those to which ceramic fine particles such as alumina and titania are adhered.
Further, the first, second or third negative electrode active material layer may be formed by applying the above-mentioned slurry to the surface of the separator on the side to be combined with the negative electrode for a lithium ion battery by the above-mentioned method.

本発明のリチウムイオン電池は、さらに、電解液と、正極活物質層と、正極集電体とを備える。
電解液としては、リチウムイオン電池の製造に用いられる、電解質及び非水溶媒を含有する公知の電解液を使用することができる。 The lithium ion battery of the present invention further includes an electrolytic solution, a positive electrode active material layer, and a positive electrode current collector.
As the electrolyte, a known electrolyte containing an electrolyte and a non-aqueous solvent, which is used for manufacturing a lithium ion battery, can be used.

電解質としては、公知の電解液に用いられているもの等が使用でき、例えば、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＳｂＦ６、ＬｉＡｓＦ６、ＬｉＣｌＯ４及びＬｉＮ（ＳＯ２Ｆ）２等の無機アニオンのリチウム塩、ＬｉＮ（ＳＯ２ＣＦ３）２、ＬｉＮ（ＳＯ２Ｃ２Ｆ５）２及びＬｉＣ（ＳＯ２ＣＦ３）３等の有機アニオンのリチウム塩等が挙げられる。これらの内、電池出力及び充放電サイクル特性の観点から好ましいのは、ＬｉＮ（ＳＯ２Ｆ）２及びＬｉＰＦ６である。 As the electrolyte, those used in known electrolytic solutions can be used. For example, lithium salts of inorganic anions such as LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 and LiN (SO 2 F) 2 , LiN (SO 2 CF 3 ) 2 , lithium salts of organic anions such as LiN (SO 2 C 2 F 5 ) 2 and LiC (SO 2 CF 3 ) 3 . Of these, LiN (SO 2 F) 2 and LiPF 6 are preferable from the viewpoint of battery output and charge / discharge cycle characteristics.

非水溶媒としては、公知の電解液に用いられているもの等が使用でき、例えば、ラクトン化合物、環状又は鎖状炭酸エステル、鎖状カルボン酸エステル、環状又は鎖状エーテル、リン酸エステル、ニトリル化合物、アミド化合物、スルホン、スルホラン等及びこれらの混合物を用いることができる。 As the non-aqueous solvent, those used in known electrolytic solutions and the like can be used. For example, lactone compounds, cyclic or chain carbonates, chain carboxylic esters, cyclic or chain ethers, phosphates, nitriles Compounds, amide compounds, sulfones, sulfolanes and the like and mixtures thereof can be used.

ラクトン化合物としては、５員環のラクトン化合物（γ−ブチロラクトン及びγ−バレロラクトン等）及び６員環のラクトン化合物（δ−バレロラクトン等）等を挙げることができる。 Examples of the lactone compound include a 5-membered lactone compound (such as γ-butyrolactone and γ-valerolactone) and a 6-membered lactone compound (such as δ-valerolactone).

環状炭酸エステルとしては、プロピレンカーボネート、エチレンカーボネート及びブチレンカーボネート等が挙げられる。
鎖状炭酸エステルとしては、ジメチルカーボネート、メチルエチルカーボネート、ジエチルカーボネート、メチル−ｎ−プロピルカーボネート、エチル−ｎ−プロピルカーボネート及びジ−ｎ−プロピルカーボネート等が挙げられる。 Examples of the cyclic carbonate include propylene carbonate, ethylene carbonate, butylene carbonate and the like.
Examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, and the like.

鎖状カルボン酸エステルとしては、酢酸メチル、酢酸エチル、酢酸プロピル及びプロピオン酸メチル等が挙げられる。
環状エーテルとしては、テトラヒドロフラン、テトラヒドロピラン、１，３−ジオキソラン及び１，４−ジオキサン等が挙げられる。
鎖状エーテルとしては、ジメトキシメタン及び１，２−ジメトキシエタン等が挙げられる。 Examples of the chain carboxylate include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.
Examples of the cyclic ether include tetrahydrofuran, tetrahydropyran, 1,3-dioxolan, 1,4-dioxane and the like.
Examples of the chain ether include dimethoxymethane and 1,2-dimethoxyethane.

リン酸エステルとしては、リン酸トリメチル、リン酸トリエチル、リン酸エチルジメチル、リン酸ジエチルメチル、リン酸トリプロピル、リン酸トリブチル、リン酸トリ（トリフルオロメチル）、リン酸トリ（トリクロロメチル）、リン酸トリ（トリフルオロエチル）、リン酸トリ（トリパーフルオロエチル）、２−エトキシ−１，３，２−ジオキサホスホラン−２−オン、２−トリフルオロエトキシ−１，３，２−ジオキサホスホラン−２−オン及び２−メトキシエトキシ−１，３，２−ジオキサホスホラン−２−オン等が挙げられる。
ニトリル化合物としては、アセトニトリル等が挙げられる。アミド化合物としては、ＤＭＦ等が挙げられる。スルホンとしては、ジメチルスルホン及びジエチルスルホン等が挙げられる。
非水溶媒は１種を単独で用いてもよいし、２種以上を併用してもよい。 Examples of the phosphate ester include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trichloromethyl) phosphate, Tri (trifluoroethyl) phosphate, tri (tripperfluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphosphoran-2-one, 2-trifluoroethoxy-1,3,2- Dioxaphospholane-2-one and 2-methoxyethoxy-1,3,2-dioxaphospholane-2-one.
Examples of the nitrile compound include acetonitrile. Examples of the amide compound include DMF. Examples of the sulfone include dimethyl sulfone and diethyl sulfone.
One type of non-aqueous solvent may be used alone, or two or more types may be used in combination.

非水溶媒の内、電池出力及び充放電サイクル特性の観点から好ましいのは、ラクトン化合物、環状炭酸エステル、鎖状炭酸エステル及びリン酸エステルであり、更に好ましいのはラクトン化合物、環状炭酸エステル及び鎖状炭酸エステルであり、特に好ましいのは環状炭酸エステルと鎖状炭酸エステルの混合液である。最も好ましいのはエチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）の混合液、又は、エチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）の混合液である。 Among the non-aqueous solvents, preferred from the viewpoint of battery output and charge / discharge cycle characteristics are lactone compounds, cyclic carbonates, chain carbonates and phosphates, and more preferred are lactone compounds, cyclic carbonates and chains. Carbonic acid esters are particularly preferred, and a mixture of cyclic carbonic acid esters and chain carbonic acid esters is particularly preferred. Most preferred is a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC), or a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC).

非水電解液の電解質濃度としては、特に限定されないが、電解液の取り扱い性及び電池容量の観点から、０．５〜５ｍｏｌ／Ｌであることが好ましく、０．８〜３ｍｏｌ／Ｌであることがより好ましく、１〜２ｍｏｌ／Ｌであることがさらに好ましい。 The electrolyte concentration of the non-aqueous electrolyte is not particularly limited, but is preferably 0.5 to 5 mol / L, and more preferably 0.8 to 3 mol / L, from the viewpoint of the ease of handling the electrolyte and the battery capacity. Is more preferable, and it is still more preferable that it is 1-2 mol / L.

正極活物質層は、正極活物質を含む層である。
正極活物質としては、リチウムと遷移金属との複合酸化物｛遷移金属が１種である複合酸化物（ＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＡｌＭｎＯ４、ＬｉＭｎＯ２及びＬｉＭｎ２Ｏ４等）、遷移金属元素が２種である複合酸化物（例えばＬｉＦｅＭｎＯ４、ＬｉＮｉ１−ｘＣｏｘＯ２、ＬｉＭｎ１−ｙＣｏｙＯ２、ＬｉＮｉ１／３Ｃｏ１／３Ａｌ１／３Ｏ２及びＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２）及び金属元素が３種類以上である複合酸化物［例えばＬｉＭａＭ’ｂＭ’’ｃＯ２（Ｍ、Ｍ’及びＭ’’はそれぞれ異なる遷移金属元素であり、ａ＋ｂ＋ｃ＝１を満たす。例えばＬｉＮｉ１／３Ｍｎ１／３Ｃｏ１／３Ｏ２）等］等｝、リチウム含有遷移金属リン酸塩（例えばＬｉＦｅＰＯ４、ＬｉＣｏＰＯ４、ＬｉＭｎＰＯ４及びＬｉＮｉＰＯ４）、遷移金属酸化物（例えばＭｎＯ２及びＶ２Ｏ５）、遷移金属硫化物（例えばＭｏＳ２及びＴｉＳ２）及び導電性高分子（例えばポリアニリン、ポリピロール、ポリチオフェン、ポリアセチレン及びポリ−ｐ−フェニレン及びポリビニルカルバゾール）等が挙げられ、２種以上を併用してもよい。
なお、リチウム含有遷移金属リン酸塩は、遷移金属サイトの一部を他の遷移金属で置換したものであってもよい。
また、正極活物質は、その表面の少なくとも一部が高分子化合物を含む被覆層により被覆された被覆活物質であってもよい。
被覆層としては、上述した被覆負極活物質と同様のものを好適に用いることができる。 The positive electrode active material layer is a layer containing a positive electrode active material.
As the positive electrode active material, a composite oxide of lithium and a transition metal 金属 a composite oxide containing one kind of transition metal (LiCoO 2 , LiNiO 2 , LiAlMnO 4 , LiMnO 2, LiMn 2 O 4, etc.), and a transition metal element Two types of composite oxides (eg, LiFeMnO 4 , LiNi 1-x Co x O 2 , LiMn 1-y Co y O 2 , LiNi 1/3 Co 1/3 Al 1/3 O 2 and LiNi 0.8 Co 0.15 Al 0.05 O 2 ) and a composite oxide having three or more metal elements [eg, LiMaM′bM ″ cO 2 (M, M ′ and M ″ are different transition metal elements, and a + b + c = 1. For example, LiNi 1/3 Mn 1/3 Co 1/3 O 2, etc.], etc., and lithium-containing transition metal phosphates (eg, LiFePO 4 , LiCoPO 4 , LiMnPO 4 and LiNiPO 4 ), transition metal oxides (eg, MnO 2 and V 2 O 5 ), transition metal sulfides (eg, MoS 2 and TiS 2 ) and conductive polymers (eg, polyaniline, polypyrrole, polythiophene, polyacetylene) And poly-p-phenylene and polyvinyl carbazole) and the like, and two or more kinds may be used in combination.
Note that the lithium-containing transition metal phosphate may be one in which part of the transition metal site is substituted with another transition metal.
Further, the positive electrode active material may be a coated active material in which at least a part of its surface is coated with a coating layer containing a polymer compound.
As the coating layer, the same as the above-described coated negative electrode active material can be suitably used.

正極集電体としては、上述した負極の集電体と同様のものを好適に用いることができる。 As the positive electrode current collector, the same as the above-described negative electrode current collector can be suitably used.

リチウムイオン電池用正極は、正極活物質を用いること以外は、上述したリチウムイオン電池用負極と同様にして作成することができる。 The positive electrode for a lithium ion battery can be prepared in the same manner as the negative electrode for a lithium ion battery described above, except that the positive electrode active material is used.

本発明のリチウムイオン電池は、上述した作製方法により得られるリチウムイオン電池用負極を用いて対極となる電極を組み合わせて、セパレータと共にセル容器に収容し、その後、電解液を注入し、セル容器を密封する等の方法により作製することができる。
また、集電体の一方の面に正極を作製し、もう一方の面に、上述した作製方法により得られるリチウムイオン電池用負極を作製してバイポーラ（双極）型電極を作製し、バイポーラ（双極）型電極をセパレータと積層する。その後、セル容器に収納し、電解液を注入してセル容器を密封することで作製することができる。
なお、セル容器内に収容する負極とセパレータとして上述した第一、第二又は第三の負極活物質層が形成されたセパレータを用いて、本発明のリチウムイオン電池を作製することもできる。 The lithium ion battery of the present invention is a combination of an electrode serving as a counter electrode using a negative electrode for a lithium ion battery obtained by the above-described manufacturing method, and is housed in a cell container together with a separator. It can be manufactured by a method such as sealing.
In addition, a positive electrode is formed on one surface of the current collector, and a negative electrode for a lithium ion battery obtained by the above-described manufacturing method is formed on the other surface to form a bipolar (bipolar) electrode. ) Laminate the mold electrode with the separator. After that, the cell container is housed in the cell container, and the cell container is sealed by injecting an electrolytic solution.
In addition, the lithium ion battery of the present invention can also be manufactured using the negative electrode accommodated in the cell container and the separator on which the first, second, or third negative electrode active material layer described above is formed as the separator.

次に本発明を実施例によって具体的に説明するが、本発明の主旨を逸脱しない限り本発明は実施例に限定されるものではない。なお、特記しない限り部は重量部、％は重量％を意味する。また、スラリーの目付量は、単位面積あたりの活物質と導電助剤の合計重量を意味する（電解液重量は含まない）。 Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to the examples unless departing from the gist of the present invention. Unless otherwise specified, parts mean parts by weight and% means% by weight. Further, the basis weight of the slurry means the total weight of the active material and the conductive auxiliary agent per unit area (excluding the weight of the electrolytic solution).

＜製造例１：樹脂集電体の作製＞
２軸押出機にて、ポリプロピレン［商品名「サンアロマーＰＬ５００Ａ」、サンアロマー（株）製］７０部、カーボンナノチューブ［商品名：「ＦｌｏＴｕｂｅ９０００」、ＣＮａｎｏ社製］２５部及び分散剤［商品名「ユーメックス１００１」、三洋化成工業（株）製］５部を２００℃、２００ｒｐｍの条件で溶融混練して樹脂混合物を得た。
得られた樹脂混合物を、Ｔダイ押出しフィルム成形機に通して、それを延伸圧延することで、膜厚８０μｍの樹脂集電体を得た。
樹脂集電体は３ｃｍ×３ｃｍに切断し、片面にニッケル蒸着を施した後、電流取り出し用の端子（５ｍｍ×３ｃｍ）を接続した。 <Production Example 1: Production of resin current collector>
In a twin-screw extruder, 70 parts of polypropylene [trade name "Sun Allomer PL500A", manufactured by Sun Allomer Co., Ltd.], 25 parts of carbon nanotubes [trade name: "FloTube 9000", manufactured by CNano], and dispersant [trade name "UMEX 1001" 5 parts manufactured by Sanyo Chemical Industries, Ltd.] were melt-kneaded at 200 ° C. and 200 rpm to obtain a resin mixture.
The obtained resin mixture was passed through a T-die extrusion film forming machine and stretched and rolled to obtain a resin current collector having a thickness of 80 μm.
The resin current collector was cut into a size of 3 cm × 3 cm, nickel-deposited on one side, and a terminal for current extraction (5 mm × 3 cm) was connected.

＜製造例２：炭素被覆された珪素系活物質粒子の作製＞
酸化珪素粒子（シグマ・アルドリッチジャパン社製、体積平均粒子径１．５μｍ）を横型加熱炉中に入れ、メタンガスを通気しながら１１００℃／１０００Ｐａ、平均滞留時間約２時間の化学蒸着操作を行い、炭素含有量が２重量％で、表面が炭素で被覆された珪素系活物質粒子（体積平均粒子径１．５μｍ）を得た。 <Production Example 2: Production of silicon-based active material particles coated with carbon>
Silicon oxide particles (Sigma-Aldrich Japan Co., Ltd., volume average particle diameter 1.5 μm) were put into a horizontal heating furnace, and a chemical vapor deposition operation was performed at 1100 ° C./1000 Pa and an average residence time of about 2 hours while passing methane gas. Silicon-based active material particles having a carbon content of 2% by weight and having a surface coated with carbon were obtained (volume average particle diameter: 1.5 μm).

＜製造例３：炭素繊維の作製＞
炭素繊維は、Ｅｉｉｃｈｉ Ｙａｓuｄａ，Ａｓａｏ Ｏｙａ，Ｓｈｉｎｙａ Ｋｏｍｕｒａ，Ｓｈｉｇｅｋｉ Ｔｏｍｏｎｏｈ，Ｔａｋａｓｈｉ Ｎｉｓｈｉｚａｗａ，Ｓｈｉｎｓｕｋｅ Ｎａｇａｔａ，Ｔａｋａｓｈｉ Ａｋａｔｓｕ、ＣＡＲＢＯＮ、５０、２０１２、１４３２−１４３４及びＥｉｉｃｈｉ Ｙａｓｕｄａ，Ｔａｋａｓｈｉ Ａｋａｔｓｕ，Ｙａｓｕｈｉｒｏ Ｔａｎａｂｅ，Ｋａｚｕｍａｓａ Ｎａｋａｍｕｒａ，Ｙａｓｕｔｏ Ｈｏｓｈｉｋａｗａ，Ｎａｏｙａ Ｍｉｙａｊｉｍａ、ＴＡＮＳＯ、２５５、２０１２、２５４〜２６５頁の製造方法を参考にして以下の方法で製造した。
炭素前駆体として合成メソフェーズピッチＡＲ・ＭＰＨ［三菱ガス化学（株）製］１０重量部とポリメチルペンテンＴＰＸ ＲＴ１８［三井化学（株）製］９０重量部を、バレル温度３１０℃、窒素雰囲気下で一軸押出機を用いて溶融混練し、樹脂組成物を調製した。
上記樹脂組成物を３９０℃で溶融押出し紡糸した。紡糸した樹脂組成物を電気炉に入れ、窒素雰囲気下２７０℃で３時間保持し炭素前駆体を安定化させた。ついで、電気炉を１時間かけて５００℃まで昇温し、５００℃で１時間保持し、ポリメチルペンテンを分解除去した。電気炉を２時間かけて１０００℃まで昇温し１０００℃で３０分間保持し、残った安定化させた炭素前駆体を導電性繊維とした。
得られた導電性繊維９０重量部、水５００重量部とφ０．１ｍｍのジルコニアボール１０００重量部をポットミル容器に入れ５分間粉砕した。ジルコニアボールを分級後、１００℃で乾燥し、炭素繊維を得た。
ＳＥＭでの測定結果より、得られた炭素繊維の平均繊維径は、０．３μｍ、平均繊維長は２６μｍ（アスペクト比８７）であり、電気伝導度は６００ｍＳ／ｃｍであった。 <Production Example 3: Production of carbon fiber>
Carbon fibers, Eiichi Yasuda, Asao Oya, Shinya Komura, Shigeki Tomonoh, Takashi Nishizawa, Shinsuke Nagata, Takashi Akatsu, CARBON, 50,2012,1432-1434 and Eiichi Yasuda, Takashi Akatsu, Yasuhiro Tanabe, Kazumasa Nakamura, Yasuto Hoshikawa, It was produced by the following method with reference to the production method of Naoya Miyajima, TANSO, 255, 2012, pages 254 to 265.
As a carbon precursor, 10 parts by weight of a synthetic mesophase pitch AR / MPH [manufactured by Mitsubishi Gas Chemical Co., Ltd.] and 90 parts by weight of polymethylpentene TPX RT18 [manufactured by Mitsui Chemicals, Inc.] at a barrel temperature of 310 ° C. under a nitrogen atmosphere. The mixture was melt-kneaded using a single screw extruder to prepare a resin composition.
The resin composition was melt-extruded at 390 ° C. and spun. The spun resin composition was placed in an electric furnace and kept at 270 ° C. for 3 hours under a nitrogen atmosphere to stabilize the carbon precursor. Then, the temperature of the electric furnace was raised to 500 ° C. over 1 hour, and the temperature was maintained at 500 ° C. for 1 hour to decompose and remove polymethylpentene. The temperature of the electric furnace was raised to 1000 ° C. over 2 hours and maintained at 1000 ° C. for 30 minutes, and the remaining stabilized carbon precursor was used as conductive fibers.
90 parts by weight of the obtained conductive fiber, 500 parts by weight of water and 1000 parts by weight of zirconia balls having a diameter of 0.1 mm were put in a pot mill container and pulverized for 5 minutes. After the zirconia balls were classified, they were dried at 100 ° C. to obtain carbon fibers.
According to the measurement result by SEM, the average fiber diameter of the obtained carbon fiber was 0.3 μm, the average fiber length was 26 μm (aspect ratio 87), and the electric conductivity was 600 mS / cm.

＜製造例４：負極活物質層用スラリー１の作製＞
エチレンカーボネート（ＥＣ）とプロピレンカーボネート（ＰＣ）の混合溶媒（体積比率１：１）にＬｉＮ（ＳＯ２Ｆ）２（以下、ＬｉＦＳＩともいう）を２ｍｏｌ／Ｌの割合で溶解させて作製した電解液１２部に製造例２で得られた珪素系活物質粒子８部、導電助剤として製造例３で得られた炭素繊維２部を添加した後、遊星撹拌型混合混練装置｛あわとり練太郎［（株）シンキー製］｝を用いて２０００ｒｐｍで５分間混合して、負極活物質層用スラリー１を作製した。 <Production Example 4: Production of slurry 1 for negative electrode active material layer>
Electrolyte prepared by dissolving LiN (SO 2 F) 2 (hereinafter also referred to as LiFSI) at a rate of 2 mol / L in a mixed solvent (volume ratio 1: 1) of ethylene carbonate (EC) and propylene carbonate (PC) After adding 12 parts of the silicon-based active material particles obtained in Production Example 2 and 8 parts of the carbon fiber obtained in Production Example 3 as a conductive aid, 2 parts of the planetary stirring type mixing and kneading apparatus {Awatori Rentaro [ The mixture was mixed at 2,000 rpm for 5 minutes using｝ to prepare a slurry 1 for a negative electrode active material layer.

＜製造例５：被覆層用高分子化合物溶液の作製＞
撹拌機、温度計、還流冷却管、滴下ロート及び窒素ガス導入管を付した４つ口フラスコにＤＭＦ４０７．９部を仕込み７５℃に昇温した。次いで、メタクリル酸２４２．８部、メチルメタクリレート９７．１部、２−エチルヘキシルメタクリレート２４２．８部、及びＤＭＦ１１６．５部を配合したモノマー配合液と、２，２’−アゾビス（２，４−ジメチルバレロニトリル）１．７部及び２，２’−アゾビス（２−メチルブチロニトリル）４．７部をＤＭＦ５８．３部に溶解した開始剤溶液とを４つ口フラスコ内に窒素を吹き込みながら、撹拌下、滴下ロートで２時間かけて連続的に滴下してラジカル重合を行った。滴下終了後、７５℃で反応を３時間継続した。次いで８０℃に昇温し反応を３時間継続し樹脂固形分濃度が５０重量％の共重合体溶液を得た。これにＤＭＦを７８９．８部加えて、樹脂固形分濃度が３０重量％である被覆層用高分子化合物溶液を得た。 <Production Example 5: Preparation of polymer compound solution for coating layer>
407.9 parts of DMF was charged into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen gas inlet tube, and the temperature was raised to 75 ° C. Next, a monomer compounding solution containing 242.8 parts of methacrylic acid, 97.1 parts of methyl methacrylate, 242.8 parts of 2-ethylhexyl methacrylate, and 116.5 parts of DMF, and 2,2′-azobis (2,4-dimethyl While blowing nitrogen into a four-necked flask, an initiator solution in which 1.7 parts of valeronitrile) and 4.7 parts of 2,2′-azobis (2-methylbutyronitrile) were dissolved in 58.3 parts of DMF was added. Under stirring, radical polymerization was carried out by dropping continuously over 2 hours with a dropping funnel. After completion of the dropwise addition, the reaction was continued at 75 ° C. for 3 hours. Next, the temperature was raised to 80 ° C., and the reaction was continued for 3 hours to obtain a copolymer solution having a resin solid content of 50% by weight. To this was added 789.8 parts of DMF to obtain a coating layer polymer compound solution having a resin solid content of 30% by weight.

＜製造例６：炭素系被覆活物質粒子１の作製＞
難黒鉛化性炭素粉末［（株)クレハ・バッテリー・マテリアルズ・ジャパン製カーボトロン（登録商標）ＰＳ（Ｆ）、数平均粒子径１８μｍ］９０部を万能混合機ハイスピードミキサーＦＳ２５［（株）アーステクニカ製］に入れ、室温、１５０ｒｐｍで撹拌した状態で、製造例５で得られた被覆層用高分子化合物溶液３０部を樹脂固形分として５重量部になるように６０分かけて滴下混合し、さらに３０分撹拌した。次いで、撹拌を維持したままアセチレンブラック［デンカ(株)製 デンカブラック（登録商標）］５重量部を３回に分けて混合し、３０分撹拌したままで７０℃に昇温し、０．０１ＭＰａまで減圧し３０分保持した。上記操作により炭素系被覆活物質粒子１を得た。 <Production Example 6: Production of carbon-based coated active material particles 1>
90 parts of non-graphitizable carbon powder [Carbotron (registered trademark) PS (F), number average particle diameter 18 μm, manufactured by Kureha Battery Materials Japan Co., Ltd.] is a universal mixer high speed mixer FS25 [Earth Corporation] Technica], and 30 parts of the coating layer polymer compound solution obtained in Production Example 5 was dropped and mixed over 60 minutes while stirring at 150 rpm at room temperature so that the resin solid content was 5 parts by weight. And further stirred for 30 minutes. Then, 5 parts by weight of acetylene black [Denka Black (registered trademark) manufactured by Denka Corporation] was mixed in three portions while maintaining the stirring, and the temperature was increased to 70 ° C. while stirring for 30 minutes, and 0.01 MPa. The pressure was reduced to and maintained for 30 minutes. Through the above operation, carbon-based coated active material particles 1 were obtained.

＜製造例７：負極活物質層用スラリー２の作製＞
エチレンカーボネート（ＥＣ）とプロピレンカーボネート（ＰＣ）の混合溶媒（体積比率１：１）にＬｉＦＳＩを２ｍｏｌ／Ｌの割合で溶解させて作製した電解液１２部に製造例６で得られた炭素系被覆活物質粒子１を８部、製造例２で得られた珪素系活物質粒子１部、導電助剤として製造例３で得られた炭素繊維１部を添加した後、遊星撹拌型混合混練装置｛あわとり練太郎［（株）シンキー製］｝を用いて２０００ｒｐｍで５分間混合して、負極活物質層用スラリー２を作製した。 <Production Example 7: Production of slurry 2 for negative electrode active material layer>
The carbon-based coating obtained in Production Example 6 was applied to 12 parts of an electrolyte prepared by dissolving LiFSI at a ratio of 2 mol / L in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio 1: 1). After adding 8 parts of the active material particles 1, 1 part of the silicon-based active material particles obtained in Production Example 2, and 1 part of the carbon fiber obtained in Production Example 3 as a conductive auxiliary, a planetary stirring type mixing and kneading apparatus was used. The mixture was mixed at 2,000 rpm for 5 minutes using Nawataro Nawataro [manufactured by Shinky Co., Ltd.] to prepare a slurry 2 for a negative electrode active material layer.

＜製造例８：負極活物質層用スラリー３の作製＞
エチレンカーボネート（ＥＣ）とプロピレンカーボネート（ＰＣ）の混合溶媒（体積比率１：１）にＬｉＦＳＩを２ｍｏｌ／Ｌの割合で溶解させて作製した電解液１３部に製造例６で得られた炭素系被覆負極活物質粒子１を１０部、導電助剤として製造例３で得られた炭素繊維１部を添加した後、遊星撹拌型混合混練装置｛あわとり練太郎［（株）シンキー製］｝を用いて２０００ｒｐｍで５分間混合して、負極活物質層用スラリー３を作製した。 <Production Example 8: Production of slurry 3 for negative electrode active material layer>
13 parts of an electrolyte prepared by dissolving LiFSI at a ratio of 2 mol / L in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio: 1: 1) was coated with the carbon-based coating obtained in Production Example 6. After adding 10 parts of the negative electrode active material particles 1 and 1 part of the carbon fiber obtained in Production Example 3 as a conductive aid, using a planetary stirring type mixing and kneading apparatus {Nawataro Nawataro [manufactured by Shinky Corporation]}. The mixture was mixed at 2,000 rpm for 5 minutes to prepare a slurry 3 for a negative electrode active material layer.

＜製造例９：リチウムイオン電池用正極１の作製＞
正極活物質粉末（ＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２粉末、体積平均粒子径４μｍ）１００部を万能混合機ハイスピードミキサーＦＳ２５［（株）アーステクニカ製］に入れ、室温、７２０ｒｐｍで撹拌した状態で、製造例５で得られた被覆層用高分子化合物溶液１１．２部を２分かけて滴下し、さらに５分撹拌した。
次いで、撹拌した状態で導電剤としてアセチレンブラック［電気化学工業（株）製 デンカブラック（登録商標）］６．２部を分割しながら２分間で投入し、３０分撹拌を継続した。その後、撹拌を維持したまま０．０１ＭＰａまで減圧し、次いで撹拌と減圧度を維持したまま温度を１４０℃まで昇温し、撹拌、減圧度及び温度を８時間維持して揮発分を留去した。得られた粉体を目開き２１２μｍの篩いで分級し、被覆正極活物質を得た。
その後、エチレンカーボネート（ＥＣ）とプロピレンカーボネート（ＰＣ）の混合溶媒（体積比率１：１）にＬｉＦＳＩを２ｍｏｌ／Ｌの割合で溶解させて作製した電解液５部に上記被覆正極活物質を１０部、導電助剤として製造例３で得られた炭素繊維１部を添加した後、遊星撹拌型混合混練装置｛あわとり練太郎［（株）シンキー製］｝を用いて２０００ｒｐｍで５分間混合して、正極活物質層用スラリーを作製した。
製造例１で得られた樹脂集電体の片面に、得られた正極活物質層用スラリーを目付量が６０ｍｇ／ｃｍ２となるように塗布し、５ＭＰａの圧力で約１０秒プレスし、リチウムイオン電池用正極１（２９ｍｍ×２９ｍｍ、厚み２４０μｍ）を作製した。 <Production Example 9: Production of positive electrode 1 for lithium ion battery>
100 parts of the positive electrode active material powder (LiNi 0.8 Co 0.15 Al 0.05 O 2 powder, volume average particle diameter of 4 μm) was put into a universal mixer, High Speed Mixer FS25 [manufactured by Earth Technica Co., Ltd.] With stirring at 720 rpm, 11.2 parts of the coating layer polymer compound solution obtained in Production Example 5 was added dropwise over 2 minutes, and the mixture was further stirred for 5 minutes.
Then, in a stirring state, 6.2 parts of acetylene black (Denka Black (registered trademark) manufactured by Denki Kagaku Kogyo KK) was added as a conductive agent over 2 minutes while dividing, and stirring was continued for 30 minutes. Thereafter, the pressure was reduced to 0.01 MPa while maintaining the stirring, then the temperature was increased to 140 ° C. while maintaining the stirring and the degree of vacuum, and the volatile components were distilled off while maintaining the stirring, the degree of vacuum and the temperature for 8 hours. . The obtained powder was classified with a sieve having an opening of 212 μm to obtain a coated positive electrode active material.
Then, 10 parts of the coated positive electrode active material was added to 5 parts of an electrolyte prepared by dissolving LiFSI at a ratio of 2 mol / L in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio 1: 1). After adding 1 part of the carbon fiber obtained in Production Example 3 as a conductive aid, the mixture was mixed at 2,000 rpm for 5 minutes using a planetary stirring type mixing and kneading device {Awatori Rintaro [manufactured by Shinky Corporation]}. Then, a slurry for a positive electrode active material layer was prepared.
On one surface of the resin current collector obtained in Production Example 1, the obtained slurry for a positive electrode active material layer was applied so as to have a basis weight of 60 mg / cm 2, and was pressed at a pressure of 5 MPa for about 10 seconds. A positive electrode 1 for an ion battery (29 mm × 29 mm, thickness 240 μm) was produced.

＜製造例１０：リチウムイオン電池用正極２の作製＞
製造例９で用いた正極活物質層用スラリーを目付量が１００ｍｇ／ｃｍ２となるように塗布した以外は製造例９と同様にしてリチウムイオン電池用正極２（２９ｍｍ×２９ｍｍ、厚み３９０μｍ）を得た。 <Production Example 10: Production of positive electrode 2 for lithium ion battery>
A positive electrode 2 for a lithium ion battery (29 mm × 29 mm, thickness 390 μm) was prepared in the same manner as in Production Example 9 except that the slurry for the positive electrode active material layer used in Production Example 9 was applied so that the basis weight was 100 mg / cm 2. Obtained.

＜製造例１１：リチウムイオン電池用正極３の作製＞
製造例９で用いた正極活物質層用スラリーを目付量が１５５ｍｇ／ｃｍ２となるように塗布した以外は製造例９と同様にしてリチウムイオン電池用正極３（２９ｍｍ×２９ｍｍ、厚み６００μｍ）を得た。 <Production Example 11: Production of positive electrode 3 for lithium ion battery>
A positive electrode for lithium ion battery 3 (29 mm × 29 mm, thickness 600 μm) was prepared in the same manner as in Production Example 9 except that the slurry for the positive electrode active material layer used in Production Example 9 was applied so that the basis weight was 155 mg / cm 2. Obtained.

（実施例１）
［評価用リチウムイオン電池の負極の作製］
製造例１で得られた樹脂集電体の片面に、製造例４で得られた負極活物質層用スラリー１を目付量０．５ｍｇ／ｃｍ２となるように塗布し、５ＭＰａの圧力で約１０秒プレスし、第二の負極活物質層を形成した。別途、アラミド不織布（日本バイリーン製、２４１５Ｒ）上に製造例７で得られた負極活物質層用スラリー２を目付量が２０ｍｇ／ｃｍ２となるように塗布し、５ＭＰａの圧力で約１０秒プレスし、第一の負極活物質層（厚み２００μｍ）を形成した。その後、樹脂集電体上に形成された第二の負極活物質層の面上に、第一の負極活物質層を重ねアラミド不織布を剥がした後に、再度１ＭＰａの圧力で約１０秒プレスして、集電体と第一の負極活物質層との間に第二の負極活物質層を有するリチウムイオン電池用負極（３ｃｍ×３ｃｍ）を作製した。 (Example 1)
[Preparation of negative electrode of lithium ion battery for evaluation]
The slurry 1 for the negative electrode active material layer obtained in Production Example 4 was applied to one surface of the resin current collector obtained in Production Example 1 so as to have a basis weight of 0.5 mg / cm 2, and was applied under a pressure of 5 MPa. Pressing was performed for 10 seconds to form a second negative electrode active material layer. Separately, the slurry 2 for the negative electrode active material layer obtained in Production Example 7 was applied on an aramid nonwoven fabric (2415R, manufactured by Japan Vilene) so that the basis weight became 20 mg / cm 2, and pressed at a pressure of 5 MPa for about 10 seconds. Then, a first negative electrode active material layer (thickness: 200 μm) was formed. After that, the first negative electrode active material layer was stacked on the surface of the second negative electrode active material layer formed on the resin current collector, and the aramid nonwoven fabric was peeled off. Then, pressing was performed again at a pressure of 1 MPa for about 10 seconds. Then, a negative electrode (3 cm × 3 cm) for a lithium ion battery having a second negative electrode active material layer between the current collector and the first negative electrode active material layer was produced.

［セパレータ本体の製造］
平板状のセルガード３５０１（ＰＰ製、厚さ２５μｍ）を４５ｍｍ×４５ｍｍの正方形に切り出して、セパレータ本体とした。 [Manufacture of separator body]
A flat cell guard 3501 (made of PP, 25 μm thick) was cut into a square of 45 mm × 45 mm to obtain a separator body.

［評価用リチウムイオン電池の作製］
得られたリチウムイオン電池用負極に予め電解液で湿らせたセパレータを乗せ（このときの負極に乗せる面は、セパレータが枠材に貼り合わされている面と逆の面）、この負極とセパレータが一体化したものと、製造例９で得られたリチウムイオン電池用正極１を重ね合わせた。その後、エチレンカーボネート（ＥＣ）とプロピレンカーボネート（ＰＣ）の混合溶媒（体積比率１：１）にＬｉＦＳＩを２ｍｏｌ／Ｌの割合で溶解させて作製した電解液を注入した。
その後、充放電測定装置「ＨＪ−ＳＤ８」［北斗電工（株）製］を用いて、定電流定電圧方式（０．１Ｃ）で４．２Ｖまで充電して、評価用リチウムイオン電池を作製した。 [Production of lithium ion battery for evaluation]
A separator pre-moistened with an electrolytic solution is placed on the obtained negative electrode for a lithium ion battery (the surface on which the negative electrode is placed is a surface opposite to the surface on which the separator is bonded to the frame material). The integrated product and the positive electrode 1 for a lithium ion battery obtained in Production Example 9 were overlaid. Thereafter, an electrolytic solution prepared by dissolving LiFSI at a ratio of 2 mol / L in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio 1: 1) was injected.
Thereafter, using a charge / discharge measuring device “HJ-SD8” (manufactured by Hokuto Denko Corporation), the battery was charged to 4.2 V by a constant current / constant voltage method (0.1 C) to produce a lithium ion battery for evaluation. .

（実施例２）
製造例１で得られた樹脂集電体の片面に、製造例７で得られた負極活物質層用スラリー２を目付量２０ｍｇ／ｃｍ２となるように塗布し、５ＭＰａの圧力で約１０秒プレスし第一の負極活物質層（厚み２００μｍ）を得た。別途、アラミド不織布（日本バイリーン製、２４１５Ｒ）上に製造例４で得られた負極活物質層用スラリー１を目付量が０．５ｍｇ／ｃｍ２となるように塗布し、５ＭＰａの圧力で約１０秒プレスし、第二の負極活物質層を形成した。その後、樹脂集電体上に形成された第一の負極活物質層の面上に、第二の負極活物質層を重ね、アラミド不織布を剥がした後に、再度１ＭＰａの圧力で約１０秒プレスして、リチウムイオン電池用負極（３ｃｍ×３ｃｍ）を作製した。
上記方法により得られたリチウムイオン電池用負極を用い、実施例１と同様にしてセパレータと製造例９で得られたリチウムイオン電池用正極１とを組み合わせて電解液を注入し、充電をすることにより、第一の負極活物質層とセパレータとの間に第二の負極活物質層を有する評価用リチウムイオン電池を作製した。 (Example 2)
The slurry 2 for the negative electrode active material layer obtained in Production Example 7 was applied to one surface of the resin current collector obtained in Production Example 1 so as to have a basis weight of 20 mg / cm 2, and a pressure of 5 MPa was applied for about 10 seconds. It pressed and obtained the 1st negative electrode active material layer (200 micrometers in thickness). Separately, the slurry 1 for the negative electrode active material layer obtained in Production Example 4 was applied on an aramid nonwoven fabric (2415R, manufactured by Japan Vilene) so that the basis weight was 0.5 mg / cm 2, and the pressure was 5 MPa and the pressure was about 10 After pressing for 2 seconds, a second negative electrode active material layer was formed. Then, the second negative electrode active material layer was stacked on the surface of the first negative electrode active material layer formed on the resin current collector, and after the aramid non-woven fabric was peeled off, it was pressed again at a pressure of 1 MPa for about 10 seconds. Thus, a negative electrode (3 cm × 3 cm) for a lithium ion battery was produced.
Using the negative electrode for a lithium ion battery obtained by the above method, combining the separator and the positive electrode 1 for a lithium ion battery obtained in Production Example 9 in the same manner as in Example 1, injecting an electrolytic solution, and charging. As a result, a lithium ion battery for evaluation having the second negative electrode active material layer between the first negative electrode active material layer and the separator was produced.

（実施例３）
製造例１で得られた樹脂集電体の片面に、製造例４で得られた負極活物質層用スラリー１を目付量０．２５ｍｇ／ｃｍ２となるように塗布し、５ＭＰａの圧力で約１０秒プレスし、第二の負極活物質層を形成した。
別途、アラミド不織布（日本バイリーン製、２４１５Ｒ）上に製造例７で得られた負極活物質層用スラリー２を目付量２０ｍｇ／ｃｍ２となるように塗布し、５ＭＰａの圧力で１０秒プレスし、第一の負極活物質層（厚み２００μｍ）を得た。さらに、アラミド不織布（日本バイリーン製、２４１５Ｒ）上に、製造例４で得られた負極活物質層用スラリー１を目付量０．２５ｍｇ／ｃｍ２となるように塗布し、第三の負極活物質層を得た。
樹脂集電体上に形成された第二の負極活物質層の面上に、第一の負極活物質層を重ね、上記アラミド不織布を第一の負極活物質層から剥がした。次いで、第一の負極活物質層の第二の負極活物質層を有する面と反対側の面上に、第三の負極活物質層を重ね、上記アラミド不織布を第一の負極活物質層から剥がした。その後、再度１ＭＰａの圧力で約１０秒プレスして、リチウムイオン電池用負極（３ｃｍ×３ｃｍ）を作製した。
上記方法により得られたリチウムイオン電池用負極を用い、実施例１と同様にしてセパレータと製造例９で得られたリチウムイオン電池用正極１とを組み合わせて電解液を注入し、充電をすることにより、集電体と第一の負極活物質層との間に第二の負極活物質層を有し、第一の負極活物質層とセパレータとの間に第三の負極活物質層を有する評価用リチウムイオン電池を作製した。 (Example 3)
The slurry 1 for a negative electrode active material layer obtained in Production Example 4 was applied to one surface of the resin current collector obtained in Production Example 1 so as to have a basis weight of 0.25 mg / cm 2, and was applied under a pressure of 5 MPa. Pressing was performed for 10 seconds to form a second negative electrode active material layer.
Separately, the slurry 2 for the negative electrode active material layer obtained in Production Example 7 was applied on an aramid nonwoven fabric (manufactured by Japan Vilene, 2415R) so as to have a basis weight of 20 mg / cm 2 and pressed at a pressure of 5 MPa for 10 seconds. A first negative electrode active material layer (thickness: 200 μm) was obtained. Furthermore, the slurry 1 for the negative electrode active material layer obtained in Production Example 4 was applied onto an aramid nonwoven fabric (2415R, manufactured by Japan Vilene) so as to have a basis weight of 0.25 mg / cm 2, and a third negative electrode active material was obtained. Layer obtained.
The first negative electrode active material layer was stacked on the surface of the second negative electrode active material layer formed on the resin current collector, and the aramid nonwoven fabric was peeled off from the first negative electrode active material layer. Next, a third negative electrode active material layer is stacked on the surface of the first negative electrode active material layer opposite to the surface having the second negative electrode active material layer, and the aramid nonwoven fabric is removed from the first negative electrode active material layer. I peeled it off. Thereafter, pressing was performed again at a pressure of 1 MPa for about 10 seconds to produce a negative electrode (3 cm × 3 cm) for a lithium ion battery.
Using the negative electrode for a lithium ion battery obtained by the above method, combining the separator and the positive electrode 1 for a lithium ion battery obtained in Production Example 9 in the same manner as in Example 1, injecting an electrolytic solution, and charging. Thereby, having a second anode active material layer between the current collector and the first anode active material layer, having a third anode active material layer between the first anode active material layer and the separator A lithium ion battery for evaluation was produced.

（実施例４）
製造例４で得られた負極活物質層用スラリー１を目付量５ｍｇ／ｃｍ２となるように塗布したこと以外は、実施例１と同様にしてリチウムイオン電池用負極を作製した。
上記方法により得られたリチウムイオン電池用負極と、製造例１０で得られたリチウムイオン電池用正極２とを用いたこと以外は、実施例１と同様にして評価用リチウムイオン電池を作製した。 (Example 4)
A negative electrode for a lithium ion battery was produced in the same manner as in Example 1, except that the slurry 1 for a negative electrode active material layer obtained in Production Example 4 was applied so as to have a basis weight of 5 mg / cm 2 .
A lithium ion battery for evaluation was produced in the same manner as in Example 1, except that the negative electrode for a lithium ion battery obtained by the above method and the positive electrode 2 for a lithium ion battery obtained in Production Example 10 were used.

（実施例５）
製造例４で得られた負極活物質層用スラリー１を目付量０．１５ｍｇ／ｃｍ２となるように塗布したこと以外は、実施例１と同様にして評価用リチウムイオン電池を作製した。 (Example 5)
A lithium ion battery for evaluation was produced in the same manner as in Example 1 except that the slurry 1 for a negative electrode active material layer obtained in Production Example 4 was applied so as to have a basis weight of 0.15 mg / cm 2 .

（実施例６）
製造例７で得られた負極活物質層用スラリー２を製造例８で得られた負極活物質層用スラリー３に変更したこと以外は、実施例１と同様にして評価用リチウムイオン電池を作製した。 (Example 6)
A lithium ion battery for evaluation was produced in the same manner as in Example 1 except that the slurry 2 for the negative electrode active material layer obtained in Production Example 7 was changed to the slurry 3 for the negative electrode active material layer obtained in Production Example 8. did.

（比較例１）
製造例１で得られた樹脂集電体の片面に、製造例７で得られた負極活物質層用スラリー２を目付量２０ｍｇ／ｃｍ２となるように塗布し、５ＭＰａの圧力で約１０秒プレスして厚み２００μｍの負極活物質層を１層のみ形成し、リチウムイオン電池用負極（３ｃｍ×３ｃｍ）を作製した。
上記方法により得られたリチウムイオン電池用負極を用いたこと以外は、実施例１と同様にして評価用リチウムイオン電池を作製した。 (Comparative Example 1)
The slurry 2 for the negative electrode active material layer obtained in Production Example 7 was applied to one surface of the resin current collector obtained in Production Example 1 so as to have a basis weight of 20 mg / cm 2, and a pressure of 5 MPa was applied for about 10 seconds. Pressing was performed to form only one negative electrode active material layer having a thickness of 200 μm to prepare a negative electrode (3 cm × 3 cm) for a lithium ion battery.
A lithium ion battery for evaluation was produced in the same manner as in Example 1, except that the negative electrode for a lithium ion battery obtained by the above method was used.

（比較例２）
製造例４で得られた負極活物質層用スラリー１を目付量８ｍｇ／ｃｍ２となるように塗布したこと以外は、実施例１と同様にして評価用リチウムイオン電池用負極を作製した。
上記方法により得られたリチウムイオン電池用負極と、製造例１１で得られたリチウムイオン電池用正極３とを用いたこと以外は、実施例１と同様にして評価用リチウムイオン電池を作製した。 (Comparative Example 2)
A negative electrode for an evaluation lithium ion battery was produced in the same manner as in Example 1, except that the slurry 1 for a negative electrode active material layer obtained in Production Example 4 was applied so as to have a basis weight of 8 mg / cm 2 .
A lithium ion battery for evaluation was produced in the same manner as in Example 1, except that the negative electrode for a lithium ion battery obtained by the above method and the positive electrode 3 for a lithium ion battery obtained in Production Example 11 were used.

（比較例３）
製造例４で得られた負極活物質層用スラリー１を目付量０．０５ｍｇ／ｃｍ２となるように塗布したこと以外は、実施例１と同様にして評価用リチウムイオン電池を作製した。 (Comparative Example 3)
A lithium ion battery for evaluation was produced in the same manner as in Example 1 except that the slurry 1 for a negative electrode active material layer obtained in Production Example 4 was applied so as to have a basis weight of 0.05 mg / cm 2 .

（釘刺し試験）
実施例１〜６及び比較例１〜３で得られた評価用リチウムイオン電池の負極が形成された面の中央部に、５ｍｍ／ｓの速度で、釘（３ｍｍ径、製品名リチウムイオンバッテリー釘刺し試験機、株式会社山本金属製作所社製）を差し込み、負極側表面の釘を刺し込んだ部分の周囲５ｍｍにおける最高到達温度を測定した。
最高到達温度が８０℃以下のものを〇と評価し、最高到達温度が８０℃を超えたものを×と評価した。 (Nail penetration test)
At the speed of 5 mm / s, a nail (3 mm diameter, product name lithium ion battery nail) was formed at the center of the surface of the lithium ion battery for evaluation obtained in Examples 1 to 6 and Comparative Examples 1 to 3 where the negative electrode was formed. A piercing tester, manufactured by Yamamoto Metal Works Co., Ltd.) was inserted, and the maximum temperature at 5 mm around the portion where the nail was pierced on the negative electrode side surface was measured.
Those with a maximum attainment temperature of 80 ° C or lower were evaluated as Δ, and those with a maximum attainment temperature exceeding 80 ° C were evaluated as x.

Figure 2020013754
Figure 2020013754

実施例１〜６に係るリチウムイオン電池では、釘刺し試験における最高到達温度が８０℃以下であり、発熱を抑制できることが確認された。実施例１〜６に係るリチウムイオン電池では、短絡が発生した部位において導電パスが好適に切断されて、発熱が抑制されたものと考えられる。特に、実施例３に係るリチウムイオン電池では、集電体と第一の負極活物質層との間に第二の負極活物質層を有し、第一の負極活物質層とセパレータとの間に第三の負極活物質層を有しているため、短絡が発生した部位において導電パスがより好適に切断されて、発熱が抑制されたものと考えられる。
一方、比較例１及び３に係るリチウムイオン電池では、短絡が発生した部位において導電パスが十分に切断されず、発熱が抑制されなかったと考えられる。
また、比較例２に係るリチウムイオン電池では、膜厚が厚く、第二の負極活物質層に含まれる珪素系活物質量が多すぎたために、第二の負極活物質層表面の固体電解質界面の分解反応に伴う発熱により、釘刺し試験における最高到達温度が高くなったと考えられる。 In the lithium ion batteries according to Examples 1 to 6, the maximum temperature reached in the nail penetration test was 80 ° C. or less, and it was confirmed that heat generation could be suppressed. In the lithium ion batteries according to Examples 1 to 6, it is considered that the conductive path was appropriately cut at the site where the short circuit occurred, and heat generation was suppressed. In particular, the lithium ion battery according to Example 3 has a second negative electrode active material layer between the current collector and the first negative electrode active material layer, and has a structure between the first negative electrode active material layer and the separator. It is considered that since the third negative electrode active material layer had the third negative electrode active material layer, the conductive path was more appropriately cut at the site where the short circuit occurred, and heat generation was suppressed.
On the other hand, in the lithium ion batteries according to Comparative Examples 1 and 3, it is considered that the conductive path was not sufficiently cut at the site where the short circuit occurred, and heat generation was not suppressed.
Further, in the lithium ion battery according to Comparative Example 2, since the film thickness was large and the amount of the silicon-based active material contained in the second negative electrode active material layer was too large, the solid electrolyte interface on the surface of the second negative electrode active material layer was It is considered that the maximum temperature reached in the nail penetration test was increased due to the heat generated by the decomposition reaction of.

本発明のリチウムイオン電池は、特に、携帯電話、パーソナルコンピューター及びハイブリッド自動車、電気自動車用に用いられるリチウムイオン電池として有用である。 The lithium ion battery of the present invention is particularly useful as a lithium ion battery used for mobile phones, personal computers, hybrid vehicles, and electric vehicles.

Claims (8)

少なくとも集電体と、負極活物質層と、セパレータとをこの順で積層した構成を備えた リチウムイオン電池であって、
前記負極活物質層は、少なくとも第一の負極活物質層と、第二の負極活物質層とを含み、
前記第二の負極活物質層の膜厚が１．５〜５０μｍであり、
前記第二の負極活物質層に含まれる珪素系活物質量が、０．１〜５ｍｇ／ｃｍ２であり、
前記第二の負極活物質層に含まれる珪素系活物質の前記第二の負極活物質層の重量に対する重量割合が、前記第一の負極活物質層に含まれる珪素系活物質の前記第一の負極活物質層の重量に対する重量割合よりも大きいことを特徴とするリチウムイオン電池。 A lithium ion battery having a configuration in which at least a current collector, a negative electrode active material layer, and a separator are stacked in this order,
The negative electrode active material layer includes at least a first negative electrode active material layer and a second negative electrode active material layer,
The thickness of the second negative electrode active material layer is 1.5 to 50 μm,
An amount of the silicon-based active material contained in the second negative electrode active material layer is 0.1 to 5 mg / cm 2 ,
The weight ratio of the silicon-based active material contained in the second anode active material layer to the weight of the second anode active material layer is the same as that of the silicon-based active material contained in the first anode active material layer. A lithium ion battery having a weight ratio larger than the weight of the negative electrode active material layer. 前記第二の負極活物質層に含まれる前記珪素系活物質の含有量は、前記第二の負極活物質層の重量に対して４０重量％以上であり、前記第一の負極活物質層に含まれる前記珪素系活物質の含有量は、前記第一の負極活物質層の重量に対して４０重量％未満である請求項１に記載のリチウムイオン電池。 The content of the silicon-based active material contained in the second negative electrode active material layer is 40% by weight or more based on the weight of the second negative electrode active material layer. 2. The lithium ion battery according to claim 1, wherein the content of the silicon-based active material is less than 40% by weight based on the weight of the first negative electrode active material layer. 3. 前記第一の負極活物質層の前記第二の負極活物質層を有する面と反対側の面上に、第三の負極活物質層を有し、前記第三の負極活物質層の膜厚が１．５〜５０μｍであり、前記第三の負極活物質層に含まれる珪素系活物質量が、０．１〜５ｍｇ／ｃｍ２であり、前記第三の負極活物質層に含まれる珪素系活物質の前記第三の負極活物質層の重量に対する重量割合が、前記第一の負極活物質層に含まれる珪素系活物質の前記第一の負極活物質層の重量に対する重量割合よりも大きい請求項１又は２に記載のリチウムイオン電池。 On the surface of the first negative electrode active material layer opposite to the surface having the second negative electrode active material layer, a third negative electrode active material layer is provided, and the film thickness of the third negative electrode active material layer Is 1.5 to 50 μm, the amount of the silicon-based active material contained in the third negative electrode active material layer is 0.1 to 5 mg / cm 2 , and the amount of silicon contained in the third negative electrode active material layer is The weight ratio of the system-based active material to the weight of the third anode active material layer is greater than the weight ratio of the silicon-based active material included in the first anode active material layer to the weight of the first anode active material layer. The lithium ion battery according to claim 1 or 2, which is large. 前記第一の負極活物質層に含まれる負極活物質は、炭素系活物質と、珪素系活物質との混合物であり、
前記珪素系活物質の重量割合が、前記第一の負極活物質層の重量に対して２０重量％以下である請求項１〜３のいずれかに記載のリチウムイオン電池。 The negative electrode active material contained in the first negative electrode active material layer is a mixture of a carbon-based active material and a silicon-based active material,
The lithium ion battery according to any one of claims 1 to 3, wherein a weight ratio of the silicon-based active material is 20% by weight or less based on a weight of the first negative electrode active material layer. 前記第一の負極活物質層に含まれる負極活物質は、炭素系活物質からなる請求項１〜３のいずれかに記載のリチウムイオン電池。 The lithium ion battery according to any one of claims 1 to 3, wherein the negative electrode active material included in the first negative electrode active material layer is made of a carbon-based active material. 前記第二の負極活物質層に含まれる前記珪素系活物質が、酸化珪素及び／又は珪素−炭素複合体である請求項１〜５のいずれかに記載のリチウムイオン電池。 The lithium ion battery according to any one of claims 1 to 5, wherein the silicon-based active material contained in the second negative electrode active material layer is a silicon oxide and / or a silicon-carbon composite. 前記集電体が樹脂集電体である請求項１〜６のいずれかに記載のリチウムイオン電池。 The lithium ion battery according to claim 1, wherein the current collector is a resin current collector. 前記第一の負極活物質層がリチウムイオン電池用電極バインダを含まない非結着体である請求項１〜７のいずれかに記載のリチウムイオン電池。 The lithium ion battery according to any one of claims 1 to 7, wherein the first negative electrode active material layer is a non-binder that does not include an electrode binder for a lithium ion battery.
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