JP6361928B2 - Method for producing positive electrode for non-aqueous electrolyte secondary battery - Google Patents
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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
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- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、非水電解液二次電池用正極の製造方法に関する。 The present invention relates to a method for producing a positive electrode for a non-aqueous electrolyte secondary battery.
リチウムイオン二次電池（リチウム二次電池）等の非水電解液二次電池は、既存の電池に比べて軽量且つエネルギー密度が高いことから、近年、パソコンや携帯端末等のいわゆるポータブル電源や車両駆動用電源として用いられている。特に、軽量で高エネルギー密度が得られるリチウムイオン二次電池は、電気自動車（ＥＶ）、ハイブリッド自動車（ＨＶ）、プラグインハイブリッド自動車（ＰＨＶ）等の車両の駆動用高出力電源として好ましく用いられている。このような需要増大に伴う電池の性能向上に対する要求に応えるべく、より高性能（高い入出力特性、高い耐久性等）な正極の開発が進められている。
例えばタングステン（Ｗ）を構成元素として含む正極活物質は、電池の各種性能（例えば、入出力特性、耐久性等）を向上し得る正極活物質として期待とされている。例えば特許文献１にはタングステンを構成元素に含む正極活物質に関して記載があり、当該タングステンを含む正極活物質と、フッ化金属（例えばフッ化リチウム）と、導電材と、バインダとを適当な溶媒中に混合してスラリー状の正極活物質層形成用組成物を調製し、該組成物を正極集電体上に塗布し乾燥することで正極を作製することが記載されている。
Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries (lithium secondary batteries) are lighter and have higher energy density than existing batteries. It is used as a driving power source. Particularly, lithium ion secondary batteries that are lightweight and obtain high energy density are preferably used as high-output power sources for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). Yes. Development of positive electrodes with higher performance (high input / output characteristics, high durability, etc.) has been underway in order to meet the demand for improved battery performance accompanying such an increase in demand.
For example, a positive electrode active material containing tungsten (W) as a constituent element is expected as a positive electrode active material that can improve various performances (for example, input / output characteristics, durability, etc.) of the battery. For example, Patent Document 1 describes a positive electrode active material containing tungsten as a constituent element. A positive electrode active material containing tungsten, a metal fluoride (for example, lithium fluoride), a conductive material, and a binder are used in an appropriate solvent. It is described that a positive electrode active material layer forming composition is prepared by mixing in, and the positive electrode is produced by applying the composition onto a positive electrode current collector and drying.
ところで、上記非水電解液二次電池について、充放電（例えば、ハイレート（急速）条件での充放電、或いは高電位まで充電される条件での充放電等）を繰り返すと、充放電回数の増加に従って電池性能（例えば電池容量、入出力特性等）が低下する場合があった。これは、上記充放電の繰り返しにおいて、正極活物質から構成元素が溶出し得ることが原因の一つとして考えられる。特に、正極活物質中のタングステンは正極活物質の表面に偏在する（例えば、正極活物質表面でのタングステンの分布にムラが生じる）傾向にあるため、正極活物質中から溶出しやすい傾向にあった。これは、正極活物質表面でのタングステンの偏在に起因して該活物質表面の反応性にムラが生じやすいことが原因の一つであり得ると考えられる。 By the way, when the non-aqueous electrolyte secondary battery is repeatedly charged / discharged (for example, charging / discharging under a high rate (rapid) condition or charging / discharging under a condition of charging to a high potential), the number of times of charging / discharging increases. Accordingly, battery performance (for example, battery capacity, input / output characteristics, etc.) may decrease. This is considered to be one of the causes that the constituent elements can be eluted from the positive electrode active material in the repeated charge / discharge. In particular, since tungsten in the positive electrode active material tends to be unevenly distributed on the surface of the positive electrode active material (eg, uneven distribution of tungsten on the surface of the positive electrode active material), it tends to be easily eluted from the positive electrode active material. It was. This is considered to be one of the reasons that unevenness of the reactivity of the active material surface is likely to occur due to uneven distribution of tungsten on the surface of the positive electrode active material.
本発明はかかる点に鑑みてなされたものであり、その主な目的は、正極活物質からの構成元素の溶出が抑制され、優れた電池特性（例えば高い入出力特性や高いサイクル特性等）を発揮し得る非水電解液二次電池用の正極、および当該正極の製造方法を提供することである。またかかる非水電解液二次電池用の正極を備えた非水電解液二次電池を提供することを他の目的とする。 The present invention has been made in view of the above points, and its main purpose is to suppress elution of constituent elements from the positive electrode active material and to provide excellent battery characteristics (for example, high input / output characteristics and high cycle characteristics). It is intended to provide a positive electrode for a non-aqueous electrolyte secondary battery that can be exhibited, and a method for producing the positive electrode. It is another object of the present invention to provide a non-aqueous electrolyte secondary battery including a positive electrode for such a non-aqueous electrolyte secondary battery.
本発明者らは、正極活物質表面にフッ化リチウム（ＬｉＦ）の被膜を形成することで、当該正極活物質から構成元素が溶出することを抑制し得ることに着目した。このことは、正極活物質の表面にＬｉＦの被膜を形成することで正極活物質表面の反応性のムラを低減（解消）することに着目するものである。しかしながら、本発明者らの検討によると、特許文献１のように、正極活物質、フッ化リチウム、導電材およびバインダを溶媒中に一度に分散させた場合、導電材（例えばアセチレンブラック）とＬｉＦとが反応して凝集しやすく、正極活物質の表面にＬｉＦを均一に分散することが困難であった。
本発明者らは、鋭意検討を重ねた結果、構成元素としてタングステンを含む正極活物質を有する正極であって、正極活物質からの構成元素の溶出がより高度に抑制された正極を作製し得る手段を見出し、本発明を完成させるに至った。
The inventors of the present invention have focused on the fact that the formation of a lithium fluoride (LiF) film on the surface of the positive electrode active material can suppress the elution of the constituent elements from the positive electrode active material. This focuses on reducing (eliminating) the unevenness of reactivity on the surface of the positive electrode active material by forming a LiF film on the surface of the positive electrode active material. However, according to the study by the present inventors, when a positive electrode active material, lithium fluoride, a conductive material, and a binder are dispersed at once in a solvent as in Patent Document 1, a conductive material (for example, acetylene black) and LiF Reacting easily and agglomerating, and it was difficult to uniformly disperse LiF on the surface of the positive electrode active material.
As a result of intensive studies, the present inventors can produce a positive electrode having a positive electrode active material containing tungsten as a constituent element, in which elution of the constituent element from the positive electrode active material is further suppressed. Means have been found and the present invention has been completed.
上記目的を実現すべく、本発明により、非水電解液二次電池用の正極を製造する方法であって、以下の（ｉ）〜（ｉｉｉ）の工程を包含する製造方法が提供される。即ち、ここで開示される非水電解液二次電池用の正極の製造方法は、
（ｉ）構成元素としてタングステン（Ｗ）を含む正極活物質と、フッ化リチウム（ＬｉＦ）とを混合して機械的エネルギーを加えることにより、該タングステン含有正極活物質（以下、「Ｗ含有正極活物質」ともいう。）の表面にフッ化リチウム被膜が形成された複合正極活物質を得る工程；
（ｉｉ）前記得られた複合正極活物質に、少なくとも導電材およびバインダを添加して造粒することにより、少なくとも該複合正極活物質、導電材およびバインダを含む造粒体を得る工程；および
（ｉｉｉ）前記得られた造粒体を用いて正極集電体の表面に正極活物質層を形成する工程；を包含する。
In order to achieve the above object, the present invention provides a method for producing a positive electrode for a non-aqueous electrolyte secondary battery, which includes the following steps (i) to (iii). That is, the manufacturing method of the positive electrode for non-aqueous electrolyte secondary batteries disclosed here is:
(I) A positive electrode active material containing tungsten (W) as a constituent element and lithium fluoride (LiF) are mixed and mechanical energy is applied, whereby the tungsten-containing positive electrode active material (hereinafter referred to as “W-containing positive electrode active material”). A step of obtaining a composite positive electrode active material having a lithium fluoride film formed on the surface thereof;
(Ii) A step of obtaining a granulated body containing at least the composite positive electrode active material, the conductive material and the binder by adding at least a conductive material and a binder to the obtained composite positive electrode active material and granulating; and and iii) forming a positive electrode active material layer on the surface of the positive electrode current collector using the obtained granulated body.
かかる製造方法によると、Ｗ含有正極活物質とＬｉＦを混合して複合正極活物質を調製することで、Ｗ含有正極活物質の表面に、分散ムラの少ない状態（好ましくは分散ムラのない状態）でＬｉＦを分散することができる。また、当該複合正極活物質を導電材およびバインダとともに造粒した造粒体を用いて正極を作製することで、上記Ｗ含有正極活物質表面のＬｉＦを該活物質表面に安定して保持した状態で正極を作製することができる。即ち、上記の製造方法によると、Ｗ含有正極活物質の表面に被覆ムラの少ない安定したＬｉＦ被膜が形成された正極を製造することができ、また、正極活物質表面の反応性のムラを低減し得る。これにより、正極活物質からの構成元素（例えばＷ元素）の溶出を効果的に抑制することができる。このため、かかる方法により製造した正極を用いた非水電解液二次電池において、電池のサイクル特性の向上（充放電の繰り返しに伴う電池性能の低下の低減）を実現し得る。
また、正極活物質表面の反応性のムラを低減することで、正極活物質と非水電解液との間（典型的には界面）での電荷担体（典型的にはリチウムイオン）の良好な移動を実現し得る。このため、かかる正極の製造方法により製造した正極を用いた非水電解液二次電池において、優れた電池特性（例えば高い入出力特性）を実現し得る。
また、正極活物質の表面を安定したＬｉＦ被膜で被覆することで、例えば高温環境下における正極活物質表面での非水電解液の酸化分解を抑制し得る。このため、かかる製造方法により製造した正極を用いた非水電解液二次電池において、熱安定性を向上し得る。
According to such a manufacturing method, by preparing a composite positive electrode active material by mixing a W-containing positive electrode active material and LiF, the surface of the W-containing positive electrode active material has a small amount of dispersion unevenness (preferably without dispersion unevenness). LiF can be dispersed. In addition, by producing a positive electrode using a granulated body obtained by granulating the composite positive electrode active material together with a conductive material and a binder, the LiF on the surface of the W-containing positive electrode active material is stably held on the surface of the active material Thus, a positive electrode can be manufactured. That is, according to the above manufacturing method, it is possible to manufacture a positive electrode in which a stable LiF film with little coating unevenness is formed on the surface of the W-containing positive electrode active material, and to reduce the unevenness of reactivity on the surface of the positive electrode active material. Can do. Thereby, the elution of the structural element (for example, W element) from a positive electrode active material can be suppressed effectively. For this reason, in the non-aqueous electrolyte secondary battery using the positive electrode manufactured by such a method, it is possible to improve the cycle characteristics of the battery (reduction in battery performance deterioration due to repeated charge / discharge).
In addition, by reducing the unevenness of reactivity on the surface of the positive electrode active material, the charge carrier (typically lithium ion) between the positive electrode active material and the non-aqueous electrolyte (typically the interface) is improved. Movement can be realized. For this reason, in the non-aqueous electrolyte secondary battery using the positive electrode manufactured by this positive electrode manufacturing method, excellent battery characteristics (for example, high input / output characteristics) can be realized.
In addition, by covering the surface of the positive electrode active material with a stable LiF coating, for example, oxidative decomposition of the nonaqueous electrolytic solution on the surface of the positive electrode active material in a high temperature environment can be suppressed. For this reason, in the nonaqueous electrolyte secondary battery using the positive electrode manufactured by this manufacturing method, thermal stability can be improved.
以下、適宜図面を参照しながら、本発明の好適な実施形態について説明する。なお、本明細書において特に言及している事項以外の事柄であって実施に必要な事柄は、当該分野における従来技術に基づく当業者の設計事項として把握され得る。本発明は、本明細書に開示されている内容と当該分野における技術常識とに基づいて実施し得る。
また、以下、本発明の好適な実施形態をリチウムイオン二次電池を例として説明するが、リチウムイオン二次電池は一例であり、本発明の技術思想は、その他の電荷担体（例えばナトリウムイオン）を備える他の非水電解液二次電池（例えばナトリウムイオン二次電池）にも適用される。
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as appropriate. Note that matters other than matters specifically mentioned in the present specification and necessary for implementation can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be implemented based on the contents disclosed in the present specification and common general technical knowledge in the field.
In the following, preferred embodiments of the present invention will be described taking a lithium ion secondary battery as an example. However, the lithium ion secondary battery is an example, and the technical idea of the present invention is other charge carriers (for example, sodium ions). The present invention is also applied to other non-aqueous electrolyte secondary batteries (for example, sodium ion secondary batteries).
ここで開示される非水電解液二次電池用正極の製造方法は、図１に示すように、複合正極活物質作製工程（Ｓ１０）、造粒工程（Ｓ２０）、正極活物質層形成工程（Ｓ３０）を包含する。以下、各工程について説明する。 As shown in FIG. 1, the manufacturing method of the positive electrode for nonaqueous electrolyte secondary batteries disclosed here includes a composite positive electrode active material preparation step (S10), a granulation step (S20), a positive electrode active material layer formation step ( S30). Hereinafter, each step will be described.
まず、複合正極活物質作製工程（Ｓ１０）について説明する。かかる工程は、少なくとも、構成元素としてタングステン（Ｗ）を含む正極活物質と、フッ化リチウム（ＬｉＦ）とを混合して機械的エネルギーを加えることにより、該タングステン含有正極活物質の表面にフッ化リチウム被膜が形成された複合正極活物質を得る工程が含まれる。 First, the composite positive electrode active material preparation step (S10) will be described. Such a step is performed by mixing at least a positive electrode active material containing tungsten (W) as a constituent element and lithium fluoride (LiF) and applying mechanical energy to fluorinate the surface of the tungsten-containing positive electrode active material. A step of obtaining a composite positive electrode active material on which a lithium film is formed is included.
上記構成元素としてタングステン（Ｗ）を含む正極活物質（以下、タングステン含有正極活物質、或いはＷ含有正極活物質ともいう）としては、構成元素としてタングステンを含む限りにおいて従来からリチウムイオン二次電池に用いられる物質の一種または二種以上を特に限定することなく使用することができる。例えば、リチウムと、タングステンと、一種または二種以上の遷移金属元素とを構成金属元素として含む酸化物（リチウム遷移金属酸化物）を主成分とする正極活物質が挙げられる。かかるリチウム遷移金属複合酸化物の例としては、リチウムニッケルコバルトマンガン複合酸化物（ＬｉＮｉＣｏＭｎＯ２、以下、「ＬＮＣＭ」ともいう）、リチウムニッケル酸化物（例えばＬｉＮｉＯ２）、リチウムコバルト酸化物（例えばＬｉＣｏＯ２）、リチウムマンガン酸化物（例えばＬｉＭｎ２Ｏ４）などの遷移金属元素の一部がタングステン（Ｗ）元素で置換された酸化物（Ｗ含有リチウム遷移金属複合酸化物）が挙げられる。 As a positive electrode active material containing tungsten (W) as the constituent element (hereinafter also referred to as a tungsten-containing positive electrode active material or a W-containing positive electrode active material), a lithium ion secondary battery has been conventionally used as long as tungsten is included as a constituent element. One kind or two or more kinds of substances to be used can be used without particular limitation. For example, a positive electrode active material mainly containing an oxide (lithium transition metal oxide) containing lithium, tungsten, and one or more transition metal elements as constituent metal elements can be given. Examples of such lithium transition metal composite oxides include lithium nickel cobalt manganese composite oxide (LiNiCoMnO 2 , hereinafter also referred to as “LNCM”), lithium nickel oxide (eg, LiNiO 2 ), lithium cobalt oxide (eg, LiCoO 2). ) And an oxide (W-containing lithium transition metal composite oxide) in which a part of a transition metal element such as lithium manganese oxide (for example, LiMn 2 O 4 ) is substituted with a tungsten (W) element.
このようなＷ含有リチウム遷移金属複合酸化物としては、例えば、一般式（Ｉ）：Ｌｉ１＋δ（ＮｉａＣｏｂＭｎｃＭｄＷｅ）Ｏ２で表される酸化物が挙げられる。δは０≦δ≦０．２５で電荷中性条件を満たすように定まる値であり、ａ，ｂ，ｃ，ｄ，ｅは、ａ＋ｂ＋ｃ＋ｄ＋ｅ≒１、０．０００１≦ｅ≦０．３およびｄ≧０を満たし、ａ，ｂ，ｃのうち少なくとも一つは０よりも大きい。上記式（Ｉ）において「ａ＋ｂ＋ｃ＋ｄ＋ｅ≒１」とは、概ね０．９≦ａ＋ｂ＋ｃ＋ｄ＋ｅ≦１．２（典型的には０．９＜ａ＋ｂ＋ｃ＋ｄ＋ｅ＜１．２、例えば０．９５≦ａ＋ｂ＋ｃ＋ｄ＋ｅ≦１．１）であり得、例えばａ＋ｂ＋ｃ＋ｄ＋ｅ＝１である。ここで、上記Ｗ含有正極活物質の全構成元素のうちの０．０１ｍｏｌ〜５ｍｏｌ％をＷ元素が占めるＷ含有リチウム遷移金属複合酸化物を好適に採用し得る。換言すると、上記式（Ｉ）におけるｅの値は凡そ０．０００４≦ｅ≦０．２が好ましい。なお、上記式（Ｉ）中のＭは、Ｌｉ、Ｎｉ，Ｃｏ，ＭｎおよびＷ以外の遷移金属元素，典型金属元素のうちの一種または二種以上であり得、例えば、０≦ｄ≦０．０２とすることができる。
なかでも、ａ，ｂ，ｃ＞０である（換言すれば、Ｎｉ，Ｃｏ，Ｍｎの全ての元素を含む）リチウムニッケルコバルトマンガン複合酸化物を好ましく用いることができる。好ましい一態様では、ａ，ｂ，ｃ（即ち、Ｎｉ，Ｃｏ，Ｍｎの量）が概ね同程度である。また、好ましい他の一態様では、ａ＞ｂかつａ＞ｃ（換言すればＮｉを構成元素として最も多く含む）である。かかるリチウム遷移金属複合酸化物は、電子伝導性および熱安定性に優れ、優れた出力特性やサイクル特性を実現し得る。
Examples of such a W-containing lithium transition metal composite oxide include an oxide represented by the general formula (I): Li 1 + δ (Ni a Co b Mn c M d W e ) O 2 . δ is a value determined to satisfy the charge neutrality condition with 0 ≦ δ ≦ 0.25, and a, b, c, d, and e are a + b + c + d + e≈1, 0.0001 ≦ e ≦ 0.3, and d ≧ 0 is satisfied, and at least one of a, b, and c is greater than 0. In the above formula (I), “a + b + c + d + e≈1” is approximately 0.9 ≦ a + b + c + d + e ≦ 1.2 (typically 0.9 <a + b + c + d + e <1.2, for example 0.95 ≦ a + b + c + d + e ≦ 1.1). For example, a + b + c + d + e = 1. Here, a W-containing lithium transition metal composite oxide in which 0.01 mol to 5 mol% of all the constituent elements of the W-containing positive electrode active material occupy the W element can be suitably employed. In other words, the value of e in the above formula (I) is preferably about 0.0004 ≦ e ≦ 0.2. Note that M in the above formula (I) may be one or more of transition metal elements and typical metal elements other than Li, Ni, Co, Mn, and W. For example, 0 ≦ d ≦ 0. 02.
Among these, lithium nickel cobalt manganese composite oxide in which a, b, c> 0 (in other words, including all elements of Ni, Co, and Mn) can be preferably used. In a preferred embodiment, a, b, and c (that is, amounts of Ni, Co, and Mn) are approximately the same. In another preferred embodiment, a> b and a> c (in other words, Ni is the most contained as a constituent element). Such a lithium transition metal composite oxide is excellent in electronic conductivity and thermal stability, and can realize excellent output characteristics and cycle characteristics.
Ｗ含有正極活物質とＬｉＦとの混合は、Ｗ含有正極活物質の表面とＬｉＦとの間に化学結合が生じる程度のエネルギー（機械的エネルギー）が加わるようにＷ含有正極活物質とＬｉＦとを混合する。これにより、Ｗ含有正極活物質の表面に好適な状態（例えば被膜ムラが少ない状態）のＬｉＦ被膜を形成することができる。
なお、Ｗ含有正極活物質とＬｉＦとを混合する際には、Ｗ含有正極活物質の表面にＬｉＦ被膜を形成し得る限りにおいて、他の成分（例えば適当な溶媒等）を添加してもよい。Ｗ含有正極活物質とＬｉＦとが接触する機会を増やしてＷ含有正極活物質の表面に好適な状態のＬｉＦ被膜を形成する観点からは、かかる他の成分は少量である（典型的にはＷ含有正極活物質とＬｉＦ以外を含まない）ことが好ましい。
また、上記Ｗ含有正極活物質とＬｉＦとの混合は、Ｗ含有正極活物質の表面とＬｉＦとの間に化学結合が生じる程度のエネルギー（機械的エネルギー）が加わる限りにおいて、従来公知の混合方法によって実施し得る。Ｗ含有正極活物質の表面にＬｉＦを好適な状態で（例えば分散ムラが少ない状態で）分散し得る方法が好ましく、紛体（個体）の混合方法として知られる方法を好適に採用し得る。例えば、各種のミキサー、ブレンダー、ミル、ニーダー等の公知の混合装置を用いた方法を採用し得る。かかる混合装置としては、例えば容器回転型、容器固定型、或いはこれらを組み合わせた複合型の何れの装置も採用可能である。一例として、ハイスピードミキサー、プラネタリーミキサー、スパルタンミキサー、リボンミキサー、ディスパー、ボールミル等が挙げられる。特に主翼（典型的にはアジテータ羽根）と解砕翼（典型的にはチョッパー羽根）とを有するハイスピードミキサーは、Ｗ含有正極活物質とＬｉＦとの間に十分な機械エネルギーを加えつつ、Ｗ含有正極活物質の表面にＬｉＦを均一に分散し得るため好適に使用し得る。
In the mixing of the W-containing positive electrode active material and LiF, the W-containing positive electrode active material and LiF are added so that energy (mechanical energy) to the extent that a chemical bond is generated between the surface of the W-containing positive electrode active material and LiF is added. Mix. Thereby, it is possible to form a LiF coating in a suitable state (for example, a state with little coating unevenness) on the surface of the W-containing positive electrode active material.
When the W-containing positive electrode active material and LiF are mixed, other components (for example, a suitable solvent) may be added as long as a LiF film can be formed on the surface of the W-containing positive electrode active material. . From the viewpoint of increasing the chance of contact between the W-containing positive electrode active material and LiF to form a LiF film in a suitable state on the surface of the W-containing positive electrode active material, the amount of such other components is small (typically W It is preferable that it contains no positive electrode active material and LiF.
The mixing of the W-containing positive electrode active material and LiF is a conventionally known mixing method as long as energy (mechanical energy) is generated to such an extent that a chemical bond is generated between the surface of the W-containing positive electrode active material and LiF. Can be implemented. A method in which LiF can be dispersed in a suitable state (for example, with little dispersion unevenness) on the surface of the W-containing positive electrode active material is preferred, and a method known as a powder (solid) mixing method can be suitably employed. For example, a method using a known mixing apparatus such as various mixers, blenders, mills, and kneaders can be employed. As such a mixing apparatus, for example, any of a container rotating type, a container fixing type, or a composite type combining these can be used. Examples include high speed mixers, planetary mixers, spartan mixers, ribbon mixers, dispersers, ball mills, and the like. In particular, a high-speed mixer having a main wing (typically an agitator blade) and a crushing blade (typically a chopper blade) adds a sufficient mechanical energy between the W-containing positive electrode active material and LiF, while the W-containing positive electrode. Since LiF can be uniformly dispersed on the surface of the active material, it can be suitably used.
上記Ｗ含有正極活物質とＬｉＦとの混合割合（質量比）は、Ｗ含有正極活物質：ＬｉＦ＝１００：０．１〜５（好ましくは１００：０．３〜５）の質量比率となるように設定することが好ましい。換言すると、Ｗ含有正極活物質の質量を１００質量％とした場合に０．１質量％〜５質量％（好ましくは０．３質量％〜５質量％）に相当する質量のＬｉＦを、Ｗ含有正極活物質と混合することが好ましい。Ｗ含有正極活物質に対するＬｉＦの混合割合が少なすぎると、Ｗ含有正極活物質表面へのＬｉＦ被膜の形成量が不足し、正極活物質表面の反応性のムラを低減する効果（例えば、構成元素の溶出抑制効果）等を十分に発揮できない虞がある。一方で、Ｗ含有正極活物質に対するＬｉＦの混合割合が多すぎると、Ｗ含有正極活物質表面のＬｉＦ被膜の被膜量が過大となり、抵抗が増大する虞がある。 The mixing ratio (mass ratio) of the W-containing positive electrode active material and LiF is a mass ratio of W-containing positive electrode active material: LiF = 100: 0.1 to 5 (preferably 100: 0.3 to 5). It is preferable to set to. In other words, when the mass of the W-containing positive electrode active material is 100 mass%, LiF having a mass corresponding to 0.1 mass% to 5 mass% (preferably 0.3 mass% to 5 mass%) is contained in W. It is preferable to mix with a positive electrode active material. When the mixing ratio of LiF with respect to the W-containing positive electrode active material is too small, the amount of LiF coating formed on the surface of the W-containing positive electrode active material is insufficient, and the effect of reducing the unevenness of reactivity on the surface of the positive electrode active material (for example, constituent elements) (Elution suppression effect) may not be fully exhibited. On the other hand, when the mixing ratio of LiF with respect to the W-containing positive electrode active material is too large, the coating amount of the LiF film on the surface of the W-containing positive electrode active material becomes excessive, and the resistance may increase.
次に、造粒工程（Ｓ２０）について説明する。かかる工程は、上記複合正極活物質作製工程（Ｓ１０）により作製した複合正極活物質に、少なくとも導電材およびバインダを添加して造粒することにより、少なくとも該複合正極活物質、導電材およびバインダを含む造粒体を得る工程が含まれる。かかる造粒体は、例えば、造粒体に含まれる成分（少なくとも上記複合正極活物質、導電材およびバインダ）が均一に分散するように混合し、該混合した混合物を適当な造粒方法で造粒することで調製し得る。 Next, the granulation step (S20) will be described. In this step, at least the composite positive electrode active material, the conductive material and the binder are granulated by adding at least a conductive material and a binder to the composite positive electrode active material prepared in the composite positive electrode active material preparation step (S10). The process of obtaining the granulated body to contain is included. Such a granulated body is, for example, mixed so that the components (at least the composite positive electrode active material, the conductive material and the binder) contained in the granulated body are uniformly dispersed, and the mixed mixture is granulated by an appropriate granulation method. It can be prepared by granulating.
上記導電材としては、非水電解液二次電池（典型的にはリチウムイオン二次電池）の導電材として用いられ得るものを、特に制限なく、1種又は２種以上用いることができる。例えば、カーボンブラック（典型的にはアセチレンブラック、ケッチェンブラック）、活性炭、黒鉛、炭素繊維等の炭素材料を好適に使用することができる。
また、上記バインダ（結着剤）としては、非水電解液二次電池（典型的にはリチウムイオン二次電池）の導電材として用いられ得るものを、特に制限なく、1種又は２種以上用いることができる。例えば、ポリフッ化ビニリデン（ＰＶＤＦ）等のハロゲン化ビニル樹脂；ポリエチレンオキサイド（ＰＥＯ）等のポリアルキレンオキサイド；等のポリマー材料を好適に使用することができる。
As said electrically conductive material, what can be used as a electrically conductive material of a non-aqueous-electrolyte secondary battery (typically lithium ion secondary battery) does not have a restriction | limiting in particular, 1 type, or 2 or more types can be used. For example, carbon materials such as carbon black (typically acetylene black and ketjen black), activated carbon, graphite, and carbon fiber can be suitably used.
In addition, as the binder (binder), one that can be used as a conductive material of a non-aqueous electrolyte secondary battery (typically a lithium ion secondary battery) is not particularly limited, and one or more kinds are usable. Can be used. For example, polymer materials such as vinyl halide resins such as polyvinylidene fluoride (PVDF); polyalkylene oxides such as polyethylene oxide (PEO); and the like can be suitably used.
なお、上記造粒体は、必要に応じて、上記正極活物質、導電材およびバインダ以外の成分を含んでもよい。例えば、造粒体を調製する際に適当な溶媒を添加することで、造粒体中の固形分率を造粒体の調製に好適な範囲に調整することが出来る。なお、導電材またはバインダは、適当な溶媒（例えば導電材またはバインダを溶解または分散し得る溶媒）中に溶解又は分散した状態で上記複合正極活物質と混合してもよい。
かかる溶媒としては、非水電解液二次電池（典型的にはリチウムイオン二次電池）の正極の作製に使用し得るものであれば特に制限なく使用可能であり、１種を単独で、もしくは２種以上を混合して（混合溶媒として）使用することができる。例えば、水、Ｎ−メチル−２−ピロリドン（ＮＭＰ）、メチルアルコール、エチルアルコール等を好適に使用することができる。なお、上記造粒体は、非水電解液二次電池の正極の作製に用いられ得る各種添加剤（例えば、増粘剤、分散剤等）をさらに含有してもよい。
In addition, the said granule may contain components other than the said positive electrode active material, a electrically conductive material, and a binder as needed. For example, by adding an appropriate solvent when preparing the granulated body, the solid content ratio in the granulated body can be adjusted to a range suitable for the preparation of the granulated body. Note that the conductive material or binder may be mixed with the composite positive electrode active material in a state of being dissolved or dispersed in a suitable solvent (for example, a solvent capable of dissolving or dispersing the conductive material or binder).
As such a solvent, any solvent can be used without particular limitation as long as it can be used for producing a positive electrode of a non-aqueous electrolyte secondary battery (typically, a lithium ion secondary battery). Two or more kinds can be mixed and used (as a mixed solvent). For example, water, N-methyl-2-pyrrolidone (NMP), methyl alcohol, ethyl alcohol and the like can be preferably used. In addition, the said granule may further contain various additives (for example, a thickener, a dispersing agent, etc.) which can be used for preparation of the positive electrode of a nonaqueous electrolyte secondary battery.
造粒体に含まれる各成分（複合正極活物質、導電材、バインダおよび必要に応じた任意成分）を混合する方法は特に限定されず、例えば、ハイスピードミキサー、ボールミル、サンドミル、ビーズミル、らい潰機、超音波分散機、ホモジナイザー、ホモミキサー、プラネタリーミキサー等の混合装置を用いた従来公知の混合方法を採用し得る。なお、造粒体に含まれる各成分の混合は、全ての成分を同時に混合してもよいし、一部の成分を混合した後で該混合成分と他の成分とを混合してもよい。 The method of mixing each component (composite positive electrode active material, conductive material, binder, and optional components as required) contained in the granulated body is not particularly limited. For example, a high speed mixer, a ball mill, a sand mill, a bead mill, a crushed crush A conventionally known mixing method using a mixing apparatus such as a mixer, an ultrasonic disperser, a homogenizer, a homomixer, or a planetary mixer can be employed. In addition, mixing of each component contained in a granulated body may mix all the components simultaneously, and after mixing one part component, you may mix this mixed component and another component.
また、上記混合した各成分を造粒する方法としては、従来公知の造粒方法を利用できる。例えば、攪拌造粒法、転動造粒法、押し出し造粒法、破砕造粒法、流動層造粒法、圧縮造粒法といった手法が挙げられる。なかでも、比較的固形分率の高い混合物の造粒に適した造粒方法（例えば、攪拌造粒法、転動造粒法、押し出し造粒法、破砕造粒法、流動層造粒法、圧縮造粒法等）が本発明の実施に好適である。また、造粒体の製造効率の観点からは、上記造粒体を構成する各成分の混合、攪拌と造粒とを一連の操作で（連続して）行い得る方法（例えば、攪拌造粒法や流動層造粒法等）を好適に採用し得る。なかでも、上記複合正極活物質を作製（Ｗ含有正極活物質とＬｉＦとを混合）することと、複合正極活物質、導電材およびバインダを含む造粒体を得ることとを、同一の装置（例えばハイスピードミキサー、プラネタリーミキサー等）を用いて行い得る手法は、製造効率の観点から特に好ましい。 Moreover, as a method of granulating each of the above mixed components, a conventionally known granulation method can be used. For example, methods such as agitation granulation method, rolling granulation method, extrusion granulation method, crushing granulation method, fluidized bed granulation method, and compression granulation method may be mentioned. Among them, a granulation method suitable for granulation of a mixture having a relatively high solid content ratio (for example, stirring granulation method, rolling granulation method, extrusion granulation method, crushing granulation method, fluidized bed granulation method, A compression granulation method or the like is suitable for the implementation of the present invention. In addition, from the viewpoint of the production efficiency of the granulated body, a method (for example, the stirring granulation method) in which mixing, stirring and granulation of each component constituting the granulated body can be performed in a series of operations (continuously). Or fluidized bed granulation method) can be suitably employed. Among them, the same apparatus (preparing the composite positive electrode active material (mixing W-containing positive electrode active material and LiF) and obtaining a granulated body containing the composite positive electrode active material, a conductive material and a binder) For example, a technique that can be performed using a high-speed mixer, a planetary mixer, or the like is particularly preferable from the viewpoint of manufacturing efficiency.
上記造粒体の固形分率は、例えば７０質量％以上、好ましくは７４質量％以上、より好ましくは８０質量％以上とすることができる。或いは、実質的に１００質量％（即ち、溶媒が除去された状態）であってもよい。固形分率が低すぎる場合は造粒体の形状を保つことが困難であり、スラリー状（ペースト状、インク状）になってしまうため好ましくない。正極集電体と正極活物質層との密着性の観点からは、上記造粒体は固形分率が９５質量％以下の湿潤状態であることが好ましい。 The solid content of the granulated body is, for example, 70% by mass or more, preferably 74% by mass or more, and more preferably 80% by mass or more. Alternatively, it may be substantially 100% by mass (that is, in a state where the solvent is removed). When the solid content is too low, it is difficult to maintain the shape of the granulated body, which is not preferable because it becomes a slurry (paste or ink). From the viewpoint of adhesion between the positive electrode current collector and the positive electrode active material layer, the granulated body is preferably in a wet state with a solid content of 95% by mass or less.
次に、正極活物質層形成工程（Ｓ３０）について説明する。かかる工程は、上記造粒工程（Ｓ２０）により得られた造粒体を用いて正極集電体の表面（少なくとも一方の面）に正極活物質層を形成する工程が含まれる。即ち、かかる正極活物質層形成工程では、正極集電体の表面（少なくとも一方の面）に上記造粒体を付与する工程を含む。 Next, the positive electrode active material layer forming step (S30) will be described. This step includes a step of forming a positive electrode active material layer on the surface (at least one surface) of the positive electrode current collector using the granulated body obtained in the granulation step (S20). That is, the positive electrode active material layer forming step includes a step of applying the granulated body to the surface (at least one surface) of the positive electrode current collector.
正極集電体は、非水電解液二次電池（典型的にはリチウムイオン二次電池）に用いられ得るものを特に制限なく使用可能であり、例えば、導電性の良好な金属（例えばアルミニウム、ニッケル、チタン、ステンレス鋼等）からなる導電性材料を好適に使用し得る。 As the positive electrode current collector, a material that can be used for a non-aqueous electrolyte secondary battery (typically a lithium ion secondary battery) can be used without particular limitation. For example, a metal having good conductivity (for example, aluminum, A conductive material made of nickel, titanium, stainless steel or the like can be preferably used.
上述の造粒体を上記正極集電体に付与する手法は特に限定されないが、例えば、正極集電体上に所望量の造粒体を直接供給（例えば散布等）する手法を採用し得る。或いはまた、所謂転写法によっても、正極集電体上に造粒体を付与することもできる。
転写法としては、例えば適当な大きさの平面を有する部材（例えば平板やシート等、ここでは転写用シートとして説明する）の平面上に造粒体を供給し、該造粒体供給面が正極集電体の正極活物質層形成面とが対向する方向で転写用シートと正極集電体を重ねあわせることで、正極集電体上に造粒体を付与（転写）する手法を採用し得る。
The method for applying the above-mentioned granulated body to the positive electrode current collector is not particularly limited, and for example, a method of directly supplying (for example, spraying) a desired amount of the granulated material onto the positive electrode current collector can be adopted. Alternatively, the granulated body can be provided on the positive electrode current collector by a so-called transfer method.
As a transfer method, for example, a granule is supplied on the plane of a member having a plane of an appropriate size (for example, a flat plate or a sheet, which will be described here as a transfer sheet), and the granule supply surface is a positive electrode. A method of applying (transferring) the granulated material to the positive electrode current collector by superimposing the transfer sheet and the positive electrode current collector in a direction in which the positive electrode active material layer forming surface of the current collector faces may be employed. .
正極集電体或いは転写用シートに造粒体を供給する方法としては、例えば、正極集電体或いは転写用シートをコンベア等の搬送手段により所定の速度で搬送し、当該正極集電体或いは転写用シートの搬送速度に合わせて所定量の造粒体を適当な供給装置を用いて供給する方法が挙げられる。例えば供給装置から篩を通じて集電体上或いは任意のシート上にふるい落とすことで、供給する造粒体の粒径を篩い分けることができる。上記供給装置としては、例えばスクリューフィーダー等を好適に用いることができる。 As a method of supplying the granulated material to the positive electrode current collector or transfer sheet, for example, the positive electrode current collector or transfer sheet is conveyed at a predetermined speed by a conveying means such as a conveyor, and the positive electrode current collector or transfer sheet is transferred. There is a method of supplying a predetermined amount of the granulated body using an appropriate supply device in accordance with the conveyance speed of the sheet. For example, the particle diameter of the granulated material to be supplied can be sieved by sieving from a supply device through a sieve onto a current collector or an arbitrary sheet. As said supply apparatus, a screw feeder etc. can be used suitably, for example.
なお、必須の処理ではないが、上記正極集電体或いは任意のシートに供給された造粒体をスキージ（スクイージ）やヘラ等で平坦化することが好ましい。正極集電体表面或いは任意のシート表面からのスキージの位置を調製することで、造粒体の目付量（単位面積当たりの造粒体の重量）や造粒体の層の厚さの厚さを調整することができる。これにより、正極活物質の目付量（正極活物質層の単位面積当たりの正極活物質の重量）や正極活物質層の厚さを調整することができる。 Although not an essential treatment, it is preferable to flatten the granule supplied to the positive electrode current collector or an arbitrary sheet with a squeegee or a spatula. By adjusting the position of the squeegee from the surface of the positive electrode current collector or any sheet surface, the weight per unit area of the granule (the weight of the granule per unit area) and the thickness of the layer of the granule Can be adjusted. Accordingly, the basis weight of the positive electrode active material (weight of the positive electrode active material per unit area of the positive electrode active material layer) and the thickness of the positive electrode active material layer can be adjusted.
また、ここで開示の正極の製造方法では、上述の方法により造粒体を付与した後の正極集電体に対して圧延処理（プレス処理）を行うことを含みうる。かかる圧延処理を行うことで、造粒体と正極集電体および造粒体どうしを互いに結合させることができる。また、かかる圧延処理により、正極活物質層の性状（例えば平均厚み、密度、空隙率、細孔径分布等）を調整することができる。圧延方法は特に限定されず、従来公知の適当な圧延方法、例えば、ロール圧延法、平板圧延法を採用することができる。
なお、正極集電体上への造粒体の付与を上記転写法により行う場合は、上記転写シートと正極集電体を重ねあわせるのと同時に圧延処理を行うことで、正極集電体上への造粒体の付与と圧延処理とを同時に行ってもよい。
Moreover, the manufacturing method of the positive electrode disclosed here may include performing a rolling process (press process) on the positive electrode current collector after the granulated body is applied by the above-described method. By performing such a rolling treatment, the granulated body, the positive electrode current collector, and the granulated body can be bonded to each other. Moreover, the properties (for example, average thickness, density, porosity, pore size distribution, etc.) of the positive electrode active material layer can be adjusted by such rolling treatment. The rolling method is not particularly limited, and a conventionally known appropriate rolling method such as a roll rolling method or a flat plate rolling method can be employed.
In addition, when performing the provision of the granulated body on the positive electrode current collector by the transfer method described above, the transfer sheet and the positive electrode current collector are overlapped with each other, and the rolling process is performed at the same time, so that the positive electrode current collector is applied. The granulation and the rolling treatment may be performed simultaneously.
上記造粒体が溶媒を含む（湿潤状態である）場合は、上記正極集電体上に付与した造粒体中の溶媒を乾燥により除去することが好ましい。例えば、加熱圧延を行うことで、圧延処理と乾燥処理とを同時に行ってもよい。或いはまた、圧延処理前後の適当なタイミングで、従来公知の手段（例えば、加熱乾燥や真空乾燥等）により、造粒体中の溶媒を除去してもよい。 When the granulated body contains a solvent (in a wet state), it is preferable to remove the solvent in the granulated body provided on the positive electrode current collector by drying. For example, you may perform a rolling process and a drying process simultaneously by performing heat rolling. Alternatively, the solvent in the granule may be removed by a conventionally known means (for example, heat drying or vacuum drying) at an appropriate timing before and after the rolling treatment.
上記製造方法によって得られる正極は、非水電解液二次電池用の正極として好適に用いることが出来る。即ち、本発明によると、上記正極を用いた非水電解液二次電池が提供される。ここで、かかる非水電解液二次電池は、本発明を特徴づける正極を備える他は従来と同様の構成であればよい。典型的な一態様を以下に示す。 The positive electrode obtained by the above production method can be suitably used as a positive electrode for a non-aqueous electrolyte secondary battery. That is, according to the present invention, a nonaqueous electrolyte secondary battery using the positive electrode is provided. Here, the non-aqueous electrolyte secondary battery may have the same configuration as the conventional one except that it includes a positive electrode that characterizes the present invention. One typical embodiment is shown below.
ここで開示される非水電解液二次電池は、上記正極と、負極とがセパレータを介して積層された電極体が、非水電解液とともに電池ケース内に収容された構成であり得る。 The non-aqueous electrolyte secondary battery disclosed herein may have a configuration in which an electrode body in which the positive electrode and the negative electrode are stacked via a separator is housed in a battery case together with the non-aqueous electrolyte.
負極は、典型的に負極集電体と当該負極集電体上に形成された負極活物質層とを備えている。負極活物質層は、負極活物質と他の任意成分（例えばバインダや増粘剤等）とを含み得る。負極集電体としては、導電性の良好な金属（例えば銅）からなる導電性材料を好適に採用し得る。負極活物質としては、例えば、黒鉛（グラファイト）等の炭素材料を採用し得る。バインダとしては、例えば、スチレンブタジエンゴム（ＳＢＲ）等を採用し得る。増粘剤としては、例えば、カルボキシメチルセルロース（ＣＭＣ）等を採用し得る。 The negative electrode typically includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. The negative electrode active material layer can include a negative electrode active material and other optional components (for example, a binder, a thickener, and the like). As the negative electrode current collector, a conductive material made of a metal having good conductivity (for example, copper) can be suitably used. As the negative electrode active material, for example, a carbon material such as graphite can be adopted. As the binder, for example, styrene butadiene rubber (SBR) or the like can be adopted. As the thickener, for example, carboxymethylcellulose (CMC) can be employed.
セパレータシートとしては、例えばポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）、ポリエステル、セルロース、ポリアミド等の樹脂から成る多孔性シート（フィルム）等を好適に用いることができる。かかる多孔性シートは、単層構造であってもよく、二層以上の積層構造（例えば、ＰＥ層の両面にＰＰ層が積層された三層構造）であってもよい。 As the separator sheet, for example, a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, or polyamide can be suitably used. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer).
非水電解質としては、非水溶媒中に支持塩を含有させたもの（非水電解液）を好適に用いることができる。支持塩としては、例えば、ＬｉＰＦ６、ＬｉＢＦ４等を採用し得る。有機溶媒としては、例えば、カーボネート類、エステル類、エーテル類等の非プロトン性溶媒を採用し得る。なかでも、カーボネート類、例えば、エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）等を好適に採用し得る。 As the non-aqueous electrolyte, a non-aqueous solvent containing a supporting salt (non-aqueous electrolyte) can be preferably used. As the supporting salt, for example, LiPF 6 , LiBF 4 or the like can be adopted. As the organic solvent, for example, aprotic solvents such as carbonates, esters and ethers can be employed. Of these, carbonates such as ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) can be preferably used.
ここに開示される正極の製造方法によると、正極活物質の表面にＬｉＦ被膜を好ましい状態（被膜量のバラつきが少ない或いは少ない状態）で形成することができ、また、正極活物質表面の反応性のムラが低減された正極を作製し得る。このため、例えば、正極活物質からの構成元素の溶出を抑制することができる。かかる正極を備えた非水電解液二次電池は、各種用途に利用可能であるが、優れた入出力特性と高い耐久性とを備えたものである。したがって、ここで開示される非水電解液二次電池は、その特徴を活かして、例えば、自動車等の車両に搭載される駆動用電源として好適に用いることができる。特にプラグインハイブリッド自動車（ＰＨＶ）、ハイブリッド自動車（ＨＶ）、電気自動車（ＥＶ）、等の駆動用電源として好適である。また、本発明によれば、ここに開示される電池（例えばリチウムイオン二次電池）を、好ましくは動力源（典型的には複数個の二次電池が相互に電気的に接続されてなる組電池）として備えた車両が提供される。 According to the method for producing a positive electrode disclosed herein, a LiF film can be formed on the surface of the positive electrode active material in a preferable state (a state in which the amount of coating is less or less), and the reactivity of the surface of the positive electrode active material A positive electrode with reduced unevenness can be produced. For this reason, elution of the constituent element from the positive electrode active material can be suppressed, for example. A non-aqueous electrolyte secondary battery including such a positive electrode can be used for various applications, but has excellent input / output characteristics and high durability. Therefore, the non-aqueous electrolyte secondary battery disclosed here can be suitably used as a driving power source mounted on a vehicle such as an automobile, taking advantage of its characteristics. In particular, it is suitable as a driving power source for plug-in hybrid vehicles (PHV), hybrid vehicles (HV), electric vehicles (EV), and the like. According to the present invention, the battery disclosed herein (for example, a lithium ion secondary battery) is preferably a power source (typically a plurality of secondary batteries are electrically connected to each other). A battery provided as a battery is provided.
以下、本発明に関する試験例を説明するが、本発明の技術範囲をかかる試験例で説明したものに限定することを意図したものではない。 Hereinafter, although the test example regarding this invention is demonstrated, it is not intending to limit the technical scope of this invention to what was demonstrated by this test example.
［正極の作製］
以下の材料、プロセスによって、例１〜例１０に係る非水電解液二次電池（リチウムイオン二次電池）用の正極を構築した。
[Production of positive electrode]
A positive electrode for a non-aqueous electrolyte secondary battery (lithium ion secondary battery) according to Examples 1 to 10 was constructed by the following materials and processes.
＜例１＞
まず、Ｗ含有正極活物質として、ＬｉＮｉ０．３２Ｃｏ０．３２Ｍｎ０．３２Ｗ０．０４Ｏ２（以下、ＬＮＣＭＷともいう）を準備した。かかるＬＮＣＭＷのタングステン含有量は１ｍｏｌ％である。そして、上記ＬＮＣＭＷとＬｉＦとをハイスピードミキサーにて混合し、正極活物質表面にＬｉＦ被膜が形成された複合正極活物質を調製した。このとき、ＬＮＣＭとＬｉＦの混合割合は、ＬＮＣＭＷ：ＬｉＦ＝１００：０．１の質量比となるようにした。
次いで、導電材としてのＡＢと、バインダとしてのＰＶＤＦとをＮＭＰ中に分散し、該ＮＭＰ中に分散したＡＢおよびＰＶＤＦを上記複合正極活物質と混合して造粒体を調製した。このとき、上記複合正極活物質中のＬＮＣＭＷと、ＡＢと、ＰＶＤＦとが９０：８：２の質量比となり、且つ造粒体中の固形分率が７７％となるように調整した。
そして、上記調製した造粒体を転写法により厚さ１５μｍのアルミニウム箔（正極集電体）の両面に付与して、例１に係る正極を作製した。
<Example 1>
First, LiNi 0.32 Co 0.32 Mn 0.32 W 0.04 O 2 (hereinafter also referred to as LNCMW) was prepared as a W-containing positive electrode active material. The tungsten content of such LNCMW is 1 mol%. And the said LNCMW and LiF were mixed with the high speed mixer, and the composite positive electrode active material by which the LiF film was formed in the positive electrode active material surface was prepared. At this time, the mixing ratio of LNCM and LiF was set to a mass ratio of LNCMW: LiF = 100: 0.1.
Next, AB as a conductive material and PVDF as a binder were dispersed in NMP, and AB and PVDF dispersed in NMP were mixed with the composite positive electrode active material to prepare a granulated body. At this time, LNCMW, AB, and PVDF in the composite positive electrode active material were adjusted to have a mass ratio of 90: 8: 2, and the solid content in the granulated body was adjusted to 77%.
And the prepared said granulated body was provided to both surfaces of 15-micrometer-thick aluminum foil (positive electrode collector) by the transfer method, and the positive electrode which concerns on Example 1 was produced.
＜例２〜例４、例６、例８＞
上記複合正極活物質調製時のＬＮＣＭＷ量（１００質量％）に対するＬｉＦ量が、表１に記載のＬｉＦ量（質量％）となるように変更した（例６および例８に係る正極については複合正極活物質を調製しない）以外は例１に係る正極と同様の材料およびプロセスにより、例２〜例４、例６、例８に係る正極を作製した。
<Example 2 to Example 4, Example 6, Example 8>
The LiF amount with respect to the LNCMW amount (100% by mass) at the time of preparing the composite positive electrode active material was changed to be the LiF amount (% by mass) shown in Table 1 (for the positive electrodes according to Examples 6 and 8, the composite positive electrode A positive electrode according to Examples 2 to 4, Example 6, and Example 8 was produced by the same material and process as the positive electrode according to Example 1 except that no active material was prepared.
＜例５＞
正極活物質中のタングステン含有量が６ｍｏｌ％のＷ含有正極活物質（ＬｉＮｉ０．２５Ｃｏ０．２５Ｍｎ０．２５Ｗ０．２４Ｏ２）を用いた以外は例２に係る正極と同様の材料およびプロセスにより、例５に係る正極を作製した。
<Example 5>
The same as the positive electrode according to Example 2 except that a W-containing positive electrode active material (LiNi 0.25 Co 0.25 Mn 0.25 W 0.24 O 2 ) having a tungsten content of 6 mol% in the positive electrode active material was used. A positive electrode according to Example 5 was produced according to the material and process.
＜例７＞
図２に示す従来の正極の作製方法と同様に、ＬＮＣＭＷ（ＬｉＮｉ０．３２Ｃｏ０．３２Ｍｎ０．３２Ｗ０．０４Ｏ２）と、ＡＢと、ＰＶＤＦとを、ＮＭＰ中に固形分率が６３％となるように分散してスラリー状（ペースト状）の正極活物質層形成用組成物を調製し、該組成物を厚さ１５μｍのアルミニウム箔（正極集電体）のの両面に付与して乾燥することにより、例７に係る正極を作製した。ここで、正極活物質層形成用組成物中のＬＮＣＭＷとＡＢとＰＶＤＦの質量比率は９０：８：２とした。
<Example 7>
Similarly to the conventional method for producing the positive electrode shown in FIG. 2, LNCMW (LiNi 0.32 Co 0.32 Mn 0.32 W 0.04 O 2 ), AB, and PVDF are mixed in NMP. Was prepared so as to be 63% and a slurry-like (paste-like) composition for forming a positive electrode active material layer was prepared, and the composition was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 15 μm. And the positive electrode which concerns on Example 7 was produced by drying. Here, the mass ratio of LNCMW, AB, and PVDF in the positive electrode active material layer forming composition was 90: 8: 2.
＜例９＞
上記正極活物質形成用組成物（スラリー状組成物）中に、該組成物中のＬＮＣＭＷ量（１００質量％）の２質量％に相当する量のＬｉＦを添加した以外は例７に係る正極と同様の材料およびプロセスにより、例９に係る正極を作製した。
<Example 9>
The positive electrode according to Example 7 except that LiF in an amount corresponding to 2% by mass of the LNCMW content (100% by mass) in the composition was added to the composition for forming a positive electrode active material (slurry composition). A positive electrode according to Example 9 was produced using the same material and process.
＜例１０＞
上記例２と同様の材料およびプロセスにより作製した複合正極活物質と、ＡＢと、ＰＶＤＦとを、ＮＭＰ中に固形分率が６３％となるように分散してスラリー状（ペースト状）の正極活物質層形成用組成物を調製し、該組成物を正極集電体の両面に付与して乾燥することにより、例１０に係る正極を作製した。即ち、例１０に係る正極の作製では造粒体の調製を行わなかった。ここで、正極活物質層形成用組成物中のＬＮＣＭＷとＡＢとＰＶＤＦの質量比率は９０：８：２とした。
<Example 10>
A composite positive electrode active material prepared by the same material and process as in Example 2 above, AB, and PVDF are dispersed in NMP so that the solid content is 63%, and a slurry-like (paste-like) positive electrode active material is obtained. A composition for forming a material layer was prepared, and the composition was applied to both surfaces of a positive electrode current collector and dried to prepare a positive electrode according to Example 10. That is, the preparation of the positive electrode according to Example 10 did not prepare a granulated body. Here, the mass ratio of LNCMW, AB, and PVDF in the positive electrode active material layer forming composition was 90: 8: 2.
［非水電解液二次電池（リチウムイオン二次電池）の作製］
上記のとおりに作製した例１〜例１０に係る正極をそれぞれ用いて、例１〜例１０に係る非水電解液二次電池（リチウムイオン二次電池）を作製した。
[Preparation of non-aqueous electrolyte secondary battery (lithium ion secondary battery)]
Using the positive electrodes according to Examples 1 to 10 manufactured as described above, non-aqueous electrolyte secondary batteries (lithium ion secondary batteries) according to Examples 1 to 10 were manufactured.
負極活物質としての天然黒鉛と、結着剤としてＳＢＲと、増粘剤としてＣＭＣとを、これらの材料の質量比が９８：１：１となるように水で混合して、ペースト状の負極活物質層形成用組成物を調製した。この組成物を、厚さ１５μｍの銅箔（負極集電体）の両面に塗付して乾燥し、その後プレスすることにより、負極を作製した。 Natural graphite as a negative electrode active material, SBR as a binder, and CMC as a thickener are mixed with water so that the mass ratio of these materials becomes 98: 1: 1. An active material layer forming composition was prepared. This composition was applied to both sides of a 15 μm thick copper foil (negative electrode current collector), dried, and then pressed to prepare a negative electrode.
上記例１〜例１０に係る正極と、上述の方法で作製した負極とを、多孔質ＰＥ層の両面に多孔質ＰＰ層が形成された三層構造のセパレータ２枚を介して長尺方向に重ねあわせ、長尺方向に捲回した後に押しつぶして拉げることで扁平形状の捲回電極体を作製した。
また、非水電解液として、ＥＣとＤＭＣとＥＭＣとを３：４：３の体積比で含む混合溶媒に、支持塩としてのＬｉＰＦ６を１．０ｍｏｌ／Ｌの濃度で溶解させたもの（基本組成の非水電解液）を調製した。なお例８に係る電池用の非水電解液には、上記基本組成の非水電解液中に、正極中のＬＮＣＭＷ量の２質量％に相当する量のＬｉＦを添加した。
次いで、上記捲回電極体と上記非水電解液とを電池ケースの内部に収容し、理論容量（電池容量）が４Ａｈの各例（例１〜１０）に係る電池を、それぞれ後述の充放電サイクル試験用および熱安定性評価用に構築した。
The positive electrode according to Examples 1 to 10 and the negative electrode produced by the above-described method are arranged in the longitudinal direction via two separators having a three-layer structure in which a porous PP layer is formed on both sides of the porous PE layer. A flat wound electrode body was prepared by overlapping, winding in the long direction, and then crushing and ablating.
Further, as a non-aqueous electrolyte, LiPF 6 as a supporting salt was dissolved at a concentration of 1.0 mol / L in a mixed solvent containing EC, DMC, and EMC at a volume ratio of 3: 4: 3 (basic A non-aqueous electrolyte solution having a composition was prepared. In addition, to the nonaqueous electrolytic solution for a battery according to Example 8, LiF in an amount corresponding to 2% by mass of the amount of LNCMW in the positive electrode was added to the nonaqueous electrolytic solution having the above basic composition.
Next, the wound electrode body and the non-aqueous electrolyte solution are housed in a battery case, and the batteries according to the examples (Examples 1 to 10) having a theoretical capacity (battery capacity) of 4 Ah are charged and discharged as described later. Built for cycle testing and thermal stability evaluation.
［活性化処理（初期充電）と初期容量測定］
上記初期充放電後の例１〜例１０に係る各電池について、活性化処理（初期充電）と、初期容量の測定を行った。
具体的には、２５℃の温度条件下において、４Ａ（１Ｃ）の充電レート（電流値）で電池電圧が４．１Ｖまで定電流（ＣＣ）充電を行った後、電流値が１／５０Ｃとなるまで定電圧（ＣＶ）充電を行い、満充電状態とした。その後、４Ａ（１Ｃ）の放電レート（電流値）で電池電圧が３．０Ｖとなるまで定電流（ＣＣ）放電し、このときの放電容量を初期容量（Ａｈ）とした。かかる初期容量（Ａｈ）を正極中の正極活物質（ＬＮＣＭＷ）量で除し、正極活物質の単位質量当たりの初期容量（ｍＡｈ／ｇ）を算出した。
ここで、「１Ｃ」とは、理論容量より予測した電池容量（Ａｈ）を一時間で充電することができる電流値いうこととする、例えば電池容量が４Ａｈの場合は１Ｃ＝４Ａである。
[Activation (initial charge) and initial capacity measurement]
About each battery which concerns on Examples 1-10 after the said initial stage charge / discharge, the activation process (initial charge) and the initial capacity were measured.
Specifically, after a constant current (CC) charge to a battery voltage of 4.1 V at a charge rate (current value) of 4 A (1 C) under a temperature condition of 25 ° C., the current value is 1/50 C. A constant voltage (CV) charge was performed until a full charge state was obtained. Thereafter, constant current (CC) discharge was performed at a discharge rate (current value) of 4 A (1 C) until the battery voltage reached 3.0 V, and the discharge capacity at this time was defined as the initial capacity (Ah). The initial capacity (Ah) was divided by the amount of the positive electrode active material (LNCMW) in the positive electrode to calculate the initial capacity (mAh / g) per unit mass of the positive electrode active material.
Here, “1C” refers to a current value that can charge the battery capacity (Ah) predicted from the theoretical capacity in one hour. For example, when the battery capacity is 4 Ah, 1C = 4A.
［初期電池抵抗（ＩＶ抵抗）の測定］
次に、上記初期容量を測定した後の各電池について、２５℃の温度条件下で、１Ｃの充電レートで定電（ＣＣ）流充電を行ってＳＯＣ６０％の充電状態に調整した後、１０Ｃで１０秒間の定電流放電を行い、この時の電流（Ｉ）−電圧（Ｖ）のプロット値の一次近似直線の傾きから初期電池抵抗（ＩＶ抵抗）（ｍΩ）を求めた。
ここで、「ＳＯＣ」（Ｓｔａｔｅ ｏｆ Ｃｈａｒｇｅ）は、上記初期容量をＳＯＣ１００％としたときの充電状態をいうこととする。
[Measurement of initial battery resistance (IV resistance)]
Next, for each battery after measuring the initial capacity, a constant current (CC) current charge was performed at a charge rate of 1 C under a temperature condition of 25 ° C. to adjust to a SOC 60% charge state, and then at 10 C. A constant current discharge was performed for 10 seconds, and the initial battery resistance (IV resistance) (mΩ) was determined from the slope of the linear approximation line of the current (I) -voltage (V) plot value at this time.
Here, “SOC” (State of Charge) refers to a state of charge when the initial capacity is SOC 100%.
［充放電サイクル試験］
次に、上記初期電池容量を測定した後の各例にかかる電池について、６０℃の温度条件下において充放電を５００サイクル繰り返す充放電サイクル試験を行い、該サイクル試験後の容量維持率（％）と抵抗増加率（倍）を算出した。具体的には以下のとおりである。
上記充放電サイクル試験は、６０℃の温度条件下において、２Ｃの充電レートでＳＯＣ１００％の充電状態まで定電流充電を行い、その後２Ｃの放電レートでＳＯＣ０％の充電状態まで定電流放電を行う充放電を１サイクルとした。上記充放電サイクル試験終了後の各電池について、上記初期容量測定および初期電池抵抗測定と同様の方法で、充放電サイクル試験後の電池容量（ｍＡ）および電池抵抗を測定した。そして、以下の式：容量維持率（％）＝充放電サイクル試験後の容量（ｍＡｈ）÷初期容量（ｍＡｈ）×１００；から容量維持率を算出し、以下の式：抵抗増加率（倍）＝充放電サイクル試験後のＩＶ抵抗÷初期電池抵抗；から抵抗増加率を算出した。結果を表１の該当欄に示す。
[Charge / discharge cycle test]
Next, the battery according to each example after the initial battery capacity was measured was subjected to a charge / discharge cycle test in which charge / discharge was repeated 500 cycles under a temperature condition of 60 ° C., and the capacity retention rate (%) after the cycle test. And the resistance increase rate (times) was calculated. Specifically, it is as follows.
The charge / discharge cycle test is a charge that performs a constant current charge to a SOC 100% charge state at a charge rate of 2C under a temperature condition of 60 ° C., and then performs a constant current discharge to a charge state of SOC 0% at a discharge rate of 2C. Discharging was 1 cycle. For each battery after completion of the charge / discharge cycle test, the battery capacity (mA) and battery resistance after the charge / discharge cycle test were measured in the same manner as the initial capacity measurement and initial battery resistance measurement. The capacity retention rate is calculated from the following formula: capacity maintenance rate (%) = capacity after charge / discharge cycle test (mAh) ÷ initial capacity (mAh) × 100; and the following formula: resistance increase rate (times) The rate of increase in resistance was calculated from: IV resistance after charge / discharge cycle test / initial battery resistance. The results are shown in the corresponding column of Table 1.
［金属溶出量の測定］
上記充放電サイクル試験後の各例に係る電池（例１〜例１０）について、正極活物質からの金属元素（ここではＮｉ、Ｃｏ、Ｍｎ、Ｗ）の溶出量を評価した。正極活物質から溶出した金属は、一般に非水電解液中を移動して負極上に析出するため、ここでは負極上に析出した金属量を測定することで、正極からの金属溶出量を評価した。
まず、上記サイクル試験後の各電池から負極を取り出し、非水電解液として用いた非水溶媒で２〜３回洗浄した後、任意の大きさに打ち抜いてＩＣＰ−ＡＥＳ分析用の測定用試料を得た。該測定用試料を酸溶媒（ここでは硫酸）中に加熱溶解させ、かかる溶液をＩＣＰ−ＡＥＳで分析することによって、Ｎｉ原子、Ｃｏ原子、Ｍｎ原子、およびＷ原子の量（μｇ）を測定した。正極の作製に用いた全正極活物質中のＮｉ原子、Ｃｏ原子、Ｍｎ原子、およびＷ原子の総量に対するこれらの溶出元素の割合、即ち金属溶出量（ｐｐｍ）を求めた。結果を表１の該当欄に示す。
[Measurement of metal elution amount]
For the batteries (Examples 1 to 10) according to each example after the charge / discharge cycle test, the amount of elution of metal elements (here, Ni, Co, Mn, W) from the positive electrode active material was evaluated. Since the metal eluted from the positive electrode active material generally moves in the non-aqueous electrolyte and deposits on the negative electrode, the amount of metal eluted from the positive electrode was evaluated by measuring the amount of metal deposited on the negative electrode here. .
First, the negative electrode is taken out from each battery after the cycle test, washed with a non-aqueous solvent used as a non-aqueous electrolyte solution 2-3 times, and then punched to an arbitrary size to prepare a measurement sample for ICP-AES analysis. Obtained. The amount of Ni atom, Co atom, Mn atom, and W atom (μg) was measured by dissolving the sample for measurement in an acid solvent (here, sulfuric acid) by heating and analyzing the solution with ICP-AES. . The ratio of these eluting elements to the total amount of Ni atoms, Co atoms, Mn atoms, and W atoms in all the positive electrode active materials used for producing the positive electrode, that is, the metal elution amount (ppm) was determined. The results are shown in the corresponding column of Table 1.
［発熱量測定］
次に、各例に係る電池について、示差走査熱量測定（Differential Scanning Calorimetry：ＤＳＣ）によって正極の発熱量を測定し、熱安定性を評価した。
まず、上記例１〜例１０に係る電池（熱安定性評価用に構築した各電池）を高ＳＯＣの充電状態（ここでは凡そＳＯＣ２２０％の状態）まで充電した後、解体して、正極と非水電解液とを測定試料として取り出した。そして、取り出した正極と非水電解液とを一緒に測定用セル内に密閉し、当該測定用試料に対して、示差走査熱量測定（Differential Scanning Calorimetry：ＤＳＣ）を行った。具体的には、ＤＳＣ測定装置（株式会社島津製作所製、型式「ＤＳＣ−６０」）を用いて、窒素雰囲気下において、１０℃／分の昇温速度で２５℃から４００℃まで温度を変化させてＤＳＣ測定を行った。そして、得られたＤＳＣ曲線の５０℃から３５０℃までの面積を測定試料の総発熱量（Ｗ）とし、この総発熱量（Ｗ）を測定試料の質量（ｇ）で除すことによって、単位質量あたりの発熱量（Ｗ／ｇ）を算出した。結果を表１の「発熱量（Ｗ／ｇ）」の欄に示す。
[Measurement of calorific value]
Next, for the batteries according to each example, the calorific value of the positive electrode was measured by differential scanning calorimetry (DSC), and the thermal stability was evaluated.
First, the batteries according to the above Examples 1 to 10 (each battery constructed for thermal stability evaluation) are charged to a high SOC charge state (here, approximately 220% SOC state), then disassembled, and the positive electrode and the non-charge The water electrolyte was taken out as a measurement sample. And the taken-out positive electrode and nonaqueous electrolyte solution were sealed together in the cell for a measurement, and the differential scanning calorimetry (DSC) was performed with respect to the said sample for a measurement. Specifically, using a DSC measuring device (manufactured by Shimadzu Corporation, model “DSC-60”), the temperature was changed from 25 ° C. to 400 ° C. at a temperature rising rate of 10 ° C./min in a nitrogen atmosphere. DSC measurement was performed. Then, the area from 50 ° C. to 350 ° C. of the obtained DSC curve is defined as the total calorific value (W) of the measurement sample, and this total calorific value (W) is divided by the mass (g) of the measurement sample, thereby obtaining a unit. The calorific value (W / g) per mass was calculated. The results are shown in the column of “Heat generation amount (W / g)” in Table 1.
表１に示すように、電池内（正極活物質層中或いは非水電解液中）にＬｉＦを添加した例１〜５および例８〜１０に係る電池は、ＬｉＦを添加しなかった例６および例７に係る電池と比較して、金属溶出量が顕著に少なかった。このことは、電池内にＬｉＦを添加することで正極活物質表面へのＬｉＦ被膜の形成が促進され、正極活物質からの構成元素の溶出が抑制されたためと考えられる。
また、これら例１〜５および例８〜１０に係る電池は、抵抗増加率が低く、容量維持率が高く、発熱量が少なかった。即ち、例１〜５および例８〜１０に係る電池は、サイクル特性および熱安定性に優れた電池であることを確認した。これらのことは、正極活物質表面に形成されたＬｉＦ被膜により、正極活物質と非水電解液間での電荷担体（典型的にはリチウムイオン）の移動が円滑になったこと、および正極活物質表面での非水電解液の分解が抑制されたこと等によるものと考えられる。
なかでも、例１〜５に係る電池は、例８〜１０に係る電池と比較して、金属溶出量がより低減されていた。このことは、本発明の一実施形態に係る正極の製造方法によって、正極活物質表面がより好ましい状態（典型的には被膜ムラが低減された状態）のＬｉＦ被膜で被覆された正極を作製することができたためと考えられる。即ち、ここで開示する正極の製造方法によると、正極活物質からの構成元素の溶出がより高度に抑制され且つ電池性能（サイクル特性）に優れた電池を提供し得ることを確認した。
As shown in Table 1, the batteries according to Examples 1 to 5 and Examples 8 to 10 in which LiF was added in the battery (in the positive electrode active material layer or in the nonaqueous electrolytic solution) Compared with the battery according to Example 7, the metal elution amount was remarkably small. This is presumably because the addition of LiF into the battery promoted the formation of a LiF film on the surface of the positive electrode active material, and the elution of constituent elements from the positive electrode active material was suppressed.
Moreover, the batteries according to Examples 1 to 5 and Examples 8 to 10 had a low resistance increase rate, a high capacity retention rate, and a small amount of heat generation. That is, it was confirmed that the batteries according to Examples 1 to 5 and Examples 8 to 10 were excellent in cycle characteristics and thermal stability. This is because the LiF coating formed on the surface of the positive electrode active material facilitates the movement of charge carriers (typically lithium ions) between the positive electrode active material and the non-aqueous electrolyte, and the positive electrode active material. This is thought to be due to the fact that the decomposition of the non-aqueous electrolyte on the surface of the substance was suppressed.
Especially, the battery which concerns on Examples 1-5 had the metal elution amount reduced more compared with the battery which concerns on Examples 8-10. This is because a positive electrode coated with a LiF coating in a more preferable state (typically a state in which coating unevenness is reduced) is produced by the positive electrode manufacturing method according to one embodiment of the present invention. It is thought that it was possible. That is, according to the positive electrode manufacturing method disclosed herein, it has been confirmed that elution of constituent elements from the positive electrode active material can be suppressed to a higher degree and a battery excellent in battery performance (cycle characteristics) can be provided.
なお、Ｗ含有正極活物質とＬｉＦとを混合して複合正極活物質を作製した後で、当該複合正極活物質と導電材とバインダと溶媒とを用いてスラリー状（即ち、固形分率が低い）の正極活物質形成用組成物を調製した（即ち、造粒体を調製しなかった）例１０に係る電池は、同様複合正極活物質と導電材とバインダと溶媒とを用いて造粒体を調製した例２に係る電池と比較して、金属溶出量が多かった。このことは、上記複合正極活物質を用いてスラリー状の正極活物質形成用組成物を調製したことで、Ｗ含有正極活物質表面に分散したＬｉＦに多量の溶媒（正極活物質形成用組成物中の溶媒）が反応してＬｉＦがＷ含有正極活物質表面から脱離した、或いはＬｉＦと溶媒（正極活物質形成用組成物中の溶媒）中の他の成分とが反応してしまいＷ含有正極活物質表面でのＬｉＦ被膜の形成が不十分となった等によるものと考えられる。 In addition, after mixing a W containing positive electrode active material and LiF and producing a composite positive electrode active material, the composite positive electrode active material, a conductive material, a binder, and a solvent are used to form a slurry (that is, the solid content is low). The battery according to Example 10 was prepared using the composite positive electrode active material, the conductive material, the binder, and the solvent. Compared with the battery according to Example 2 prepared, the metal elution amount was large. This is because a slurry-like composition for forming a positive electrode active material was prepared using the composite positive electrode active material, and a large amount of solvent (a composition for forming a positive electrode active material) was dispersed in LiF dispersed on the surface of the W-containing positive electrode active material. LiF is desorbed from the surface of the W-containing positive electrode active material due to reaction, or LiF reacts with other components in the solvent (solvent in the positive electrode active material forming composition) to contain W. This is considered to be due to insufficient formation of the LiF film on the surface of the positive electrode active material.
また、複合正極活物質中のＬｉＦ量が異なる例１〜４に係る電池を比較すると、複合正極活物質層中のＬｉＦ量がＷ含有正極活物質の０．１質量％〜５質量％である例１〜３に係る電池は、ＬｉＦ量が比較的多い例４に係る電池と比較して、金属溶出量がより少なかった。また、例１〜３に係る電池は、例４に係る電池と比較して、抵抗増加率が低く、容量維持率が高かった。
また、Ｗ含有正極活物質（ＬＮＣＭＷ）中のタングステン含有量が異なる例２と例５に係る電池を比較すると、タングステン含有量が０．０１ｍｏｌ％〜５ｍｏｌ％の範囲内である例２に係る電池の方が、例５に係る電池よりも金属溶出量が少なく、抵抗増加率が低く、容量維持率が高かった。
Moreover, when the batteries according to Examples 1 to 4 having different LiF amounts in the composite positive electrode active material are compared, the LiF amount in the composite positive electrode active material layer is 0.1% by mass to 5% by mass of the W-containing positive electrode active material. The batteries according to Examples 1 to 3 had a smaller amount of metal elution than the battery according to Example 4 having a relatively large amount of LiF. In addition, the batteries according to Examples 1 to 3 had a low resistance increase rate and a high capacity maintenance rate as compared with the battery according to Example 4.
Further, when the batteries according to Example 2 and Example 5 having different tungsten contents in the W-containing positive electrode active material (LNCMW) are compared, the battery according to Example 2 in which the tungsten content is in the range of 0.01 mol% to 5 mol%. The metal elution amount was smaller than that of the battery according to Example 5, the resistance increase rate was low, and the capacity maintenance rate was high.
以上、本発明の具体例を詳細に説明したが、これらは例示にすぎず、請求の範囲を限定するものではない。請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。 As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
Ｓ１０ 複合正極活物質調製工程
Ｓ２０ 造粒工程
Ｓ３０ 正極活物質層形成工程
S10 Composite positive electrode active material preparation step S20 Granulation step S30 Positive electrode active material layer formation step
Claims (1)
構成元素としてタングステン（Ｗ）を含む正極活物質と、フッ化リチウム（ＬｉＦ）とを混合して機械的エネルギーを加えることにより、該タングステン含有正極活物質の表面にフッ化リチウム被膜が形成された複合正極活物質を得る工程；
前記得られた複合正極活物質に、少なくとも導電材およびバインダを添加して造粒することにより、少なくとも該複合正極活物質、導電材およびバインダを含む造粒体を得る工程；および
前記得られた造粒体を用いて正極集電体の表面に正極活物質層を形成する工程；
を包含し、
前記タングステン含有正極活物質とフッ化リチウムとの質量比が、１００：０．１〜５である、
非水電解液二次電池用正極の製造方法。 A method for producing a positive electrode for a nonaqueous electrolyte secondary battery, comprising the following steps:
A lithium fluoride film was formed on the surface of the tungsten-containing positive electrode active material by mixing a positive electrode active material containing tungsten (W) as a constituent element and lithium fluoride (LiF) and applying mechanical energy. Obtaining a composite cathode active material;
A step of obtaining a granulated body containing at least the composite positive electrode active material, the conductive material and the binder by adding at least a conductive material and a binder to the obtained composite positive electrode active material and granulating; and the obtained Forming a positive electrode active material layer on the surface of the positive electrode current collector using the granulated body;
It encompasses,
The mass ratio of the tungsten-containing positive electrode active material and lithium fluoride is 100: 0.1 to 5,
A method for producing a positive electrode for a non-aqueous electrolyte secondary battery.
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