JPH11339804A - Positive electrode material for nonaqueous electrolyte secondary battery and battery with the same - Google Patents
Positive electrode material for nonaqueous electrolyte secondary battery and battery with the sameInfo
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- JPH11339804A JPH11339804A JP10148964A JP14896498A JPH11339804A JP H11339804 A JPH11339804 A JP H11339804A JP 10148964 A JP10148964 A JP 10148964A JP 14896498 A JP14896498 A JP 14896498A JP H11339804 A JPH11339804 A JP H11339804A
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- lithium
- positive electrode
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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)
Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は、非水電解液二次電
池の、特に正極活物質に関するものである。The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a positive electrode active material.
【0002】[0002]
【従来の技術】非水電解液二次電池は、小型、軽量で、
かつ高エネルギー密度を有するため、機器のポータブル
化、コードレス化が進む中で、その期待は高まってい
る。2. Description of the Related Art Non-aqueous electrolyte secondary batteries are small, lightweight,
In addition, due to the high energy density, the expectation is increasing as portable and cordless devices are progressing.
【0003】従来、非水電解液二次電池用の正極活物質
としてLiCoO2、LiNiO2、LiMn2O4などの
リチウム含有金属酸化物が提案されている。一方、負極
としては金属リチウム、リチウム合金、リチウムイオン
を吸蔵・放出することのできる黒鉛材料などが提案さ
れ、実用化されている。このうち特に、LiMn2O4は
安価な正極材料として注目を浴びている。Conventionally, lithium-containing metal oxides such as LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 have been proposed as a positive electrode active material for a non-aqueous electrolyte secondary battery. On the other hand, as a negative electrode, metallic lithium, a lithium alloy, a graphite material capable of inserting and extracting lithium ions, and the like have been proposed and put to practical use. Among them, LiMn 2 O 4 is particularly attracting attention as an inexpensive cathode material.
【0004】しかしながら、このスピネル構造のLiM
n2O4は出発物質や処理温度条件などの合成条件に極め
て敏感で電気化学的な挙動に大きな影響をもたらす。電
気化学的活性度が高く、初期において高容量が得られた
としても電気化学的な可逆性が十分得られるということ
とは必ずしも合致することではなく、しばしばサイクル
特性において他のコバルト系やニッケル系よりも特性が
劣ることがあった。これは、充放電に伴う結晶相変化で
結晶構造が次第に崩壊したり、一部マンガンイオンが電
解液に溶解することなどにより引き起こされていた。However, this spinel-structured LiM
n 2 O 4 is extremely sensitive to synthesis conditions such as starting materials and processing temperature conditions, and has a great influence on electrochemical behavior. Electrochemical activity is high, and even if a high capacity is obtained in the initial stage, it is not always the case that sufficient electrochemical reversibility can be obtained. Properties were inferior. This has been caused by a crystal phase gradually changing due to a crystal phase change accompanying charge / discharge, or a part of manganese ions dissolving in the electrolytic solution.
【0005】このため、種々の添加元素をマンガンの一
部に固溶させ充放電に伴う結晶相変化を緩和する方法
(J.Elecrochem.Soc.,138(’9
1)2859)が提案されて可逆性の改良が試みられて
いる。また、Mn部分の改良のみならずLiMn2O4の
表面を他の物質相で被覆してマンガン溶解の制御あるい
は結晶構造を安定化させ可逆性の向上をねらった取り組
み(J.Elecrochem.Soc.,145(’
98)194)が提案されている。For this reason, various additive elements are dissolved in a part of manganese to reduce the crystal phase change accompanying charge and discharge (J. Electrochem. Soc., 138 ('9)
1) 2859) has been proposed to improve reversibility. In addition, efforts to improve the reversibility by controlling the dissolution of manganese or stabilizing the crystal structure by coating the surface of LiMn 2 O 4 with another material phase as well as improving the Mn portion (J. Electrochem. Soc. , 145 ('
98) 194) have been proposed.
【0006】[0006]
【発明が解決しようとする課題】確かに上記の従来要素
技術を駆使すれば可逆性の改善は確認されるが、電池特
性に有用な他の所特性、たとえば電極での比容量の低下
あるいはリチウムイオンの移動など動的因子を低下させ
高負荷特性などに悪影響がもたらされる。Although the reversibility can be improved by making full use of the above-mentioned conventional elemental technology, other characteristics useful for battery characteristics, such as a decrease in specific capacity at an electrode or lithium. Dynamic factors such as ion migration are reduced, which adversely affects high load characteristics and the like.
【0007】電極容量の低下はLiMn2O4のMn内に
種々の添加元素が固溶されているため、可動マンガン原
子価が制限を受け十分な可逆容量が得られないことに起
因しており、電極高負荷特性の低下はLiMn2O4粒子
表面を他の物質相で被覆することにより界面での電気化
学的な物質輸送に悪影響をもたらすことに起因している
と考えられる。The decrease in the electrode capacity is due to the fact that various manganese valences of LiMn 2 O 4 are dissolved in solid solution, so that the movable manganese valency is limited and a sufficient reversible capacity cannot be obtained. It is considered that the decrease in the electrode high-load characteristics is caused by coating the surface of the LiMn 2 O 4 particles with another material phase, which adversely affects electrochemical mass transport at the interface.
【0008】本発明は、このような課題を解決するもの
で、一般式LiMn2O4で表されるスピネル型のリチウ
ム含有マンガン酸化物を正極材料として用いる際、マン
ガンに他元素を添加したり、表面を被覆することなく、
高容量で高負荷特性に優れた材料を提供するものであ
る。The present invention solves such a problem. When a spinel-type lithium-containing manganese oxide represented by the general formula LiMn 2 O 4 is used as a cathode material, other elements may be added to manganese. Without coating the surface,
It is intended to provide a material having high capacity and excellent high load characteristics.
【0009】[0009]
【発明の実施の形態】これらの課題を解決するために、
本発明は、主として空間群Fd3m(No.227)に
属し、一般式LiMn2O4で表されるスピネル型のリチ
ウム含有マンガン酸化物であって、比表面積を0.5〜
1.9m2/gとし、粉末X線回折パターンの回折ピー
ク(111)のピーク強度に対する半価幅の比を用いた
結晶化パラメータαが各回折ピーク(311)、(22
2)、(400)、(440)のαに対し1.1〜2.
3であり、かつリチウム核を用いた固体NMRスペクト
ル、特にMAS/spin−echo法(マジック角回
転法(回転数8〜10kHz)とスピンエコー法の併
用)で測定されるLiClを0ppm基準においたスペ
クトルにおいて、線幅が1000ppmを越えるブロー
ドなスペクトル(a)と少なくとも100ppm以下の
スピニングサイドバンド(b)で構成されるスペクトル
のうち、スペクトル(a)に対するスペクトル(b)の
面積比が30%以上50%未満となる正極材料を用いる
ものであり、この材料を用いた正極と、リチウムを吸
蔵、放出できる負極材料を用いた負極と非水電解質によ
り非水電解質二次電池を提供するものである。DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve these problems,
The present invention mainly relates to a spinel-type lithium-containing manganese oxide belonging to the space group Fd3m (No. 227) and represented by the general formula LiMn 2 O 4 and having a specific surface area of 0.5 to
The crystallization parameter α using the ratio of the half width to the peak intensity of the diffraction peak (111) of the powder X-ray diffraction pattern was set to 1.9 m 2 / g, and the crystallization parameter α was calculated for each diffraction peak (311), (22
2), (400), 1.1 to 2.440 with respect to α of (440).
3, and LiCl measured by a MAS / spin-echo method (combined use of a magic angle rotation method (rotation speed of 8 to 10 kHz) and a spin echo method), and based on 0 ppm LiCl. In the spectrum, among the broad spectrum (a) having a line width exceeding 1000 ppm and the spinning side band (b) having at least 100 ppm or less, the area ratio of the spectrum (b) to the spectrum (a) is 30% or more. A non-aqueous electrolyte secondary battery is provided by using a positive electrode material that is less than 50%, a positive electrode using this material, a negative electrode using a negative electrode material capable of inserting and extracting lithium, and a non-aqueous electrolyte. .
【0010】スピネル型のリチウム含有マンガン酸化物
は、繰り返し充放電を行うと粉末X線回折パターンで示
される種々の回折ピークが次第にブロード化し、これに
伴いサイクル特性の低下が見られる。これは、充放電に
伴う結晶構造変化が起こり構造破壊を招くことおよび一
部の固相中のマンガンが電解液へ溶解するために結晶構
造が低結晶化することなどが原因と考えられている。In the spinel-type lithium-containing manganese oxide, when repeatedly charged and discharged, various diffraction peaks indicated by a powder X-ray diffraction pattern gradually broaden, and the cycle characteristics are reduced accordingly. This is thought to be due to the fact that the crystal structure changes due to charge / discharge and causes structural destruction, and that the manganese in a part of the solid phase dissolves in the electrolyte, resulting in a low crystal structure. .
【0011】もともと、コバルト系などが分子間力で形
成される層構造を有す空間にリチウムイオンを吸放出す
るという原理を持つのに対し、スピネル系のリチウム含
有マンガン酸化物はクーロン力で引き合う3次元マトリ
ックスの空間にリチウムイオンを吸放出するという原理
を持つため、リチウムを電気化学的に引き抜いた後の結
晶構造はマンガン系の方が若干不安定になりやすい。従
って、充放電により繰り返し動的にリチウムの吸放出を
繰り返すと構造変化を来たしサイクル初期の結晶状態と
異なった形態を持ちやすくなる。しかもリチウム引き抜
きの反応過程でその不安定さ故、一部のマンガンイオン
が電解液に排出する現象が起こるため一層の結晶構造崩
壊を助長する。Originally, the principle of absorbing and releasing lithium ions in a space having a layered structure formed by an intermolecular force, for example, of a cobalt-based compound, whereas the spinel-based lithium-containing manganese oxide attracts by Coulomb force. Because of the principle of absorbing and releasing lithium ions in the space of the three-dimensional matrix, the manganese-based crystal structure after lithium is electrochemically extracted tends to be slightly unstable. Therefore, when the absorption and desorption of lithium are repeatedly and dynamically repeated by charging and discharging, the structure is changed, and it is easy to have a form different from the crystal state at the beginning of the cycle. In addition, because of the instability during the lithium extraction reaction process, a phenomenon occurs in which some manganese ions are discharged into the electrolyte, which further promotes the collapse of the crystal structure.
【0012】本発明者らはこのような解析事実に基づ
き、比容量密度や高負荷特性を低下させず、かつサイク
ル特性の向上を図るため、スピネル型リチウム含有マン
ガン酸化物の結晶化度の向上とマンガン溶出の活性を減
少させる目的で電解液との接触界面の低減、すなわち低
比表面積化を図ることにした。On the basis of such analysis facts, the present inventors have attempted to improve the crystallinity of the spinel-type lithium-containing manganese oxide without lowering the specific capacity density or high load characteristics and improving the cycle characteristics. In order to reduce the activity of dissolving manganese and manganese, it was decided to reduce the contact interface with the electrolytic solution, that is, to reduce the specific surface area.
【0013】また、バルクの結晶構造や比表面積の制御
のみならず、内在するリチウムの化学状態をも制御され
た材料を提供するため、リチウムの固体NMRを用い固
相内でのリチウムの存在状態を検知することにした。Further, in order to provide a material in which not only the bulk crystal structure and specific surface area but also the chemical state of lithium contained therein are controlled, the solid state NMR of lithium is used to determine the state of lithium in the solid phase. Was detected.
【0014】すなわち、NMRの解析情報からスピネル
型リチウム含有マンガン酸化物中に存在するスピネル系
の3次元構造を安定化させる適正リチウム収容サイトで
の占有量を制御することで特性向上を図るものである。That is, the characteristics are improved by controlling the occupation amount at an appropriate lithium accommodating site for stabilizing the three-dimensional structure of the spinel system existing in the spinel-type lithium-containing manganese oxide based on NMR analysis information. is there.
【0015】固体NMR測定において、通常はリチウム
含有遷移金属酸化物中にあるリチウムの状態を観測する
のにMAS法を用いることが多い。しかし、MAS法に
よる測定だけでは遷移金属酸化物中にあるリチウムはそ
の遷移金属の常磁性の影響を受けその存在状態の解釈が
非常に困難である。そこで、さらにpulse−spi
n−echo法を併用した7Li−NMRによるリチウ
ムの電子状態を測定することで、緩和時間の観点からも
リチウムの存在状態をより詳細に検討することができ
る。In solid-state NMR measurement, the MAS method is often used to observe the state of lithium in a lithium-containing transition metal oxide. However, it is very difficult to interpret the state of lithium in the transition metal oxide due to the paramagnetism of the transition metal only by the measurement using the MAS method. Therefore, further pulse-spi
n-echo method by measuring the electron state of the lithium by 7 Li-NMR in combination with, it is possible to consider the presence state of lithium in more detail in terms of relaxation times.
【0016】結晶化度については、種々の測定方法があ
るが、ここでは各回折ピークの半価幅に対する回折強度
を用いることにした。これは単に回折強度因子のみによ
る判断ではなく半価幅が結晶子等の成長程度を知る因子
でもあるので両者のパラメータの影響を含んだ関数とし
て数値化しサイクル特性などとの因果関係を知る手立て
とした。There are various methods for measuring the degree of crystallinity. Here, the diffraction intensity for the half width of each diffraction peak is used. This is not only a judgment based on the diffraction intensity factor, but also because the half width is a factor that knows the degree of growth of crystallites and so on. did.
【0017】(111)はマンガン原子の配列を如実に
示したメイン回折ピークであり、この回折ピークの結晶
化度は如何なる手法で合成あるいは表面改質等を加えて
も大きな変化を示さない。そこでこのピークを基準とし
た時に他の回折ピークの結晶化度の変化をパラメータα
として数値化した。本発明者らがサイクル特性の向上を
種々の手法を用いて鋭意検討したところ、特性を向上さ
せる要素は(111)のαが(311)(222)(4
00)(440)の各ピークのαに対し1.1〜2.3
の範囲であることを見い出した。(111) is a main diffraction peak which clearly shows the arrangement of manganese atoms, and the crystallinity of this diffraction peak does not show a significant change even if synthesis or surface modification is performed by any method. Therefore, when this peak is used as a reference, the change in crystallinity of the other diffraction peaks is determined by the parameter α.
It was digitized as The present inventors have conducted intensive studies on the improvement of cycle characteristics using various techniques. As a result, α of (111) is (311) (222) (4).
00) (440) 1.1 to 2.3 with respect to α of each peak.
Range.
【0018】(111)以外の回折ピークの回折強度の
増加と先鋭化は結晶性の向上が酸素配列や、酸素−マン
ガン間の配列などに如実に現れることであり、これがバ
ルク固体全体の結晶化度向上に大きく寄与していると考
えられる。なお、測定中αが2.3以上の高結晶性化を
行うと初期の比容量密度が低下した。従って、αは2.
3が上限と考えられる。The increase and sharpening of the diffraction intensity of the diffraction peaks other than (111) means that the improvement in crystallinity is apparent in the oxygen arrangement and the arrangement between oxygen and manganese, and this is the crystallization of the bulk solid as a whole. It is thought that it has greatly contributed to the improvement of the degree. During the measurement, when the crystallinity was increased to α of 2.3 or more, the initial specific capacity density decreased. Therefore, α is 2.
3 is considered the upper limit.
【0019】また、マンガンの電解液への溶出について
も上記合成手法に準拠して行ったところ、0.5〜1.
9m2/gで溶出が抑制されることを見い出した。窒素
ガスを用いたBET法によって測定を行ったが、0.5
m2/g以下を測定することはできなかった。また、
1.9m2/g以上では、理由は定かでないが、マンガ
ンの電解液への溶解量が急激に増え始めるので上限値と
して1.9m2/gとしたものである。The leaching of manganese into the electrolyte was carried out in accordance with the above synthesis method.
It was found that elution was suppressed at 9 m 2 / g. The measurement was performed by the BET method using nitrogen gas.
m 2 / g or less could not be measured. Also,
At 1.9 m 2 / g or more, the reason is not clear, but since the amount of manganese dissolved in the electrolytic solution starts to increase rapidly, the upper limit is set to 1.9 m 2 / g.
【0020】さらに、固体NMRの解析情報から次のこ
とを導いた。スピネル構造(空間群Fd3m)には、M
nから距離の異なる4配位と6配位の2種のLiサイト
8aサイト、16cサイトが存在することは知られた事
実である。本発明者らは常磁性の特質の強いMnからの
距離が異なるこれらの2つのLiサイトへ与える影響を
鑑み、Mnからの距離が近い16cサイトの方がより強
い常磁性の影響を受け低磁場側へケミカルシフトし、8
aサイトの方は常磁性の影響をあまり強く受けず高磁場
へケミカルシフトするものと考え、NMR解析により格
子内の異種リチウムサイトの区別が可能になると考え
た。電気化学的活性度と8aサイトを反映するシグナル
(スピニングサイドバンドのスペクトルb)には明らか
な相関があり、このシグナルのピーク面積がブロードな
シグナル(線幅1000ppm程度のスペクトルa)の
面積比で30%以上あればサイクルの初期容量を示す単
極の比容量密度は良好になり、しかも結晶構造中のリチ
ウムの置かれている化学的環境が常磁性種のマンガンの
影響をどれくらい強く受けるかがケミカルシフトで理解
できるためリチウムとマンガンの結晶周期性、すなわち
結晶内の微細な結晶化度の判断ができ、良好なサイクル
特性を示す条件として位置づけることができる。Further, the following was derived from the analysis information of solid-state NMR. The spinel structure (space group Fd3m) has M
It is a known fact that there are two types of Li sites, 8a site and 16c site, of 4-coordinate and 6-coordinate having different distances from n. The present inventors consider the influence on these two Li sites that are different in distance from Mn, which has strong paramagnetic properties, and that the 16c site that is closer to Mn is more affected by stronger paramagnetism and has a lower magnetic field. Chemical shift to the side, 8
The a-site was considered not to be strongly affected by paramagnetism and was chemically shifted to a high magnetic field, and it was thought that it was possible to distinguish heterogeneous lithium sites in the lattice by NMR analysis. There is a clear correlation between the electrochemical activity and the signal reflecting the 8a site (spinning sideband spectrum b), and the peak area of this signal is determined by the area ratio of the broad signal (spectrum a having a line width of about 1000 ppm). If it is 30% or more, the specific capacity density of the monopole, which indicates the initial capacity of the cycle, becomes good, and how strongly the chemical environment where lithium in the crystal structure is placed is affected by the paramagnetic manganese. Since it can be understood by the chemical shift, the crystal periodicity of lithium and manganese, that is, the fine crystallinity in the crystal can be determined, and can be positioned as a condition showing good cycle characteristics.
【0021】MAS法の回転数をさらに上げるとスペク
トル面積比が若干異なったり、16cサイトの高分解能
化が可能となりシグナルの先鋭化とスピニングサイドバ
ンドの出現が期待できるので一概にスペクトル(b)と
(a)の面積比が30%以上と決定することは困難であ
るが、8〜10kHzの回転条件下では高特性を引き出
す条件として30%以上が好ましい。実験上ピーク比が
50%を越えることはなかったが、ただし、これは先の
設備の分解能と深い関連がありこの数値の限定は困難で
ある。When the rotational speed of the MAS method is further increased, the spectral area ratio is slightly different, and the resolution of the 16c site can be increased, and sharpening of the signal and appearance of the spinning side band can be expected. It is difficult to determine that the area ratio of (a) is 30% or more, but it is preferable that the area ratio is 30% or more as a condition for extracting high characteristics under the rotation condition of 8 to 10 kHz. Experimentally, the peak ratio did not exceed 50%, but this is closely related to the resolution of the previous equipment, and it is difficult to limit this value.
【0022】[0022]
【実施例】以下、図面と共に本発明の実施例を説明す
る。Embodiments of the present invention will be described below with reference to the drawings.
【0023】MAS/spin−echo法の測定条件
を記す。測定周波数116.75MHz、観測幅125
kHz、パルス幅90°、パルス(3μsec)、Pr
e−refocus(100μsec)、Post−r
efocus(98.4μsec)、繰り返し時間(1
sec)、試料回転数(10kHz)、積算回数(51
2回)、測定(室温)、化学シフト基準(LiCl;0
ppm) 比表面積の測定は窒素ガス吸着のBET法で行った。The measurement conditions of the MAS / spin-echo method are described. Measurement frequency 116.75 MHz, observation width 125
kHz, pulse width 90 °, pulse (3 μsec), Pr
e-refocus (100 μsec), Post-r
efocus (98.4 μsec), repetition time (1
sec), sample rotation speed (10 kHz), integration frequency (51
2), measurement (room temperature), chemical shift standard (LiCl; 0)
ppm) The specific surface area was measured by the BET method of nitrogen gas adsorption.
【0024】結晶化度の測定はパワー40kV,40m
AでCukαのX線回折装置を用いた。The crystallinity was measured at a power of 40 kV and 40 m.
In A, a Cukα X-ray diffractometer was used.
【0025】次に図1に本発明の正極材料を評価するた
めの評価用電池の縦断面図を示す。図1において、1は
耐有機電解液性のステンレス鋼板を加工した電池ケー
ス、2は同材料の封口板、3は絶縁パッキング、4は極
板群、5は一般式LiMn2O4で表される材料を用いた
正極板、6はリチウムを吸蔵、放出可能な炭素材料を用
いた負極板、7はポリプロピレン樹脂製の微孔性セパレ
ータ、8は極板群の上下面の絶縁を良くするために配置
された絶縁リングである。Next, FIG. 1 shows a longitudinal sectional view of an evaluation battery for evaluating the positive electrode material of the present invention. In FIG. 1, reference numeral 1 denotes a battery case processed from a stainless steel plate having resistance to organic electrolyte, 2 denotes a sealing plate of the same material, 3 denotes an insulating packing, 4 denotes an electrode group, and 5 denotes a general formula LiMn 2 O 4. Plate 6 using a carbon material capable of occluding and releasing lithium, 7 a microporous separator made of polypropylene resin, and 8 for improving the insulation of the upper and lower surfaces of the electrode plate group. Is an insulating ring arranged in the
【0026】この評価用電池の寸法は直径20mm、電
池総高1.6mmである。電解液はEC−DEC等体積
混合溶媒に1.5mol/LのLiPF6を溶解したも
のを用いた。The size of the battery for evaluation is 20 mm in diameter and the total height of the battery is 1.6 mm. As the electrolytic solution, a solution in which 1.5 mol / L of LiPF6 was dissolved in an EC-DEC equal volume mixed solvent was used.
【0027】充放電の条件は電流密度の0.33mA/
cm2の定電流充放電とし、2V〜4.3V(Li基
準)の電位領域で可逆容量および酸化還元の開回路電位
を測定した。休止時間は1時間とした。The charge / discharge condition is a current density of 0.33 mA /
The reversible capacity and the open-circuit potential of the oxidation-reduction were measured in a potential range of 2 V to 4.3 V (based on Li) with constant current charging and discharging of cm 2 . The downtime was one hour.
【0028】本発明のスピネル型リチウム含有マンガン
酸化物の合成は、例えばマンガン源として二酸化マンガ
ン、リチウム源として炭酸リチウムあるいは水酸化リチ
ウムを用いることができる。これらの出発材料をLiM
nO4組成になるように所定比で混合し、酸化性雰囲気
に調整された反応環境下で750〜900℃の温度で焼
成して得られるが、所望の物性値を得るためには、原材
料の粒径、比表面積、反応過程での温度ステップや反応
雰囲気の調整を行う必要がある。In the synthesis of the spinel-type lithium-containing manganese oxide of the present invention, for example, manganese dioxide can be used as a manganese source, and lithium carbonate or lithium hydroxide can be used as a lithium source. These starting materials are LiM
It is obtained by mixing at a predetermined ratio so as to have an nO 4 composition and calcining at a temperature of 750 to 900 ° C. in a reaction environment adjusted to an oxidizing atmosphere. It is necessary to adjust the particle size, the specific surface area, the temperature step in the reaction process and the reaction atmosphere.
【0029】各種試料を用いたコイン型電池を試作し、
初期放電時の比容量密度および、100サイクル後の初
期に対する放電容量維持率を結晶化度パラメータαの関
係で検討した。その結果を図2に示す。図から分かるよ
うに(111)のαに対する各(311)(222)
(400)(440)ピークのαの比率が1.1を越え
ると容量維持率が高くサイクル特性が良好であることを
支持する。初期放電の比容量密度は依存せずほぼ125
mAh/g前後の特性であるが、αの比率が2.3を越
えると急激に容量密度が低下する。従ってαの比率とし
ては1.1〜2.3とすべきである。次に比表面積との
関係で検討した。その結果を図3に示す。図から分かる
ように比表面積が1.9m2/gまでは容量維持率が高
くサイクル特性が良好であることを支持するが、それを
越えると急激に悪化する。初期放電の比容量密度はαの
比率に依存せずほぼ125mAh/g前後の特性を示
す。従って、比表面積としては0.5〜1.9m2/g
とすべきである。次にNMRのスペクトル(a)に対す
る(b)の面積比率との関係を検討した。その結果を図
4に示す。図からわかるようにスペクトル面積比が30
%を越えると容量維持率が高くなりサイクル特性が良好
であることを支持するが、それ以下では優れた特性を示
さない。また、初期放電の比容量密度も同様の傾向でス
ペクトル面積比が大きくなるに連れ増加傾向にある。従
ってスペクトル面積比としては30〜50%とすべきで
ある。50%以上については先述のように実験的に信頼
できる結果が得られないのでNMRの回転数が10kH
z以内であればこの範囲で高特性が期待できる。Prototype coin-type batteries using various samples were prepared.
The specific capacity density at the time of initial discharge and the discharge capacity retention ratio with respect to the initial state after 100 cycles were examined in relation to the crystallinity parameter α. The result is shown in FIG. As can be seen from the figure, each of (311) and (222) for α of (111)
When the ratio of α of the (400) and (440) peaks exceeds 1.1, it supports that the capacity retention ratio is high and the cycle characteristics are good. The specific capacity density of the initial discharge does not depend and is approximately 125
Although the characteristics are around mAh / g, when the ratio of α exceeds 2.3, the capacity density rapidly decreases. Therefore, the ratio of α should be 1.1 to 2.3. Next, the relationship with the specific surface area was examined. The result is shown in FIG. As can be seen from the figure, up to a specific surface area of 1.9 m 2 / g, it is supported that the capacity retention ratio is high and the cycle characteristics are good. The specific capacity density of the initial discharge shows a characteristic of about 125 mAh / g without depending on the ratio of α. Therefore, the specific surface area is 0.5 to 1.9 m 2 / g.
Should be. Next, the relationship between the NMR spectrum (a) and the area ratio of (b) to (a) was examined. FIG. 4 shows the results. As can be seen from the figure, the spectral area ratio is 30.
%, The capacity retention rate is increased to support good cycle characteristics, but below this value, excellent characteristics are not exhibited. In addition, the specific capacity density of the initial discharge has the same tendency and tends to increase as the spectral area ratio increases. Therefore, the spectral area ratio should be 30 to 50%. If the value is 50% or more, reliable results cannot be obtained experimentally as described above.
Within the range of z, high characteristics can be expected in this range.
【0030】以上のサイクル特性を決める3つの物性因
子はそれぞれ独立事象であるが、実際はこれらのファク
ターに共通性があり、初期の放電比容量密度が125m
Ah/g程度で、かつ100サイクル後の放電容量維持
率を90%以上得るためにはこれら3つの要素が併合し
た条件設定になる。この理由は定かではないが、結晶性
を向上させる過程で当然結晶化度は高くなり収容される
リチウムの存在も結晶化度を最大限に高める作用をもた
らす適正サイトに多く占有することが等価的におこるも
のと推察される。The three physical factors that determine the cycle characteristics described above are independent events, but in reality, these factors have a commonality, and the initial discharge specific capacity density is 125 m.
In order to obtain a discharge capacity retention rate of about Ah / g and a discharge capacity retention rate after 100 cycles of 90% or more, a condition setting in which these three factors are combined is adopted. Although the reason for this is not clear, the degree of crystallinity naturally increases during the process of improving the crystallinity, and it is equivalent to occupy a large amount of lithium contained in the appropriate site that has the effect of maximizing the degree of crystallinity. It is presumed to occur.
【0031】同時に比表面積の推移もこれを支持するよ
うに、結晶子の成長や結晶配向面の規則性の向上などに
より表面の結晶性を向上させる方向で粒子の比表面積は
低下するのではないかと考えられる。At the same time, the specific surface area of the particles does not decrease in the direction of improving the crystallinity of the surface by growing crystallites and improving the regularity of the crystal orientation plane so that the change in the specific surface area also supports this. It is thought.
【0032】これらの物性因子を備えたスピネル型リチ
ウム含有マンガン酸化物を正極活物質に用いるとMnの
中に他の固溶元素を含まず、また粒子表面を被覆処理し
ていないので、高負荷での界面における電気化学的な物
質移動に際し大きな反応過電圧を被ることはなく、また
初期放電の比容量密度を犠牲にして125mAh/g以
下に低落することはない。When a spinel-type lithium-containing manganese oxide having these physical factors is used as a positive electrode active material, Mn does not contain other solid solution elements and the surface of the particles is not coated, so that high load is applied. Does not suffer from a large reaction overpotential during the electrochemical mass transfer at the interface at, and does not drop below 125 mAh / g at the expense of the specific capacity density of the initial discharge.
【0033】一方、Mnの一部に他の元素を固溶させた
正極活物質を用いた場合には、電流密度3.3mA/c
m2の高負荷で充放電させた場合、放電容量維持率80
%以上となったが、初期放電の比容量密度は120mA
h/gを下回る結果となった。On the other hand, when a positive electrode active material in which another element is dissolved in part of Mn is used, the current density is 3.3 mA / c.
When charge / discharge is performed with a high load of m 2 , the discharge capacity retention ratio is 80
%, But the specific capacity density of the initial discharge is 120 mA.
h / g.
【0034】また、正極活物質粒子表面を被覆処理した
場合では初期放電の比容量密度は低下しないものの上記
の高負荷試験を行うと放電容量は半減した。In the case where the surface of the positive electrode active material particles was coated, the specific capacity density of the initial discharge did not decrease, but the discharge capacity was reduced by half in the high load test.
【0035】本発明では上記の高負荷の充放電でも初期
放電あるいは比容量密度いずれの犠牲も最小限に抑えら
れた。According to the present invention, the sacrifice of either the initial discharge or the specific capacity density was minimized even in the high-load charge / discharge described above.
【0036】さらに、本発明では容量維持率が優れるこ
とから充放電途中で固相からマンガンが電解液に溶出す
る頻度は極めて低いと考えられ、それ故サイクル特性の
改善が成されたものと推察している。Further, in the present invention, since the capacity retention rate is excellent, it is considered that the frequency of manganese elution from the solid phase into the electrolyte during charging / discharging is extremely low, and it is presumed that the cycle characteristics were improved. doing.
【0037】以上のように初期放電の比容量密度に優
れ、かつサイクル特性に優れた本発明のスピネル型リチ
ウム含有マンガン酸化物を正極活物質に、リチウムを吸
蔵・放出できる材料、例えば黒鉛などの炭素材、合金、
無機化合物を負極活物質に、リチウムを含む非水電解質
で二次電池を構成することができる。As described above, a material capable of inserting and extracting lithium, such as graphite, is used as the positive electrode active material with the spinel-type lithium-containing manganese oxide of the present invention having excellent initial discharge specific capacity density and excellent cycle characteristics. Carbon materials, alloys,
A secondary battery can be formed using an inorganic compound as a negative electrode active material and a nonaqueous electrolyte containing lithium.
【0038】[0038]
【発明の効果】以上のように、本発明は一般式LiMn
2O4で表されるスピネル型リチウム含有マンガン酸化物
に比表面積とX線回折パターンにおける所定の結晶化パ
ラメータの比、およびリチウム核を用いた固体NMRス
ペクトルにおける所定のスペクトルの比を規定したもの
を正極活物質に用いているので、活物質の比容量密度、
放電容量維持率が高く、電池のサイクル特性および高負
荷特性に優れた非水電解質二次電池を提供することがで
きる。As described above, the present invention relates to the general formula LiMn
A spinel-type lithium-containing manganese oxide represented by 2 O 4 in which a specific surface area and a ratio of a predetermined crystallization parameter in an X-ray diffraction pattern, and a ratio of a predetermined spectrum in a solid-state NMR spectrum using lithium nuclei are specified. Is used for the positive electrode active material, the specific capacity density of the active material,
A nonaqueous electrolyte secondary battery having a high discharge capacity retention rate and excellent battery cycle characteristics and high load characteristics can be provided.
【図1】本発明の非水電解質二次電池の縦断面図FIG. 1 is a longitudinal sectional view of a non-aqueous electrolyte secondary battery of the present invention.
【図2】正極活物質の結晶化度パラメータαの比率と電
気化学的特性の関係を示す図FIG. 2 is a diagram showing the relationship between the ratio of the crystallinity parameter α of the positive electrode active material and the electrochemical characteristics.
【図3】正極活物質の比表面積と電気化学的特性の関係
を示す図FIG. 3 is a diagram showing a relationship between a specific surface area of a positive electrode active material and electrochemical characteristics.
【図4】正極活物質のNMRスペクトル面積比と電気化
学的特性の関係を示す図FIG. 4 is a diagram showing a relationship between an NMR spectrum area ratio of a positive electrode active material and electrochemical characteristics.
1 電池ケース 2 封口板 3 絶縁パッキング 4 極板群 5 正極板 6 負極板 7 セパレータ 8 絶縁リング DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulation packing 4 Electrode plate group 5 Positive electrode plate 6 Negative electrode plate 7 Separator 8 Insulation ring
───────────────────────────────────────────────────── フロントページの続き (72)発明者 橋本 彰 大阪府門真市大字門真1006番地 松下電器 産業株式会社内 (72)発明者 有元 真司 大阪府門真市大字門真1006番地 松下電器 産業株式会社内 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Akira Hashimoto 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.
Claims (2)
7)に属し、一般式LiMn2O4で表されるスピネル型
のリチウム含有マンガン酸化物であって、比表面積が
0.5〜1.9m2/gで、粉末X線回折パターンの回
折ピーク(111)のピーク強度に対する半価幅の比を
用いた結晶化パラメータαが各回折ピーク(311)、
(222)、(400)、(440)のαに対し1.1
〜2.3であり、かつリチウム核を用いた固体NMRス
ペクトル、特にMAS/spin−echo法(マジッ
ク角回転法とスピンエコー法の併用)で測定されるLi
Clを0ppm基準においたスペクトルにおいて、線幅
が1000ppmを越えるブロードなスペクトル(a)
と少なくとも100ppm以下のスピニングサイドバン
ド(b)で構成されるスペクトルのうち、スペクトル
(a)に対するスペクトル(b)の面積比が30%以上
50%未満となる非水電解質二次電池用正極材料。1. A space group Fd3m (No. 22)
7) A spinel-type lithium-containing manganese oxide represented by the general formula LiMn 2 O 4 , which has a specific surface area of 0.5 to 1.9 m 2 / g and a diffraction peak of a powder X-ray diffraction pattern The crystallization parameter α using the ratio of the half width to the peak intensity of (111) is calculated for each diffraction peak (311),
1.1 for α of (222), (400), and (440)
To 2.3 and measured by the solid-state NMR spectrum using a lithium nucleus, particularly the MAS / spin-echo method (combination of magic angle rotation method and spin echo method).
A broad spectrum with a line width exceeding 1000 ppm in a spectrum based on Cl at 0 ppm (a)
And a cathode material for a non-aqueous electrolyte secondary battery, wherein the area ratio of the spectrum (b) to the spectrum (a) is at least 30% and less than 50% in the spectrum composed of the spinning side band (b) of at least 100 ppm or less.
きる負極材料と非水電解質で構成される非水電解質二次
電池。2. A non-aqueous electrolyte secondary battery comprising the positive electrode material, a negative electrode material capable of inserting and extracting lithium, and a non-aqueous electrolyte.
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JP10148964A JPH11339804A (en) | 1998-05-29 | 1998-05-29 | Positive electrode material for nonaqueous electrolyte secondary battery and battery with the same |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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JP10148964A JPH11339804A (en) | 1998-05-29 | 1998-05-29 | Positive electrode material for nonaqueous electrolyte secondary battery and battery with the same |
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Publication Number | Publication Date |
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JPH11339804A true JPH11339804A (en) | 1999-12-10 |
Family
ID=15464610
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1998
- 1998-05-29 JP JP10148964A patent/JPH11339804A/en active Pending
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