JP5245084B2 - Olivine-type compound ultrafine particles and method for producing the same - Google Patents
Olivine-type compound ultrafine particles and method for producing the same Download PDFInfo
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Description
本発明は非水電解質二次電池用電極活物質等として有用な超微粒子のオリビン型化合物を得る技術に関する。 The present invention relates to a technique for obtaining an ultrafine olivine type compound useful as an electrode active material for a nonaqueous electrolyte secondary battery.
オリビン型化合物から成る正極活物質は、高電圧と高容量を併せ持つ、次世代リチウムイオン電池用正極活物質として期待される。特に、ＬｉＭｎＰＯ４は、エネルギー密度が大きく、現在、代表的に使用されているコバルト酸リチウム（ＬｉＣｏＯ２）をも凌駕するが、導電率が非常に小さいことが弱点であった。 A positive electrode active material composed of an olivine type compound is expected as a positive electrode active material for a next-generation lithium ion battery having both high voltage and high capacity. In particular, LiMnPO 4 has a large energy density and surpasses lithium cobalt oxide (LiCoO 2 ), which is typically used at present, but has a weak electrical conductivity.
従来よりＬｉＭｎＰＯ４等のオリビン型化合物は、固相法により製造されるのが一般的であった。すなわち、原料となるリチウム化合物とリチウム以外の金属の化合物とを、リン源とともに、固相状態で混合した後、混合物を仮焼成を経て800℃以上の高温で焼成することにより、ＬｉＭｎＰＯ４等のオリビン型化合物を得ていた〔例えば、M. Th. Paques-Ledent, Ind. Chim. Belg., Vol.39, (1974)
845-858（非特許文献１）〕。このようにして得られたオリビン型化合物は、粒子が互いに凝集しマイクロメータオーダの粒径を有しており、このことが低導電率の一因であった。正極活物質の導電性を向上させ、高出力の電池を得るためには、正極活物質を構成する粒子の粒径を可及的に小さくして電荷移動の速度を高めることが必要と考えられるが、これを実現し得る簡便な量産技術は見当たらない。
845-858 (Non-Patent Document 1)]. In the olivine type compound thus obtained, the particles agglomerate with each other and have a particle size on the order of micrometers, which contributes to low conductivity. In order to improve the conductivity of the positive electrode active material and obtain a high output battery, it is considered necessary to increase the speed of charge transfer by reducing the particle size of the particles constituting the positive electrode active material as much as possible. However, there is no simple mass production technology that can realize this.
本発明の目的は、リチウムイオン電池に代表される非水電解質二次電池に用いられる正極活物質として好適なオリビン型化合物の超微粒子を製造することのできる新しい技術を提供することにある。 An object of the present invention is to provide a new technique capable of producing ultrafine particles of an olivine type compound suitable as a positive electrode active material used in a non-aqueous electrolyte secondary battery typified by a lithium ion battery.
本発明者は、検討を重ねた結果、従来の固相法とは全く異なる方法により、ナノメートルサイズの粒径を有するＬｉＭｎＰＯ４等のオリビン型化合物の合成に成功した。
すなわち、本発明は、一般式ＬｉＭＰＯ４（ＭはＭｎ、Ｆｅ、ＣｏまたはＮｉを表す）で表されるオリビン型化合物を製造する方法であって、（i）金属Mの水溶性塩、リチウムＬｉの水溶性塩、およびリン酸を、モル比で、金属Mの水溶性塩に対して、リチウムＬｉの水溶性塩を10倍以上、且つ、リン酸を5倍以上の割合で水中に溶かし攪拌・加熱して水分を除去する工程、（ii）前記工程（i）で得られた混合物を500〜700℃の温度下に焼成する工程、および（iii）前記工程（ii）で得られた粉末をリン酸二水素アンモニウムまたはリン酸一水素アンモニウムの水溶液で洗浄する工程、を含むことを特徴とする方法を提供するものである。
As a result of repeated studies, the inventor succeeded in synthesizing an olivine-type compound such as LiMnPO 4 having a nanometer-size particle size by a method completely different from the conventional solid phase method.
That is, the present invention is a method for producing an olivine type compound represented by the general formula LiMPO 4 (M represents Mn, Fe, Co, or Ni), and (i) a water-soluble salt of metal M, lithium Li The water-soluble salt and phosphoric acid are dissolved in water at a molar ratio of water-soluble salt of lithium Li in water at a ratio of 10 times or more and phosphoric acid at a ratio of 5 times or more with respect to the water-soluble salt of metal M. A step of removing moisture by heating, (ii) a step of firing the mixture obtained in step (i) at a temperature of 500 to 700 ° C., and (iii) a powder obtained in step (ii) And a step of washing with an aqueous solution of ammonium dihydrogen phosphate or ammonium monohydrogen phosphate.
本発明に従えば、さらに、上記の方法によって製造され200〜800nmの粒径を有することを特徴とするオリビン型化合物超微粒子が提供される。 According to the present invention, there is further provided an olivine-type compound ultrafine particle produced by the above method and having a particle size of 200 to 800 nm.
本発明の方法に従えば、ＬｉＭｎＰＯ４をはじめとするオリビン型化合物について数百ナノメートルオーダー（200〜800nm、好ましくは200〜500nm）の超微粒子が得られる。このオリビン型化合物超微粒子を非水電解質二次電池の電極活物質として用いると、電荷移動のための反応表面積の拡大とＬｉ拡散パス（リチウムイオンの拡散距離）の低減が図られ、レート特性などの特性の飛躍的に向上した電池が得られる。 According to the method of the present invention, ultrafine particles of the order of several hundred nanometers (200 to 800 nm, preferably 200 to 500 nm) can be obtained for olivine type compounds including LiMnPO 4 . When these olivine-type compound ultrafine particles are used as the electrode active material of a non-aqueous electrolyte secondary battery, the reaction surface area for charge transfer can be increased and the Li diffusion path (lithium ion diffusion distance) can be reduced. A battery with dramatically improved characteristics can be obtained.
本発明に従うオリビン型化合物の製造方法の特徴の一つは、大過剰のリチウムの水溶性塩（例えば、酢酸リチウム）およびリン酸とともに少量の金属Ｍの水溶性塩（例えば、酢酸マンガン）を液相中（水中）で均一に混合することにある。すなわち、モル比で、金属Ｍの水溶性塩に対して、リチウムＬｉの水溶性塩を10倍以上、好ましくは20倍以上、特に好ましくは30〜50倍（例えば40倍）とし、且つ、リン酸を5倍以上、好ましくは8倍以上、特に好ましくは10〜20倍（例えば、14〜15倍）とする。 One of the characteristics of the method for producing an olivine type compound according to the present invention is that a large amount of a water-soluble salt of lithium (for example, lithium acetate) and phosphoric acid are mixed with a small amount of a water-soluble salt of metal M (for example, manganese acetate). It is to mix uniformly in the phase (in water). That is, in terms of molar ratio, the water-soluble salt of lithium Li is 10 times or more, preferably 20 times or more, particularly preferably 30 to 50 times (for example, 40 times) with respect to the water-soluble salt of metal M, and phosphorus The acid is 5 times or more, preferably 8 times or more, particularly preferably 10 to 20 times (for example, 14 to 15 times).
リチウムＬｉの水溶性塩および金属Ｍの水溶性塩として、特に好ましいのは、有害ガスの発生の少ないこと、安価であり、水に特に溶けやすいことなどの理由から、それぞれの酢酸塩であるが、この他に、ギ酸塩、クエン酸塩、リンゴ酸塩、硝酸塩なども使用可能である。 Particularly preferred as the water-soluble salt of lithium Li and the water-soluble salt of metal M are the respective acetate salts because they generate less harmful gas, are inexpensive, and are particularly soluble in water. In addition, formate, citrate, malate, nitrate and the like can also be used.
本発明に従い一般式ＬｉＭＰＯ４で表されるオリビン型化合物を製造することができるのは、Ｌｉ２ＭＰＯ４やＬｉ３ＭＰＯ４というようなリチウム（Ｌｉ）のリッチな組成が存在しないような金属Ｍに関してである。この点から、本発明の方法は、金属Ｍがマンガン（Ｍｎ）である場合、すなわち、ＬｉＭｎＰＯ４を製造するのに特に適しているが、其の他に、ＭがＦｅ、ＣｏまたはＮｉであるＬｉＦｅＰＯ４、ＬｉＣｏＰＯ４またはＬｉＮｉＰＯ４を製造するのにも適用される。 The olivine type compound represented by the general formula LiMPO 4 can be produced according to the present invention because the metal M is free from a lithium (Li) -rich composition such as Li 2 MPO 4 or Li 3 MPO 4. It is about. In this respect, the method according to the invention is particularly suitable when the metal M is manganese (Mn), ie for producing LiMnPO 4 , but in addition, M is Fe, Co or Ni. It also applies to the production of LiFePO 4 , LiCoPO 4 or LiNiPO 4 .
このようにして、大過剰のリチウムの水溶性塩およびリン酸とともに少量の金属Ｍの水溶性塩を水に溶かし攪拌・加熱して水分を除去することにより各成分が均一に混ざった混合物が得られる。この際の加熱温度は100℃を少し超える120〜150℃（例えば、140℃）とする。 In this way, a small amount of the water-soluble salt of metal M is dissolved in water together with a large excess of water-soluble salt and phosphoric acid, and the mixture is stirred and heated to remove the water, thereby obtaining a mixture in which each component is uniformly mixed. It is done. The heating temperature at this time is 120 to 150 ° C. (for example, 140 ° C.) slightly exceeding 100 ° C.
得られた混合物は、その後、焼成工程に供される。この焼成により、所望のオリビン型化合物ＬｉＭＰＯ４（例えばＬｉＭｎＰＯ４）が生成されるとともに、大過剰のリチウムの水溶性塩（例えば酢酸リチウム）とリン酸が反応してリン酸リチウム（Ｌｉ３ＰＯ４）が生成される。焼成温度は、低温すぎると不純物が増え、高温すぎるとリン酸リチウムが溶融してしまうので、500〜700℃、好ましくは550〜650℃（例えば600℃）とする。この点、従来の固相法におけるような800℃もしくはそれ以上の高温の焼成は回避しなければならない。なお、焼成時間は、通常、20〜30時間（例えば、24時間）とする。 The resulting mixture is then subjected to a firing step. By this firing, a desired olivine-type compound LiMPO 4 (for example, LiMnPO 4 ) is generated, and a large excess of a water-soluble salt of lithium (for example, lithium acetate) and phosphoric acid react to form lithium phosphate (Li 3 PO 4). ) Is generated. If the firing temperature is too low, impurities increase, and if it is too high, the lithium phosphate melts, so that the firing temperature is 500 to 700 ° C., preferably 550 to 650 ° C. (eg 600 ° C.). In this regard, firing at a high temperature of 800 ° C. or higher as in the conventional solid phase method must be avoided. The firing time is usually 20 to 30 hours (for example, 24 hours).
上記のような焼成工程で得られた粉末は、次いで、洗浄工程に供される。ここで、本発明の更なる特徴は、洗浄に、通常用いられているような水ではなく、特殊な溶媒、すなわち、リン酸二水素アンモニウム（ＮＨ４Ｈ２ＰＯ４）またはリン酸一水素アンモニウム（ＮＨ４ＨＰＯ４）の水溶液を使用することである。このリン酸二水素アンモニウム水溶液またはリン酸一水素アンモニウム水溶液は、ＬｉＭＰＯ４（例えば、ＬｉＭｎＰＯ４）を溶かさず、Ｌｉ３ＰＯ４だけを溶かすので、過剰のＬｉ塩（Ｌｉ３ＰＯ４）を選択的に溶解、除去することができる。かくして、その後、純水で洗浄し遠心分離により不純物を除去した粉末を乾燥することにより所望のオリビン型化合物ＬｉＭＰＯ４の微粒子が得られる。 The powder obtained in the baking process as described above is then subjected to a cleaning process. Here, a further feature of the present invention, the cleaning, rather than water, such as commonly used, special solvents, i.e., ammonium dihydrogen phosphate (NH 4 H 2 PO 4) or hydrogen phosphate of ammonium Use an aqueous solution of (NH 4 HPO 4 ). This aqueous solution of ammonium dihydrogen phosphate or aqueous solution of ammonium monohydrogen phosphate does not dissolve LiMPO 4 (for example, LiMnPO 4 ), but dissolves only Li 3 PO 4. Therefore, an excess of Li salt (Li 3 PO 4 ) is selectively used. Can be dissolved and removed. Thus, fine particles of desired olivine type compound LiMPO 4 are obtained by drying the powder after washing with pure water and removing impurities by centrifugation.
図１は、本発明の方法に従いオリビン型化合物微粒子が得られる様子（Ａ）を従来の固相法（Ｂ）と対比して模式的に示すものである。図１の（Ａ）に示す本発明では、リチウムの水溶性塩および金属Ｍの水溶性塩として、それぞれ、酢酸リチウムおよび酢酸マンガンを用い、オリビン型化合物としてＬｉＭｎＰＯ４を得る場合を例としている。大過剰の酢酸リチウムとリン酸と少量の酢酸マンガンを均一になるように混合し（図１（Ａ）のＩ）、得られた混合物を焼成すると、大過剰の酢酸リチウムとリン酸が反応してリン酸リチウムＬｉ３ＰＯ４が生成し、このリン酸リチウムがＬｉＭｎＰＯ４の粒子同士の接触を妨げ、粒成長を抑制する（図１（Ａ）のII）。これをリン酸二水素アンモニウムまたはリン酸一水素アンモニウムの水溶液で洗浄してＬｉ３ＰＯ４を選択的に溶解除去することにより、数百ナノメートルサイズのＬｉＭｎＰＯ４微粒子が得られる（図１（Ａ）のIII）。 FIG. 1 schematically shows the state (A) in which olivine-type compound fine particles are obtained according to the method of the present invention in comparison with the conventional solid phase method (B). In the present invention shown in FIG. 1A, an example is given in which LiMnPO 4 is obtained as an olivine type compound using lithium acetate and manganese acetate as the water-soluble salt of lithium and the water-soluble salt of metal M, respectively. When a large excess of lithium acetate, phosphoric acid and a small amount of manganese acetate are mixed uniformly (I in FIG. 1 (A)) and the resulting mixture is baked, the large excess of lithium acetate and phosphoric acid react. Thus, lithium phosphate Li 3 PO 4 is generated, and this lithium phosphate prevents the LiMnPO 4 particles from contacting each other and suppresses the grain growth (II in FIG. 1A). This is washed with an aqueous solution of ammonium dihydrogen phosphate or ammonium hydrogen phosphate to selectively dissolve and remove Li 3 PO 4, thereby obtaining LiMnPO 4 fine particles having a size of several hundred nanometers (FIG. 1 (A III).
これに対して、図１の（Ｂ）に示すような従来法では固相反応で生成したＬｉＭＰＯ４（図ではＬｉＭｎＰＯ４）がそのまま焼成されるので、焼結により粒子は大きくなってしまう。
以下に本発明の特徴を更に具体的に示すために実施例を記すが、本発明は以下の実施例によって制限されるものではない。
On the other hand, in the conventional method as shown in FIG. 1B, LiMPO 4 (LiMnPO 4 in the figure) produced by the solid-phase reaction is baked as it is, so that the particles are enlarged by sintering.
Examples are given below to illustrate the features of the present invention more specifically, but the present invention is not limited to the following examples.
オリビン型化合物ＬｉＭｎＰＯ ４ の合成
酢酸リチウム〔ＣＨ３ＣＯＯＬｉ・２Ｈ２Ｏ〕と、酢酸マンガン〔(ＣＨ３ＣＯＯ)２Ｍｎ・４Ｈ２Ｏ〕と、リン酸〔Ｈ３ＰＯ４〕とを、モル比で、40：1：14、22：1：8、4：1：2、および1：1：1となるように秤量した。
それぞれの場合において、先ず、酢酸リチウムと酢酸マンガンを純水に溶かし、その後、リン酸を加えたところ、沈殿物が生じた。140℃で加熱しながら攪拌を続け水分を完全に除去して薄桃色の混合物を得た。この混合物をアルミナ乳鉢で粉砕・混合し粉末にした。
Synthesis of olivine type compound LiMnPO 4 Lithium acetate [CH 3 COOLi · 2H 2 O], manganese acetate [(CH 3 COO) 2 Mn · 4H 2 O], and phosphoric acid [H 3 PO 4 ] in a molar ratio And were weighed so as to be 40: 1: 14, 22: 1: 8, 4: 1: 2, and 1: 1: 1.
In each case, first, lithium acetate and manganese acetate were dissolved in pure water, and then phosphoric acid was added to form a precipitate. Stirring was continued while heating at 140 ° C. to completely remove the water to obtain a light pink mixture. This mixture was pulverized and mixed in an alumina mortar to make a powder.
次に、得られた混合物（粉末）を大気中、600℃で24時間焼成した。
焼成して得られた混合物を多量の、濃度１Ｍのリン酸二水素アンモニウム（ＮＨ４Ｈ２ＰＯ４）水溶液で洗浄し、その後純水で洗浄し、遠心分離に供し、不純物を除去した。
次に、大気中で80℃、24時間乾燥させることにより所望のＬｉＭｎＰＯ４微粒子を得た。
なお、比較のために、以下のように、従来法（固相法）によるＬｉＭｎＰＯ４の合成も行った：Ｌｉ２ＣＯ３とＭｎ２Ｏ３とＰ２Ｏ５をモル比1：1：1になるようにアルゴン雰囲気グローブボックス内で秤量し混合した。この混合物を大気中500℃で15時間仮焼成した後、大気中800℃で36時間本焼成することによりＬｉＭｎＰＯ４を得た。
Next, the obtained mixture (powder) was fired at 600 ° C. for 24 hours in the air.
The mixture obtained by firing was washed with a large amount of 1M ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) aqueous solution, then washed with pure water, and centrifuged to remove impurities.
Next, desired LiMnPO 4 fine particles were obtained by drying in the atmosphere at 80 ° C. for 24 hours.
For comparison, LiMnPO 4 was also synthesized by a conventional method (solid phase method) as follows: Li 2 CO 3 , Mn 2 O 3, and P 2 O 5 in a molar ratio of 1: 1: 1. Weighed and mixed in an argon atmosphere glove box. This mixture was calcined at 500 ° C. for 15 hours in the air, and then finally calcined at 800 ° C. for 36 hours in the air to obtain LiMnPO 4 .
＜ＸＲＤ測定とＳＥＭ観察＞
図２に、酢酸リチウム：酢酸マンガン：リン酸＝40：1：14および22：1：8（モル比）の場合の焼成後（洗浄前）と洗浄後のＸＲＤ（Ｘ線回折）プロファイルを示す。いずれも、ＬｉＭｎＰＯ４の単相が得られていることが理解される。酢酸リチウム：酢酸マンガン：リン酸＝4：1：2および1：1：1の場合についてもＸＲＤ測定を行ったところ、前者についてはＬｉＭｎＰＯ４の単相が得られたことが認められ、後者についてはほぼＬｉＭｎＰＯ４の単相が得られたことが認められた。
<XRD measurement and SEM observation>
FIG. 2 shows XRD (X-ray diffraction) profiles after firing (before washing) and after washing in the case of lithium acetate: manganese acetate: phosphoric acid = 40: 1: 14 and 22: 1: 8 (molar ratio). . In any case, it is understood that a single phase of LiMnPO 4 is obtained. When XRD measurement was also performed for lithium acetate: manganese acetate: phosphoric acid = 4: 1: 2 and 1: 1: 1, it was confirmed that a single phase of LiMnPO 4 was obtained for the former, and the latter It was confirmed that a single phase of LiMnPO 4 was obtained.
図３に、酢酸リチウム／酢酸マンガン／リン酸のモル比のいろいろな場合について得られたＬｉＭｎＰＯ４粒子のＳＥＭ（走査型電子顕微鏡）画像を示している。1：1：1の場合は10〜15μm程度の大きな粒子が生成していることが認められる。4：1：2の場合、粒子の大きさは0.5〜1μm程度であるが激しく凝集している。22：1：8では粒径は400〜800nm程度と小さくなり凝集も少なくなっている。40：1：14では、粒径200〜500nm程度の粒子の生成が認められ凝集も生じていない。このように本発明に従い大過剰のリチウムを用いる合成により数百ナノメートルオーダー超微粒子が得られる。なお、図４には、従来法（固相法）により得られたＬｉＭｎＰＯ４粒子のＳＥＭ画像を示している。粒径は20〜150μm程度であり、本発明の場合に比べて著しく大きく、このままのサイズでは塗布化することができない。 FIG. 3 shows SEM (scanning electron microscope) images of LiMnPO 4 particles obtained for various cases of the molar ratio of lithium acetate / manganese acetate / phosphoric acid. In the case of 1: 1: 1, it is recognized that large particles of about 10 to 15 μm are generated. In the case of 4: 1: 2, the size of the particles is about 0.5 to 1 μm, but they are intensively aggregated. At 22: 1: 8, the particle size is as small as about 400-800 nm and aggregation is reduced. In 40: 1: 14, the production | generation of the particle | grains with a particle size of about 200-500 nm is recognized, and aggregation has not arisen. As described above, ultrafine particles on the order of several hundred nanometers are obtained by synthesis using a large excess of lithium according to the present invention. FIG. 4 shows an SEM image of LiMnPO 4 particles obtained by the conventional method (solid phase method). The particle size is about 20 to 150 μm, which is significantly larger than that in the case of the present invention.
オリビン化合物ＬｉＭｎＰＯ ４ の充放電試験
酢酸リチウム：酢酸マンガン：リン酸＝40：1：14のモル比で実施例１において合成したＬｉＭｎＰＯ４を正極活物質とする非水電解質二次電池（リチウム電池）を作製して充放電試験を行った。比較のために、上記の従来法（固相法）により合成されたＬｉＭｎＰＯ４を正極活物質とする電池についても同様に充放電試験を行った。
Charge / discharge test of olivine compound LiMnPO 4 Nonaqueous electrolyte secondary battery (lithium battery) using LiMnPO 4 synthesized in Example 1 in a molar ratio of lithium acetate: manganese acetate: phosphoric acid = 40: 1: 14 as a positive electrode active material And a charge / discharge test was conducted. For comparison, a charge / discharge test was similarly performed on a battery using LiMnPO 4 synthesized by the conventional method (solid phase method) as a positive electrode active material.
図５は、充放電試験に用いたコイン型電池の断面図であり、１は正極、２は負極、３はセパレータ＋電解液、４は正極ケース、５は負極蓋を示す。
正極は、正極活物質：ＡＢ（アセチレンブラック）：ＰＴＦＥ（結着剤）＝70：25：5（重量％）の組成とした。すなわち、正極活物質をＡＢとともに遊星ボールミル（伊藤製作所製、ＬＰ−４／２）にて乾式混合した後、アルゴン雰囲気中600℃で1時間アニール処理し、次にＰＴＦＥを加えてペレットを作成して正極とした。負極はＬｉ金属（本城金属製）であり、また、電解液は１ＭのＬｉＰＦ６／ＥＣ：ＤＭＣ（1：1vol％）（富山薬品工業製）である。
充放電試験は、次のように行った：充電は、4.5Vまで0.1mA/cm2で定電流充電し、その後、4.5Vで170mAh/gまで定電圧充電することにより行った。放電は、0.1、1.0、2.0、および5.0mA/cm2の各電流密度で2Vまで定電流放電することにより行った。
FIG. 5 is a cross-sectional view of a coin-type battery used in the charge / discharge test, wherein 1 is a positive electrode, 2 is a negative electrode, 3 is a separator + electrolyte, 4 is a positive electrode case, and 5 is a negative electrode lid.
The positive electrode had a composition of positive electrode active material: AB (acetylene black): PTFE (binder) = 70: 25: 5 (% by weight). That is, the positive electrode active material was dry-mixed with AB in a planetary ball mill (manufactured by Ito Seisakusho, LP-4 / 2), then annealed at 600 ° C. for 1 hour in an argon atmosphere, and then PTFE was added to form a pellet. To make a positive electrode. The negative electrode is Li metal (manufactured by Honjo Metal), and the electrolyte is 1M LiPF 6 / EC: DMC (1: 1 vol%) (manufactured by Toyama Pharmaceutical).
The charge / discharge test was performed as follows: Charging was performed by charging at a constant current of 0.1 mA / cm 2 up to 4.5V and then charging at a constant voltage of up to 170 mAh / g at 4.5V. Discharging was performed by discharging constant current to 2 V at each current density of 0.1, 1.0, 2.0, and 5.0 mA / cm 2 .
図６は、放電電流密度をパラメータとして放電容量（mAh/g）と放電電圧（V）の関係を示すものであり、図７は、放電電流密度（mA/cm2）に対する放電容量（mAh/g）の関係を示す。本発明に従いリチウム過剰法により合成されたＬｉＭｎＰＯ４を正極活物質とする電池は、固相法によるＬｉＭｎＰＯ４を用いる場合に比べて、低電流密度から高電流密度にわたり、放電電圧および放電容量の高い優れた電池を提供できることが理解される。
図８は、Ｃレートと放電容量との関係を示す。本発明によるＨｉＭｎＰＯ４を正極活物質とする電池は、固相法により合成したＬｉＭｎＯ４を用いる電池よりも、レート特性が著しく向上しており、長時間にわたり大放電容量を有することが分かる。
FIG. 6 shows the relationship between the discharge capacity (mAh / g) and the discharge voltage (V) using the discharge current density as a parameter. FIG. 7 shows the discharge capacity (mAh / g) with respect to the discharge current density (mA / cm 2 ). The relationship of g) is shown. Battery for the LiMnPO 4 synthesized by lithium-rich method in accordance with the present invention as a positive electrode active material, as compared with the case of using the LiMnPO 4 by solid phase method, over a high current density from a low current density, high discharge voltage and discharge capacity It is understood that an excellent battery can be provided.
FIG. 8 shows the relationship between C rate and discharge capacity. It can be seen that the battery using HiMnPO 4 as the positive electrode active material according to the present invention has significantly improved rate characteristics and a large discharge capacity over a long period of time, compared with a battery using LiMnO 4 synthesized by the solid phase method.
本発明に従うオリビン型化合物は、次世代の安価なリチウムイオン電池用正極の活物質としての利用が考えられる。 The olivine type compound according to the present invention is considered to be used as an active material for a next-generation inexpensive lithium ion battery positive electrode.
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| US8974957B2 (en) | 2008-10-22 | 2015-03-10 | Lg Chem, Ltd. | Cathode active material providing improved efficiency and energy density of electrode |
| JP5532350B2 (en) * | 2009-12-15 | 2014-06-25 | トヨタ自動車株式会社 | Method for producing positive electrode active material for lithium secondary battery |
| JP5820566B2 (en) * | 2010-02-17 | 2015-11-24 | 株式会社Ｇｓユアサ | Method for producing positive electrode material |
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