LITHIUM ION SECONDARY BATTERY

• Main Authors: OCHIAI TERUAKI, MIKAMI MAYUMI, TAKAHASHI MASAHIRO, MONMA YOHEI, KAWAKAMI TAKAHIRO, TSURUTA SAE
• Format: Patent
• Language: English; Japanese
• Published: 06.07.2023
• Subjects: BASIC ELECTRIC ELEMENTS; ELECTRICITY; PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSIONOF CHEMICAL INTO ELECTRICAL ENERGY

To provide a positive electrode active material which can improve cycle characteristics of a secondary battery.SOLUTION: Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy. Since the crystal structure and the two kinds of regions are topotaxy, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte is the compound of representative elements which is chemically stable, a secondary battery having excellent cycle characteristics can be obtained.SELECTED DRAWING: Figure 1 【課題】二次電池のサイクル特性を向上できる正極活物質を提供する。【解決手段】層状岩塩型の結晶構造を有する、コバルト酸リチウム等の正極活物質の表層部に、２種の領域を設ける。内側の領域はチタン等の遷移金属を有する不定比化合物、外側の領域は酸化マグネシウム等の典型元素の化合物とする。２種の領域はどちらも岩塩型の結晶構造を有する。また内部の層状岩塩型の結晶構造と、表層部の２種の領域はトポタキシである。これらがトポタキシであるため、充放電によって生じる正極活物質の結晶構造の変化を効果的に抑制できる。また電解液と接触する外側の被覆層が、化学的に安定した典型元素の化合物であるため、サイクル特性の優れた二次電池とすることができる。【選択図】図１