NEGATIVE ELECTRODE MATERIAL FOR LITHIUM ION SECONDARY BATTERY AND METHOD OF MANUFACTURING THE SAME, AND NEGATIVE ELECTRODE AND LITHIUM ION SECONDARY BATTERY INCLUDING THE NEGATIVE ELECTRODE MATERIAL

• Main Authors: MADOKORO YASUSHI, IJIRI MAKIKO, KITAGAWA TOMOKI, SAKAI MINORU
• Format: Patent
• Language: English; Japanese
• Published: 11.10.2021
• Subjects: BASIC ELECTRIC ELEMENTS; ELECTRICITY; PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSIONOF CHEMICAL INTO ELECTRICAL ENERGY

To provide a negative electrode material for a lithium ion secondary battery that exhibits less expansion and contraction at charge and discharge and that is composed of high-capacity graphitic carbon particles, and to provide a negative electrode including the negative electrode material.SOLUTION: Provided is a negative electrode material for a lithium ion secondary battery that contains a mixture of at least two kinds of particles of graphite particles A having an average breaking strength of 5 MPa or more and less than 50 MPa and graphite particles B having an average breaking strength of 50-150 MPa. A particle diameter ratio (dB/dA) of the particle diameter dB of the graphite particles B to the particle diameter dA of the graphite particles A is less than 0.25. A mass ratio (MB/(MA+MB)) of the mass MB of the graphite particles B to a total mass (MA+MB) of the mass MA of the graphite particles A and the mass MB of the graphite particles B is equal to or less than 0.30. Also provided is a negative electrode including the negative electrode material.SELECTED DRAWING: Figure 1 【課題】充放電時の膨張収縮が小さく、高容量の黒鉛質炭素粒子からなるリチウムイオン二次電池用負極材およびそれを用いた負極を提供する。【解決手段】平均破壊強度が５ＭＰａ以上、５０ＭＰａ未満である黒鉛質粒子Ａと平均破壊強度が５０ＭＰａ〜１５０ＭＰａである黒鉛質粒子Ｂの少なくとも２種以上の混合物を含み、前記黒鉛質粒子Ａの粒径ｄAに対する前記黒鉛質粒子Ｂの粒径ｄBの粒径比（ｄB／ｄA）が０．２５未満で、かつ前記黒鉛質粒子Ａの質量ＭAと前記黒鉛質粒子Ｂの質量ＭBの合計質量（ＭA＋ＭB）に対する前記黒鉛質粒子Ｂの質量ＭBの質量比（ＭB／（ＭA＋ＭB））が０．３０以下であるリチウムイオン二次電池用負極材であり、その負極材を用いた負極である。【選択図】図１