Effect of Ni²⁺ on Lithium-Ion Diffusion in Layered LiNi_1−x−yMn_xCo_yO₂ Materials

• Published in: Crystals
• Main Authors: Yuanyuan Zhu, Yang Huang, Rong Du, Ming Tang, Baotian Wang, Junrong Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Subjects: lithium-ion batteries; Li-ion diffusion; Li/Ni anti-site; molecular dynamics
• Online Access: https://www.mdpi.com/2073-4352/11/5/465

<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>LiNi</mi></mrow><mrow><mn>1</mn><mo>−</mo><mi mathvariant="normal">x</mi><mo>−</mo><mi mathvariant="normal">y</mi></mrow></msub><msub><mrow><mi>Mn</mi></mrow><mi mathvariant="normal">x</mi></msub><msub><mrow><mi>Co</mi></mrow><mi mathvariant="normal">y</mi></msub><msub><mi mathvariant="normal">O</mi><mn>2</mn></msub></mrow></semantics></math></inline-formula> materials are a typical class of layered cathode materials with excellent electrochemical performance in lithium-ion batteries. Molecular dynamics simulations are performed for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>LiNi</mi></mrow><mrow><mn>1</mn><mo>−</mo><mi mathvariant="normal">x</mi><mo>−</mo><mi mathvariant="normal">y</mi></mrow></msub><msub><mrow><mi>Mn</mi></mrow><mi mathvariant="normal">x</mi></msub><msub><mrow><mi>Co</mi></mrow><mi mathvariant="normal">y</mi></msub><msub><mi mathvariant="normal">O</mi><mn>2</mn></msub></mrow></semantics></math></inline-formula> materials with different transition metal ratios. The Li/Ni exchange ratio, ratio of anti-site <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>Ni</mi></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></mrow></semantics></math></inline-formula> to total <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>Ni</mi></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></mrow></semantics></math></inline-formula>, and diffusion coefficient of Li ions in these materials are calculated. The results show that the Li-ion diffusion coefficient strongly depends on the ratio of anti-site <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>Ni</mi></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></mrow></semantics></math></inline-formula> to total <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>Ni</mi></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></mrow></semantics></math></inline-formula> because their variation tendencies are similar. In addition, the local coordination structure of the Li/Ni anti-site is analyzed.