High Rate Capability of Li(Ni_1/3Mn_1/3Co_1/3)O₂Electrode for Li-Ion Batteries

The rate capability of Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 (NMC) electrode is studied in this paper at the particle scale. Experimental results obtained on thin electrodes show that NMC is an extremely high-rate material capable of charge and discharge at rates exceeding 100C. The high capacity retention has not been previously reported in the literature. Even higher rate capability was seen on charge. The transport properties of the material were explored by combining experiments on thin electrodes with a continuum model of a single spherical particle. The use of thin electrodes minimized porous electrode effects and allowed the assumption of a uniform current distribution in the electrode. A qualitative estimate of the lithium diffusion coefficient in the NMC particle was obtained by comparing the experimental and simulated potentials during open-circuit relaxation at various states of charge. The fitting results show that the lithium diffusion coefficient increases with increasing state of charge. The value ranges from 10 −16 m 2 /s when completely discharged to 10 −14 m 2 /s when completely charged, suggesting that the use of a varying diffusion coefficient is necessary for studying the transport processes in this material and for further application to the macroscopic porous electrode models.