Lithium-ion batteries (LIBs) are extensively used in portable electronics ever since their commercialization in 1991; over the years their applications are widened especially in e-mobility because of high energy density, power density, cycle life and design flexibility. The electrochemical performance of the lithium-ion cell depends on the electrode active material’s intrinsic properties and extrinsic electrode characteristics. Electrodes in the LIBs are porous composite, consisting of active material for electrochemical energy storage, a conductive additive (carbon black) for improving electrode conductivity and a binder (Polyvinylidene difluoride, PVDF) to interconnect the particles and the current collector. The performance of lithium-ion cell depends on the morphology and distribution of these components in the electrode. Therefore, it is essential to investigate and understand the complex, interdependent large number of intermediate process steps which significantly affect the battery performance.
LiNi1-x-yMnxCoyO2 (NMC) with nano-microhierarchical structure is a commercially important cathode material for electric vehicle applications. The commonly used slurry preparation method is to dry-mix the active material with a conductive additive and then disperse it in the binder solution. The energy imparted during premixing, while helping in controlling the distribution of carbon black to establish conducting network, can deteriorate NMC by deagglomerating secondary particles and thus influencing deliverable energy and power. Herein, a comprehensive effort is put forward on the understanding of dry-mixing by high-energy ball-milling. The variation of ball-milling collision frequency and impact energy on the disintegration of carbon black (CB) and deagglomeration of LiNi1/3Mn1/3Co1/3O2 (NMC) is revealed and correlated with the rheological properties of slurry and electrochemical performance. An application-driven slurry preparation process is proposed for electrode fabrication in LIBs and will be discussed in the presentation. In continuation to this work, a mixed conductive additive with equal proportions of multilayer-graphene (MLG) and carbon black (CB) is used in LiNi1/3Mn1/3Co1/3O2 (NMC-CB-MLG) electrodes. The electrochemical performance of these electrodes is compared at coin cell and pouch cell level with that of the LiNi1/3Mn1/3Co1/3O2 (NMC) electrodes prepared with CB alone as a conductive additive (NMC-CB). While CB alone increases rate capability, mixing MLG with CB as conductive additive enhances cyclic stability. The pouch cells fabricated using NMC-CB-MLG electrode shows superior capacity retention of 80% after 730 cycles at 1C, compared to 65% at 320 cycles of NMC-CB. The differences in the capacity retention of both cells are correlated to the electrolyte uptake, and stability of the electrode-electrolyte interface. The main reasons for the capacity fade and corresponding failure mechanism of both cells will be discussed in detail during the presentation.