Abstract:

Lithium-ion batteries (LIBs) are extensively used in the portable electronics ever since their commercialization in 1991, over the years its 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. Nonetheless, major research activities in lithium-ion battery are concentrated on developing new materials which can operate at high voltage and give high capacity, simultaneously lead to high energy density. However, the studies on the electrode level understanding of batteries are scarce. 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 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. The slurry preparation methods is first and foremost step in battery electrode fabrication. The slurry preparation method influences the electrode’s electronic and ionic conducting pathways, which determines the rate capability of the cell. LiNi1-x-yMnxCoyO2 (NMC) with nano-microhierarchical structure is a commercially important cathode material for electric vehicle application. 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. This work aims to understand the effect of processing conditions on the slurry behavior and the electrode morphology and in turn to the electrochemical performance of battery. A critical review of literature on the role of electrode processing and electrode morphology on electrochemical performance of lithium-ion cell will be presented. Based on the review, the gaps in understanding electrode processing effects are identified and research plan will be presented. The experimental research plan involves fabrication of electrodes by varying mixing sequences and evaluating electrochemical performance in half cell and full cell configuration. The variation in mixing sequence resulted in disintegration of carbon black (CB) and deagglomeration of LiNi1/3Mn1/3Co1/3O2 (NMC) and is correlated with the rheological properties of slurry and electrochemical performance and the same will be discussed.