The Carbon-Based 3D-Hierarchical Cathode Architecture for Li-Ion Batteries

Abstract

High-purity NMC111 nanoparticles are obtained by sol-gel synthesis. NMC111/MWCNTs freestanding hybrid composite cathodes are produced by a simple vacuum filtration process without detriment to both the crystalline and morphologic structures of the NMC111 nanoparticles. NMC111/MWCNTs freestanding hybrid composite cathode materials exhibit enhanced cycling stability, long cycle life, and high specific discharge capacity compared with pure NMC111 electrode, which is prepared by the classic slurry method. After 1000 cycles, within 2.5-4.6 V working potential range (at 1 C-rate), the specific discharge capacity of NMC111/MWCNTs freestanding hybrid composite cathode is 118.5 mAh g(-1) with a capacity loss rate of 44.2%, considerably higher than the result of pure NMC111 cathode electrode (84.9 mAh g(-1) with a capacity loss rate of 59.2%). NMC111/MWCNTs freestanding hybrid cathode has shown lower polarization and good cyclic stability when compared with the pristine NMC111 cathode electrode in the cyclic voltammetry (CV) analysis. MWCNTs in the electrode have high electron conductivity and easies the electron transfer during the electrochemical charge/discharge. Graphite@NMC111/MWCNTs full cells were fabricated to support results acquired with the half cells. To analyze the working of MWCNTs-reinforced freestanding composite cathode in full cell, graphite@NMC111/MWCNTs combination was constituted and obtained a specific discharge capacity of 150.7 mAh g(-1) with a capacity loss of 30.4% after 1000 cycles. Extreme cycling and structural stability increased conductivity, and a high cycle number is reached by compressing the NMC111 nanoparticles between MWCNTs. Highly electrical conductive MWCNTs, which are homogeneously dispersed on around the NMC111 nanoparticles, are employed as both structural strengthening components and surface improvers for NMC111 cathode electrodes, not only for enhancing the electrical conductivity but also supplying powerful guarding to the side reactions with the liquid electrolyte. The results have shown that the MWCNTs-based freestanding electrode form can be widely used electrode type for high-level featured lithium-ion batteries.