Li[Li0.2Ni 0.16Mn 0.56Co 0.08]O 2 Nanoparticle/Carbon Composite Using Polydopamine Binding Agent for Enhanced Electrochemical Performance

Abstract

Li[Li0.2Ni0.16Mn0.56Co0.08]O2 nanoparticles were composited with carbon (Super P) in order to achieve an enhanced rate capability. A polydopamine pre-coating layer was introduced to facilitate the adhesion between Super P and pristine nanoparticles. The Super P particles were dispersed on the surface of Li[Li0.2Ni0.16Mn0.56Co0.08]O2 powders. The composite samples that were heat-treated in a N2 atmosphere showed increased capacity and enhanced rate capability, which was caused by the improved electronic conductivity owing to the presence of carbon. However, the composite samples that were heat-treated in air did not present these carbon-related effects clearly. The capacity changes observed during the first several cycles may be due to the oxygen deficiency of the structure caused by the heat-treatment process.

Fig. 1

Schematic diagram of the procedure used for the synthesis of the Li[Li_0.2Ni_0.16Mn_0.56Co_0.08]O₂/Super P composite using a polydopamine pre-coating layer

Fig. 2

SEM images of the samples: a pristine H, b pristine G, c composite HA, d composite GA, e composite HN, and f composite GN

Fig. 3

a XRD patterns of the pristine and composite samples; b TGA results for the samples

Fig. 4

Discharge capacities and cyclic performances of the samples in a voltage range of 4.8–2.0 V; a discharge capacity of pristine H, composite HA, and composite HN at current densities of 44, 110, 220, 440, and 1320 mA g⁻¹; b discharge capacity of pristine G, composite GA, and composite GN at current densities of 44, 110, 220, 440, and 1320 mA g⁻¹; c cyclic performance of pristine H, composite HA, and composite HN at a current density of 110 mA g⁻¹; d cyclic performance of pristine G, composite GA, and composite GN at a current density of 110 mA g⁻¹

Fig. 5

Charge-discharge profiles of the samples during the five initial cycles; a pristine H, b composite HN, c pristine G, and d composite GN

Fig. 6

Nyquist plots of the samples: a pristine H, and composites HA and HN before electrochemical testing; b pristine G, and composites GA and GN before electrochemical testing; c pristine H, and composites HA and HN after 50 cycles; d pristine G, and composites GA and GN after 50 cycles