The Influence of Starch-Based Carbon Aerogels Modifications on Their Irreversible Capacity during Initial Cycles in Li-Ion Cells
Authors: Kubicka Marcelina , Bakierska Monika , Chudzik Krystian , Molenda Marcin 
Published: December 2020

Carbon aerogels derived from starch (CAGs) are the new class of anode materials for Li-ion battery developed in our group [1-4]. They possess well-defined continuous structure of covalently bonded carbon atoms and exhibit special properties such as: large surface area, chemical and thermal stability, determined porosity, high electrical conductivity and high capacitance. These materials based on rice (RS), maize (MS) and potato (PS) starch represent better electrochemical parameters than graphite- higher specific capacity and the possibility of working properly under high current loads. All these features make them competitive not only in terms of the ecology and economy but also in terms of their behavior in Li-ion cell [1-4].
Although the amorphous carbons derived from biomass are one of the promising candidates among widely studied anode materials, they also have disadvantages. The main issue preventing their commercialization is their huge irreversible capacity, that results from the active lithium losses, during the first cycles of working in Li-ion battery. This low initial coulombic efficiency is caused by the lithium consuming parasitic reactions. One of them can be ascribed to the solid electrolyte interphase (SEI) formation that is created by the reductive decomposition of the electrolyte solvents and the irreversible reaction of Li+ with functional groups (such as carboxyl, hydroxyl etc.) on the carbon surface. The other is connected with the irreversible insertion of lithium ions, that can be trapped into closed micropores in the carbon matrix [5-7].
The main goal of this project is to determine the effect of carbon aerogels surface modification on their irreversible capacity during the initial cycling. The surface modification of bio-derived aerogels is performed by using different pyrolysis conditions (temperature, gas medium) as well as by chemical treatment. This process is needed for changing the morphology of studied materials (improve the porosity with maintain the proper surface development) in order to reduce the effect of trapping lithium ions and remove the easily reducible surface groups. The key parameter is to find the optimum between surface development, porosity and electrochemical behavior of the carbon materials. All these actions aimed to ameliorate the reversibility during first cycle of operation in Li-ion battery. Following experimental methods are used in characterization of the modified materials and evaluation of the applied methods: powder X-ray powder diffraction (XRD), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), low temperature nitrogen adsorption/desorption method (N2-BET), galvanostatic charge-discharge tests (GCDT), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

ACKNOWLEDGMENT

This work is supported by the National Science Centre – Poland, under grants no. 2019/33/N/ST8/01687.
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