Identifying the Association between Surface Heterogeneity and Electrochemical Properties in Graphite.

Jaewon Kim,Byungwoo Park,Alan Jiwan Yun,Kyeu Yoon Sheem

doi:10.3390/nano11071813

Jaewon Kim, Byungwoo Park + Show 2 more

Open Access

https://doi.org/10.3390/nano11071813

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Journal: Nanomaterials	Publication Date: Jul 13, 2021
Citations: 7	License type: CC BY 4.0

Affiliation: Seoul National University, Samsung (South Korea)

Abstract

Graphite materials for commercial Li-ion batteries usually undergo special treatment to control specific parameters such as particle size, shape, and surface area to have desirable electrochemical properties. Graphite surfaces can be classified into basal and edge planes in the aspect of the structure of carbons, with the existing defect sites such as functional groups and dislocations. The solid-electrolyte interphase (SEI) mostly forms at the edge plane and defect sites, as Li-ions only intercalate through these non-basal planes, whereas the electrochemical properties of graphite largely depend on its surface heterogeneity due to the difference of reactivity on each plane. In order to quantify the detailed surface structure of graphite materials, local-absorption isotherms were utilized, and the analyzed nanostructural parameters of various commercial graphite samples were correlated with the electrochemical properties of each graphite anode. Thereby, we have confirmed that the fraction of non-basal plane and fast-charging capability has strong linear relations. The pore/non-basal sites are also related to the cycle life by affecting the SEI formation, and the determination of surface heterogeneity and pores of graphite materials can provide powerful parameters that imply the electrochemical performances of commercial graphite.

Highlights

Graphite is an excellent anode material for Li-ion batteries in terms of energy density, due to its low operating voltage (~0.1 V), acceptable theoretical capacity (372 mAh g−1 ), high electrical conductivity, and relatively low volume expansion (~13%) during lithiation/delithiation [1,2,3]
Our group confirmed that the exposed pores in graphite, which can act as sites to promote solid-electrolyte interphase (SEI) formation, are defective planes that reduce the cyclability of the graphite anode [22]
The electrochemical properties of commercial graphites were categorized with its nanostructural properties and surface heterogeneity of graphite

Summary

Introduction

Graphite is an excellent anode material for Li-ion batteries in terms of energy density, due to its low operating voltage (~0.1 V), acceptable theoretical capacity (372 mAh g−1 ), high electrical conductivity, and relatively low volume expansion (~13%) during lithiation/delithiation [1,2,3]. Low cost makes graphite more attractive as an anode material for current and post Li-ion batteries than other candidates (Si, Sn-alloying type, Li4 Ti5 O12 , Li metal, etc.) [4,5,6,7,8,9,10,11]. Many groups have confirmed that the cycle life of graphite electrode is majorly affected by the solid-electrolyte interphase (SEI) formation on the graphite surface, as a thin and dense SEI layer can suppress additional side reactions [19,20,21]. It is clear that the surface and particle conditions of the graphite is closely related to the cycle

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