Theoretical Study on Graphite and Lithium Metal as Anode Materials for Next-Generation Rechargeable Batteries

This thesis describes in-depth theoretical efforts to understand the reaction mechanism of graphite and lithium metal as anodes for next-generation rechargeable batteries. The first part deals with Na intercalation chemistry in graphite, whose understanding is crucial for utilizing graphite as an anode for Na-ion batteries. The author demonstrates that Na ion intercalation in graphite is thermodynamically unstable because of the unfavorable Na-graphene interaction. To address this issue, the inclusion of screening moieties, such as solvents, is suggested and proven to enable reversible Na-solvent cointercalation in graphite. Furthermore, the author provides the correlation between the intercalation behavior and the properties of solvents, suggesting a general strategy to tailor the electrochemical intercalation chemistry. The second part addresses the Li dendrite growth issue, which is preventing practical application of Li metal anodes. A continuum mechanics study considering various experimental conditions reveals the origins of irregular growth of Li metal. The findings provide crucial clues for developing effective counter strategies to control the Li metal growth, which will advance the application of high-energy-density Li metal anodes.

Autorentext

Dr. Gabin Yoon received a B.Sc. degree (2013) and Ph.D. degree (2019) in materials science and engineering from Seoul National University.

His research interest lies in the theoretical study of electrode materials for Li and Na rechargeable batteries using density functional theory and continuum mechanics.

Inhalt

1 Introduction 1

1.1 Demands for energy storage system 1

1.2 Li-ion batteries 1

1.3 Post Li-ion batteries 3

1.3.1 Na-ion batteries 3

1.3.2 Li metal batteries 5

1.4 References 6

2 Na intercalation chemistry in graphite 9

2.1 Introduction 9

2.2 Experimental and computational details 10

2.2.1 Materials 10

2.2.2 Electrode preparation and electrochemical measurements 10

2.2.3 Operando XRD analysis 11

2.2.4 Computational details 11

2.3 Staging behavior upon Na-solvent co-intercalation 12

2.4 Na-solvent co-intercalation into graphite structure 15

2.5 Solvent dependency on electrochemical properties 20

2.6 Conclusions 24

2.7 References 27

3 Conditions for reversible Na intercalation in graphite 31

3.1 Introduction 31

3.2 Computational details 32

3.3 Unstable Na intercalation in graphite 33

3.3.1 Destabilization energy of metal reconstruction 35

3.3.2 Destabilization energy of graphite framework upon intercalation 37

3.3.3 Local interaction between alkali metal ions and the graphite framework 37

3.3.4 Mitigating the unfavorable local interaction between Na and graphene layers 39

3.4 Conditions of solvents for reversible Na intercalation into graphite 41

3.4.1 Solvent dependency on reversible Na-solvent co-intercalation behavior 41

3.4.2 Thermodynamic stability of Na-solvent complex 43

3.4.3 Chemical stability of Na-solvent complex 46

3.4.4 Unified picture of Na-solvent co-intercalation behavior 47

3.5 Conclusions 48

3.6 References 48

4 Electrochemical deposition and stripping behavior of Li metal 53

4.1 Introduction 53

4.2 Computational details 55

4.3 Effect of deposition rate 57

4.4 Effect of surface geometry 60

4.5 Implications of SEI layer properties 63

4.6 Consequences of the history of deposition and stripping 70

4.7 Conclusions 72

4.8 References 72