One of promising cathode for lithium ion battery is LiMn2O4 (LMO) due to its low cost and environmental inertness. However, LMO suffers from Mn dissolution followed by cell degradation. Mn-dissolution is heavily affected by electrode surface and electrolyte, so it is electrode/electrolyte interfacial phenomenon. However, more methodical research about the relationship between the electrolyte property and Mn-dissolution has not been carried out so far. This study examine the dependence of the Mn-dissolution on electrolyte constitution at various temperature and its kinetics. The Mn2+ ion concentration in the electrolyte at vari-ous temperature storage was analyzed by using atomic absorption spectroscopy (AAS). It was revealed that increasing EC content, storage duration and elevated temperature acceler-ates Mn-dissolution. It is diffusion controlled through the product layer. When increasing EC content, it diminish the activation energy of dissolution on electrode/electrolyte interface. ⓒ 2015 DGIST
Table Of Contents
Ⅰ. Surface free energy measurement to assess metal dissolution behavior of layered oxide LiNi0.6Co0.2Mn0.2O 2 -- 1.1 Introduction 1 -- 1.1.1 Overview 1 -- 1.1.2 Theory of surface free energy calculation 2 -- 1.1.3 Capillary rising method for porous materials 8 -- 1.1.4 Examples of surface free energy usages to analyze the Li ion batteries 10 -- 1.2 Experimental 11 -- 1.2.1 Adsorption method 11 -- 1.2.2 Preparation of NCM electrode 14 -- 1.2.3 Metal dissolution 15 -- 1.3 Results and discussion 16 -- 1.3.1 Metal dissolution and SFE of Al coated LiNi0.6Co0.2Mn0.2O2 16 -- 1.3.2 Analysis of the morphology of Al coated LiNi0.6Co0.2Mn0.2O2 19 -- 1.3.3 Connection between SFE and metal dissolution of Al coated LiNi0.6Co0.2Mn0.2O2 20 -- 1.4 Conclusions 24 -- Ⅱ. Influence of the electrolyte constitution on the dissolution kinetics of manganese from LiMn2O4 cathode for lithium ion battery -- 2.1 Introduction 25 -- 2.2 Experimental 27 -- 2.3 Results and discussion 29 -- 2.3.1 Effects of EC content, reaction temperature and storage time on Mn dissolution 29 -- 2.3.2 Kinetics of Mn dissolution 31 -- 2.3.3 Chemical reaction controlled 33 -- 2.3.4 Diffusion controlled through the product layer 36 -- 2.3.5 Activation energy determination 39 -- 2.3.6 Effect of solvation energy and HF 41 -- 2.4 Conclusions 44 -- Ⅲ. Analysis of surface free energy in battery electrolytes. -- 3.1 Introduction 45 -- 3.2 Experimental 46 -- 3.3 Results and discussion 48 -- 3.3.1 Characterization of reference materials 48 -- 3.3.2 The surface free energy calculation of propylene carbonate 51 -- 3.4 Conclusions 53
