Please consider attending the following tomorrow, Friday, Oct. 20, at 9:00 a.m., in HAMP 2107: MATERIALS ENGINEERING SEMINAR "Current Cathode Materials and Their Limitations in Lithium Ion Batteries" By Zhimin Qi Purdue MSE Ph.D. Preliminary Exam Advisor: Professor Haiyan Wang ABSTRACT Lithium ion batteries is one of the most intriguing and promising energy storage in the modern society, and it has been extensively explored since 1990s. A lithium ion battery contains three main component, cathode, anode, and electrolyte, and the performance of battery depends on each component and the compatibility between them. In this review, a general introduction of anode and electrolyte is given, and a detailed discussion in main types of cathode materials and their limitations is made. Electrolyte act as a conduction medium of lithium ions and the incompatibility with electrodes would directly cause decomposition of electrolyte. Anode usually has much higher capacity and very low voltage (vs Li+/Li0), which makes cathode the limiting factor in the battery. There are three main types of cathode materials in terms of lithium transportation dimension. 1-D olivine structure (LiFePO4) has a very stable structure and electrochemical performance, but it suffers both conductivity. Electrically conductive coating layer and size reduction methods were introduced to solve the problem. 2-D layered structure (LiCoO2) has a high theoretical capacity, moderate conductivity but structural instability when x in LixCoO2 is smaller than 0.5 and under elevated temperature. Partial substitution of Co ion leads to (Li(NiyMnzCo1-y-z)O2 (NMC)) and improves the thermal stability and reversible capacity. Further, the incorporation of Li2MnO3 gave rise to Li-rich composite material and improvement of the capacity and operation voltage. 3-D spinel structure LiMn2O4 is usually applied as high power cathode material but suffers from Mn3+ dissolution and phase transformation upon cycling. Preventive coating and dopant ion were introduced to relieve the problem. Fundamental limiting factors in cathode materials were also discussed. Different crystal structures, chemical bonding environment, and compatibility with electrolyte should all be considered when it comes to design a cathode material for lithium ion battery system. Cathode material has the intrinsic upper voltage limit due to fermi level pinning at the top of anion p band. Cathode solid electrolyte interphase is critical regarding the electrochemical performance of the material. Despite the complicate formation mechanism and developing process during cycling, surface protective layer was usually applied to solve the issue. Date: Friday, October 20, 2017 Time: 9:00 A.M. Place: HAMP 2107