Title: Progress in High-Capacity Gradient Cathode Materials for Rechargeable Lithium Batteries

Speaker: Yang-Kook Sun, Hanyang University, South Korea 

Date/Time: 10:00 AM, Nov. 10, 2017 (Fri.)

Location: Chemistry Lecture Hall 

Abstract:

High-energy-density rechargeable batteries are needed to fulfill various demands such as self-monitoring analysis and reporting technology (SMART) devices,energy storage systems, and (hybrid) electric vehicles. As a result, high-energy electrodematerials enabling a long cycle life and reliable safety need to be developed. To ensure theserequirements, new material chemistries can be derived from combinations of at least twocompounds in a secondary particle with varying chemical composition and primary particlemorphologies having a core−shell structure and spherical cathode-active materials,specifically a nanoparticle core and shell, nanoparticle core and nanorod shell, and nanorodcore and shell. To this end, several layer gradient cathode materials were developed toensure high capacity, reliability, and safety. One of the most promising oxides is full concentration gradient (FCG) lithium nickel-cobalt-manganese oxide composed of a Mn-rich outer surface providing excellent safety and Ni-rich center achieving high capacity.  In addition, we extended the FCG concept and report a new novel Li[Ni_xCo_yMn_z]O₂ cathode material with two-sloped full concentration gradients (TSFCG) of Ni, Co, and Mn ions throughout the cathode particles to maximize the average Ni concentration at the core as active redox species and the Mn concentration in the area near the particle surface. The Ni-rich TSFCG delivers a discharge capacity in excess of 200 mAh g^-1 (at 4.3 V cutoff voltage and 0.1 C rate) with excellent cycle life and thermal stability. Comparison of electrochemical and thermal properties of the TSFCG with those of NCA and conventional cathode Li[Ni_xCo_yMn_z]O₂ is presented.