Cathode materials of Li-ion batteries
Insight of structures and properties of cathode materials of Li-ion batteries.
Abstract
Insight of structures and properties of cathode materials of Li-ion batteries
Insight into relationship between Crystal/Interface structure and properties of capacity, stability and rate capability are important for developing advanced Li-ion batteries. Using theoretical calculations combined with experimental in-situ tests, we did extensive studies on the kinetic of Li-ion diffusion for two representative cathode materials: layered Li(NixMnyCoz)O2 (NMC) (x + y + z = 1) and LiFePO4. We not only focus on the bulk kinetics, but also the kinetics across electrode/electrolyte solid-liquid interface and in the electrolytes. For example, we first proposed that "Janus" solid-liquid interface would facilitate the Li-ion transport in battery and introducing some disordering in non-active cathode materials would activate them for Li-ion storage. Finally, we also developed some in-situ technologies for battery studies. For example, using electrochemical quartz crystal microbalance (EQCM), we achieve an in situ experimental investigation of the LiFePO4 (LFP) and NaFePO4 (NFP)/electrolyte interfacial kinetics for Li(Na)-batteries. (Ref. 1)
For high energy and power density applications (e.g., EVs), the safety becomes especially important. Using ab initio calculations combined with experiments, we clarified how the thermal stability of NMC materials can be tuned by the most unstable oxygen, which is determined by the local coordination structure unit (LCSU) of oxygen (TM(Ni, Mn, Co)3-O-Li3-x’): each O atom bonds with three of transition metal (TM) from the TM-layer and three to zero of Li from fully discharged to charged states from the Li-layer. Under this model, how the lithium content, valence states of Ni, contents of Ni, Mn, and Co, and Ni/Li disorder to tune the thermal stability of NMC materials by affecting the sites, content, and the release temperature of the most unstable oxygen is proposed. (Ref. 2)
Reference:
1. (a)F. Pan el al., “Kinetics Tuning of Li-ion Diffusion in Layered Li(NixMnyCoz)O2”, J. Am. Chem. Soc., 2015, 137, 8364; (b) "Optimized Temperature Effect of Li-Ion Diffusion with Layer Distance in Li(NixMnyCoz)O2 Cathode Materials for High Performance Li-Ion Battery", Adv. Energy Mater., 2015, 1501309(1-9).(c) "Janus Solid–Liquid Interface Enabling Ultrahigh Charging and Discharging Rate for Advanced Lithium-Ion Batteries", Nano Lett,2015, 15 (9), pp 6102 (d)“Single-particle performances and properties of LiFePO4 nanocrystals for Li-ion batteries” Adv. Energy Mater., (Front page ) 2016, 1601894 (e) Excess Li-ion storage on reconstructed surfaces of nanocrystals to boost battery performance, Nano Lett, 2017, 17, 6018−6026, (f) “In-situ Study of Solid-liquid Interfacial Kinetics of Li(Na)FePO4 Nanocrystals for Li(Na)-ion Batteries”, Nano Energy 2017 37, 90 (g) Tuning Li-ion diffusion in α-LiMn1-xFexPO4 nanocrystals by antisite defects and embedded β-phase for advanced Li-ion batteries, Nano Lett., 2017, 17 (8), 4934
2. (a) F. Pan el al., “Tuning of Thermal Stability in Layered Li(NixMnyCoz)O2”, J. Am. Chem. Soc., 2016, 138 (40), 13326, (b)“Aligned Li+ Tunnels in Core−Shell Li(NixMnyCoz)O2@LiFePO4 Enhances Its High Voltage Cycling Stability as Li-ion Battery Cathode” Nano Letters 2016, 16 (10), pp 6357; (c) “Prelithiation Activates Li(Ni0.5Mn0.3Co0.2)O2 for High Capacity and Excellent Cycling Stability", Nano Letters, 2015, 15, 5590; (d)The Role of Super-Exchange Interaction on Tuning of Ni/Li Disordering in Layered Li (NixMnyCoz) O2, J. Phys. Chem. Lett., 2017, 8 (22), 5537; (e) Nano Energy 49 2018,49,77
About the speaker
Professor Feng Pan
Prof. Feng Pan, National 1000-plan Professor, Founding Dean of School of Advanced Materials,Peking University Shenzhen Graduate School, Director of National Center of Electric Vehicle Power Battery and Materials for International Research, got B.S. from Dept. Chemistry, Peking University in 1985 and PhD from Dept. of P&A Chemistry,University of Strathclyde, Glasgow, UK, with "Patrick D. Ritchie Prize” for the best Ph.D. in 1994. With more than a decade experience in large international corporations, Prof. Pan has been engaged in fundamental research and product development of novel optoelectronic and energy storage materials and devices. As Chief Scientist, Prof. Pan led 8 entities in Shenzhen to win the 150 million RMB grant for the national EV-battery innovation project in 2013-16. As Chief Scientist, Prof. Pan led 12 entities to win National Key project of Material Genomic Engineering for Solid State Li-ion Battery in China in 2016. He has published more than 200 peer-reviewed papers in international journals and book chapters and 80 patents for inventions. He has been selected as one of the 2016 winner of Outstanding Research Award of Advanced Lithium Batteries for Automobile Applications (ABAA) and the 2018 winner of ECS Battery Division Technology Award.