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Yoon, Gabin,Moon, Sehwan,Ceder, Gerbrand,Kang, Kisuk American Chemical Society 2018 Chemistry of materials Vol.30 No.19
<P>Metallic lithium (Li) is a promising anode candidate for high-energy-density rechargeable batteries because of its low redox potential and high theoretical capacity. However, its practical application is not imminent because of issues related to the dendritic growth of Li metal with repeated battery operation, which presents a serious safety concern. Herein, various aspects of the electrochemical deposition and stripping of Li metal are investigated with consideration of the reaction rate/current density, electrode morphology, and solid electrolyte interphase (SEI) layer properties to understand the conditions inducing abnormal Li growth. It is demonstrated that the irregular (i.e., filamentary or dendritic) growth of Li metal mostly originates from local perturbation of the surface current density, which stems from surface irregularities arising from the morphology, defective nature of the SEI, and relative asymmetry in the deposition/stripping rates. Importantly, we find that the use of a stripping rate of Li metal that is slower than the deposition rate seriously aggravates the formation of disconnected Li debris from the irregularly grown Li metal. This finding challenges the conventional belief that high-rate stripping/plating of Li in an electrochemical cell generally results in more rapid cell failure because of the faster growth of Li metal dendrites.</P> [FIG OMISSION]</BR>
High-rate performance of a mixed olivine cathode with off-stoichiometric composition.
Kim, Jae Chul,Li, Xin,Kang, Byoungwoo,Ceder, Gerbrand The Royal Society of Chemistry 2015 Chemical communications Vol.51 No.68
<P>We highlight that the off-stoichiometric compositional variation is a simply effective method to improve the power density of LiFe0.6Mn0.4PO4. This strategy does not require a supplementary separate coating and is likely applicable to other compositions given the feasibility of the method.</P>
Zhang, Yangning,Kim, Sooran,Feng, Guangyuang,Wang, Yan,Liu, Lei,Ceder, Gerbrand,Li, Xin The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.7
<P>Recently, Cu element has been introduced into layered sodium transition metal oxides (Na<SUB>x</SUB>TMO<SUB>2</SUB>) as cathode materials for sodium ion batteries to engineer rate and cycling performance. To study the unique role provided by Cu, we designed, synthesized and tested four different compositions of P2-type Na<SUB>x</SUB>(Mn<SUB>y</SUB>Fe<SUB>z</SUB>Co<SUB>1-y-z</SUB>)O<SUB>2</SUB> and three compositions of P2-type Na<SUB>x</SUB>(Mn<SUB>y</SUB>Fe<SUB>z</SUB>Cu<SUB>1-y-z</SUB>)O<SUB>2</SUB> cathode materials. When cycled in the full voltage range of 1.5∼4.5 V under different rates 0.1 C, 1 C and 10 C, the cyclability of MnFeCu-based compounds is better than that of MnFeCo-based ones. Using X-ray diffraction, we observed the P2 to O2-like phase transition of MnFeCu-based materials upon charging and studied its influence on battery performance. Limiting the P2-O2 phase transition delivers less capacity, but improves cyclability. By DFT simulations, we showed that different Na diffusivity and site preference in the high voltage phase contribute to the difference in the electrochemical performances of these cathode materials.</P>
Gwon, Hyeokjo,Kim, Sung-Wook,Park, Young-Uk,Hong, Jihyun,Ceder, Gerbrand,Jeon, Seokwoo,Kang, Kisuk American Chemical Society 2014 Inorganic Chemistry Vol.53 No.15
<P>An ion-exchange process can be an effective route to synthesize new quasi-equilibrium phases with a desired crystal structure. Important layered-type battery materials, such as LiMnO<SUB>2</SUB> and LiNi<SUB>0.5</SUB>Mn<SUB>0.5</SUB>O<SUB>2</SUB>, can be obtained through this method from a sodium-containing parent structure, and they often show electrochemical properties remarkably distinct from those of their solid-state synthesized equivalents. However, while ion exchange is generally believed to occur via a simple topotactic reaction, the detailed phase transformation mechanism during the process is not yet fully understood. For the case of layered LiNi<SUB>0.5</SUB>Mn<SUB>0.5</SUB>O<SUB>2</SUB>, we show through ex situ X-ray diffraction (XRD) that the ion-exchange process consists of several sequential phase transformations. By a study of the intermediate phase, it is shown that the residual sodium ions in the final structure may greatly affect the electrochemical (de)lithiation mechanism.</P><P>The ion exchange in NaNi<SUB>0.5</SUB>Mn<SUB>0.5</SUB>O<SUB>2</SUB> is not a simple two-phase process but rather involves several intermediate complex compounds. In the early stage of ion exchange, the intermediate phase, which contains randomly distributed sodium and lithium ions in the lithium layers, forms almost immediately, with extremely fast exchange kinetics. Successively, a rather slower two-phase conversion occurred, involving a structural shuffling process.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/inocaj/2014/inocaj.2014.53.issue-15/ic501069x/production/images/medium/ic-2014-01069x_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ic501069x'>ACS Electronic Supporting Info</A></P>
Fabricating genetically engineered high-power lithium-ion batteries using multiple virus genes.
Lee, Yun Jung,Yi, Hyunjung,Kim, Woo-Jae,Kang, Kisuk,Yun, Dong Soo,Strano, Michael S,Ceder, Gerbrand,Belcher, Angela M American Association for the Advancement of Scienc 2009 Science Vol.324 No.5930
<P>Development of materials that deliver more energy at high rates is important for high-power applications, including portable electronic devices and hybrid electric vehicles. For lithium-ion (Li+) batteries, reducing material dimensions can boost Li+ ion and electron transfer in nanostructured electrodes. By manipulating two genes, we equipped viruses with peptide groups having affinity for single-walled carbon nanotubes (SWNTs) on one end and peptides capable of nucleating amorphous iron phosphate(a-FePO4) fused to the viral major coat protein. The virus clone with the greatest affinity toward SWNTs enabled power performance of a-FePO4 comparable to that of crystalline lithium iron phosphate (c-LiFePO4) and showed excellent capacity retention upon cycling at 1C. This environmentally benign low-temperature biological scaffold could facilitate fabrication of electrodes from materials previously excluded because of extremely low electronic conductivity.</P>
A New Strategy for High-Voltage Cathodes for K-Ion Batteries: Stoichiometric KVPO<sub>4</sub> F
Kim, Haegyeom,Seo, Dong-Hwa,Bianchini, Matteo,Clé,ment, Raphaë,le J.,Kim, Hyunchul,Kim, Jae Chul,Tian, Yaosen,Shi, Tan,Yoon, Won-Sub,Ceder, Gerbrand Wiley (John WileySons) 2018 Advanced energy materials Vol.8 No.26
Stoichiometric Layered Potassium Transition Metal Oxide for Rechargeable Potassium Batteries
Kim, Haegyeom,Seo, Dong-Hwa,Urban, Alexander,Lee, Jinhyuk,Kwon, Deok-Hwang,Bo, Shou-Hang,Shi, Tan,Papp, Joseph K.,McCloskey, Bryan D.,Ceder, Gerbrand American Chemical Society 2018 Chemistry of materials Vol.30 No.18
<P>K-ion batteries are promising alternative energy storage systems for large-scale applications because of the globally abundant K reserves. K-ion batteries benefit from the lower standard redox potential of K/K<SUP>+</SUP> than that of Na/Na<SUP>+</SUP> and even Li/Li<SUP>+</SUP>, which can translate into a higher working voltage. Stable KC<SUB>8</SUB> can also be formed via K intercalation into a graphite anode, which contrasts with the thermodynamically unfavorable Na intercalation into graphite, making graphite a readily available anode for K-ion battery technology. However, to construct practical rocking-chair K-ion batteries, an appropriate cathode material that can accommodate reversible K release and storage is still needed. We show that stoichiometric KCrO<SUB>2</SUB> with a layered O3-type structure can function as a cathode for K-ion batteries and demonstrate a practical rocking-chair K-ion battery. In situ X-ray diffraction and electrochemical titration demonstrate that K<SUB><I>x</I></SUB>CrO<SUB>2</SUB> is stable for a wide K content, allowing for topotactic K extraction and reinsertion. We further explain why stoichiometric KCrO<SUB>2</SUB> is unique in forming the layered structure unlike other stoichiometric K-transition metal oxide compounds, which form nonlayered structures; this fundamental understanding provides insight for the future design of other layered cathodes for K-ion batteries.</P> [FIG OMISSION]</BR>