State-of-the-art lithium (Li)-ion batteries are approaching their specific energy limits yet are challenged by the ever-increasing demand of today’s energy storage and power applications, especially for electric vehicles. Li metal is considered an ultimate anode material for future high-energy rechargeable batteries when combined with existing or emerging high-capacity cathode materials. However, much current research focuses on the battery materials level, and there have been very few accounts of cell design principles. Here we discuss crucial conditions needed to achieve a specific energy higher than 350 Wh kg−1, up to 500 Wh kg−1, for rechargeable Li metal batteries using high-nickel-content lithium nickel manganese cobalt oxides as cathode materials. We also provide an analysis of key factors such as cathode loading, electrolyte amount and Li foil thickness that impact the cell-level cycle life. Furthermore, we identify several important strategies to reduce electrolyte-Li reaction, protect Li surfaces and stabilize anode architectures for long-cycling high-specific-energy cells. Jun Liu and Battery500 Consortium colleagues contemplate the way forward towards high-energy and long-cycling practical batteries.

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Pathways for practical high-energy long-cycling lithium metal batteries

This Review covers a sequence of key discoveries and technical achievements that eventually led to the birth of the lithium-ion battery. In doing so, it not only sheds light on the history with the advantage of contemporary hindsight but also provides insight and inspiration to aid in the ongoing quest for better batteries of the future. A detailed retrospective on ingenious designs, accidental discoveries, intentional breakthroughs, and deceiving misconceptions is given: from the discovery of the element lithium to its electrochemical synthesis; from intercalation host material development to the concept of dual-intercalation electrodes; and from the misunderstanding of intercalation behavior into graphite to the comprehension of interphases. The onerous demands of bringing all critical components (anode, cathode, electrolyte, solid-electrolyte interphases), each of which possess unique chemistries, into a sophisticated electrochemical device reveal that the challenge of interfacing these originally inco...

Before Li Ion Batteries

The detailed chemical structure of graphite oxide (GO), a layered material prepared from graphite almost 150 years ago and a precursor to chemically modified graphenes, has not been previously resolved because of the pseudo-random chemical functionalization of each layer, as well as variations in exact composition. Carbon-13 (13C) solid-state nuclear magnetic resonance (SSNMR) spectra of GO for natural abundance 13C have poor signal-to-noise ratios. Approximately 100% 13C-labeled graphite was made and converted to 13C-labeled GO, and 13C SSNMR was used to reveal details of the chemical bonding network, including the chemical groups and their connections. Carbon-13–labeled graphite can be used to prepare chemically modified graphenes for 13C SSNMR analysis with enhanced sensitivity and for fundamental studies of 13C-labeled graphite and graphene.

http://science.sciencemag.org/content/sci/321/5897/1815.full.pdf

Synthesis and solid-state NMR structural characterization of 13C-labeled graphite oxide.

Solid-state electrolytes (SSEs) have emerged as high-priority materials for safe, energy-dense and reversible storage of electrochemical energy in batteries. In this Review, we assess recent progress in the design, synthesis and analysis of SSEs, and identify key failure modes, performance limitations and design concepts for creating SSEs to meet requirements for practical applications. We provide an overview of the development and characteristics of SSEs, followed by analysis of ion transport in the bulk and at interfaces based on different single-valent (Li+, Na+, K+) and multivalent (Mg2+, Zn2+, Ca2+, Al3+) cation carriers of contemporary interest. We analyse the progress in overcoming issues associated with the poor ionic conductivity and high interfacial resistance of inorganic SSEs and the poor oxidative stability and cation transference numbers of polymer SSEs. Perspectives are provided on the design requirements for future generations of SSEs, with a focus on the chemical, geometric, mechanical, electrochemical and interfacial transport features required to accelerate progress towards practical solid-state batteries in which metals are paired with energetic cathode chemistries, including Ni-rich and Li-rich intercalating materials, sustainable organic materials, S8, O2 and CO2. Solid-state batteries based on electrolytes with low or zero vapour pressure provide a promising path towards safe, energy-dense storage of electrical energy. In this Review, we consider the requirements and design rules for solid-state electrolytes based on inorganics, organic polymers and organic–inorganic hybrids.

Designing solid-state electrolytes for safe, energy-dense batteries

Extreme fast charging, with a goal of 15 minutes recharge time, is poised to accelerate mass market adoption of electric vehicles, curb greenhouse gas emissions and, in turn, provide nations with greater energy security. However, the realization of such a goal requires research and development across multiple levels, with battery technology being a key technical barrier. The present-day high-energy lithium-ion batteries with graphite anodes and transition metal oxide cathodes in liquid electrolytes are unable to achieve the fast-charging goal without negatively affecting electrochemical performance and safety. Here we discuss the challenges and future research directions towards fast charging at the level of battery materials from mass transport, charge transfer and thermal management perspectives. Moreover, we highlight advanced characterization techniques to fundamentally understand the failure mechanisms of batteries during fast charging, which in turn would inform more rational battery designs. Along with high energy density, fast-charging ability would enable battery-powered electric vehicles. Here Yi Cui and colleagues review battery materials requirements for fast charging and discuss future design strategies.

Challenges and opportunities towards fast-charging battery materials

Whereas standard transmission electron microscopy studies are unable to preserve the native state of chemically reactive and beam-sensitive battery materials after operation, such materials remain pristine at cryogenic conditions. It is then possible to atomically resolve individual lithium metal atoms and their interface with the solid electrolyte interphase (SEI). We observe that dendrites in carbonate-based electrolytes grow along the (preferred), , or directions as faceted, single-crystalline nanowires. These growth directions can change at kinks with no observable crystallographic defect. Furthermore, we reveal distinct SEI nanostructures formed in different electrolytes.

Atomic structure of sensitive battery materials and interfaces revealed by cryo–electron microscopy

The reactions which occur between amorphous carbon and a number of first transition metals (Ti, Cr, Fe, Co, Ni, and Cu) have been studied by transmission electron microscopy (TEM). The materials are in thin-film form with the metal layer sandwiched between thicker carbon layers. In four cases, the predominant reaction is the graphitization of the amorphous carbon, at temperatures well below 800 degrees C. This is brought about by the elements themselves in the case of Co and Ni, and by metastable carbides in the case of Fe (Fe3C) and Cr (Cr3C2-x). The Ti-C and Cu-C systems do not exhibit graphitization. For the former, only TiC is produced up to 1000 degrees C, while the carbon does not react at all with copper. In situ TEM studies show the mechanism to be of the dissolution-precipitation type, which is equivalent to the metal-mediated crystallization process for amorphous silicon and germanium. The heat of graphitization is found to be 18-19 kcal/mol-C by differential scanning calorimetry.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1431927602020226

In Situ TEM Studies of Metal–Carbon Reactions

Dr. M. Lanza, M. Reguant, G. Zou, P. Lv, Prof. H. Duan State Key Laboratory for Turbulence and Complex System Department of Mechanics and Engineering Science, CAPT College of Engineering, Peking University Beijing 100871 , China E-mail: hlduan@pku.edu.cn H. Li, D. Yu Department of Physics State Key Laboratory for Mesoscopic Physics Peking University Beijing 100871 , China R. Chin Stanford Nanocharacterization Laboratory McCullough 225, 476 Lomita Mall Stanford University California 94305-4045 , United States of America H. Liang Department of Modern Mechanics University of Science and Technology of China Hefei , Anhui 230027 , China Y. Zhang, Z. Liu Center for Nanochemistry (CNC) Beijing National Laboratory for Molecular Sciences State Key Laboratory for Structural Chemistry of Unstable and Stable Species College of Chemistry and Molecular Engineering Academy for Advanced Interdisciplinary Studies Peking University Beijing 100871 , China

High-Performance Piezoelectric Nanogenerators Using Two-Dimensional Flexible Top Electrodes

This article describes the establishment, over a period of ten years or so, of a multi-user, institution-wide facility for the characterization of materials and devices at the nano-scale. Emphasis is placed on the type of equipment that we have found to be most useful for our users, and the business strategy that maintains its operations. A central component of our facility is an aberration-corrected environmental transmission electron microscope and its application is summarized in the studies of plasmon energies of silver nanoparticles, the band gap of PbS quantum dots, atomic site occupancy near grain boundaries in yttria stabilized zirconia, the lithiation of silicon nanoparticles, in situ observations on carbon nanotube oxidation and the electron tomography of varicella zoster virus nucleocapsids.

Richard Chin

Papers

Atomic structure of sensitive battery materials and interfaces revealed by cryo–electron microscopy

In Situ TEM Studies of Metal–Carbon Reactions

High-Performance Piezoelectric Nanogenerators Using Two-Dimensional Flexible Top Electrodes

The Stanford Nanocharacterization Laboratory (SNL) and Recent Applications of an Aberration-Corrected Environmental Transmission Electron Microscope.