There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The challenges for further development of Li rechargeable batteries for electric vehicles are reviewed. Most important is safety, which requires development of a nonflammable electrolyte with either a larger window between its lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) or a constituent (or additive) that can develop rapidly a solid/ electrolyte-interface (SEI) layer to prevent plating of Li on a carbon anode during a fast charge of the battery. A high Li-ion conductivity (σ Li > 10 ―4 S/cm) in the electrolyte and across the electrode/ electrolyte interface is needed for a power battery. Important also is an increase in the density of the stored energy, which is the product of the voltage and capacity of reversible Li insertion/extraction into/from the electrodes. It will be difficult to design a better anode than carbon, but carbon requires formation of an SEI layer, which involves an irreversible capacity loss. The design of a cathode composed of environmentally benign, low-cost materials that has its electrochemical potential μ C well-matched to the HOMO of the electrolyte and allows access to two Li atoms per transition-metal cation would increase the energy density, but it is a daunting challenge. Two redox couples can be accessed where the cation redox couples are "pinned" at the top of the O 2p bands, but to take advantage of this possibility, it must be realized in a framework structure that can accept more than one Li atom per transition-metal cation. Moreover, such a situation represents an intrinsic voltage limit of the cathode, and matching this limit to the HOMO of the electrolyte requires the ability to tune the intrinsic voltage limit. Finally, the chemical compatibility in the battery must allow a long service life.

Challenges for Rechargeable Li Batteries

Li-ion batteries have transformed portable electronics and will play a key role in the electrification of transport. However, the highest energy storage possible for Li-ion batteries is insufficient for the long-term needs of society, for example, extended-range electric vehicles. To go beyond the horizon of Li-ion batteries is a formidable challenge; there are few options. Here we consider two: Li-air (O(2)) and Li-S. The energy that can be stored in Li-air (based on aqueous or non-aqueous electrolytes) and Li-S cells is compared with Li-ion; the operation of the cells is discussed, as are the significant hurdles that will have to be overcome if such batteries are to succeed. Fundamental scientific advances in understanding the reactions occurring in the cells as well as new materials are key to overcoming these obstacles. The potential benefits of Li-air and Li-S justify the continued research effort that will be needed.

Li-O2 and Li-S batteries with high energy storage.

Energy storage using batteries offers a solution to the intermittent nature of energy production from renewable sources; however, such technology must be sustainable. This Review discusses battery development from a sustainability perspective, considering the energy and environmental costs of state-of-the-art Li-ion batteries and the design of new systems beyond Li-ion. Images: batteries, car, globe: © iStock/Thinkstock.

Towards greener and more sustainable batteries for electrical energy storage

We report that a heat-treated Li2S–P2S5 glass-ceramic conductor has an extremely high ionic conductivity of 1.7 × 10−2 S cm−1 and the lowest conduction activation energy of 17 kJ mol−1 at room temperature among lithium-ion conductors reported to date. The optimum conditions of the heat treatment reduce the grain boundary resistance, and the influence of voids, to increase the Li+ ionic conductivity of the solid electrolyte so that it is greater than the conductivities of liquid electrolytes, when the transport number of lithium ions in the inorganic electrolyte is unity.

A sulphide lithium super ion conductor is superior to liquid ion conductors for use in rechargeable batteries

Rechargeable solid-state batteries are promising sources of energy for a range of applications. Hayashi et al. examine the electrochemistry of solid-state sodium batteries, and present an electrolyte that operates at room temperature.

/pdf/superionic-glass-ceramic-electrolytes-for-room-temperature-38mlp67lj9.pdf

Superionic glass-ceramic electrolytes for room-temperature rechargeable sodium batteries

New, Highly Ion-Conductive Crystals Precipitated from Li2S–P2S5 Glasses

All-solid-state secondary batteries that employ inorganic solid electrolytes are desirable because they are potentially safer than conventional batteries. The ionic conductivities of solid electrolytes are currently attracting great attention. In addition to the conductivity, the mechanical properties of solid electrolytes are important for improving the energy density and cycle performance. However, the mechanical properties of sulfide electrolytes have not been clarified in detail. Here, we demonstrate the unique mechanical properties of sulfide electrolytes. Sulfide electrolytes show room temperature pressure sintering. Ionic materials with low bond energies and a highly covalent character, which is promising for achieving a high ionic conductivity, tend to be suitable for room-temperature processing. The Young's moduli of sulfide electrolytes were measured to be about 20 GPa, which is an intermediate value between those of typical oxides and organic polymers.

/pdf/sulfide-solid-electrolyte-with-favorable-mechanical-property-4h9lqy9hrt.pdf

Sulfide Solid Electrolyte with Favorable Mechanical Property for All-Solid-State Lithium Battery

In all-solid-state lithium secondary batteries, both the electrode and electrolyte materials are solid. The electrode and solid electrolyte interface’s structure and morphology affect a battery’s electrochemical performance. Observation of the interface between LiCoO2 positive electrode and highly lithium-ion-conducting Li2S−P2S5 solid electrolyte was conducted using transmission electron microscopy. An interfacial layer was formed at the interface between LiCoO2 electrode and Li2S−P2S5 solid electrolyte after the battery’s initial charge. Furthermore, mutual diffusions of Co, P, and S at the interface between LiCoO2 and Li2S−P2S5 were observed. The mutual diffusion and the formation of the interfacial layer were suppressed using LiCoO2 particles coated with Li2SiO3 thin film. Results showed that all-solid-state cells using Li2SiO3-coated LiCoO2 had better electrochemical performance than those using noncoated LiCoO2. The all-solid-state cells functioned at −30 °C. Moreover, the all-solid-state cell using...

Interfacial Observation between LiCoO2 Electrode and Li2S−P2S5 Solid Electrolytes of All-Solid-State Lithium Secondary Batteries Using Transmission Electron Microscopy†

Akitoshi Hayashi

Papers

A sulphide lithium super ion conductor is superior to liquid ion conductors for use in rechargeable batteries

Superionic glass-ceramic electrolytes for room-temperature rechargeable sodium batteries

New, Highly Ion-Conductive Crystals Precipitated from Li2S–P2S5 Glasses

Sulfide Solid Electrolyte with Favorable Mechanical Property for All-Solid-State Lithium Battery

Interfacial Observation between LiCoO2 Electrode and Li2S−P2S5 Solid Electrolytes of All-Solid-State Lithium Secondary Batteries Using Transmission Electron Microscopy†