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

In the previous paper Ralph Brodd and Martin Winter described the different kinds of batteries and fuel cells. In this paper I will describe lithium batteries in more detail, building an overall foundation for the papers that follow which describe specific components in some depth and usually with an emphasis on the materials behavior. The lithium battery industry is undergoing rapid expansion, now representing the largest segment of the portable battery industry and dominating the computer, cell phone, and camera power source industry. However, the present secondary batteries use expensive components, which are not in sufficient supply to allow the industry to grow at the same rate in the next decade. Moreover, the safety of the system is questionable for the large-scale batteries needed for hybrid electric vehicles (HEV). Another battery need is for a high-power system that can be used for power tools, where only the environmentally hazardous Ni/ Cd battery presently meets the requirements. A battery is a transducer that converts chemical energy into electrical energy and vice versa. It contains an anode, a cathode, and an electrolyte. The anode, in the case of a lithium battery, is the source of lithium ions. The cathode is the sink for the lithium ions and is chosen to optimize a number of parameters, discussed below. The electrolyte provides for the separation of ionic transport and electronic transport, and in a perfect battery the lithium ion transport number will be unity in the electrolyte. The cell potential is determined by the difference between the chemical potential of the lithium in the anode and cathode, ∆G ) -EF. As noted above, the lithium ions flow through the electrolyte whereas the electrons generated from the reaction, Li ) Li+ + e-, go through the external circuit to do work. Thus, the electrode system must allow for the flow of both lithium ions and electrons. That is, it must be both a good ionic conductor and an electronic conductor. As discussed below, many electrochemically active materials are not good electronic conductors, so it is necessary to add an electronically conductive material such as carbon * To whom correspondence should be addressed. Phone and fax: (607) 777-4623. E-mail: stanwhit@binghamton.edu. 4271 Chem. Rev. 2004, 104, 4271−4301

http://www.chemie.uni-regensburg.de/Anorganische_Chemie/Vortrag/StudentenWS06-07/Vortrag_Amereller.pdf

Lithium Batteries and Cathode Materials

Energy storage is more important today than at any time in human history. Future generations of rechargeable lithium batteries are required to power portable electronic devices (cellphones, laptop computers etc.), store electricity from renewable sources, and as a vital component in new hybrid electric vehicles. To achieve the increase in energy and power density essential to meet the future challenges of energy storage, new materials chemistry, and especially new nanomaterials chemistry, is essential. We must find ways of synthesizing new nanomaterials with new properties or combinations of properties, for use as electrodes and electrolytes in lithium batteries. Herein we review some of the recent scientific advances in nanomaterials, and especially in nanostructured materials, for rechargeable lithium-ion batteries.

Nanomaterials for rechargeable lithium batteries

Li-ion battery materials: present and future

Lithium batteries: Status, prospects and future

Improved capacity retention in rechargeable 4 V lithium/lithium- manganese oxide (spinel) cells

Anodes of Li4MnsO12, Li4Ti5012, and Li2Mn409 with a spinel-type structure have been evaluated in room-temperature lithium cells. The cathodes that were selected for this study were the stabilized spinels, Li1.03Mnl.g704 and LiZnoo25Mn1.9504, and layered LiCoO2. The electrochemical data demonstrated that Li + ions will shuttle between two transition-metal host structures (anode and cathode) at a reasonably high voltage with a concomitant change in the oxidation state of the transition metal cations so that the Li § ions do not reduce to the metallic state at the anode during charge. These cells reduce the safety hazards associated with cells containing metallic-lithium, lithium-alloy, and lithium-carbon anodes.

https://iopscience.iop.org/article/10.1149/1.2059324/pdf

Spinel Anodes for Lithium‐Ion Batteries

The electrochemical and structural properties of spinel phases in the Li-Mn-O system are discussed as insertion electrodes for rechargeable lithium batteries. In this paper the performance of button-type cells containing electrodes from the Li{sub 2}O yMnO{sub 2} system, e.g., the stoichiometric spinel Li{sub 4}Mn{sup 5}O{sub 12}(y = 2.5) and the defect spinel Li{sub 2}Mn{sub 4}O{sub 9}(y = 4.0), is highlighted and compared with a cell containing a standard LiMn{sub 2}O{sub 4} spinel electrode.

A. De Kock

Papers

Improved capacity retention in rechargeable 4 V lithium/lithium- manganese oxide (spinel) cells

Spinel Anodes for Lithium‐Ion Batteries

Spinel Electrodes from the Li‐Mn‐O System for Rechargeable Lithium Battery Applications

Structural aspects of lithium-manganese-oxide electrodes for rechargeable lithium batteries

Synthesis and structural characterization of defect spinels in the lithium-manganese-oxide system