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

Each cell of a battery stores electrical energy as chemical energy in two electrodes, a reductant (anode) and an oxidant (cathode), separated by an electrolyte that transfers the ionic component of the chemical reaction inside the cell and forces the electronic component outside the battery. The output on discharge is an external electronic current I at a voltage V for a time Δt. The chemical reaction of a rechargeable battery must be reversible on the application of a charging I and V. Critical parameters of a rechargeable battery are safety, density of energy that can be stored at a specific power input and retrieved at a specific power output, cycle and shelf life, storage efficiency, and cost of fabrication. Conventional ambient-temperature rechargeable batteries have solid electrodes and a liquid electrolyte. The positive electrode (cathode) consists of a host framework into which the mobile (working) cation is inserted reversibly over a finite solid–solution range. The solid–solution range, which is...

The Li-ion rechargeable battery: a perspective.

2.1. Solvents 4307 2.1.1. Propylene Carbonate (PC) 4308 2.1.2. Ethers 4308 2.1.3. Ethylene Carbonate (EC) 4309 2.1.4. Linear Dialkyl Carbonates 4310 2.2. Lithium Salts 4310 2.2.1. Lithium Perchlorate (LiClO4) 4311 2.2.2. Lithium Hexafluoroarsenate (LiAsF6) 4312 2.2.3. Lithium Tetrafluoroborate (LiBF4) 4312 2.2.4. Lithium Trifluoromethanesulfonate (LiTf) 4312 2.2.5. Lithium Bis(trifluoromethanesulfonyl)imide (LiIm) and Its Derivatives 4313

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Nonaqueous liquid electrolytes for lithium-based rechargeable batteries.

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

Research Development on Sodium-Ion Batteries

Li/graphite and Li/petroleum coke cells using a in a 50:50 mixture of propylene carbonate (PC) and ethylene carbonate (EC) electrolyte exhibit irreversible reactions only on the first discharge. These irreversible reactions are associated with electrolyte decomposition and cause the formation of a passivating film or solid electrolyte interphase on the surface of the carbon. The amount of electrolyte decomposition is proportional to the specific surface area of the carbon electrode. When all the available surface area is coated with the film of decomposition products, further decomposition reactions stop. In subsequent cycles, these cells exhibit excellent reversibility and can be cycled without capacity loss.

https://iopscience.iop.org/article/10.1149/1.2086855/pdf

Studies of Lithium Intercalation into Carbons Using Nonaqueous Electrochemical Cells

We report electrochemical and x-ray-diffraction studies of the intercalation of lithium in graphite and in disordered carbons. The phase diagram of electrochemically intercalated graphite agrees well with previous work on samples prepared by chemical methods. The well-known staged phases present in intercalated graphite are absent in intercalated petroleum coke. Furthermore, the voltage V(x) of Li/${\mathrm{Li}}_{\mathit{x}}$${\mathrm{C}}_{6}$ cells differs greatly when graphite or coke is used as the host. By heating coke to successively higher temperatures, we are able to increase the graphitization or crystalline order of the host in a continuous fashion and study the effect of this variation on the phase diagram of ${\mathrm{Li}}_{\mathit{x}}$${\mathrm{C}}_{6}$ and on V(x). We find that staged phases are suppressed at room temperature for hosts less ordered than a ``critical disorder.'' A lattice-gas model with random site energies is used to model the effects of host disorder and qualitatively explains the suppression of staged phases and the changes in V(x) with increasing disorder in the host. For a rectangular ``density of sites,'' staged phases are suppressed when the width of the site energy distribution is greater than the magnitude of the mean-field attractive Li-Li interaction, which causes island growth and staging in intercalated graphite.

Suppression of Staging in Lithium-Intercalated Carbon by Disorder in the Host

The charge and discharge mechanisms of Li/FeS{sub 2} and Li/Li{sub 2} FeS{sub 2} cells near room temperature are studied by in situ x-ray diffraction and in situ {sup 57}Fe Mossbauer spectroscopy. The electrochemical behavior of these cells are compared, and their cell reactions are described, For 0{lt}x{le}0.8, the cycling behavior of Li{sub 2 {minus} x} FeS{sub 2} is reversible. However, for x{gt}0.8, structural decomposition of Li{sub 2 {minus} x} FeS{sub 2} occurs, and disproportionation to nonstoichiometric FeS (FeS{sub y}) and S is observed. Similarly, when Li/FeS{sub 2} cells are recharged to 2.8V, the cathode is a mixture of FeS{sub y} and S. Examination of the mixture by differential scanning calorimetry shows that FeS{sub y} and S react to form FeS{sub 2} above 200{degrees}C. This explains why high temperature Li/FeS{sub 2} cells reversibly while ambient temperature Li/FeS{sub 2} cells show poor reversibility.

https://iopscience.iop.org/article/10.1149/1.2096426/pdf

Electrochemistry of Pyrite‐Based Cathodes for Ambient Temperature Lithium Batteries

Lithiated nickel dioxide cathode-active materials for electrochemical cellsaving the formula Li x Ni 2-x-y M y O 2 , with x being between about 0.8 and about 1.0, M being one or more metals selected from cobalt, iron, chromium, titanium, manganese and vanadium, and y being less than about 0.2, with the proviso that y is less than about 0.5 for cobalt, which material is substantially free of lithium hydroxide and lithium carbonate. The materials are prepared by providing a substantially homogeneous dry intermediate mixture of a starting material containing a nickel compound selected from nickel oxide, nickel hydroxide, and mixtures thereof, and optionally including one or more oxides or hydroxides of a transition metal selected from cobalt, iron, chromium, titanium, manganese and vanadium, together with between about a 10 and about a 25% stoichiometric excess of lithium hydroxide. The mixture is heat treated at a temperature above about 600° C. in an atmosphere substantially free of carbon dioxide and having a partial pressure ratio of oxygen to water vapor greater than about 15, after which any lithium hydroxide or lithium carbonate present in the mixture is removed. Thermally stable lithiated nickel dioxide having a BET surface area less than about 3.0 m 2 /g, and is also disclosed, as well as electrochemical cells prepared from the disclosed lithiated nickel dioxides.

Lithiated nickel dioxide and secondary cells prepared therefrom

A rechargeable battery of alkali metal, organic elec-trolyte type has a low surface area particulate carbona-ceous electrode (20) intercalable with the alkali metal and experiences little capacity loss upon intercalation of the carbonaceous electrode with the alkali metal. The carbona-ceous electrode (20) may include a multi-phase composi-tion including both highly graphitized (70) and less graphi-tized (80) phases or may include a single phase, highly graphitized composition which has been subjected to inter-calation of lithium at above about 50°C. Incorporation of an electrically conductive filamentary material (80) such as carbon black intimately interspersed with the carbona-ceous composition (70) minimizing capacity loss upon re-peated cycling.

Rosamaria Fong

Papers

Studies of Lithium Intercalation into Carbons Using Nonaqueous Electrochemical Cells

Suppression of Staging in Lithium-Intercalated Carbon by Disorder in the Host

Electrochemistry of Pyrite‐Based Cathodes for Ambient Temperature Lithium Batteries

Lithiated nickel dioxide and secondary cells prepared therefrom

Carbonaceous electrodes for lithium cells