An example for ThTFA oxidation reaction

http://dx.doi.org/10.1016/j.jelechem.2007.11.034

Challenges Facing Lithium Batteries and Electrical Double-Layer Capacitors

http://onlinelibrary.wiley.com/store/10.1002/anie.201201429/asset/9994_ftp.pdf?v=1&t=h7kl03y6&s=31963e2a8782673a20be65d4d6991d07c262f719

Accessing the Synthetic Chemistry of Radical Ions

http://onlinelibrary.wiley.com/doi/10.1002/ejoc.201101071/abstract

Organic reactions involving radical cation and radical anion intermediates are synthetically powerful umpolung processes that enable electronically mismatched couplings between pairs of electron-rich or pairs of electron-poor organic fragments. Nevertheless, the adoption of these reactions as synthetic methods has been relatively slow in comparison with that of reactions involving more conventional reactive intermediates such as carbanions, carbocations, and neutral radicals. This Microreview provides a brief survey of radical ion chemistry and highlights the use of transition metal photocatalysis as a convenient means to investigate radical-ion-mediated transformations.

Applications of Metallocenes in Rechargeable Lithium Batteries for Overcharge Protection

http://jes.ecsdl.org/content/139/1/5

One problem encountered in the development of rechargeable lithium batteries is the protection of individual cells from overcharging. In this work the addition of metallocene derivatives to cell electrolytes to provide overcharge protection was investigated. Eleven ferrocene derivatives were studied in terms of their redox potentials and mass transport properties in electrochemical cells and “AA”‐size  rechargeable cells employing  in 50/50 volume percent propylene carbonate/ethylene carbonate (PC/EC) as the electrolyte. The chemical and electrochemical properties of these metallocene derivatives were also studied in terms of the chemical stability of the derivatives toward cell components and electrochemical reversibility in long‐term cycling studies. It was found that adsorption of one derivative, dimethylaminomethylferrocene, on the  electrode ( based on the Langmuir adsorption isotherm), blocked the intercalation of Li⁺ ions into the  electrode.

n‐Butylferrocene for Overcharge Protection of Secondary Lithium Batteries

http://jes.ecsdl.org/content/137/6/1856

Electrochemical Characterization of SEI-Type Passivating Films Using Redox Shuttles

http://jes.ecsdl.org/content/159/7/A1057.full.pdf+html?sid=f006219b-2c67-4fed-94d0-99ad7757ade6

substituents on ferrocene and Hammet coefficients

In situUV–visible spectroscopy: characterization of overcharge protection additives for secondary lithiumbatteries

http://www.sciencedirect.com/science/article/pii/S0378775399001792

In situ spectroscopic investigation of the anodic oxidation of 1,4-dimethoxybenzene at platinum electrodes

http://www.sciencedirect.com/science/article/pii/S0379677997038277

Surface Modification Patent - Stephen!

http://www.google.com/patents?id=6AgSAgAAEBAJ&pg=PA1&lpg=PA1&dq=khalil+amine&source=bl&ots=2bneVum69x&sig=77NOtn3gpnSpQqJqaGIHO3ZPqnU&hl=en&sa=X&ei=WWc_UI2aAefU2AWzuIHIDA&ved=0CC8Q6AEwAA#v=onepage&q=khalil%20amine&f=false

Polymerizable Additives as Redox Shuttles - Patent

http://www.google.com/patents?id=0WMWAAAAEBAJ&printsec=frontcover&dq=Redox+shuttles+for+high+voltage+cathodes&source=bl&ots=EK2uvNZGit&sig=mShPdCAdWb7aVcrylImgajejCas&hl=en&sa=X&ei=92Y_UI2hCqbe2AWWvICoDQ&ved=0CDcQ6AEwAzgU

2. A non-aqueous rechargeable lithium battery as claimed in claim 1 wherein the monomer additive comprises less than about 5% by volume of the mixture of liquid electrolyte and monomer.

3. A non-aqueous rechargeable lithium ion battery having a maximum operating charging voltage and overcharge protection comprising:

a lithium insertion compound cathode;

a lithium insertion compound anode;

a separator;

a non-aqueous liquid electrolyte incapable of polymerizing at voltages greater than the maximum operating voltage of the lithium ion battery such that the battery is protected during overcharge abuse; and

an aromatic additive mixed in said liquid electrolyte, said additive polymerizing at battery voltages greater than the maximum operating voltage thereby increasing the internal resistance of the lithium ion battery and protecting the battery during overcharge abuse.

Dahn's thianthrene redox shuttle

http://www.google.com/patents?id=qZQXAAAAEBAJ&printsec=frontcover&dq=Redox+shuttles+for+high+voltage+cathodes&source=bl&ots=pTckq6ntnI&sig=0-tTKcgF0J-o3qjM8s39TeEinm0&hl=en&sa=X&ei=2GQ_UMrOGoeq2gX6i4G4DQ&ved=0CEoQ6AEwCQ

18. A method for providing a rechargeable, electrochemical cell, comprising the steps of

providing an anode and a cathode,

providing an electrolyte in contact with said anode and said cathode; and

dissolving within said electrolyte a thianthrene based compound for acting as a redox shuttle reagent to provide overcharge protection to the cell.

19. A method for providing a rechargeable, electrochemical cell according to claim 18 wherein the step of providing an electrolyte includes the step of providing a Li salt dissolved in an organic solvent or a solvent mixture selected from ethers, carbonates esters, sulfones, ketones and lactones.

20. A method for providing a rechargeable, electrochemical cell according to claim 18 wherein the step of providing an electrolyte includes the step of providing a polymer electrolyte comprised of a Li salt, a polymer host and a plasticizer solvent.

21. A method for providing a rechargeable, electrochemical cell according to claim 18 wherein the step of providing a thianthrene containing compound includes the step of providing 2,7-diacetyl thianthrene.

Dahn's patent on fluorinated alkoxybenzene derivatives

http://www.google.com/patents?id=1RYCAgAAEBAJ&printsec=frontcover&dq=Redox+shuttles+for+high+voltage+cathodes&source=bl&ots=3pTaki2M4H&sig=S66F-BlIKxrSvwxEBAlllbaCaFs&hl=en&sa=X&ei=G2Y_UOSwLcm42wXv3IHIDQ&ved=0CC8Q6AEwAA

1. A rechargeable electrochemical cell comprising:

a positive electrode having at least one electroactive material having a recharged potential;

a negative electrode;

a charge-carrying electrolyte comprising a charge carrying medium and an electrolyte salt; and

a cyclable redox chemical shuttle comprising an aromatic compound substituted with at least one tertiary alkyl group and at least one halogenated alkoxy group, dissolved in or dissolvable in the electrolyte and having an oxidation potential above the recharged potential of at least one of the electroactive materials of the positive electrode principal electroactive material.

2. The cell according to claim 1, wherein at least one alkoxy group comprises a fluorinated alkoxy group.

3. The cell according to claim 2, wherein the partially fluorinated alkoxy group comprises from one to about four carbon atoms.

4. The cell according to claim 3, wherein the partially fluorinated alkoxy group(s) are selected from —OCH2F, —OCH2CF3, —OCH2CF2CF3, —OCH2CF2CF2CF3, —OCH2CF2CF2H and —OCH2CF2CFHCF3.

5. The cell according to claim 1, wherein the aromatic compound is substituted with at least two tertiary alkyl groups and at least two halogenated alkoxy groups.

6. The cell according to claim 1, wherein at least one tertiary alkyl group comprises a butyl group.

7. The cell according to claim 1, wherein the shuttle comprises a compound having the formula:

wherein R1 and R2 can each, independently, be H or a tertiary alkyl group with four to twelve carbon atoms, wherein at least one of R1 or R2 is a tertiary alkyl group, wherein each Rf can, independently, be H or a halogenated alkoxy group having the formula —OR′ where R′ is a halogenated alkyl group having up to 10 carbon atoms, and wherein at least one Rf is a halogenated alkoxy group.

Amine's patent on phosphonate redox shuttles

http://www.google.com/patents?id=Auv-AQAAEBAJ&pg=PA11&lpg=PA11&dq=Redox+shuttles+for+high+voltage+cathodes&source=bl&ots=wVbU5r1XK4&sig=2DusT_PibwmwGfJZWRq9q3t438U&hl=en&sa=X&ei=2GQ_UMrOGoeq2gX6i4G4DQ&ved=0CDIQ6AEwAQ#v=onepage&q=Redox%20shuttles%20for%20high%20voltage%20cathodes&f=false

Dahn's 2,5-di-tert-butyl-1,4-dimethoxybenzene patent

http://www.google.com/patents?id=EYaVAAAAEBAJ&printsec=frontcover&dq=Redox+shuttles+for+high+voltage+cathodes&source=bl&ots=eMYfFrnM5a&sig=wd70Otm0sspe242rxxr24UG9Zhw&hl=en&sa=X&ei=2GQ_UMrOGoeq2gX6i4G4DQ&ved=0CDsQ6AEwBA

1. A lithium ion cell electrolyte comprising a charge carrying medium, lithium salt and cyclable redox chemical shuttle comprising an aromatic compound substituted with at least one tertiary carbon organic group and at least one alkoxy group.
2. An electrolyte according to claim 1 wherein the charge carrying medium comprises ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane or combination thereof and the lithium salt comprises LiPF6, lithium bis(oxalato)borate or combination thereof.
3. An electrolyte according to claim 1 wherein the aromatic compound has a single organic ring.
4. An electrolyte according to claim 1 wherein the aromatic compound is substituted with two tertiary carbon groups, each tertiary carbon group independently having up to 12 carbon atoms.
5. An electrolyte according to claim 1 wherein the tertiary carbon group is tert-butyl.
6. An electrolyte according to claim 1 wherein the aromatic compound is substituted with two alkoxy groups, each alkoxy group independently having up to 10 carbon atoms.
7. An electrolyte according to claim 1 wherein the aromatic compound comprises 2,5-di-tert-butyl- 1 ,4-dimethoxybenzene.

Dahn's Phenothiazine Patent

http://www.google.com/patents?id=ftiZAAAAEBAJ&printsec=frontcover&dq=Redox+shuttles+for+high+voltage+cathodes&source=bl&ots=V318sPtkA3&sig=VypaNE89_PbRaUxiHHRS2bF1nqA&hl=en&sa=X&ei=2GQ_UMrOGoeq2gX6i4G4DQ&ved=0CDgQ6AEwAw

A cell according to claim 1 wherein the phenothiazine compound is substituted with one or more acyl, acyloxy, alkaryl, alkoxy, acetamido, amido, amino, aryl, aralkyl, alkyl carboxyl, aryl carboxyl, alkylsulfonyl, benzoyl, carbamoyl, carbamido, carboxy, cyano, formyl, halo, haloacetamido, haloacyl, haloalkylsulfonyl, haloaryl, hydroxyl, isothiocyanato, methylsulfonyloxyl, nitro, oxo, oxybenzoyl or phosphenoxy groups or combination thereof.

A cell according to claim 1 wherein the phenothiazine compound comprises 10-methyl-phenothiazine, 10-ethyl-phenothiazine, 3-chloro-10-ethyl-phenothiazine, 10-isopropyl-phenothiazine or 10-acetyl-phenothiazine or mixture thereof.

A cell according to claim 1 wherein the phenothiazine compound comprises 2-perfluoromethyl-phenothiazine, 2-chloro-10-methyl-phenothiazine, 2-ethyl-10-methyl-phenothiazine, 3-bromo-10-ethyl-phenothiazine, 3-chloro-10-methyl-phenothiazine, 3-iodo-10-methyl-phenothiazine, 10-methyl-phenothiazin-3-ol, 10-methyl-phenothiazin-3-ylamine, 2,10-dimethyl-phenothiazine, 3,10-dimethyl-phenothiazine, 3-methyl-10-ethyl-phenothiazine, 4,10-dimethyl-phenothiazine, 3,7,10-trimethyl-phenothiazine, 10-(2-chloroethyl)-phenothiazine, 10-formyl-phenothiazine, 10-methoxy-phenothiazine, 10-methoxymethyl-phenothiazine, 10-phenyl-phenothiazine, 10-propionyl-phenothiazine, 10-methyl-phenothiazine-4-carboxylic acid or mixture thereof.

A cell according to claim 1 wherein the phenothiazine compound comprises 2-cyano-10-perfluoromethylsulfonyl-phenothiazine, 2-methoxy-10-perfluoromethylsulfonyl-phenothiazine, 2-perfluoromethyl-10-perfluoromethylsulfonyl-phenothiazine, 10-perfluoromethyl-phenothiazine, 10-perfluoromethylsulfonyl-phenothiazine, 10-(1,1,1,2,3,3)-hexafluoropropyl-phenothiazine or mixture thereof.

BCN-BuPT

http://www.ingentaconnect.com/content/ben/loc/2012/00000009/00000003/art00011?token=00581c08a96421bbf79c6e58654624317b42316b74217e662a77535e4e2663433b393f6a333f256681955087

and

http://www.sciencedirect.com/science/article/pii/S0040403908005236

monoCN-EPT procedure

http://pubs.acs.org/doi/abs/10.1021/la8027226?source=chemport

dibromo-N-ethylphenothiazine crystal structure

http://journals.iucr.org/c/issues/1986/12/00/a26259/a26259.pdf

All-Organic Vapor Sensor Using Inkjet-Printed Reduced Graphene Oxide

Films of graphene oxide and reduced graphene oxide are printed onto a flexible plastic surface (see picture), using inkjet techniques, which are used to detect chemically aggressive vapors such as NO₂ and Cl₂. Vapors in the 100 ppm–500 ppb concentration range can be detected in an air sample without the aid of a vapor concentrator.

http://onlinelibrary.wiley.com/doi/10.1002/anie.200905089/abstract


Angew. Chem. Int. Ed. 2010, 49, 2154 –2157

Dispersion of Alkyl-Chain-Functionalized Reduced Graphene Oxide Sheets in Nonpolar Solvents

Alkyl chains were grafted onto reduced graphene oxide sheets to allow their dispersion in toluene, a common and representative nonpolar solvent. The grafting occurred on a variety of oxygen-containing functionalities already present on reduced graphene oxide, such as hydroxyl and epoxide groups. The structure and the defect density of the sheets were not significantly altered during the synthesis. When dispersed in water−toluene mixtures, phase transfer from the aqueous to the organic phase was observed upon grafting. In addition, the dry powder obtained readily disperses in common organic solvents without the assistance of any sonication treatment.

http://pubs.acs.org/doi/abs/10.1021/la2051614

Langmuir. 2012, 28, 6691−6697

Graphene-Based Conducting Inks for Direct Inkjet Printing of Flexible Conductive Patterns and Their Applications in Electric Circuits and Chemical Sensors

A series of inkjet printing processes have been studied using graphene-based inks. Under optimized conditions, using water-soluble single-layered graphene oxide (GO) and few-layered graphene oxide (FGO), various high image quality patterns could be printed on diverse flexible substrates, including paper, poly(ethylene terephthalate) (PET) and polyimide (PI), with a simple and low-cost inkjet printing technique. The graphene-based patterns printed on plastic substrates demonstrated a high electrical conductivity after thermal reduction, and more importantly, they retained the same conductivity over severe bending cycles. Accordingly, flexible electric circuits and a hydrogen peroxide chemical sensor were fabricated and showed excellent performances, demonstrating the applications of this simple and practical inkjet printing technique using graphene inks. The results show that graphene materials—which can be easily produced on a large scale and possess outstanding electronic properties—have great potential for the convenient fabrication of flexible and low-cost graphene based electronic devices, by using a simple inkjet printing technique.

http://nanocenter.nankai.edu.cn/script/nanocenter/PDF/Nano%20Res_2011_LH.pdf

Nano Res. 2011, 4(7): 675–684

Structural evolution during the reduction of chemically derived graphene oxide

The excellent electrical, optical and mechanical properties of graphene have driven the search to find methods for its large-scale production, but established procedures (such as mechanical exfoliation or chemical vapour deposition) are not ideal for the manufacture of processable graphene sheets. An alternative method is the reduction of graphene oxide, a material that shares the same atomically thin structural framework as graphene, but bears oxygen-containing functional groups. Here we use molecular dynamics simulations to study the atomistic structure of progressively reduced graphene oxide. The chemical changes of oxygen-containing functional groups on the annealing of graphene oxide are elucidated and the simulations reveal the formation of highly stable carbonyl and ether groups that hinder its complete reduction to graphene. The calculations are supported by infrared and X-ray photoelectron spectroscopy measurements. Finally, more effective reduction treatments to improve the reduction of graphene oxide are proposed.


http://www.nature.com/nchem/journal/v2/n7/abs/nchem.686.html

Nature Chemistry, 2010,

2,

 

581–587.

High-quality single-layer graphene via reparative reduction of graphene oxide

Reduction of graphene oxide (GO) is a promising low-cost synthetic approach to bulk graphene, which offers an accessible route to transparent conducting films and flexible electronics. Unfortunately, the release of oxygen-containing functional groups inevitably leaves behind vacancies and topological defects on the reduced GO sheet, and its low electrical conductivity hinders the development of practical applications. Here, we present a strategy for real-time repair of the newborn vacancies with carbon radicals produced by thermal decomposition of a suitable precursor. The sheet conductivity of thus-obtained single-layer graphene was raised more than six-fold to 350–410 S/cm (whilst retaining >96% transparency). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy revealed that the conductivity enhancement can be attributed to the formation of additional sp2-C structures. This method provides a simple and efficient process for obtaining highly conductive transparent graphene films.


http://www.springerlink.com/content/k127017578016174/

Nano Res. 2011, 4(5): 434–439

Highly Heat and Oxidation-Resistant Materials Prepared Using Silicon- Containing Thermosetting Polymers

Highly heat and oxidation-resistant materials prepared using the silicon-containing thermosetting polymer, poly[(phenylsilylene)ethynylene-1,3-phenyleneethynylene] [-Si(Ph)(H)-C􀀁C-C6H4-C􀀁C-] are summarized. This polymer is light, moldable, soluble in solvent, and highly heat resistant. It is prepared by the dehydrogenative cross-coupling reaction of the Si-H bond of phenylsilane and the C-H bond of 1,3 diethynylbenzene in the presence of base catalysts. Applications of the polymer to particularly composite and ceramic materials are reviewed. Other polymers with molecules containing [Si(H)~C􀀁C] units are discussed. The chemistry and possible applications of the [Si(H)~C􀀁C] unit are also discussed.


http://www.benthamscience.com/open/tomsj/articles/V005/152TOMSJ.pdf

The Open Materials Science Journal, 2011, 5, 152-161

Solvent effects on the charge storage ability in polypyrrole

Solvent e€ect on the charge storage ability of the polypyrrole have been studied in two di€erent ways: analyzing
both the ion-solvent and polymer-solvent interactions and by a multiple regression procedure. The first way was not sucient to explain all the results obtained. By the multiple regression, influence of the four di€erent variables of the solvents simultaneously has been obtained. Solvents having high dipole moments and low polarizability and having a high capacity to donate electrons are the best solvents among those investigated in this paper to obtain high charge storage abilities.


http://www.upct.es/~equimica/laboratorio/ArticulosenPDF/Electrochim.%20Acta/1999%20Electrochim.%20Acta%2044pg2053.pdf

Electrochimica Acta 44 (1999) 2053±2059

Challenges in the development of advanced Li-ion batteries: a review

http://pubs.rsc.org/en/content/articlepdf/2011/ee/c1ee01598b

Li-ion battery technology has become very important in recent years as these batteries show great promise as power sources that can lead us to the electric vehicle (EV) revolution. The development of new materials for Li-ion batteries is the focus of research in prominent groups in the field of materials science throughout the world. Li-ion batteries can be considered to be the most impressive success story of modern electrochemistry in the last two decades. They power most of today's portable devices, and seem to overcome the psychological barriers against the use of such high energy density devices on a larger scale for more demanding applications, such as EV. Since this field is advancing rapidly and attracting an increasing number of researchers, it is important to provide current and timely updates of this constantly changing technology. In this review, we describe the key aspects of Li-ion batteries: the basic science behind their operation, the most relevant components, anodes, cathodes, electrolyte solutions, as well as important future directions for R&D of advanced Li-ion batteries for demanding use, such as EV and load-leveling applications.

Studying the Characteristics of Polypyrrole and its Composites

Polypyrrole and its composites were prepared chemically using FeCl3 as an oxidant in aqueous and non-aqueous media. The effect of various solutions such as water, ethylacetate, acetonitrile, methylacetate, methanol, ethylmethylketone and surface active agents, poly (ethylene glycol) and poly (vinyl acetate) on the properties of product were studied. The electrically conducting polymer and its composites have been characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. The results indicate that the morphology, conductivity and structure of products are dependent on the type of solution and additive.

World Journal of Chemistry. 2007, 2 (2), 67-74.

http://idosi.org/wjc/2(2)07/3.pdf

Polymers with Tailored Electronic Structure for High Capacity Lithium Battery Electrodes

A conductive polymer is developed for solving the long-standing volume change issue in lithium battery electrodes. A combination of synthesis, spectroscopy and simulation techniques tailors the electronic structure of the polymer to enable in situ lithium doping. Composite anodes based on this polymer and commercial Si particles exhibit 2100 mAh g⁻¹ in Si after 650 cycles without any conductive additive.


Adv. Mater. 2011, 23, 4679–4683

http://onlinelibrary.wiley.com/doi/10.1002/adma.201102421/pdf

Selection of Conductive Additives in Li-Ion Battery Cathodes

The lithium-ion cell has been successively improved with adoption of new cathode electrochemistries, from LiCoO₂ to higher-capacity LiNi_1−xCo_xO₂ to lower cost LiNi_1−xCo_xO₂. The addition of conductive additives to cathode materials has been demonstrated to improve each type. Four systems have emerged as important cathodes in recent studies: (i) the spinel LiMn₂O₄, (ii) LiFePO₄, (iii) the “Gen 2” material, Li(Ni_0.8Co_0.15Al_0.05)O₂, and (iv) the Li(Ni_1/3Co_1/3Mn_1/3)O₂system. The architectures of model composite cathodes weregenerated using our prior approach in simulating packing of polydisperse arrangements; conductivity was then simulated for several realizations of each case. A key finding was that the conductive coatings significantly improve overall conductivity. Percolation was achieved for the volume fraction of active material (30%) in studied cases, which was larger than the percolation threshold (29%) for a 3D spherical particulate system. Neither surface nor bulk modifications of active-material particle conductivities seem desirable targets for improvement of laminate conductivity at present. As part of future work, trade-offs between conductivity and capacity will be considered. 



J. Electrochem. Soc. 154, A978 (2007)

http://dx.doi.org/10.1149/1.2767839

Electrical energy storage for transportation—approaching the limits of, and going beyond, lithium-ion batteries

Electrical energy storage for transportation—approaching the limits of, and going beyond, lithium-ion batteries

The escalating and unpredictable cost of oil, the concentration of major oil resources in the hands of a few politically sensitive nations, and the long-term impact of CO2 emissions on global climate constitute a major challenge for the 21st century. They also constitute a major incentive to harness alternative sources of energy and means of vehicle propulsion. Today’s lithium-ion batteries, although suitable for small-scale devices, do not yet have sufficient energy or life for use in vehicles that would match the performance of internal combustion vehicles. Energy densities 2 and 5 times greater are required to meet the performance goals of a future generation of plug-in hybrid-electric vehicles (PHEVs) with a 40–80 mile all-electric range, and all-electric vehicles (EVs) with a 300–400 mile range, respectively. Major advances have been made in lithium-battery technology over the past two decades by the discovery of new materials and designs through intuitive approaches, experimental and predictive reasoning, and meticulous control of surface structures and chemical reactions. Further improvements in energy density of factors of two to three may yet be achievable for current day lithium-ion systems; factors of five or more may be possible for lithium–oxygen systems, ultimately leading to our ability to confine extremely high potential energy in a small volume without compromising safety, but only if daunting technological barriers can be overcome.

Tryptophan Accelerated Electron flow

 http://www.sciencemag.org/content/320/5884/1760.full.pdf

Redox Shuttle Additives for Lithium-Ion Battery

Redox Shuttle Additives for Lithium-Ion Battery
Overcharge of lithium-ion batteries can be dangerous. Overcharge generally occurs when a
current is forced through a cell, and the charge delivered exceeds its charge-storing
capability.1-3 Overcharge of lithium-ion batteries can lead to the chemical and electrochemical
reaction of batteries components, rapid temperature elevation, self-accelerating reactions, and
even explosion. Redox shuttle additives have been proposed for overcharge protection of secondary lithium-ion batteries for decades.4-8 Generally, the redox shuttle molecule can be reversibly oxidized
and reduced at a defined potential slightly higher than the end-of-charge potential of the
cathode. This mechanism can protect the cell from overcharge by locking the potential of the
cathode at the oxidation potential of the shuttle molecules. The detailed mechanism is
shown in Figure 1. On the overcharged cathode surface, the redox shuttle molecule (S) is
oxidized to its (radical) cation form (S+), which, via diffusion across the cell electrolyte,
would be reduced back to its original or reduced state on the surface of the anode. The
reduced form would then diffuse back to the cathode and oxidize again. The “oxidationdiffusion-
reduction-diffusion” cycle can be repeated continuously due to the reversible nature of the redox shuttle to shunt the overcharge current. The redox shuttling mechanism at overcharge can be regarded as a controlled internal short, and the net result of the shuttling is to convert the overcharge electricity power into heat, which avoids the reactions that occur between the electrodes and electrolyte at high voltage. Redox shuttles can also be used for automatic capacity balancing during battery manufacturing and repair.

Organic compounds with heteroatoms as overcharge protection additives for lithium cells

Organic compounds with heteroatoms as overcharge protection additives for lithium cells

 Various organic compounds with heteroatoms (N, O, F, Si, P, S) were tested as overcharge protection additives for 4-V class lithium cells. It was found that trimethyl-3,5-xylylsilane exhibited preferable oxidation potential (Eox) as overcharge protection additive, and charge.discharge cycling efficiency (Eff) of lithium anode in electrolyte with arylsilanes was as high as tolyladamantanes, reported previously by us. From room temperature to 60 .C, Eox of trimethyl-3,5-xylylsilane decreased only 0.07V. Difference in Eox among regioisomers of tolyltrimethylsilanes is smaller than that among tolyladamantanes. 1H NMR and UV spectra suggest the steric repulsion between tolyl group and trimethylsilyl group in o-tolyltrimethylsilane is smaller than that of the related substituents of o-tolyladamantane.

 2006 Elsevier B.V. All rights reserved.