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Interfacial importance and nanopore structures of single wall nanocarbons such as single wall carbon nanotube (SWCNT) and single wall carbon nanohorn (SWCNH) are described in terms of intermolecular interaction theory. The relationships between the nanopore structure and nanoconfinement effect for molecules and ions are shown using examples on supercritical H2 adsorption on SWCNT, quantum molecular sieving effect of SWCNT for H2 and D2 below 77 K, water structure and hydration structure of Rb, Cs, and Sr ions in nanopores of activated carbon fiber and SWCNH, and capacitance storage of SWCNH. The SWCNT produced by laser ablation shows upward-curved adsorption isotherm of H2 at 77 K, suggesting the presence of the strong sites. The adsorption amount of D2 on this SWCNT at 77 K was clearly larger than that of H2 by about 20% at 77 K due to quantum effect. The hydration number around Cs and Sr ions in 1.1 nm slit pores of ACF reduced by more than 20 %. The capacitance depended on the opening of SWCNH and charging time for organic electrolyte (C2H5)4NBF4 in propyrene carbonate.

The kinetics of lithium electroinsertion into a Pt/{lambda}-MnO{sub 2} thin-film electrode in a 10 mmol/dm{sup 3} LiCl solution was studied by ac impedance spectroscopy between 10{sup {minus}4} and 10{sup 2} Hz at 25 C. The interfacial charge-transfer process was found to be independent of the composition x in Li{sub x}Mn{sub 2}O{sub 4}, and the exchange current density was 1.3 {times} 10{sup {minus}6} A/cm{sup 2} irrespective of x, whereas the chemical diffusion coefficient, D{sub Li}, and the partial conductivity, {sigma}{sub Li}, of lithium depended greatly on x because of the effect of the thermodynamic enhancement factor, W. The {tilde D}{sub Li} value varied between 1.9 {times} 10{sup {minus}12} and 3.1 {times} 10{sup {minus}11} cm{sup 2}/s, reaching a minimum when x = 0.2 approximately. The {sigma}{sub Li} value was in the range from 2.8 {times} 10{sup {minus}6} to 1.2 {times} 10{sup {minus}5} S/cm. This low {sigma}{sub Li} value indicates the predominant contribution of electronic conductivity to the total conductivity of Li{sub x}Mn{sub 2}O{sub 4}, which is in the order of 10{sup {minus}4} S/cm. The results show that solid-state diffusion of Li{sup +} ions is a rate-determining process in the system. Application is to secondary batteries.

Kinetic properties of a Pt/{lambda}-MnO{sub 2} electrode for the electrochemical insertion of lithium ions were studied in t aqueous phase by cyclic voltammetry (CV) and potential step chronoamperometry (PSCA). The cyclic voltammogram showed that the electrochemical insertion reaction of lithium ions proceeds in two steps in the potential range between 0.6 and 0.98 V (vs. saturated calomel electrode). The chemical diffusion coefficients of lithium ions in the manganese oxide the authors evaluated from the PSCA data using a finite diffusion model. They were in the range of 6.6 {times} 10{sup {minus}11} to 1.4 {times} 10{sup {minus}10} cm{sup 2}/s, depending slightly on the applied potential. The activation energy of the diffusion was evaluated as about 44 kJ/mol from the temperature dependence of the PSCA. These results suggested that lithium ions diffuse by a hopping mechanism in the spinel phase. The diffusion coefficients, transfer coefficients, and standard rate constants also were estimated from the CV data. The diffusion coefficients agreed reasonable, well with those obtained by PSCA.

Equilibrium potentials of spinel-type manganese oxide, λ-MnO 2 , were measured in various aqueous solutions. The Pt/λ-MnO 2 electrode showed a near-Nernstian response to lithium ions and not to other alkali metal and alkaline earth metal ions in the concentration range between 3×10 -6 and 0.5 mol/dm.. The selectivity coefficents for lithium ions against sodium, and potassium ions and protons were found to be: log k LiNa pot =-4.8, log k LiK pot =-4.6, and log k LiH pot =+1.9. The equilibrium potential was stable and pH-independent over a wide pH range (pH 4 to 9.5) in a solution with a lithium ion concentration above 5 mmol/dm 3

Raman spectra of λ ‐ MnO 2 and LiMn 2 O 4 are characterized by two intense peaks at 593 and 628 cm − 1 . Although the Raman intensity of λ ‐ MnO 2 is generally much greater than that of LiMn 2 O 4 , the logarithm of the ratio of the intensity at 593 cm − 1 to that at 628 cm − 1 , log ( I 593 / I 628 ) has been found to be a good measure of the change of the lithium content, x, in Li x Mn 2 O 4 . The relationship between log ( I 593 / I 628 ) and the electrode potential (E) correlated well with that between E and x obtained by coulometric titration. In situ measurement of Li + electroinsertion into a Pt / λ ‐ MnO 2 electrode in an aqueous solution showed spectra similar to the ex situ spectra. The change in log ( I 593 / I 628 ) of the electrode equilibrated at each potential corresponded to the cyclic voltammogram. Raman spectroscopy could be one of the best in situ methods for analyzing the electrochemical reaction of spinel‐type manganese oxide with Li + . ©1998 The Electrochemical Society

Electrochemical insertion/extraction reactions of spinel-type manganese oxide with Li{sup +} ions have been extensively studied from the standpoint of the development of alternative materials for secondary batteries. electrochromic properties of thin manganese oxide films have been examined for application to electrochromic materials. Electrochromism of spinel-type manganese oxide accompanying an Li{sup +}-insertion in an aqueous phase was examined by visual light spectrometry. An absorbance spectrum for lithiated manganese oxide gave lower absorbance in the wave-length range < 700 nm than did an Li{sup +}-extracted one. The greatest difference was observed at {approximately} 450 nm and is explained by the difference between the spectra for Mn{sup 3+} and Mn{sup 4+}. A reversible change in absorbance at 450 nm occurred with the Li{sup +}-insertion/extraction reaction. Cyclic voltammetry indicated that the absorbance change couples with the electrochemical response of the manganese oxide to Li{sup +} ions.

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A hollandite-type manganese dioxide (HolMO), without foreign metal cations (K[sup +], NH[sup +][sub 4], Na[sup +]) in the (2 [times] 2) tunnel, was prepared directly by reacting LiMnO[sub 4] with Mn(NO[sub 3])[sub 2] in an H[sub 2]SO[sub 4] acidic solution. The HolMO belonged to a body-centered tetragonal system (space group 14.m) and could be expressed by the formula H[sub 4x]Mn[sub 8[minus]x]O[sub 16][center dot]yH[sub 2]O. A preliminary electrochemical study suggested that the HolMO is promising as the cathode for a lithium rechargeable battery.