Physical and chemical sensor technologies developed at Lawrence Livermore National Laboratory

The increasing emphasis on envirorunental issues, waste reduction, and improved efficiency for industrial processes has mandated the development of new chemical and physical sensors for field or in-plant use. The Lawrence Livermore National Laboratory (LLNL) has developed a number of technologies for sensing physical and chemical properties. Table 1 gives some examples of several sensors. that have been developed recently for environmental, industrial, commercial or government applications. Physical sensors of pressure, temperature, acceleration, acoustic vibration spectra, and ionizing radiation have been developed. Sensors developed at LLNL for chemical species include inorganic solvents, heavy metal ions`, and gaseous atoms and compounds. Primary sensing technologies we have employed have been based on optical fibers, semiconductor optical or radiation detectors, electrochemical activity, micromachined electromechanical (MEMs) structures, or chemical separation technologies. The complexities of these sensor systems range from single detectors to more advanced micro-instruments on-a-chip. For many of the sensors we have developed the necessary intelligent electronic support systems for both local and remote sensing applications. Each of these sensor technologies are briefly described in the remaining sections of this paper

Effect of conducting additives on the properties of composite cathodes for lithium-ion batteries

In an attempt to achieve lithium-ion batteries with high rate capability, the effect of conducting additives with various shapes and contents on the physical and electrochemical performances was evaluated. Although the density of the cathode decreased upon the addition of the additives, the electrical conductivity and electrochemical performance were greatly improved. The composite cathodes with well-dispersed multi-walled carbon nanotubes (MWCNTs) exhibited excellent high rate capabilities and cyclabilities. In the case of cathode with 8 wt.% of MWCNTs (low density-LD), the highest discharge capacity of 136 mAh/g was obtained at 5 C-rate and capacity retention of 97% for 50 cycles was observed at 1 C-rate of discharge. The cathode with a mixture of 2 wt.% of Super P and 4 wt.% of MWCNTs (LD) also exhibits improved cycle performances. The volume changes in the charge and discharge processes were successfully controlled by the bundles distributed between the host particles.close8

Effect of MWCNT on the performances of the rounded shape natural graphite as anode material for lithium-ion batteries

Multi-walled carbon nanotube (MWCNT) with bundle-type morphology was introduced as a new functional additive working as a particle connector or an expansion absorber in the anodes of lithium-ion batteries. By controlling the dispersion process, the MWCNT bundles were successfully divided and dispersed between the host particles. The composite anode consisting of rounded shape natural graphite and 2 wt.% of MWCNT exhibited the capacity of 300 mAh g -1 at 3 C rate and excellent cyclability. The well-dispersed MWCNT bundles made it possible to relieve the large strains developed at high discharge C rates and to keep the electrical contact between the host particles during repeated intercalation/deintercalation. This study has also emphasized that when high C-rate applications of lithium-ion batteries are targeted, it is important to get optimum content of MWCNT as well as uniform dispersion of their bundles in the composite anodes.close3