Dendrites lithium alloys

Coin and Button Cell Commercial Systems. Initial commercialization of rechargeable lithium technology has been through the introduction of coin or button cells. The eadiest of these systems was the Li—C system commercialized by Matsushita Electric Industries (MEI) in 1985 (26,27). The negative electrode consists of a lithium alloy and the positive electrode consists of activated carbon [7440-44-0J, carbon black, and binder. The discharge curve is not flat, but rather slopes from about 3 V to 1.5 V in a manner similar to a capacitor. Use of lithium alloy circumvents problems with cycle life, dendrite formation, and safety. However, the system suffers from generally low energy density. 

There are some other matters that should be considered when comparing metallic lithium alloys with the lithium-carbons. The specific volume of some of the metallic alloys can be considerably lower than that of the carbonaceous materials. As will be seen later, it is possible by selection among the metallic materials to find good kinetics and electrode potentials that are sufficiently far from that of pure lithium for there to be a much lower possibility of the potentially dangerous formation of dendrites or filamentary deposits under rapid recharge conditions. 

Matsuda and co-workers [39-41] proposed the addition of some inorganic ions, such as Mg2+, Zn2+, In3+, Ga3+, Al3+,and Sn2+, to PC-based electrolytes in order to improve cycle life. They observed the formation of thin layers of Li/M alloys on the electrode surface during the cathodic deposition of lithium on charge-discharge cycling. The resulting films suppress the dendritic deposition of lithium [40, 41]. The Li/Al layer exhibited low and stable resistance in the electrolyte, but the... 

In a liquid-carbonate electrolyte, dendrites form on an elemental Lithium anode that can grow across the electrolyte to short-circuit a cell on repeated cycling. Therefore, carbon or an alloy buffered by carbon is used with a liquid electrolyte [8]. 

Some fusible alloys composed of Bi, Pb, Sn, and Cd exhibit good characteristics as material for the negative electrode of secondary lithium batteries. The alloy can absorb the lithium into the negative electrode during charge and it can release the absorbed lithium into the electrolyte as ions during discharge. Dendritic deposition... 

The mechanical mixing of silicon and graphite produces a composite of Q.8Sio.2 whose reversible capacity can be as high as 1039 mAh/g and after 20 cycles can still be 794 mAh/g. It seems that the introduced silicon can promote the diffusion of lithium into the interior of carbon materials and effectively prevent the production of dendrites. The increase in reversible capacity cannot be completely ascribed to the formation of Li,.Si alloy because silicon is present in part in the form of Si/O compounds, and therefore further investigation is required. 

The other negative electrode materials mainly include Al-based alloys, Pb-based alloys, and its oxides. Of course, Li metal can also be used as a negative electrode. However, the lithium metal rechargeable battery will not be discussed here, although great progress has been made, especially with the inhibition of lithium dendrite formation. 

Zinc can form alloys with Li, and the alloys can act as negahve electrode materials for lithium-ion batteries. Microstructure such as particle size, orientation, component composition, and porosity can be controlled, and also affects its electrochemical performance. Since lithium moves very fast in Zn-based alloys, the formation of lithium dendrites or fibers is mostly inhibited. Furthermore, some inert components can also be introduced to modify their electrochemical performance. 

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