Rechargeable lithium-ion batteries of today operate by an electrochemical process that involves intercalation reactions that warrants the use of electrode materials having very specific structures and properties. Further, they are limited to the insertion of one Li per 3D metal. One way to circumvent this intrinsic limitation and achieve higher capacities would be the use of electrode materials in which the metal-redox oxidation state could reversibly change by more than one unit. Through the discovery of conversion or displacement reactions, it is possible to reversibly change by more than one unit. Further, the need for materials with open structures or good electronic ionic conductivity is eliminated, thus leading to a new area in materials for lithium ion battery. In this paper, we present a review enlightens new reaction schemes and their potential impact on applications.

We report the fabrication of a carbon-based high energy density Li-ion hybrid electrochemical capacitor (Li-HEC) from low cost and eco-friendly materials. High surface area (2448±20 m(2)  g(-1) ) activated carbon (AC) is derived from the environmentally threatening plant, Prosopis juliflora, and used as the positive electrode in a Li-HEC assembly. Natural graphite is employed as negative electrode and electrochemically pre-lithiated prior to the Li-HEC fabrication. The Li-HEC delivers a specific energy of 162.3 Wh kg(-1) and exhibits excellent cyclability (i.e., ∼79 % of initial capacity is retained after 7000 cycles). The superior electrochemical performance of Li-HEC benefits from the tube-like unique structural features of the AC. Also, the presence of a graphitic nanocarbon network improves the ion transport, and the formed micro- and meso-porous network acts as reservoir for the accommodation of charge carriers.

The discharge performance of lead-acid battery is improved by adding multi-walled carbon nanotubes (MWCNTs) as an alternate conductive additive in Negative Active Mass (NAM). We report that MWCNTs added to the negative electrode, exhibits high capacity, excellent cycling performances at 10-h rate, high rate partial state of charge (HRPSoC) cycling and various rates of discharge. It significantly reduces the irreversible lead sulfate on the NAM, increases the active material utilization and improves the electrode performance. The improvement of capacity and cyclic performance of the cell is attributed to the nanoscale dimension of the MWCNTs as additive. Subsequent characterization using high resolution transmission electron microscopy and scanning electron microscopy were carried out to understand the influence of MWCNTs on the negative electrode of lead-acid battery.

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