Unlocking the potential of weberite-type metal fluorides in electrochemical energy storage

Sodium-ion batteries (NIBs) are a front-runner among the alternative battery technologies suggested for substituting the state-of-the-art lithium-ion batteries (LIBs). The specific energy of Na-ion batteries is significantly lower than that of LIBs, which is mainly due to the lower operating potentials and higher molecular weight of sodium insertion cathode materials. To compete with the high energy density of LIBs, high voltage cathode materials are required for NIBs. Here we report a theoretical investigation on weberite-type sodium metal fluorides (SMFs), a new class of high voltage and high energy density materials which are so far unexplored as cathode materials for NIBs. The weberite structure type is highly favorable for sodium-containing transition metal fluorides, with a large variety of transition metal combinations (M, M’) adopting the corresponding Na2MM’F7 structure. A series of known and hypothetical compounds with weberite-type structure were computationally investigated to evaluate their potential as cathode materials for NIBs. Weberite-type SMFs show two-dimensional pathways for Na+ diffusion with surprisingly low activation barriers. The high energy density combined with low diffusion barriers for Na+ makes this type of compounds promising candidates for cathode materials in NIBs

Selective recovery of lithium from seawater using a novel MnO2 type adsorbent III - benchmark evaluation

The granulation method of λ-MnO2 adsorbent employing chitin-based binder, which has efficient selectivity towards lithium ion, has been developed. The granules of ca. 1 – 2 mm with high resistance to the column operation for seawater (pH = 8.1) can be achieved. The laboratory scale column separation with the granulated adsorbent shows that lithium ions from seawater can be selectively recovered against the majority of co-existing cations. In addition, the elution of Mn from the adsorbent can be prevented. The benchmark column separation plant with seawater intake 200 L/h has been built and the whole process was verified and evaluated. The composition analysis of dried precipitated salts showed ca. 35 % efficiency of lithium recovery in the benchmark plant. In order to enhance the lithium recovery efficiency the following recovery steps are expected when routine techniques are applied

Selective recovery of lithium from seawater using a novel MnO2 type adsorbent. II – Enhancement of lithium ion selectivity of the adsorbent

A novel spinel-type manganese dioxide adsorbent has been developed for the selective recovery of Li+ from seawater. The adsorbent can be prepared from a lithium-rich component of spinel-type lithium dimanganese tetraoxide Li1.5Mn2O4, followed by ion exchange of Li+ by H+ with diluted hydrochloric acid. The X-ray analysis of the adsorbent suggests the adsorption-elution cycle of Li+ progresses under γ expansion-shrinking mechanism of the adsorbent. The adsorption of Li+ progresses via cation exchange, and the selective recovery of Li+ can be carried out, even when the large amount of Na+ coexists in seawater. The chromatographic selective recovery of Li+ from the artificial seawater shows that Li+ can be selectively adsorbed with remaining most of Na+ in the feed solution in the break through step, while Li+ of high purity can recover and concentrate into the elutant in the elution step