Graphite is used commercially as the active material in lithium ion batteries, frequently as part of a graphite/SiOx composite. Graphite is used in conjunction with SiOx to overcome the limited energy density of graphite, and to lessen the adverse effects of volume expansion of Si. However, electrodes based on graphite/SiOx composites can be made with only 3–5 wt % SiOx because of the increased failure of electrodes with higher SiOx contents. Here, we developed a new polymer binder, by combining dopamine-grafted heparin with the commercial binder carboxymethyl cellulose (CMC)/styrene butadiene rubber (SBR), in order to more effectively hold the SiOx particles together and prevent disintegration of the electrode during charging and discharging. The crosslinking using acid-base interactions between heparin and CMC and the ion-conducting sulfonate group in heparin, together with the strong adhesion properties of dopamine, yielded better physical properties for the dopamine-heparin-containing CMC/SBR-based electrodes than for the commercial CMC/SBR-based electrodes, and hence yielded excellent cell performance with a retention of 73.5% of the original capacity, a Coulombic efficiency of 99.7% at 150 cycles, and a high capacity of 200 mAh g−1 even at 20 C. Furthermore, a full cell test using the proposed electrode material showed stable cell performance with 89% retention at the 150th cycle.
For practical, high-energy lithium ion batteries, we introduce an egg-shell structured LiCoO2, enabling a credible performance with a high cut-off potential of 4.4 V, simply prepared by only stirring in 0.5 mM Cu(NO3)2 aqueous solution at room temperature without costly heat treatment.
Fluoroethylene carbonate (FEC) was studied as an additive for the electrolyte in lithium ion batteries with the LiNi(LNMO) spinel cathode operating at a high potential beyond 4.7 V (vs. Li/Li + ). It was found that the FEC additive was electrochemically active for the 1 s t charge cycle on the LNMO cathode. The presence of a large amount of FEC (more than 40 vol%) in the electrolyte caused severe side reactions with abnormally long voltage plateaus. In contrast, when the electrolyte contained less than 30 vol% FEC , the surface of the LNMO cathode was stabilized by the formation of the solid-electrolyte interphase (SEI), leading to improved cyclability. However, the resistance from the SEI limited the rate capability because of sluggish lithium transportation through the SEI and electronic insulation between the particles in the electrode.
Fluoroethylene carbonate (FEC) was studied as an additive for the electrolyte in lithium ion batteries with the LiNi 0. 5 Mn 1. 5 O 4 (LNMO) spinel cathode operating at a high potential beyond 4.7 V (vs. Li/Li +). It was found that the FEC additive was electrochemically active for the 1 s t charge cycle on the LNMO cathode. The presence of a large amount of FEC (more than 40 vol%) in the electrolyte caused severe side reactions with abnormally long voltage plateaus. In contrast, when the electrolyte contained less than 30 vol% FEC , the surface of the LNMO cathode was stabilized by the formation of the solid-electrolyte interphase (SEI), leading to improved cyclability. However, the resistance from the SEI limited the rate capability because of sluggish lithium transportation through the SEI and electronic insulation between the particles in the electrode.
For lithium‐ion batteries (LIBs), MoS2, which has conversion reaction pathways that can accommodate lithium ions during charge, is a very special inorganic material that has a two‐dimensional planar structure similar to graphite. For reliable performance of high‐energy LIBs, Se–molybdenum chalcogenides with sulfide and selenide (Se–MC) were prepared via the incorporation of a carbon nanotube (CNT) conducting matrix to solve the crucial limitations of MoS2, which include poor electronic conductivity and severe volume changes during cycling. For the preparation of Se–MC/CNT, a facile, one‐pot synthetic method using molybdic acid, selenium dioxide, and thioacetamide, which are the precursors for molybdenum, selenide, and sulfide, respectively, and CNT was developed. A detailed investigation of the surfaces and crystal structures of the prepared samples was conducted using transmission electron microscopy and X‐ray photoelectron spectroscopy analyses. Furthermore, LIBs containing the Se–MC/CNT exhibited a significantly extended cycle life and an improved rate capability that revealed the synergetic effect of the CNTs and selenide for controlling the morphology.
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