can suppress the polysulfide shuttling and exhibit excellent redox electrocatalytic properties for lithium polysulfides decomposition. The batteries with heterostructure-modified separators show a high initial discharge capacity of 1068.4 mAh g −1 at 0.5 C, excellent rate performances (719.6 mAh g −1 at 5C), and a remarkable cycling ability. Even with a high sulfur loading of 6.4 mg cm −2 , the pouch cell can deliver an areal capacity of 5.54 mAh cm −2 at 0.2 C. This work not only provides a new route for preparing SA-catalysts, but also sheds new lights into engineering electronic structures of heterointerfaces for developing high-performance Li-S batteries.

Heat generation, accumulation, and runaway severely affect the practical applications of lithium-ion batteries (LIBs) using Ni-rich Ni/Co/Mn ternary cathode materials. In principle, the aforementioned thermal characteristics of a LIB are mainly determined by the heat generation power of the cathode and anode materials during charging/discharging. In this work, the heat generation power of the LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode material coated with and without reduced graphene oxide (rGO) is studied systematically. By coupling an electrochemical workstation with a multichannel microcalorimeter, the heat generation power of NCM811 under different charging/discharging conditions was measured on coin cells. Meanwhile, a theoretical model was also proposed to analyze the intrinsic factors of the NCM811 that possibly affect its heat generation power during electrochemical charging/discharging. The results show that the particle size, lithium-ion diffusion coefficient, specific heat capacity, thermal conductivity, and electric conductivity can all affect the heat generation power. Different from that, the particle size and the lithium-ion diffusion coefficient of NCM811 are the dominating factors. It is demonstrated further that by coating rGO onto NCM811, the lithium-ion diffusion coefficient of NCM811 is improved, and the heat generation power is reduced accordingly. KEYWORDS: heat generation power, LiNi 0.8 Co 0.1 Mn 0.1 O 2 , cathode, lithium-ion diffusion coefficient, reduced graphene oxide

The operation temperature is one of the key factors affecting the electrochemical reactions and further performances of secondary-ion batteries. In this work, the electrochemical reactions of the SnO 2 nanoparticles supported on reduced graphene oxide (SnO 2 /rGO) as an anode in sodium-ion batteries at the operating temperatures from 10 to 50 °C are systematically investigated. It is illustrated that the alloying reaction between metallic Sn and Na + is hard to take place at relatively lower temperature (10 °C), and there is dead tin accumulated at relatively high temperature (50 °C) during sodiation/desodiation, which results in the lower specific capacity of SnO 2 /rGO for sodium storage. The reason why the alloying reaction takes place hardly at low temperature is mainly attributed to the severe polarization of electrodes, but not the low diffusion coefficient of Na + within tin. The formation of dead tin at 50 °C arises from the agglomeration of larger SnO 2 nanograins in which the Sn generated during the sodiation cannot be fully oxidized during the following desodiation process forming finally the dead Sn after long-term cycling.

The heat generation power of an electrode is one of the key factors affecting the operation safety and even the electrochemical performances of lithium-ion batteries. Herein, the heat generation power of a LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode at different cycling stages at an elevated temperature (50 °C) is studied. The internal and external factors, such as Li+ diffusion coefficient and Li+/Ni2+ cation mixing, affecting probably the heat generation are elaborated experimentally and theoretically. It is illustrated that the cation mixing of Li+/Ni2+ occurred during charge/discharge cycling reduces severely the diffusion coefficient of Li+ in NCM811 that accounts further for the increase in the as-generated heat amount and the heat generation power of the NCM811 with the cycling process.

Volume variation, pulverization, and dead Sn accumulation that occur during lithiation/delithiation cycling are the main drawbacks of using SnO2 particles as anodes in lithium ion batteries (LIBs). In this work, we fabricated [001]-oriented SnO2 nanorods with different thicknesses (55–105 nm) on carbon cloth and sealed them with a layer of partially reduced graphene oxide (rGO@SnO2@CC). Through systematic evaluation, we found that in the thinnest SnO2 nanorods (≲55 nm), there is no dead Sn observed after 100 cycles of lithiation/delithiation in LIBs. The pulverization of the thinnest SnO2 nanorod as an anode is also greatly suppressed. In contrast, the pulverization of SnO2 nanorods and severe aggregation of dead Sn occurred in the thicker SnO2 (75 and 105 nm), which severely affects its electrochemical performance. The property of the rGO@SnO2@CC with thinner SnO2 nanorods makes it a promising anode material for LIBs. The work should also be beneficial for the development of SnO2-based anode materials for LIBs.