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Biomass-derived hard carbon is a promising anode material for sodium-ion batteries. However, ensuring the consistency of hard carbon poses a challenge due to the intricate properties of biomass precursors, impacting their large-scale and stable supply. In this study, we used a two-step acid treatment and a two-stage heat treatment process to modulate the properties of the biomass precursor and design the structure of hard carbon materials. During the acid treatment, the removal of both the amorphous region of cellulose and hemicellulose fosters the formation of additional graphite microcrystals while concurrently decreasing the specific surface area of the resulting hard carbon. Moreover, adjustments in the pre-carbonization conditions lead to the enlargement of the carbon interlayer spacing, reduction of open pores, and the introduction of more oxygen-containing groups into the carbon structure. As a result, the optimized sample demonstrates an impressive specific capacity of 342.4 mA h g−1 with an initial coulombic efficiency (ICE) of 87.19% at 30 mA g−1, sustaining a reversible capacity of 128.3 mA h g−1 at 10 A g−1. Additionally, the sodium storage mechanism of the resulting hard carbon material was confirmed to be "adsorption-intercalation-filling" by kinetics and structural evolution analysis. This work sheds light on the effective obtaining of biomass-derived hard carbon for enhanced sodium ion storage. [ABSTRACT FROM AUTHOR]

With the large-scale application of lithium-ion batteries (LIBs) in various fields, spent LIBs are considered one of the most important secondary resources. Few studies have focused on recycling anode materials despite their high value. Herein, a new efficient recycling and regeneration method of spent anode materials through the combination of thermal and wet metallurgical approaches and restored graphite performance is presented. Using this method, the lithium recycling ratio from spent anode materials reaches 87%, with no metal impurities detected in the leaching solution. The initial Coulombic efficiency of the recycled graphite (RG) materials is 90.5%, with a reversible capacity of 350.2 mAh/g. Moreover, RG shows better rate performance than commercial graphite. The proposed method is simple and efficient and does not involve toxic substances. Thus, it has high economic value and application potential in graphite recycling from spent LIBs. [ABSTRACT FROM AUTHOR]

Transition metal sulfides with designed nanostructures are expected to provide superior electrochemical performance when used as electrode materials for pseudocapacitors compared to their oxide counterparts. In this paper, hollow Co3S4 dodecahedra were successfully prepared using cobalt‐based zeolite imidazolium skeleton (ZIF‐67) as the precursor and thioacetamide (TAA) as the sulfur source combined with a facile one‐step vulcanization process. The hollow cavity structure not only shortens the carrier transport distance but also provides a higher specific surface area and abundant active sites, which promotes an efficient mass transfer process. In addition, the one‐step synthesis of hollow Co3S4 has greater advantages than the one‐step synthesis in terms of cost control and process simplification. The specific capacitance of the produced hollow Co3S4 nanopolyhedra was 668 F/g at 1 A/g and remained at 353 F/g at 10 A/g when used as a pseudocapacitor electrode, demonstrating its superior multiplication capability. In addition, the capacitance retention is 86.4% after 5000 cycles at 4 A/g, indicating its long cycle stability. Notably, employing commercial activated carbon as negative electrode and the as‐prepared hollow Co3S4 polyhedrons as positive electrode, the assembled asymmetry supercapacitor device delivers a high energy density of 20.7 Wh/kg at a power density of 716 kW/kg. The capacitance value of the device remains up to 81.4% after 2000 charging/discharging cycles. The simple synthesis process opens new opportunities to develop advanced hollow nanostructures exhibiting potential for various applications. [ABSTRACT FROM AUTHOR]

Affected by the monsoon climate,there are abrupt changes,non-smoothing and variation in monthly runoff.However,good accuracy cannot be realized if the monthly runoff is simulated and predicted directly by the gray self-memory model.This paper proposes a new monthly runoff smoothing method (that is,smoothing method without seasonal fluctuations).First,the seasonal index is used to remove the “seasonal fluctuations” of monthly runoff,then,the three-point smoothing method is applied to smooth the monthly runoff without seasonal fluctuations,and finally the gray self-memory model is adopted to simulate and predict the smoothed data.After being applied to the Yanling Hydrological Station in Hunan Province,the results show that the average error of fitting and forecasting value of monthly runoff after seasonal fluctuation removing and smoothing is less than 20% compared with the measured value.At the same time,the short-term monthly runoff data is used to simulate and forecast monthly runoff by this method,which also meets the requirements of the specification.