No abstract

Hard carbon is considered as one of the most promising anodes in sodium-ion batteries due to its high capacity, low cost, and abundant resources. However, the available capacity and low initial Coulombic efficiency (ICE) limits the practical application of hard carbon anode. This issue results from the unclear understanding of the Na storage mechanism in hard carbon. In this work, a series of hard carbons with different microstructures are synthesized through an "up to down" approach by using a simple ball-milling method to illustrate the sodium-ion storage mechanism. The results demonstrate that ball-milled hard carbon with more defects and smaller microcrystalline size shows less low-potential-plateau capacity and lower ICE, which provides further evidence to the "adsorption-insertion" mechanism. This work might give a new perspective to design hard carbon material with a proper structure for efficient sodium-ion storage to develop high-performance sodium-ion batteries.

Hard carbons are deemed to be promising anodes for commercialized sodium-ion batteries due to their abundant resources, low cost, and low-plateau potential (∼0.1 V versus Na+/Na). However, the practical application of hard carbon anodes has been hindered by their unstable long-time cycling performance. Herein, a hard carbon anode derived from a camellia (TS1300) seed shell exhibits a high reversible capacity of 299.1 mA h g−1 together with a superior stable capacity retention of 93.8% over 1000 cycles. Further experimental results reveal that the proper graphene interlayer spacing (0.375 nm) and graphitic-like nanodomain structure are critical to excellent electrochemical performance. Therefore, this hard carbon material derived from the camellia seed shell is a promising anode for high-performance sodium-ion batteries.

Aims Plantations play important roles in modifying regional carbon budget and maintaining regional carbon balance. In this study, we assessed larch plantation (Larix gmelinii var. principis-rupprechtii) carbon dynamics in Weichang County from a perspective of the forest biomass-soil-wood-products chain. Our objectives were to elucidate the carbon sink capacity of larch plantation and the influences of biomass, soil and wood product pools on carbon balance. Methods CO2FIX model was used to evaluate the carbon storage and flow of larch plantation over a time span of 120 years. Input data for model were derived from practical investigations and published papers. We validated the simulated results and found that this model was suitable in the region and the simulated results were reliable. Important findings (1) Soil was the largest carbon pool for larch plantation and the wood product pool had the smallest carbon storage. Meanwhile, carbon storage in wood products gradually increased with time. (2) In a rotation of 50 years from secondary poplar-birch forest to larch plantation, 250 t C•hm-2 was sequestrated by the larch plantation. 70% of the carbon was transferred into soil in the form of litter and logging slash and the other 30% was transferred into wood products. (3) Larch plantation was a carbon sink during most of its growing period and turned to temporary carbon source when it was harvested. Larch plantation could sequestrate about 0.3 t C•hm-2 •a-1 in the long term. Our results indicated the importance of wood product carbon pool in carbon dynamics of plantation, which facilitated our understanding in the carbon dynamics and capacity of plantation.