Enhancing high-rate plateau capacity of hard carbons by TiC-mediated closed pore formation and heterojunction engineering for sodium-ion batteries

Mild pretreatment synthesis of coal-based phosphorus-doped hard carbon with extended plateau capacity as anodes for sodium-ion batteries

Revealing the effect of hard carbon structure on the sodium storage behavior by using a model hard carbon precursor

Cross-linking matters: Building hard carbons with enhanced sodium-ion storage plateau capacities

Extended plateau capacity of phosphorus-doped hard carbon used as an anode in Na- and K-ion batteries

Synthesis strategies of hard carbon anodes for sodium-ion batteries

Toward high-performance hard carbon as an anode for sodium-ion batteries: Demineralization of biomass as a critical step

Tuning microstructures of hard carbon for high capacity and rate sodium storage

Ti, F Codoped Sodium Manganate of Layered P2-Na _0.7 MnO _2.05 Cathode for High Capacity and Long-Life Sodium-Ion Battery

Chemically modified lignin toward high-performance hard carbon anodes in sodium-ion batteries.

Biomass-derived hard carbon is a promising anode material for commercial sodium-ion batteries due to its low cost, high capacity, and stable cycling performance. However, the intrinsic tight lignocellulosic structure in biomass hinders the formation of sufficient closed pores, limiting the specific capacity of obtained hard carbons. In this contribution, a mild, industrially mature pretreatment method is utilized to selectively regulate biomass components. The hard carbon with a rich closed pore structure is prepared by optimizing the appropriate ratio of biomass composition. Optimized etching conditions enhanced the closed pore volume of hard carbon from 0.15 to 0.26 cm3 g-1. Consequently, the engineered hard carbon exhibited excellent electrochemical performance, including a high reversible capacity of 346 mAh g-1 with a high plateau capacity of 254 mAh g⁻¹ at 50 mA g⁻¹, robust rate capability, and cycling stability. The optimized hard carbon shows an 88 mAh g⁻¹ increase in plateau capacity compared to hard carbon from directly carbonizing bamboo fibers. This mature approach provides an easy-to-operate industrial pathway for designing high-capacity biomass-based hard carbons for sodium-ion batteries.

Hard carbon (HC) remains the most viable choice as a negative electrode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) owing to its higher energy density (discharge up to zero volts), higher capacity (distinct storage mechanisms), and cycling stability. Herein, a biomass jute fiber precursor HC anode (JPC) with varying porosity is reported for the first time as a low-cost and sustainable high-performance HC anode for SIBs and PIBs. Direct carbonization results in micro-meso porous HC (JPC-D), and micro-wave pretreated jute fiber results in ultramicroporous HC (JPC-M). The mesoporosity generated in JPC-D during synthesis outperforms the ultramicroporous JPC-M with a high reversible capacity of 328 mAh g-1 (iCE = 66%) at a current density of 30 mA g-1 (0.1C) with superior capacity retention of 84% after 100 cycles in SIBs. The Na+ ion and K+ ion storage in HCs, especially at lower voltages, shows distinct storage mechanisms that depend on the morphology and porosity of the material. JPC-D contributed 39% of its total capacity through the plateau region capacity (PRC), suggesting more pore filling from hierarchical porosity in SIBs. JPC-D and JPC-M exhibit more insertion-based capacity than pore-filling processes in PIBs. The presence of inorganic impurities (Ca, Si, Al, and Fe) encapsulated in the carbon structure plays a critical role in developing mesopores. The yield (%) of HC from direct carbonization per kilogram of jute is ∼34%, which makes it cheaper than HC from sugar-based precursors and 1.5 times more affordable than other biomass-derived HC. The jute-based micro-mesoporous HC is a novel, cost-effective, sustainable approach to designing HC for a PRC-based battery-type anode in SIBs and PIBs.

Developing hard carbon (HC) anodes with dual‐high slope capacity (Cs) and plateau capacity (Cp) is one of the most efficient ways to realize high energy and power Sodium‐ion batteries (SIBs). Herein, three cellulose‐derived HCs are prepared to investigate the precursor effects of crystallinity, side chains, and the oxygen‐containing functional groups on carbon structures. It is revealed that the precursor factors play different roles in regulating the carbon structures (e.g., microcrystal size, defect density, interlayer spacing, and closed pore). The effects of carbon structures on Cs/Cp are further explored, guiding the correction of the structure‐performance relationship. Considering sodium ion diffusion and storage, Cs is found to relate with microcrystal size, carbon layer spacing, and defect density. A structural factor µHC that has a linear relationship with Cs is proposed. Moreover, the Cp is found to show a linear relationship with the closed pore content. High µHC and closed pore content also lead to high Cs/Cp retentions under high currents. Therefore, the hydroxyethyl cellulose‐derived HC with high µHC and closed pore content simultaneously delivers high Cs/Cp (177.3/216.7 mAh g−1), exhibiting good rate and cycling performance in half cells. Furthermore, the assembled Ah‐level pouch cell also demonstrates high energy density and long cycle life.

Regulation plateau capacity and initial coulombic efficiency of furfural residues-derived hard carbon via components engineering

The induced formation and regulation of closed-pore structure for biomass hard carbon as anode in sodium-ion batteries

Sodium-ion batteries are increasingly being promoted as a promising alternative to current lithium-ion batteries. The substitution of lithium by sodium offers potential advantages under environmental aspects due to its higher abundance and availability. However, sodium-ion (Na-ion) batteries cannot rely on graphite for the anodes, requiring amorphous carbon materials (hard carbons). Since no established market exists for hard carbon anode materials, these are synthesised individually for each Na-ion battery from selected precursors. The hard carbon anode has been identified as a relevant driver for environmental impacts of sodium-ion batteries in a recent work, where a significant improvement potential was found by minimising the impacts of the hard carbon synthesis process. In consequence, this work provides a detailed process model of hard carbon synthesis processes as basis for their environmental assessment. Starting from a review of recent studies about hard carbon synthesis processes from different precursors, three promising materials are evaluated in detail. For those, the given laboratory synthesis processes are scaled up to a hypothetical industrial level, obtaining detailed energy and material balances. The subsequent environmental assessment then quantifies the potential environmental impacts of the different hard carbon materials and their potential for further improving the environmental performance of future Na-ion batteries by properly selecting the hard carbon material. Especially organic waste materials (apple pomace) show a high potential as precursor for hard carbon materials, potentially reducing environmental impacts of Na-ion cells between 10 and 40% compared to carbohydrate (sugar) based hard carbons (the hard carbon material used by the current reference work). Waste tyres are also found to be a promising hard carbon precursor, but require a more complex pre-treatment prior to carbonisation, why they do not reach the same performance as the pomace based one. Finally, hard carbons obtained from synthetic resins, another promising precursor, score significantly worse. They obtain results in the same order of magnitude as the sugar based hard carbon, mainly due to the high emissions and energy intensity of the resin production processes.