Key Takeaways & Executive Findings
- •• Pitch-derived soft carbons with tunable structures were synthesized by carbonization at 600–1400 °C, revealing clear correlations between carbon microstructure and potassium storage performance. • The carbon obtained at 700 °C exhibited a high degree of disorder and large interlayer spacing, delivering a high reversible capacity of 329.4 mAh g−1 and an initial coulombic efficiency of 72.81%. • The low-potential plateau capacity correlates with carbon crystal size, while the sloping region capacity is linked to the degree of structural disorder, providing mechanistic insights into K+ storage. • The optimized carbon anode maintained a high capacity of 144.2 mAh g−1 at a high current rate of 5 C, demonstrating excellent rate capability for potassium-ion batteries.
Abstract
Potassium-ion batteries (PIBs) hold promise for large-scale energy storage, necessitating the development of high-performance anode materials. Carbons with the advantage of structural versatility, are recognized as the most promising anode materials for their commercialization, however the relationship between the carbon anode structure and its electrochemical performance remains unclear. A series of pitch-based soft carbons with different structures were fabricated using carbonization temperatures in the range 600–1400 °C, and their changes in carbon configuration and K-storage performance as a function of carbonization temperature were investigated. Correlations between the carbon crystal size and the low-potential plateau region capacity and between the degree of structural disorder of the carbons with their sloping region capacity were revealed. Among all samples, that obtained by carbonization at 700 °C had a relatively high degree of disorder and a large interlayer spacing, and had a high reversible capacity of 329.4 mAh g−1 with a high initial coulombic efficiency of 72.81%, and maintained a high capacity of 144.2 mAh g−1 at the current rate of 5 C. These findings improve our fundamental understanding of the K-storage process in carbon anodes, and thus facilitate the advance of PIBs.
1. Introduction
Lithium-ion batteries (LIBs) have been widely developed on a large scale in modern society, such as portable electronic devices and electric vehicles (EVs). However, the continuous consumption and the low content of lithium resources lead to the much-increased price of LIBs, which greatly restrict the further development of LIBs. Due to its resource abundance, low cost and relatively low redox potential of K+/K (−2.93 V vs. standard hydrogen electrode), potassium-ion batteries (PIBs) have been considered as a promising alternative to LIBs, especially in the field of large-scale energy storage.
Graphite, which is commonly used as the anode material in LIBs, can also be utilized to store potassium (K) in the form of KC8. This can provide a theoretical K-storage capacity of 279 mAh g−1 with a low-potential plateau region. However, because of the large ionic size of K+ (1.38 Å vs. 0.76 Å for Li+), a huge volume change of about 60% will occur during the storage of K+ in graphite with a small interlayer spacing (0.337 nm). Besides, the sluggish K+ kinetics leads to inadequate cycle stability and rate performance, which restricts the further development of PIBs.
Amorphous carbon materials have gained significant interest as low-cost, eco-friendly anode materials for PIBs due to their wide availability. These materials can be classified as either hard carbons or soft carbons, depending on their structure and electrochemical performance. Hard carbons have a highly disordered carbon structure, abundant defect sites, and the much larger interlayer spacing than graphite, which is beneficial to K+ transportation in the carbon structure. As a result, hard carbon anodes could deliver superior rate performance than graphite anodes. Nevertheless, the lack of regularly arranged carbon layers in hard carbons also results in a typical K-storage curve in a high-potential sloping region, which is unsuitable for practical application as anode materials. Soft carbons exhibit a higher disordered degree and larger interlayer spacing compared to graphite, while also possessing a higher level of graphitization and more regularly arranged carbon layers than hard carbons. Thus, it has been recognized as a promising candidate for anode materials in PIBs. The charge-discharge curves of soft carbons consist of a sloping region in high potential and a plateau region in low potential, leading to enhanced energy density and cycling stability.
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JIANG Ming-chi, SUN Ning, YU Jia-xu, WANG Ti-zheng, Razium Ali Somoro, JIA Meng-qiu, XU Bin (2025). Synthesis of pitch-derived carbon anodes for high-performance potassium-ion batteries. SinoTechIntel Verified Research. https://doi.org/10.1016/S1872-5805(NCM2024-39-06-05)
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
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Frequently Asked Questions
What is the significance of pitch-derived carbon anodes for potassium-ion batteries?
Pitch-derived soft carbons offer a low-cost, eco-friendly anode material with tunable structure, providing high reversible capacity and rate capability for potassium-ion batteries, making them promising for large-scale energy storage.
How does carbonization temperature affect the structure and performance of pitch-derived carbons?
Carbonization temperature in the range 600–1400 °C tunes the degree of disorder, interlayer spacing, and crystal size of the carbons. The sample carbonized at 700 °C showed optimal performance with high disorder and large interlayer spacing, yielding a reversible capacity of 329.4 mAh g−1 and high initial coulombic efficiency.
What are the key correlations between carbon structure and potassium storage?
The study revealed that the low-potential plateau capacity correlates with carbon crystal size, while the sloping region capacity is linked to the degree of structural disorder. These correlations provide mechanistic insights into K+ storage in carbon anodes.
What is the rate performance of the optimized pitch-derived carbon anode?
The optimized carbon anode (carbonized at 700 °C) maintained a high capacity of 144.2 mAh g−1 at a high current rate of 5 C, demonstrating excellent rate capability for potassium-ion batteries.
Why are soft carbons considered promising anode materials for PIBs?
Soft carbons combine a higher disordered degree and larger interlayer spacing than graphite, while having more regularly arranged carbon layers than hard carbons. This results in a sloping region at high potential and a plateau at low potential, leading to enhanced energy density and cycling stability.
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