Hard carbons for sodium-ion batteries and beyond

Abstract

Sodium-ion batteries (SIBs) are one of the most promising alternatives to lithium-ion batteries (LIBs), due to the much more abundant resources of Na compared with Li in the world. Developing SIB technology to satisfy the increased demand for energy storage is therefore a significant task . However, one of the biggest bottlenecks is the design of high-performance and low-cost anode materials, since the graphite anode in commercial LIBs is not suitable for SIBs due to thermal dynamic issues. Hard carbon materials have been regarded as having the greatest potential as anodes in commercial SIBs owing to their excellent cost-effectiveness, but their relatively limited performance compared to the graphite in LIBs as well as the dimness of the sodium storage mechanisms still need further investigation. In this review, we summarize the progress of recent research into hard carbons for SIB applications, including the fundamentals of SIBs, sodium storage mechanisms, structures and the electrochemical performances of different types of hard carbons in SIBs and other types of sodium-based energy storage as well as the main challenges in this field. We aim to provide a general insight into hard carbons and their applications in SIBs, opening up future perspectives and possible research directions.

Defects in Hard Carbon: Where Are They Located and How Does the Location Affect Alkaline Metal Storage?

“…[ 7,38,39,74 ] The effect of surface, interlayer distance, pore size, carbon morphology, defects, and heteroatoms will be dependent on pyrolysis/carbonization temperature (with less surface area, fewer defects, and more graphitic character observed with increasing pyrolysis temperature) and the initial reagents (where oxygen and nitrogen dopants can be introduced to tune material properties). [ 21,27,36,39,75 ] Additionally, the main contribution to Li storage in HC comes from intercalation, with initial contribution from surface adsorption as confirmed by in situ Raman analysis of Li in HCs. [ 33,65,76–79 ] For KIBs, the graphitic stacks’ interlayer distances accessible to Na + and Li + storage can be inaccessible, with greater interlayer distances required.…”

Insights into the sodiation mechanism of hard carbon-like materials from electrochemical impedance spectroscopy

“…17,18,26,27 So far, the common view on the sodiation mechanism of HCs is mainly based on the results of charge/discharge and cyclic voltammetry measurements combined with (ex situ) structural analysis. 9,20,28,29 Another characterization tool that is widely applied for the investigation of practically all kinds of electrochemical processes is electrochemical impedance spectroscopy (EIS). 30 Though, more detailed insights into the sodiation process of hard carbons might be gained from EIS, the possibilities of this method have not been exploited to their full extent yet.…”

A review on the Use of Carbon Nanostructures as Anodes of Na-ion batteries

“…Na-iyon pillerde teorik özgül kapasite bir bileşiğin Na + iyonu depolama kapasitesini belirlemek için kullanılmaktadır. Maksimum teorik özgül enerji elektrotta gerçekleşen tepkime türüne, stokiyometriye ve bileşik molar ağırlığa göre değişmektedir [8]. Bir elektrot malzemesinin teorik özgül kapasitesi (Q t ) mAh/g cinsinden aşağıdaki denklemde belirtilen Faraday Yasası ile hasaplanmaktadır:…”

“…Burada I (mA) şarj/deşarj akımını, Δt saat cinsinden şarj/deşarj süresini ve m ise g cinsinden aktif malzemenin kütlesini ifade etmektedir. Elektrotların gerçekte ulaşabileceği kapasite değerleri, karbon esaslı malzemelerde morfoloji, gözenek yapısı, kristalografi ve kusurlar gibi birçok özellik ile değişmektedir [8]. Bir Na-iyon pil tam hücresinin gravimetrik enerji yoğunluğu, voltaj ve özgül kapasite değerlerinin sonucu olarak elde edilir ve teorik enerji yoğunluğu aşağıda belirtildiği gibi Gibb serbest enerjisinden faydalanılarak bulunmaktadır.…”

“…Kapasitenin deşarj hızı ile ilişkisini gösteren Peukert yasası ise bir elektrokimyasal hücrenin deşarj hızı açısından iletilen kapasitesini tanımlar. Artan hızlarda veya akım yoğunluklarında, mevcut kapasitenin azaldığı ve hücrenin daha az kullanılmasına neden olduğu bilinmektedir ve ampirik bir formül olarak geliştirilen Peukert yasası aşağıdaki gibi yazılabilir: [8,[11][12][13]. Her bir şarj-deşarj döngüsünden sonra geri kazanılmayan kapasite, tersinir olmayan kapasite olarak tanımlanır ve parazitik tepkimelere ve gerçekleşen yüzey mekanizmalarına bağlıdır.…”