Boosting Sodium Storage of Double‐Shell Sodium Titanate Microspheres Constructed from 2D Ultrathin Nanosheets via Sulfur Doping

Abstract

with abundant natural resources, much lower cost, and ubiquitous presence around the globe. Therefore, sodiumion batteries (SIBs) are expected to be the most promising candidates as nextgeneration batteries. [1,2] The commercial LIB anode (graphite), however, exhibits extremely poor sodium storage (capacity of only 31 mAh g −1 ) in ester-based electrolytes, and has a low insertion voltage (close to 0 V, which easily causes sodium plating and arouses safety concerns), which largely restricts it in practical use in SIBs. [2][3][4] Alloying and conversion-type materials also suffer from huge volume changes during cycling that will lead to electrode pulverization and thus capacity fading. [5][6][7] Therefore, searching for suitable anodes with high capacity, long cycling stability, and high rate capability is the critical issue for bringing SIBs into practical application.As a typical Ti-based compound, sodium titanate (Na 2 Ti 3 O 7 ) comprises zigzag layers of titanium and oxygen octahedral, where 3.5 Na ions per formula unit can be easily inserted into the interlayer space, resulting in a capacity of 310 mAh g −1 . [8] In addition, Na 2 Ti 3 O 7 displays the lowest average Na intercalation potential (0.3 V for Na + insertion, but above the voltage for the formation of Na dendrites) compared to the reported insertion-type oxides, which is beneficial for achieving high operating voltage and energy density in full batteries. [9,10] In particular, the large interlayered spacing of ≈0.83 nm is favorable for the charge storage properties and the diffusion of electrolyte ions. [11][12][13][14] Notwithstanding, there are still some shortcomings of Na 2 Ti 3 O 7 anode [15][16][17][18][19] : i) the low electronic conductivity caused by the large bandgap (3.7 eV) results in ineffective charge transport and thus limits the rate performance of SIBs; [8][9][10][11] ii) the aggregation and overlapping of Na 2 Ti 3 O 7 layers due to the large surface energy leads to fast capacity decay during Na + insertion/extraction; [15] and iii) the stability and lifetime concerns aroused by the volume expansion upon Na uptake are still an obstacle to the use of Na 2 Ti 3 O 7 in large-scale SIB application. [8] To address these issues, a series of effective strategies have been developed, including widening the interlayer spacing of Na 2 Ti 3 O 7 , [16] regulating the morphology on the nanoscale, [8,10,12] and using carbonaceous materials as a conductive matrix. [14,17] Sodium-ion batteries (SIBs) have drawn remarkable attention due to their low cost and the practically inexhaustible sodium sources. The major obstacle for the practical application of SIBs is the absence of suitable negative electrode materials with long cycling stability and high rate performance. Here, sulfur-doped double-shell sodium titanate (Na 2 Ti 3 O 7 ) microspheres constructed from 2D ultrathin nanosheets are synthesized via a templating route combined with a low-temperature sulfurization process. The resulting double-shell microspheres deliver a high specific capaci...

A Selective Reduction Approach to Construct Robust Cu1.81S Truss Structures for High-Performance Sodium Storage

“…In addition, the intrinsically low conductivity severely impedes the electron and ion migration, leading to sluggish Na + diffusion kinetics and poor rate performance. To address these concerns, structural design of TMSs (e.g., hollow structures, [20][21][22][23][24] multi-shell structures, 4,[25][26][27] heterostructures [28][29][30][31][32][33] ) has been widely adopted. However, although these strategies can inhibit volume expansion and accelerate the transport of ions and electrons, it is still difficult to achieve a high rate capability while simultaneously obtaining stable cycling performance (over 1,000 cycles).…”

Tailored Synthesis of Coral‐Like CoTiO3/Co3O4/TiO2 Nanobelts with Superior Lithium Storage Capability

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Advancements and Challenges in Potassium Ion Batteries: A Comprehensive Review

“…For instance, the graphite volume changes in KIBs while K + insertion process is over six times greater than during the Li + insertion in LIBs. In the case of alloying and conversion type anodes for KIBs, the volume changes are even worse (a few hundred percentage), leading to electrode pulverization, and poor cycling performances . Accelerated secondary reactions, due to the low electrochemical voltage of potassium, is another major concern of KIBs; which results in excessive consumption of electrolytes and eventually lead to capacity fading.…”