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Bismuth (Bi) possesses an ultrahigh theoretical volume capacity (3800 mAh cm−3) and low embedding potential stimulated considerable attention as anodes for sodium‐ion batteries (SIBs). However, its practical application is still hampered by the huge volume variation during the charge/discharge process. To settle this issue, Bi@C nanosheet arrays (Bi@C‐NSA) are fabricated on copper foam via a facile galvanic replacement followed by in situ polymerization of dopamine and an annealing procedure. The carbon‐coated nanosheet array structure not only accommodates the volume expansion during cycling and maintains electrode stability, but also facilitates rapid electron/ion transport. Due to the unique structural design, this Bi@C‐NSA exhibits an impressive capacity of 315.72 mAh g−1 after 1500 cycles under 1 A g−1. Furthermore, a series of in situ/ex situ techniques reveal that this Bi@C‐NSA possesses superior reaction kinetics and undergoes a typical alloying/dealloying storage mechanism. Furthermore, Bi@C‐NSA also achieves commendable reversible capacity and cycling stability in a wide temperature range (0 °C–60 °C). Notably, the assembled Na3V2(PO4)3//Bi@C‐NSA full cell demonstrates a capacity of 325 mAh g−1 after 50 cycles at 0.05 A g−1, which promises for practical applications. This galvanic replacement strategy spearheads a way to prepare nanoarray electrodes and will accelerate the development of sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

A sodium bis(fluorosulfonyl)imide (NaFSI)‐based multifunctional electrolyte is developed by partially replacing NaPF6 salt in the electrolyte to improve the wide temperature range working capability of NaNi1/3Fe1/3Mn1/3O2/hard carbon (NNFM111/HC) sodium‐ion batteries (SIBs). The capacity retention of the SIBs with NaFSI‐NaPF6 dual salt electrolyte increases from 47.2 % to 75.5 % after 250 cycles at 25 °C, and from 51.0 % to 82.3 % after 80 cycles at 45 °C, and the 1 C discharge capacity retention at the low temperature of −20 °C also increases 26.8 %. In the single salt system, NaPF6 effectively passivate the aluminum foil and NaFSI passivate the electrode/electrolyte interface. The synergistic effect of NaPF6 and NaFSI greatly improves the battery performance in a wide temperature range. This NaFSI‐based dual salt electrolyte also effectively overcomes the flaws when the SIBs using NaFSI or NaPF6 independently, and makes it more suitable for SIBs, indicating promising prospects in the commercial application of NNFM111/HC SIBs. [ABSTRACT FROM AUTHOR]

The lithium‐ion batteries (LIBs) with high nickel cathode have high specific energy, but as the nickel content in the cathode active material increases, batteries are suffering from temperature limitations, unstable performance, and transition metal dissolution during long cycling. In this work, a functional electrolyte with P‐phenyl diisothiocyanate (PDITC) additive is developed to stabilize the performance of LiNi0.8Co0.1Mn0.1O2 (NCM811)/graphite LIBs over a wide temperature range. Compared to the batteries without the additive, the capacity retention of the batteries with PDITC‐containing electrolyte increases from 23 % to 74 % after 1400 cycles at 25 °C, and from 15 % to 85 % after 300 cycles at 45 °C. After being stored at 60 °C, the capacity retention rate and capacity recovery rate of the battery are also improved. In addition, the PDITC‐containing battery has a higher discharge capacity at −20 °C, and the capacity retention rate increases from 79 % to 90 % after 500 cycles at 0 °C. Both theoretical calculations and spectroscopic results demonstrate that PDITC is involved in constructing a dense interphase, inhibiting the decomposition of the electrolyte and reducing the interfacial impedance. The application of PDITC provides a new strategy to improve the wide‐temperature performance of the NCM811/graphite LIBs. [ABSTRACT FROM AUTHOR]

A functional electrolyte containing propyl 4-methylbenzenesulfonate (PMBS) additive is developed to improve the performance of the LiNi0.8Co0.1Mn0.1O2 (NCM811)/graphite pouch full cells, especially the cycling lifetime under low temperature. It is indicated that the addition of PMBS into the electrolyte facilitates the formation of stable and low impedance interfacial films of the NCM811 cathode and graphite anode due to the preferential decomposition of PMBS over solvent molecules. Compared to the cells without additives, the cells containing 2% PMBS exhibit enhanced performance, and the capacity retention rate increases from 55.97% to 87.20% after 1200 cycles at 25 °C. And under the temperature condition of −10 °C, the capacity retention rate increases from 55.37% to 98.02% after 100 cycles, indicating the unique effect of PMBS on the low-temperature cycling performance of high-nickel lithium-ion batteries. [ABSTRACT FROM AUTHOR]