Regulating the Zn deposition orientation is an efficient
way to
suppress Zn dendrites and stabilize Zn anodes in aqueous Zn ion batteries
(ZIBs). Few studies have been conducted to control Zn(002) deposition
by altering the Zn2+ solvation structure with a cosolvent.
Herein, the bifunctional high-polarity cosolvent hexamethylphosphoramide
(HMPA) is proposed in an aqueous electrolyte. It not only suppresses
the H2 evolution reaction via the reshaped Zn2+ solvation structure with decreased H2O activity but also
induces Zn(002) deposition with a hexagonal-close-packed morphology
due to the strong absorption ability of HMPA to Zn(002). With the
optimized electrolyte, Zn dendrites and the HER are suppressed and
an ultralong cycle life of 1500 cycles with 99.6% Coulombic efficiency
is achieved in Zn||Cu cells. Zn||NH4V5O10 and Zn||polyaniline full cells exhibit improved cycling
performances compared to that of the bare electrolyte. Our finding
provides a feasible and promising way to stabilize Zn anodes and promote
the commercial application of ZIBs.
The applications of Na metal batteries
(SMBs) are restricted owing
to the capacity attenuation and safety hazards during the cycling
process, while a rational design of the electrolyte is critical on
solving this problem. In this work, an electrolyte is designed by
adding 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (TTE)
into a 3.8 M sodium bis(fluorosulfonyl)imide/1,2-dimethoxyethane (NaFSI/DME)
electrolyte, forming the localized high-concentration electrolyte
(LHCE) for constructing a stable solid electrolyte interface (SEI)
for SMBs. Ab initio molecular dynamics (AIMD) results indicate that
the solvation degree of Na+ ions with DME molecules in
LHCE is lower than that in HCE, which leads to more FSI– anions but less DME molecules to decompose on the Na metal anode.
And the TTE could also decompose on the Na metal anode, which synergistically
builds a NaF-rich compact SEI with low surface resistance and good
mechanical property so that it is favorable for the transportation
of Na+ ions and suppression of the Na dendrite growth.
Therefore, the optimized LHCE electrolyte in SMBs exhibits an outstanding
electrochemical performance. This study provides an updated perspective
on the understanding and design of localized high-concentration electrolytes
for SMBs.
A lithium
metal anode and high nickel ternary cathode are considered
viable candidates for high energy density lithium metal batteries
(LMBs). However, unstable electrode–electrolyte interfaces
and structure degradation of high nickel ternary cathode materials
lead to serious capacity decay, consequently hindering their practical
applications in LMBs. Herein, we introduced N,O-bis(trimethylsilyl) trifluoro acetamide (BTA) as a multifunctional
additive for removing trace water and hydrofluoric acid (HF) from
the electrolyte and inhibiting corrosive HF from disrupting the electrode–electrolyte
interface layers. Furthermore, the BTA additive containing multiple
functional groups (C–F, Si–O, Si–N, and CN)
promotes the formation of LiF-rich, Si- and N-containing solid electrolyte
interfacial films on a lithium metal anode and LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode surfaces,
thereby improving the electrode–electrolytes interfacial stability
and mitigating the capacity decay caused by structural degradation
of the layered cathode. Using the BTA additive had tremendous benefits
through modification of both anode and cathode surface layers. This
was demonstrated using a Li||NMC811 metal battery with the BTA electrolyte,
which exhibits remarkable cycling and rate performances (122.9 mA
h g–1 at 10 C) and delivers a discharge capacity
of 162 mA h g–1 after 100 cycles at 45 °C.
Likewise, this study establishes a cost-effective approach of using
a single additive to improve the electrochemical performance of LMBs.
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