Hybrid Aqueous/Nonaqueous Water‐in‐Bisalt Electrolyte Enables Safe Dual Ion Batteries

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.201905838. Recently, a new class of aqueous electrolytes named "waterin-salt (WiS)" formulated with superconcentrated lithium salts Dual ion batteries (DIBs) have recently attracted ever-increasing attention owing to the potential advantages of low material cost and good environmental friendliness. However, the potential safety hazards, cost, and environmental concerns mainly resulted from the commonly used nonaqueous organic solvents severely hinder the practical application of DIBs. Herein, a hybrid aqueous/nonaqueous water-in-bisalt electrolyte with both broad electrochemical stability window and excellent safety performance is developed. The lithium-based DIB assembled using KS6 graphite and niobium pentoxide as the active materials in the cathode and anode exhibits good comprehensive performance including capacity, cycling stability, rate performance, and medium discharge voltage. Initial capacities of ≈47.6 and 29.6 mAh g −1 retention after 300 cycles can be delivered with a medium discharge voltage of around 2.2 V in the voltage window of 0-3.2 V at the current density of 200 mA g −1 . Good rate performance for the battery can be indicated by 29.7 mAh g −1 discharge capacity retention at 400 mA g −1 . It is noteworthy that the coulombic efficiency of the battery can reach as high as 93.9%, which is comparable to that of the corresponding DIBs using nonaqueous organic electrolytes.www.advancedsciencenews.com

The Applications of Water‐in‐Salt Electrolytes in Electrochemical Energy Storage Devices

“…Compared to organic electrolyte, the limited ESW of WISE brings a challenge on the choice of electrode materials for DIBs. [ 28 ] Placke et al. used H1N1 (1–5.1 V vs Li/Li + ) as WISE, and selected LiTi 2 (PO 4 ) 3 as the anode, and graphite as the cathode material, building a DIB.…”

“…Compared to organic electrolyte, the limited ESW of WISE brings a challenge on the choice of electrode materials for DIBs. [28] Placke et al used H1N1 (1-5.1 V vs Li/Li + ) as WISE, and selected LiTi 2 (PO 4 ) 3 as the anode, and graphite as the cathode material, building a DIB. [54] The initial discharge capacity of the assembled DIB performed 42 mAh g −1 and 71% retention after 500 cycles at 200 mA g −1 under 1.5 V discharge voltage.…”

“…[ 2,15,19–24 ] Obviously, there are some disadvantages of WISEs hindering their practical applications compared to traditional aqueous electrolytes and organic electrolytes: 1) The high viscosity and low conductivity compared with the traditional dilute electrolytes will deteriorate the rate performance of the devices employing WISEs; 2) the high cost of WISEs caused by high concentration and ionic liquids commonly used is a key factor limiting their industrial application; 3) the strong corrosivity of some WISEs resulting from the high concentration puts forward higher requirements for the current collectors, diaphragms, and packaging materials; 4) WISEs have poor wettability to the electrodes, which will increase the impedance of the devices, deteriorate the cycling performance and lead to the longer time for the electrolyte injection process; 5) the low temperature application of WISEs is limited by the salting‐out because of the decrease of solubility at lower temperatures. [ 25–30 ] Therefore, the dedicated discussion on some studies focusing on solving these shortcomings of WISEs will be conducted in Section 3.…”

Design Strategies for High‐Voltage Aqueous Batteries

“…Zhang et al reported a water/PC hybrid electrolyte offering a wide electrochemical window up to 2.8 V, the intensified cation-anion association benefits the formation of electrode/ electrolyte interphase and stabilizes water molecules against the reduction (Figure 4d). [41] In view of high working voltage need of DIBs, Zhu et al developed a hybrid water/dimethyl electrolyte (0.65 mS cm À1 ) to support the operation of DIBs with 4.0 V voltage window, thus facilitating the practical application of DIBs, [42] the lithium-based DIB with KS6 graphite cathode, niobium pentoxide anode, and the aforementioned hybrid electrolyte exhibited an energy density of 100 Wh kg À1 .…”

Cracked bark-inspired ternary metallic sulfide (NiCoMnS4) nanostructure on carbon cloth for high-performance aqueous asymmetric supercapacitors

“…Electrochemical energy storage is one of the most commonly used energy-storage technologies available today. Lithium-ion (Li + ) batteries occupy a large proportion of the energy-storage market and are extensively used in electric vehicles and mobile electronic devices, such as cell phones, laptops, and digital cameras, on account of their high energy density, operating voltage, and safety and long lifetime [1][2][3][4][5][6][7][8]. However, the relatively low power density and limited and uneven distribution of Li resources are the main bottlenecks associated with Li + batteries [9,10].…”