Closo‐Borate Gel Polymer Electrolyte with Remarkable Electrochemical Stability and a Wide Operating Temperature Window

Abstract

A major challenge in the pursuit of higher-energy-density lithium batteries for carbon-neutral-mobility is electrolyte compatibility with a lithium metal electrode. This study demonstrates the robust and stable nature of a closo-borate based gel polymer electrolyte (GPE), which enables outstanding electrochemical stability and capacity retention upon extensive cycling. The GPE developed herein has an ionic conductivity of 7.3 × 10 −4 S cm −2 at room temperature and stability over a wide temperature range from −35 to 80 °C with a high lithium transference number (t + Li = 0.51). Multinuclear nuclear magnetic resonance and Fourier transform infrared are used to understand the solvation environment and interaction between the GPE components. Density functional theory calculations are leveraged to gain additional insight into the coordination environment and support spectroscopic interpretations. The GPE is also established to be a suitable electrolyte for extended cycling with four different active electrode materials when paired with a lithium metal electrode. The GPE can also be incorporated into a flexible battery that is capable of being cut and still functional. The incorporation of a closo-borate into a gel polymer matrix represents a new direction for enhancing the electrochemical and physical properties of this class of materials.

Polymorphism, ionic conductivity and electrochemical properties of lithium closo-deca- and dodeca-borates and their composites, Li2B10H10–Li2B12H12

“…44 This material was used for preparation of a gel-based electrolyte with a wide operating temperature range, which formed the basis for a flexible and functional battery. 45…”

“…44 This material was used for preparation of a gel-based electrolyte with a wide operating temperature range, which formed the basis for a exible and functional battery. 45 The ionic conductivities of selected composites of (1 À x) Li 2 B 12 H 12 -xLi 2 B 10 H 10 , i.e. s9, s12 and s15, compared to the heat treated (T ¼ 380 C and p(H 2 ) ¼ 450 bar) sample s4 and s8 are shown in Fig.…”

Enhanced Electrochemical Performance of the Li2B12H12-Li2B10H10-LiBH4 Electrolyte

“…Closo -borates, such as Li 2 B 12 H 12 and Li 2 B 10 H 10 , were observed as typical intermediates during the hydrogen sorption reaction of LiBH 4 , and show great chemical and thermal stability. − Regarding the low ionic conductivity of 10 –8 S cm –1 at RT, , various approaches have been developed to improve the conduction properties, e.g., ball milling, , the creation of polymer-based electrolytes, , interface engineering, and building anion-mixed composite . In our previous work, a composite of Li 2 B 12 H 12 -5Li 2 B 10 H 10 shows the enhanced ionic conductivity of 10 –5 S cm –1 at RT, attributing to a formation of hydrogen-deficient γ-Li 2 B 10 H 10– x . , …”

Selective Functionalization of Carbonyl Closo-Decaborate [2-B10H9CO]− with Building Block Properties via Grignard Reagents

“…The closo -borate anions [B n H n ] 2− (n = 6–12), particularly the closo -decaborate [B 10 H 10 ] 2− , represent one of the most multifaceted and appealing compounds in polyhedral architecture [ 1 , 2 , 3 ]. Their physiochemical properties, such as thermodynamic stability [ 4 ], electrochemical properties [ 5 , 6 ], three-dimensional aromaticity [ 3 ], modulated biological compatibility [ 7 , 8 ], as well as their tunable hydrophobicity have encouraged their integration in a wide spectrum of applications ranging from metal complexation [ 9 ], medicine [ 7 ] and catalysis [ 10 ] to material sciences [ 11 , 12 , 13 ], solid-state batteries [ 14 , 15 , 16 ] and hydrogen storage [ 17 , 18 ]. Functionalized or derivatized compounds of the polyhedral boron clusters are often regarded as versatile and circumventive building blocks, particularly in the biomedical field.…”