Redox‐Active Metal‐Centered Oxalato Phosphate Open Framework Cathode Materials for Lithium Ion Batteries

Abstract

Discovering revolutionary cathode materials for lithium ion batteries (LIBs) with a high power/energy density to confront the existing energy, economic, and ecologic crises is one of the persistent challenges in materials research. [1] The most promising olivine phosphate LiMPO 4 electrode materials (M = Fe, Mn, or Co) [2] have already attained maximum capacity through the development of new synthetic methods, such as downsizing, [3] conductive wiring, [3b, 4] and doping. [5] Recently, hierarchical olivine-based materials produced by soft synthetic strategies have been shown to have higher bulk density, superior performance at high rates, and better cycling stability. [6] Besides commercialization of olivine phosphates, current research is also focused on enhancing the performance of LIBs for high-current applications by developing new electrode materials. Many alternative candidates, such as Li 3 M 2 (PO 4 ) 3 , [7] Li 2 MSiO 4 , [8] LiMSO 4 F, [9] LiMBO 3 [1d, 10] (M = Fe, V, Mn, Co, etc.) LiVOPO 4 , [11] LiVPO 4 F, [12] and Li 2 FeP 2 O 7 [13] have been pursued as cathode materials. Further to these inorganic materials, new organic [14] and metal-organic framework [15] (MOF) materials have also shown promise as electrode materials for LIBs. The major challenges ahead in the utilization of MOFs as electrode materials for LIBs are the high molecular weight, low density, difficulty of synthesizing large quantities, and challenging isolation of robust MOFs with redox-active metal centers, compared to inorganic materials. [15a,c] These drawbacks may delay their utilization and commercialization as cathode materials.For this reason, it is worthwhile to investigate energy storage in an entirely new class of phosphate-based hybrid materials. [16] Metal organic-phosphate open frameworks (MOPOF) are hybrid materials with multidimensional architectures constructed from transition-metal phosphates crosslinked by simple organic linkers, which in turn can encapsulate a diverse range of alkali ions (Li + , Na + , and K + ) between the layers.Though MOPOFs are well known for their structural diversity and for conventional industrial applications, such as redox reactions, catalysis, gas storage, and MRI contrast agents, these materials have not been investigated as energy storage materials. [17] The presence of mixed organic oxalate and inorganic phosphate anions is expected to enhance the redox properties of the transition-metal ions, provide robustness to the material, and reduce the synthesis temperature required, along with the versatility offered by the organic ligands. Furthermore, the synthetic simplicity of MOPOFs with redox-active metal centers and the possible two-dimensional migration pathways for M + ions (deduced from careful analysis of the packing patterns of the reported crystal structures) motivated us to investigate these MOPOFs as cathode materials for LIBs. Herein, we disclose for the first time the lithium storage performance of MOPOFs K 2.5 [(VO) 2 (HPO 4 ) 1.5 (PO 4 ) 0.5 (C 2 O 4 )], 1, Na 2 [(VO...

Studies on Bare and Mg-doped LiCoO2 as a cathode material for Lithium ion Batteries

“…Galvanostatic cycling using Bitrode battery tester (USA) was done to evaluate the performance of the battery via. charge-discharge cycling at ambient temperature, with further details given in [28][29][30].…”

Metal–Organic Frameworks Containing Missing‐Linker Defects Leading to High Hydroxide‐Ion Conductivity

“…Nevertheless, the connectivity of the clusters diminish from twelve in the originalf rameworks 1-3 down to eleven for the 1@KOH and 3@KOH systemsa nd ten for the 2@KOH material, as can be deduced from the elemental analysis and the increased accessibility to the porous structure as concluded from N 2 adsorption (see detailsi nr eference [12]). All theses tructural modificationsw ere expected to have ap ositive impacto nt he ionm obility of the hydroxide ions, as ac onsequence of the higher porosity of the materials and increased basicity and hydrophilicity (see below) of the [Ni 8 (OH) 5 (EtO)] 10 + clusters after the treatment with KOH/EtOH. In this regard, since the measurement of the ion conductivity of these materials is carried out in the form of pressed pellets, we carried out as tudy on the effect of the mechanical stress on the structure of these materials by pressing them up to 0.2 GPa.…”

“…[10] Moreover,t he effect of the deliberate introduction of defects as am eanst ob oost the ionic conductivity of MOFs hasonly been poorly studied. [11] The current report is focused on the study of ionic-conductivity characterization of the previously reported face-centered cubic (fcu)[ Ni 8 (OH) 4 (H 2 O) 2 (BDP_X) 6 ]( H 2 BDP_X = 1,4-bis(pyrazol-4-yl)benzene-4-X with X = H( 1), OH (2), NH 2 (3)) MOFs and their related modified materials K[Ni 8 (OH) 5 (EtO)(BDP_X) 5.5 ] (1@KOH, 3@KOH)a nd K 3 [Ni 8 (OH) 3 (EtO)(BDP_O) 5 ]( 2@KOH), which contain missing-linker defects, obtained after ap ost-synthetic treatment with solutions of KOH in ethanol (Figure 1). These modified materials have already been proven by us to boost carbon-capture properties as ac onsequence of their enhanced pore accessibility as ar esult of their missing-linker defect nature and increased basicity of the deprotonated [Ni 8 (OH) 5 (EtO)] 10 + clusters (Figure 1).…”

“…[11] The current report is focused on the study of ionic-conductivity characterization of the previously reported face-centered cubic (fcu)[ Ni 8 (OH) 4 (H 2 O) 2 (BDP_X) 6 ]( H 2 BDP_X = 1,4-bis(pyrazol-4-yl)benzene-4-X with X = H( 1), OH (2), NH 2 (3)) MOFs and their related modified materials K[Ni 8 (OH) 5 (EtO)(BDP_X) 5.5 ] (1@KOH, 3@KOH)a nd K 3 [Ni 8 (OH) 3 (EtO)(BDP_O) 5 ]( 2@KOH), which contain missing-linker defects, obtained after ap ost-synthetic treatment with solutions of KOH in ethanol (Figure 1). These modified materials have already been proven by us to boost carbon-capture properties as ac onsequence of their enhanced pore accessibility as ar esult of their missing-linker defect nature and increased basicity of the deprotonated [Ni 8 (OH) 5 (EtO)] 10 + clusters (Figure 1). [12] We show now that this structural modification also leads to as ignificant enhancement of the hydroxide ion conductive properties of up to four orders of magnitude as ac onsequence of their missing-linker defects, increased basicity,a nd hydrophilicity of the KOH treated materials.…”

“…[3] Ta king all the above, it is of high interesttodevelop efficient hydroxide-ion conducting materials in order to integratet hem into anion-exchange membranes. In this regard, an ew class of highly designable crystalline porousm aterials, namely metalorganicf rameworks (MOFs), is receiving ac onsiderable amount of attention due to its possible application as advancede lectronic conductive materials, [4] electrodes, [5] and ionconducting materials.…”