Marinite Li₂Ni(SO₄)₂ as a New Member of the Bisulfate Family of High-Voltage Lithium Battery Cathodes

Abstract

Development of sustainable, economic, and high-voltage cathode materials forms the cornerstone of cathode design for Li-ion batteries. Sulfate chemistry offers a fertile ground to discover high-voltage cathode materials stemming from a high electronegativity-based inductive effect. Herein, we have discovered a new polymorph of high-voltage m-Li 2 Ni II (SO 4 ) 2 bisulfate using a scalable spray drying route. Neutron and synchrotron diffraction analysis revealed a monoclinic structure (s.g. P2 1 / c, #14) built from corner-shared NiO 6 octahedra and SO 4 tetrahedra locating all Li + in a distinct site. Low-temperature magnetic susceptibility and neutron diffraction measurements confirmed long-range A-type antiferromagnetic ordering in m-Li 2 Ni II (SO 4 ) 2 below 15.2 K following the Goodenough−Kanamori−Anderson rule. In situ X-ray powder diffraction displayed an irreversible (monoclinic → orthorhombic) phase transformation at ∼400 °C. The m-Li 2 Ni II (SO 4 ) 2 framework offers two-dimensional Li + migration pathways as revealed by the bond valence site energy (BVSE) approach. The electronic structure obtained using first-principles (DFT) calculation shows a large electronic band gap (E g ∼ 3.8 eV) with a trapped state near the Fermi energy level triggering polaronic conductivity. As per the DFT study, m-Li 2 Ni II (SO 4 ) 2 can work as a 5.5 V (vs Li + /Li 0 ) cathode for Li-ion batteries, with suitable electrolytes, coupling both cationic (Ni II/III ) and anionic (O − ) redox activity.

First principles investigation of anionic redox in bisulfate lithium battery cathodes

“…26 However, we do note that ref. 26 is a computational prediction and a detailed experimental characterisation of the redox process is required to verify anionic redox.…”

“…1a, has been reported by Tarascon and co-workers, 20,23,25 while some of us have recently synthesized the Ni-analogue, m-Li 2 Ni(SO 4 ) 2 . 26 The marinite framework is built with MO 6 octahedra (green polyhedra in Fig. 1a) and SO 4 tetrahedra (brown polyhedra).…”

“…The enthalpy of formation of bisulfates decreases (i.e., becomes more negative) with the increase in the ionic radius of the TM in both polymorphs (except for the Ni analogues). 22,26 The bisulfates can deliver high cationic redox voltage approaching 3.8 V, as indicated by the example of Li 2 Fe(SO 4 ) 2 . 20 In addition, they can trigger anionic redox activity at high voltage (45 V) leading to high capacity, which is difficult to experimentally realize due to the lack of high-voltage electrolytes.…”

Facile synthesis and phase stability of Cu-based Na2Cu(SO4)2·xH2O (x = 0–2) sulfate minerals as conversion type battery electrodes

“…Indeed, the metastable monoclinic Li 2 Ni(SO 4 ) 2 was reported using the spray drying synthesis (SDS) route. 22 Additional factors such as presence of the Jahn–Teller active cation ( e.g. Mn 2+ , Cu 2+ ) may further introduce a metastability factor in the phase stability of materials.…”

“…25 In a typical calorimetry test, 6-8 mg of sample was pressed into a pellet and then dropped into 25 g of 5 M HCl placed in the sample chamber of the calorimeter as mentioned elsewhere. 22,36 The sample dissolution causes a heat flow due to the temperature difference and is recorded as a calorimetric signal. The integrated area under the recorded microwatt signal from a linear baseline corresponds to total heat effects, which on conversion into joules with KCl calibration corresponds to the enthalpy of sample dissolution (ΔH ds ).…”