Probing Capacity Trends in MLi2_2Ti6_6O14_{14} Lithium-Ion Battery Anodes Using Calorimetric Studies

Due to higher packing density, lower working potential, and area specific impedance, the MLi$_2$Ti$_6$O$_{14}$ (M = 2Na, Sr, Ba, and Pb) titanate family is a potential alternative to zero-strain Li$_4$Ti$_5$O$_{12}$ anodes used commercially in Li-ion batteries. However, the exact lithiation mechanism in these compounds remains unclear. Despite its structural similarity, MLi$_2$Ti$_6$O$_{14}$ behaves differently depending on charge and size of the metal ion, hosting 1.3, 2.7, 2.9, and 4.4 Li per formula unit, giving charge capacity values from 60 to 160 mAh/g in contrast to the theoretical capacity trend. However, high-temperature oxide melt solution calorimetry measurements confirm strong correlation between thermodynamic stability and the observed capacity. The main factors controlling energetics are strong acid–base interactions between basic oxides MO, Li$_2$O and acidic TiO$_2$, size of the cation, and compressive strain. Accordingly, the energetic stability diminishes in the order Na$_2$Li$_2$Ti$_6$O$_{14}$ > BaLi$_2$Ti$_6$O$_{14}$ > SrLi$_2$Ti$_6$O$_{14}$ > PbLi$_2$Ti$_6$O$_{14}$. This sequence is similar to that in many other oxide systems. This work exhibits that thermodynamic systematics can serve as guidelines for the choice of composition for building better batteries

First principles investigation of anionic redox in bisulfate lithium battery cathodes

The search for an alternative high-voltage polyanionic cathode material for Li-ion batteries is vital to improve the energy densities beyond the state-of-the-art, where sulfate frameworks form an important class of high-voltage cathode materials due to the strong inductive effect of the S$^{6+}$ ion. Here, we have investigated the mechanism of cationic and/or anionic redox in Li$_x$M(SO$_4$)$_2$ frameworks (M = Mn, Fe, Co, and Ni and 0 $\leq$ x $\leq$ 2) using density functional calculations. Specifically, we have used a combination of Hubbard $U$ corrected strongly constrained and appropriately normed (SCAN+$U$) and generalized gradient approximation (GGA+$U$) functionals to explore the thermodynamic (polymorph stability), electrochemical (intercalation voltage), geometric (bond lengths), and electronic (band gaps, magnetic moments, charge populations, etc.) properties of the bisulfate frameworks considered. Importantly, we find that the anionic (cationic) redox process is dominant throughout delithiation in the Ni (Mn) bisulfate, as verified using our calculated projected density of states, bond lengths, and on-site magnetic moments. On the other hand, in Fe and Co bisulfates, cationic redox dominates the initial delithiation (1 $\leq$ x $\leq$ 2), while anionic redox dominates subsequent delithiation (0 $\leq$ x $\leq$ 2). In addition, evaluation of the crystal overlap Hamilton population reveals insignificant bonding between oxidizing O atoms throughout the delithiation process in the Ni bisulfate, indicating robust battery performance that is resistant to irreversible oxygen evolution. Finally, we observe both GGA+$U$ and SCAN+$U$ predictions are in qualitative agreement for the various properties predicted. Our work should open new avenues for exploring lattice oxygen redox in novel high voltage polyanionic cathodes, especially using the SCAN+$U$ functional.Comment: Draft and supporting information included, 40 pages tota

Na0.5_{0.5}Bi0.5_{0.5}TiO3_3 perovskite anode for lithium-ion batteries

Lithium-ion battery technology, currently the most popular form of mobile energy storage, primarily uses graphite as the anode. However, the graphite anode, owing to its low working voltage at high current density, is susceptible to lithium plating and related safety risks. In this direction, perovskite oxides like CaSnO$_3$, more recently PbTiO$_3$, have been explored as alternate anode materials due to their higher operational voltage. Extending this family of perovskites, we introduce a widely used lead-free piezoelectric ceramic Na$_{0.5}$Bi$_{0.5}$TiO$_3$ (NBT) as a potential anode for lithium-ion batteries. NBT has an average voltage of 0.7 V and a high capacity of 220 mA h g(-1). Ex situ diffraction and spectroscopy tools were used to understand the charge storage mechanism. The oxide undergoes an irreversible conversion reaction in the first discharge, followed by reversible (de)alloying of Bi with Li in the subsequent cycles. This material is airstable, with a capacity retention of 82% up to 50 cycles at a high current of 100 mA g(-1) without any optimization. Furthermore, limiting the voltage window increases the cycle life to 200 cycles. Perovskite-type Na$_{0.5}$Bi$_{0.5}$TiO$_3$ is proposed as a new Bi-based conversion alloying anode for lithium-ion batteries

Alternative Polymorph of the Hydroxysulfate Li x FeSO 4 OH Yields Improved Lithium-Ion Cathodes

Use of sustainable electrode components in Li-ion battery technology is essential for large-scale applications while addressing environmental concerns. Considering elemental abundance, Fe-based compounds can, in principle, work as the most economic cathodes. Fe-based hydroxysulfates LixFeSO$_4$OH (x = 0 –1) can be harnessed as low-cost, sustainable, high-voltage, and moisture-resistant battery cathode materials. In this system, monoclinic (m) FeSO$_4$OH and layered m-FeSO4OH were previously reported as Li-ion battery cathode materials. Here, we introduce orthorhombic (o) FeSO4OH as a potential low-cost cathode for Li-ion batteries synthesized by using a facile low-temperature hydrothermal route. The o-FeSO$_4$OH cathode delivers a reversible capacity of 100 mA h/g at a current rate of C/20 (1e– = 159 mAh/g) at a working potential of ca. 3.2 V vs Li$^+$/Li. A higher overpotential and faster rate kinetics compared with that of m-FeSO4OH stem from the subtle deviations in the structural framework affecting the Li coordination environment. Operando analytical tools, electrochemical titration techniques, and computational modeling are combined to characterize the complex phase transformation during the (de)lithiation process

A 3.8-V earth-abundant sodium battery electrode

Rechargeable lithium batteries have ushered the wireless revolution over last two decades and are now matured to enable green automobiles. However, the growing concern on scarcity and large-scale applications of lithium resources have steered effort to realize sustainable sodium-ion batteries, ​Na and ​Fe being abundant and low-cost charge carrier and redox centre, respectively. However, their performance is limited owing to low operating voltage and sluggish kinetics. Here we report a hitherto-unknown material with entirely new composition and structure with the first alluaudite-type sulphate framework, Na2Fe2(SO4)3, registering the highest-ever Fe3+/Fe2+ redox potential at 3.8 V (versus ​Na, and hence 4.1 V versus ​Li) along with fast rate kinetics. Rare-metal-free Na-ion rechargeable battery system compatible with the present Li-ion battery is now in realistic scope without sacrificing high energy density and high power, and paves way for discovery of new earth-abundant sustainable cathodes for large-scale batteries.UTokyo Research掲載「新物質発見で電池のレアメタル使用ゼロに」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/materials-discovery-for-earth-abundant-battery/UTokyo Research "Materials discovery for earth-abundant battery" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/materials-discovery-for-earth-abundant-battery

Water‐Soluble Inorganic Binders for Lithium‐Ion and Sodium‐Ion Batteries

Inorganic materials form an emerging class of water-soluble binders for battery applications. Their favourable physicochemical properties, such as intrinsic ionic conductivity, high thermal stability (>1000 °C), and compatibility to coat a diverse range of electrode materials make them useful binders for lithium-ion and sodium-ion batteries. Li and Na containing phosphates and silicates are attractive choices as multifunctional inorganic aqueous binders (IABs). This review discusses these binders\u27 structural, thermal, and ionic properties, followed by exploiting their ionically conducting nature for all-solid-state batteries. Subsequently, the application of these compounds as binders and surface coating agents for different anodes and cathodes in lithium-ion and sodium-ion batteries is discussed. Eventually, a first evaluation of their environmental impacts and economic aspects is presented as well

Greener, Safer and Better Performing Aqueous Binder for Positive Electrode Manufacturing of Sodium Ion Batteries

P2-type cobalt-free MnNi-based layered oxides are promising cathode materials for sodium-ion batteries (SIBs) due to their high reversible capacity and well chemical stability. However, the phase transformations during repeated (dis)charge steps lead to rapid capacity decay and deteriorated Na+ diffusion kinetics. Moreover, the electrode manufacturing based on polyvinylidene difluoride (PVDF) binder system has been reported with severely defluorination issue as well as the energy intensive and expensive process due to the use of toxic and volatile N-methyl-2-pyrrolidone (NMP) solvent. It calls for designing a sustainable, better performing, and cost-effective binder for positive electrode manufacturing. In this work, we investigated inorganic sodium metasilicate (SMS) as a viable binder in conjunction with P2-Na0.67Mn0.55Ni0.25Fe0.1Ti0.1O2 (NMNFT) cathode material for SIBs. The NMNFT-SMS electrode delivered a superior electrochemical performance compared to carboxy methylcellulose (CMC) and PVDF based electrodes with a reversible capacity of ~161 mAh/g and retaining ~83 % after 200 cycles. Lower cell impedance and faster Na+ diffusion was also observed in this binder system. Meanwhile, with the assistance of TEM technique, SMS is suggested to form a uniform and stable nanoscale layer over the cathode particle surface, protecting the particle from exfoliation/cracking due to electrolyte attack. It effectively maintained the electrode connectivity and suppressed early phase transitions during cycling as confirmed by operando XRD study. With these findings, SMS binder can be proposed as a powerful multifunctional binder to enable positive electrode manufacturing of SIBs and to overall reduce battery manufacturing costs

Sulfate Chemistry for High-Voltage Insertion Materials: Synthetic, Structural and Electrochemical Insights

Rechargeable batteries based on Li and Na ions have been growing leaps and bounds since their inception in the 1970s. They enjoy significant attention from both the fundamental science point of view and practical applications ranging from portable electronics to hybrid vehicles and grid storage. The steady demand for building better batteries calls for discovery, optimisation and implementation of novel positive insertion (cathode) materials. In this quest, chemists have tried to unravel many future cathode materials by taking into consideration their eco-friendly synthesis, material/process economy, high energy density, safety, easy handling and sustainability. Interestingly, sulfate-based cathodes offer a good combination of sustainable syntheses and high energy density owing to their high-voltage operation, stemming from electronegative SO42- units. This review delivers a sneak peak at the recent advances in the discovery and development of sulfate-containing cathode materials by focusing on their synthesis, crystal structure and electrochemical performance. Several family of cathodes are independently discussed. They are 1) fluorosulfates AMSO(4)F], 2) bihydrated fluorosulfates AMSO(4)F2H(2)O], 3) hydroxysulfate AMSO(4)OH], 4) bisulfates A(2)M(SO4)(2)], 5) hydrated bisulfates A(2)M(SO4)(2)nH(2)O], 6) oxysulfates Fe-2(SO4)(2)O] and 7) polysulfates A(2)M(2)(SO4)(3)]. A comparative study of these sulfate-based cathodes has been provided to offer an outlook on the future development of high-voltage polyanionic cathode materials for next-generation batteries