Sodium-ion battery anodes from carbon depositions

Significant interest is directed towards converting CO to high-value feedstock chemicals. Here, the performance of carbon deposited from carbonate fluxes under CO environments are reported for direct use as anodes in sodium-ion batteries. The generated carbon is found to be amorphous hard carbon, evidenced by X-ray diffraction (XRD) data and I /I ratios of the D- and G- bands of graphite in Raman spectroscopy. Furthermore, the role of washing and removing the deposit is evaluated for the carbon generated and the subsequent electrochemical performance. The best performing samples were grown on a copper substrate, which delivered initial reversible capacities of 209 ± 23 mAh/g mAh/g on the 5th cycle at a rate of 10 mA/g, and feature a capacity retention of 86.6 ± 1.8 % after 50 cycles. The value in this approach to generate carbons lies in the fact that these fluxes are designed to be similar to that used for molten salts in solar thermal plants and, if coupled appropriately to CO sources, they can be used to convert CO into carbons. A model system is proposed on how this can be achieved to possibly produce a carbon negative anode for sodium-ion batteries, with potential for an overall carbon negative sodium-ion battery. 2 2 D G 2

Phase Evolution and Intermittent Disorder in Electrochemically Lithiated Graphite Determined Using in Operando Neutron Diffraction

Since their commercialization in 1991, lithium-ion batteries (LIBs) have revolutionized our way of life, with LIB pioneers being awarded the 2019 Nobel Prize in Chemistry. Despite the widespread use of LIBs, many LIB applications are not realized due to performance limitations, determined largely by the ability of electrode materials to reversibly host lithium ions. Overcoming such limitations requires knowledge of the fundamental mechanism for reversible ion intercalation in electrode materials. In this work, the still-debated structure of the most common commercial electrode material, graphite, during electrochemical lithiation is revisited using in operando neutron powder diffraction of a commercial 18650 lithium-ion battery. We extract new structural information and present a comprehensive overview of the phase evolution for lithiated graphite. Charge–discharge asymmetry and structural disorder in the lithiation process are observed, particularly surrounding phase transitions, and the phase evolution is found to be kinetically influenced. Notably, we observe pronounced asymmetry over the composition range 0.5 > x > 0.2, in which the stage 2L phase forms on discharge (delithiation) but not charge (lithiation), likely as a result of the slow formation of the stage 2L phase and the closeness of the stage 2L and stage 2 phase potentials. We reconcile our measurements of this transition with a stage 2L stacking disorder model containing an intergrown stage 2 and 2L phase. We resolve debate surrounding the intercalation mechanism in the stage 3L and stage 4L phase region, observing stage-specific reflections that support a first-order phase transition over the 0.2 > x > 0.04 range, in agreement with minor changes in the slope of the stacking axis length, despite relatively unchanging 00l reflection broadening. Our data support the previously proposed /ABA/ACA/ stacking for the stage 3L phase and an /ABAB/BABA/ stacking sequence of the stage 4L phase alongside experimentally derived atomic parameters. Finally, at low lithium content 0 x < 0.04, we find an apparently homogeneous modification of the structure during both charge and discharge. Understanding the phase evolution and mechanism of structural response of graphite to lithiation under battery working conditions through in operando measurements may provide the information needed for the development of alternative higher performance electrode materials

Evidence of Solid-Solution Reaction upon Lithium Insertion into Cryptomelane K_0.25Mn₂O₄ Material

Cryptomelane-type K_0.25Mn₂O₄ material is prepared via a template-free, one-step hydrothermal method. Crypto­melane K_0.25Mn₂O₄ adopts an <i>I</i>4/<i>m</i> tetragonal structure with a distinct tunnel feature built from MnO₆ units. Its structural stability arises from the inherent stability of the MnO₆ framework which hosts potassium ions, which in turn permits faster ionic diffusion, making the material attractive for application as a cathode in lithium-ion batteries. Despite this potential use, the phase transitions and structural evolution of cryptomelane during lithiation and delithiation remain unclear. The coexistence of Mn³⁺ and Mn⁴⁺ in the compound during lithiation and delithiation processes induces different levels of Jahn–Teller distortion, further complicating the lattice evolution. In this work, the lattice evolution of the cryptomelane K_0.25Mn₂O₄ during its function as a cathode within a lithium-ion battery is measured in a customized coin cell using in situ synchrotron X-ray diffraction. We find that the lithiation–delithiation of cryptomelane cathode proceeds through a solid-solution reaction, associated with variations of the <i>a</i> and <i>c</i> lattice parameters and a reversible strain effect induced by Jahn–Teller distortion of Mn³⁺. The lattice parameter changes and the strain are quantified in this work, with the results demonstrating that cryptomelane is a relatively good candidate cathode material for lithium-ion battery use

Constructing nitrided interfaces for stabilizing Li metal electrodes in liquid electrolytes

Traditional Li ion batteries based on intercalation-type anodes have been approaching their theoretical limitations in energy density. Replacing the traditional anode with metallic Li has been regarded as the ultimate strategy to develop next-generation high-energy-density Li batteries. Unfortunately, the practical application of Li metal batteries has been hindered by Li dendrite growth, unstable Li/electrolyte interfaces, and Li pulverization during battery cycling. Interfacial modification can effectively solve these challenges and nitrided interfaces stand out among other functional layers because of their impressive effects on regulating Li+flux distribution, facilitating Li+diffusion through the solid-electrolyte interphase, and passivating the active surface of Li metal electrodes. Although various designs for nitrided interfaces have been put forward in the last few years, there is no paper that specialized in reviewing these advances and discussing prospects. In consideration of this, we make a systematic summary and give our comments based on our understanding. In addition, a comprehensive perspective on the future development of nitrided interfaces and rational Li/electrolyte interface design for Li metal electrodes is included

Manipulating the Solvation Structure of Nonflammable Electrolyte and Interface to Enable Unprecedented Stability of Graphite Anodes beyond 2 Years for Safe Potassium-Ion Batteries

Potassium-ion batteries (PIBs) are attractive for low-cost and large-scale energy storage applications, in which graphite is one of the most promising anodes. However, the large size and the high activity of K ions and the highly catalytic surface of graphite largely prevent the development of safe and compatible electrolytes. Here, a nonflammable, moderate-concentration electrolyte is reported that is highly compatible with graphite anodes and that consists of fire-retardant trimethyl phosphate (TMP) and potassium bis(fluorosulfonyl)imide (KFSI) in a salt/solvent molar ratio of 3:8. It shows unprecedented stability, as evidenced by its 74% capacity retention over 24 months of cycling (over 2000 cycles) at the 0.2 C current rate. Electrolyte structure and surface analyses show that this excellent cycling stability is due to the nearly 100% solvation of TMP molecules with K cations and the formation of FSI -derived F-rich solid electrolyte interphase (SEI), which effectively suppresses the decomposition of the solvent molecules toward the graphite anode. Furthermore, excellent performance on high-mass loaded graphite electrodes and in a full cell with perylenetetracarboxylic dianhydride cathode is demonstrated. This study highlights the importance of the compatibility of both electrolyte and the interface, and offers new opportunities to design the electrolyte–SEI nexus for safe and practical PIBs. + +

Lithium Migration in Li₄Ti₅O₁₂ Studied Using in Situ Neutron Powder Diffraction

We used in situ neutron powder diffraction (NPD) to study the migration of Li in Li₄Ti₅O₁₂ anodes with different particle sizes during battery cycling. The motivation of this work was to uncover the mechanism of the increased capacity of the battery made with a smaller-particle-sized anode. In real time, we monitored the anode lattice parameter, Li distribution, and oxidation state of the Ti atom, and these suggested an increase in the rate of Li incorporation into the anode rather than a change in the migration pathway as a result of the particle size reduction. The lattice of these anodes during continuous lithiation undergoes expansion followed by a gradual contraction and then expansion again. The measured lattice parameter changes were reconciled with Li occupation at specific sites within the Li₄Ti₅O₁₂ crystal structure, where Li migrates from the 8<i>a</i> to 16<i>c</i> sites. Despite these similar Li-diffusion pathways, in larger-particle-sized Li₄Ti₅O₁₂ the population of Li at the 16<i>c</i> site is accompanied by Li depopulation from the 8<i>a</i> site, which is in contrast to the smaller-particle-sized anode where our results suggest that Li at the 8<i>a</i> site is replenished faster than the rate of transfer of Li to the 16<i>c</i> site. Fourier-difference nuclear density maps of both anodes suggest that 32<i>e</i> sites are involved in the diffusion pathway of Li. NPD is again shown to be an excellent tool for the study of electrode materials for Li-ion batteries, particularly when it is used to probe real-time crystallographic changes of the materials in an operating battery during charge–discharge cycling

Addressing cation mixing in layered structured cathodes for lithium-ion batteries: A critical review

High-performance lithium-ion batteries (LIB) are important in powering emerging technologies. Cathodes are regarded as the bottleneck of increasing battery energy density, among which layered oxides are the most promising candidates for LIB. However, a limitation with layered oxides cathodes is the transition metal and Li site mixing, which significantly impacts battery capacity and cycling stability. Despite recent research on Li/Ni mixing, there is a lack of comprehensive understanding of the origin of cation mixing between the transition metal and Li; therefore, practical means to address it. Here, a critical review of cation mixing in layered cathodes has been provided, emphasising the understanding of cation mixing mechanisms and their impact on cathode material design. We list and compare advanced characterisation techniques to detect cation mixing in the material structure; examine methods to regulate the degree of cation mixing in layered oxides to boost battery capacity and cycling performance, and critically assess how these can be applied practically. An appraisal of future research directions, including superexchange interaction to stabilise structures and boost capacity retention has also been concluded. Findings will be of immediate benefit in the design of layered cathodes for high-performance rechargeable LIB and, therefore, of interest to researchers and manufacturers

A Robust Coin-Cell Design for In Situ Synchrotron-based X-Ray Powder Diffraction Analysis of Battery Materials

Understanding structure/chemistry-function relationships of active battery materials is crucial for designing higher-performance batteries, with in situ synchrotron-based X-ray powder diffraction widely employed to gain this understanding. Such measurements cannot be performed using a conventional cell, with modifications necessary for the X-ray diffraction measurement, which unfortunately compromises battery performance and stability. Consequently, these measurements may not be representative of the typical behaviour of active materials in unmodified cells, particularly under more extreme operating conditions, such as at high voltage. Herein, we report a low-cost, simple, and robust coin-cell design enabling representative and typical cell performance during in situ X-ray powder diffraction measurements, which we demonstrate for the well-known high-voltage electrode material LiNi0.5Mn1.5O4. In addition to excellent cell stability at high voltage, the modified cell delivered an electrochemical response comparable to the standard 2032-type coin cell. This work paves an efficient way for battery researchers to perform high-quality in situ structural analysis with synchrotron X-ray radiation and will enable further insight into complex electrochemical processes in batteries

Synergistic Effects of Phase Transition and Electron-Spin Regulation on the Electrocatalysis Performance of Ternary Nitride

Transition metal nitrides (TMNs) have great potential use in energy storage and conversion owing to tunable electronic and bonding characteristics. Novel iron rich nitrides nanoparticles anchored on the N-doped porous carbon, named as (CoxFe1–x)3N@NPC (0 ≤ x < 0.5) are designed here. The synergistic effects of phase transition and electron-spin regulation on oxygen electrocatalysis are testified. A core–shell structure of (CoxFe1–x)3N with high dispersibility is induced by an intermediate phase transition process, which significantly suppresses coarsening of the metallic nitrides. The Co incorporation regulates d-band electrons spin polarization. The t2g5eg1 of FeII with the ideal eg electron filling boosts intrinsic activity. (Co0.17Fe0.83)3N@NPC with optimal cobalt content holds electronic configuration with moderate eg electron filling (t2g5eg1), which balances the adsorption of *O2 and the hydrogenation of *OH, improving bifunctional catalytic performances. Both liquid and solid-state zinc–air batteries assembled based (Co0.17Fe0.83)3N@NPC cathodes substantially deliver higher peak power density and remarkable energy density