ANSTO :: Browsing by Author "Guo, ZP"

Browsing by Author "Guo, ZP"

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Br-doped Li4Ti5O12 and composite TiO2 anodes for Li-ion batteries: synchrotron x-ray and in situ neutron diffraction studies
(John Wiley & Sons, Inc, 2011-09-01) Du, GD; Sharma, N; Peterson, VK; Kimpton, JA; Jia, DZ; Guo, ZP
Synchrotron X-ray diffraction data were used to determine the phase purity and re-evaluate the crystal-structure of Li4Ti5O12-xBrx electrode materials (where the synthetic chemical inputs are x = 0.05, 0.10 0.20, 0.30). A maximum of x′ = 0.12 Br, where x′ is the Rietveld-refined value, can be substituted into the crystal structure with at least 2% rutile TiO2 forming as a second phase. Higher Br concentrations induced the formation of a third, presumably Br-rich, phase. These materials function as composite anodes that contain mixtures of TiO2, Li4Ti5O12-xBrx, and a Br-rich third, unknown, phase. The minor quantities of the secondary phases in combination with Li4Ti5O12-xBrx where x′ ∼ 0.1 were found to correspond to the optimum in electrochemical properties, while larger quantities of the secondary phases contributed to the degradation of the performance. In situ neutron diffraction of a composite anatase TiO2/Li4Ti5O12 anode within a custom-built battery was used to determine the electrochemical function of the TiO2 component. The Li4Ti5O12 component was found to be electrochemically active at lower voltages (1.5 V) relative to TiO2 (1.7 V). This enabled Li insertion/extraction to be tuned through the choice of voltage range in both components of this composite or in the anatase TiO2 phase only. The use of composite materials may facilitate the development of multi-component electrodes where different active materials can be cycled in order to tune power output. Copyright © 2011 Wiley-VCH Verlag GmbH & Co.
Developing high-voltage spinel LiNi0.5Mn1.5O4 cathodes for high-energy-density lithium-ion batteries: current achievements and future prospects
(Royal Society of Chemistry, 2020-05-22) Liang, GM; Peterson, VK; See, KW; Guo, ZP; Pang, WK
High-voltage spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode for the next-generation high-performance lithium-ion batteries (LIBs) due to its high energy density (650 W h kg−1), high operating voltage (∼4.7 V vs. Li), low fabrication cost, and low environmental impact. However, the short cycle life of LNMO caused by rapid capacity decay during cycling limits its wide application and commercialization. Intense research effort to improve the electrochemical performance of LNMO has been moderately successful. Accordingly, it is absolutely necessary to revisit and summarize the up-to-date findings and deeper understanding of how to modify LNMO. In this review, the crystallographic structure and electrochemical properties of LNMO spinel, as well as its existing issues and corresponding solutions, are discussed in detail. In addition, the current accomplishments relating to LNMO application in full-cell configurations are also discussed. Finally, some insight into the future prospects for LNMO cathode developments is provided. © The Royal Society of Chemistry 2020
Direct evidence of concurrent solid-solution and two-phase reactions and the nonequilibrium structural eEvolution of LiFePO(4)
(American Chemical Society, 2012-05-09) Sharma, N; Guo, XW; Du, GD; Guo, ZP; Wang, JZ; Wang, ZX; Peterson, VK
Lithium-ion batteries power many portable devices and in the future are likely to play a significant role in sustainable-energy systems for transportation and the electrical grid. LiFePO(4) is a candidate cathode material for second-generation lithium-ion batteries, bringing a high rate capability to this technology. LiFePO(4) functions as a cathode where delithiation occurs via either a solid-solution or a two-phase mechanism, the pathway taken being influenced by sample preparation and electrochemical conditions. The details of the delithiation pathway and the relationship between the two-phase and solid-solution reactions remain controversial. Here we report, using real-time in situ neutron powder diffraction, the simultaneous occurrence of solid-solution and two-phase reactions after deep discharge in nonequilibrium conditions. This work is an example of the experimental investigation of nonequilibrium states in a commercially available LiFePO(4) cathode and reveals the concurrent occurrence of and transition between the solid-solution and two-phase reactions. © 2012, American Chemical Society.
Effect of AlF3-coated Li4Ti5O12 on the performance and function of the LiNi0.5Mn1.5O4||Li4Ti5O12 full battery—an in-operando neutron powder diffraction study
(Frontiers Media S.A., 2018-09-10) Liang, GM; Pillai, AS; Peterson, VK; Ko, KY; Chang, CM; Lu, CZ; Liu, CE; Liao, SC; Chen, JM; Guo, ZP; Pang, WK
The LiNi0.5Mn1.5O4 ||Li4Ti5O12 (LMNO||LTO) battery possesses a relatively-high energy density and cycle performance, with further enhancement possible by application of an AlF3 coating on the LTO electrode particles. We measure the performance enhancement to the LMNO||LTO battery achieved by a AlF3 coating on the LTO particles through electrochemical testing and use in-operando neutron powder diffraction to study the changes to the evolution of the bulk crystal structure during battery cycling. We find that the AlF3 coating along with parasitic Al doping slightly increases capacity and greatly increases rate capability of the LTO electrode, as well as significantly reducing capacity loss on cycling, facilitating a gradual increase in capacity during the first 50 cycles. Neutron powder diffraction reveals a structural response of the LTO and LNMO electrodes consistent with a greater availability of lithium in the battery containing AlF3-coated LTO. Further, the coating increases the rate of structural response of the LNMO electrode during charge, suggesting faster delithiation, and enhanced Li diffusion. This work demonstrates the importance of studying such battery performance effects within full configuration batteries. Copyright © 2018 Liang, Pillai, Peterson, Ko, Chang, Lu, Liu, Liao, Chen, Guo and Pang.
Electrochemistry and structure of the cobalt-free Li1+xMO2 (M = Li, Ni, Mn, Fe) composite cathode
(Royal Society of Chemistry, 2014-07-01) Pang, WK; Kalluri, S; Peterson, VK; Dou, SX; Guo, ZP
The development of cathode materials with high capacity and cycle stability is essential to emerging electric-vehicle technologies, however, of serious environmental concern is that materials with these properties developed so far contain the toxic and expensive Co. We report here the Li-rich, Co-free Li1+xMO2 (M = Li, Ni, Mn, Fe) composite cathode material, prepared via a template-free, one-step wet-chemical method followed by conventional annealing in an oxygen atmosphere. The cathode has an unprecedented level of cation mixing, where the electrochemically-active component contains four elements at the transition-metal (3a) site and 20% Ni at the active Li site (3b). We find Ni2+/Ni3+/Ni4+ to be the active redox-center of the cathode with lithiation/delithiation occurring via a solid-solution reaction where the lattice responds approximately linearly with cycling, differing to that observed for iso-structural commercial cathodes with a lower level of cation mixing. The composite cathode has ∼75% active material and delivers an initial discharge-capacity of ∼103 mA h g−1 with a reasonable capacity retention of ∼84.4% after 100 cycles. Notably, the electrochemically-active component possesses a capacity of ∼139 mA h g−1, approaching that of the commercialized LiCoO2 and Li(Ni1/3Mn1/3Co1/3)O2 materials. Importantly, our operando neutron powder-diffraction results suggest excellent structural stability of this active component, which exhibits ∼80% less change in its stacking-axis than for LiCoO2 with approximately the same capacity, a characteristic that may be exploited to enhance significantly the capacity retention of this and similar materials.
Elucidation of the high-voltage phase in the layered sodium ion battery cathode material P3–Na0.5Ni0.25Mn0.75O2
(Royal Society of Chemistry, 2020-09-30) Liu, JT; Didier, C; Sale, M; Sharma, N; Guo, ZP; Peterson, VK; Ling, CD
The P3-type layered oxide Na0.5Ni0.25Mn0.75O2 is a promising manganese-rich positive electrode (cathode) material for sodium ion batteries, with a high working voltage of 4.2–2.5 V vs. Na+/Na and a high capacity of over 130 mA h g−1 when cycled at 10 mA g−1. However, its structural evolution during battery cycling – specifically, the nature of the high-voltage phase above 4 V – has never been fully understood, which has hindered efforts to rationally modify and improve its performance. In this work we use in situ neutron diffraction to show that the phase above 4 V is a modification of the intermediate O3 phase from which all sodium has been removed, and which consequently has a dramatically shorter interlayer distance. We label this fully Na-depleted phase O3s, such that the phase evolution with increasing voltage is P3 → O3 → O3s. Having elucidated its structure, we used first-principles calculations of the electronic structure as a function of sodium content to show that reversible oxygen redox plays a key role in the electrochemical activity of this O3s phase above 4 V. We also calculated the energies of oxygen/transition metal vacancies and found that the O3s phase should be relatively stable against their formation. The results will guide future research aimed at understanding and stabilizing the O3s phase, in order to improve the performance and cycling stability of this material in sodium ion batteries. © The Royal Society of Chemistry 2020
Enhanced high voltage stability of spinel‐type structured LiNi0.5Mn1.5O4 electrodes: targeted octahedral crystal site modification
(Wiley, 2024-05-01) Zou, JS; Liang, G; Zhang, SH; Thomsen, L; Fan, Y; Pang, WK; Guo, ZP; Peterson, VK
High‐voltage spinel‐type structured LiNi0.5Mn1.5O4 (LNMO) shows promise as a next‐generation high‐energy‐density lithium‐ion battery cathode material, however, capacity decay on extended cycling hinders its widespread adoption, underscoring an urgent need for further development. In this work, we introduce Zn at octahedral 16c crystal sites in LNMO with Fdm space group to improve rate capability and reduce the rapid capacity decay otherwise experienced during extended cycling. The current work resolves the detailed influence of isolated modification at octahedral 16c crystal sites, unveiling the mechanism for these performance improvements. We show that occupation of Zn at previously empty 16c sites prevents the migration of Ni/Mn to adjacent 16c sites, eliminating transformation to a rock‐salt type structured Ni0.25Mn0.75O2 phase above 4.8 V, preventing structure degradation and suppressing voltage polarization. This study provides insights into the fundamental structure‐function relationship of the LNMO battery cathode, pointing to pathways for the crystal structure engineering of materials with superior performance. © 2024 The Authors. Batteries & Supercaps published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Enhancing the reaction kinetics and structural stability of high-voltage LiCoO 2 via polyanionic species anchoring
(Royal Society of Chemistry (RSC), 2024-05-16) Zheng, W; Liang, GM; Guo, H; Li, JX; Zou, JS; Yuwono, JA; Shu, H; Zhang, S; Peterson, VK; Johannessen, B; Thomsen, L; Hu, WB; Guo, ZP
Increasing the charging voltage to 4.6 V directly enhances battery capacity and energy density of LiCoO2 cathodes for lithium-ion batteries. However, issues of the activated harmful phase evolution and surface instability in high-voltage LiCoO2 lead to dramatic battery capacity decay. Herein, polyanionic PO43− species have been successfully anchored at the surface of LiCoO2 materials, achieving superior battery performance. The polyanionic species acting as micro funnels at the material surface, could expand LiCoO2 surface lattice spacing by 10%, contributing to enhanced Li diffusion kinetics and consequent excellent rate performance of 164 mA h g−1 at 20C (1C = 274 mA g−1). Crucially, polyanionic species with high electronegativity could stabilize surface oxygen at high voltage by reducing O 2p and Co 3d orbital hybridization, thus suppressing surface Co migration and harmful H1–3 phase formation and leading to superior cycling stability with 84% capacity retention at 1C after 300 cycles. Furthermore, pouch cells containing modified LiCoO2 and Li metal electrodes deliver an ultra-high energy density of 513 W h kg−1 under high loadings of 32 mg cm−2. This work provides insightful directions for modifying the material surface structure to obtain high-energy-density cathodes with high-rate performance and long service life. © Royal Society of Chemistry 2024.
Evidence of solid-solution reaction upon lithium insertion into cryptomelane K0.25Mn2O4 material
(ACS Publications, 2014-02-05) Pang, WK; Peterson, VK; Sharma, N; Zhang, CF; Guo, ZP
Cryptomelane-type K0.25Mn2O4 material is prepared via a template-free, one-step hydrothermal method. Cryptomelane K0.25Mn2O4 adopts an I4/m 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 K0.25Mn2O4 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 a and c 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. © 2014, American Chemical Society.
High rate capability core–shell lithium titanate@ceria nanosphere anode material synthesized by one-pot co-precipitation for lithium-ion batteries
(Elsevier, 2014-07-01) Yang, XJ; Huang, YD; Wang, XC; Jia, DZ; Pang, WK; Guo, ZP; Tang, XC
Core–shell Li4Ti5O12@CeO2 nanosphere has been synthesized by a one-pot co-precipitation method. The structure and morphology of the as-prepared materials have been analyzed by X-ray diffraction and transmission electron microscopy. The results show that CeO2 is successfully coated on the surface of the Li4Ti5O12 besides partial doping of Ce4+ into the Li4Ti5O12 structure. The Li4Ti5O12@CeO2 nanosphere exhibits excellent capacity of 152 mAh g−1 even after 180 cycles at 10 C, with no noticeable capacity fading. Furthermore, the sample shows much improved rate capability at 40 C compared with pure Li4Ti5O12 when used as anode material for lithium-ion batteries. The introduction of CeO2 enhances not only the electric conductivity of Li4Ti5O12, but also the lithium ion diffusivity in Li4Ti5O12, resulting in significantly improved electrochemical performance of the Li4Ti5O12. © 2014, Elsevier B.V.
In situ neutron diffraction study on layered oxides Na0.5Ni0.25Mn0.75O2
(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Liu, J; Didier, C; Sale, M; Sharma, N; Guo, ZP; Peterson, VK; Ling, CD
Layered oxides based on first-row transition metals dominate cathode materials for commercial batteries and remain highly interesting as well as challenging in their structural study during electrochemical reactions. Neutron diffraction is a powerful method to obtain periodic structural information complementary to that obtained by X-ray diffraction. Although inferior to X-ray diffraction in signal resolution, neutron diffraction reveals more reliable structural evolution as the whole bulk of materials are fluxed with neutron beam. Na0.5Ni0.25Mn0.75O2 is a potential sodium ion battery cathode due to its high operating voltage 3.2 V vs Na+/Na and high capacity 130 mAh/g. Its stoichiometry is designed to only utilize the redox couple Ni4+/Ni2+ to avoid the unstable redox couple Mn4+/Mn3+. The high voltage phase for this material has been under debate. The fact that sodium-containing layered oxides are highly hydroscopic, especially at low sodium content, makes it hard to study the final phase ex situ. In the work presented here, we have pushed the signal resolution of in situ neutron diffraction to the limit by loading the optimized material mass at the positive side and the corresponding amount of amorphous hard carbon at the negative side of a pouch cell. The result is the first robust proof of the reversible structural evolution from P3, O3 to O3s on charging and back to O3, P3 on discharging. © 2020 The authors.
In situ neutron powder diffraction using custom-made lithium-ion batteries
(Jove, 2014-011-10) Brant, WR; Schmid, S; Du, GD; Brand, G; Pang, HEA; Peterson, VK; Guo, ZP; Sharma, N
Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric vehicles.1,2 However, many challenges, such as energy density and battery lifetimes, need to be overcome before this particular battery technology can be widely implemented in such applications.3 This research is challenging, and we outline a method to address these challenges using in situ NPD to probe the crystal structure of electrodes undergoing electrochemical cycling (charge/discharge) in a battery. NPD data help determine the underlying structural mechanism responsible for a range of electrode properties, and this information can direct the development of better electrodes and batteries. We briefly review six types of battery designs custom-made for NPD experiments and detail the method to construct the ‘roll-over’ cell that we have successfully used on the high-intensity NPD instrument, WOMBAT, at the Australian Nuclear Science and Technology Organisation (ANSTO). The design considerations and materials used for cell construction are discussed in conjunction with aspects of the actual in situ NPD experiment and initial directions are presented on how to analyze such complex in situ data.
In-situ neutron diffraction study of the MoS2 anode using a custom-built li-ion battery
(Elsevier, 2011-09-28) Sharma, N; Du, GD; Studer, AJ; Guo, ZP; Peterson, VK
This work presents the first in-situ neutron diffraction study of the MoS2 electrode, undertaken in a custom-built li-ion battery during discharge. A review of custom-designed cells for in-situ neutron diffraction experiments is presented along with our optimised cell, which we use to show real-time information corresponding to Li-insertion into MoS2 via disappearance of the (103) reflection and increase in the d-spacing of the (002) reflection. The changes in the diffraction patterns begin at the 1.1 V plateau and are complete during the 0.5 V plateau. Sequential Rietveld-refinement indicates the presence of an intermediate lithiated phase (LixMoS2) between MoS2 and LiMoS2. We observe the disappearance of all reflections for the MoS2, corresponding to the loss of long-range order, during the 0.5 V plateau and no new diffraction peaks appear with further electrochemical cycling. This result is indicative of a transformation from long-range ordered MoS2 to short-range ordered LiMoS2, a result that we confirm using ex-situ synchrotron X-ray and neutron diffraction. © 2011, Elsevier Ltd.
Insight of a phase compatible surface coating for long-durable Li-rich layered oxide cathode
(John Wiley & Sons, Inc, 2019-07-28) Hu, SJ; Li, Y; Chen, YH; Peng, JM; Zhou, TF; Pang, WK; Didier, C; Peterson, VK; Wang, HQ; Li, QY; Guo, ZP
Li-rich layered oxides (LLOs) can deliver almost double the capacity of conventional electrode materials such as LiCoO2 and LiMn2O4; however, voltage fade and capacity degradation are major obstacles to the practical implementation of LLOs in high-energy lithium-ion batteries. Herein, hexagonal La0.8Sr0.2MnO3−y (LSM) is used as a protective and phase-compatible surface layer to stabilize the Li-rich layered Li1.2Ni0.13Co0.13Mn0.54O2 (LM) cathode material. The LSM is Mn O M bonded at the LSM/LM interface and functions by preventing the migration of metal ions in the LM associated with capacity degradation as well as enhancing the electrical transfer and ionic conductivity at the interface. The LSM-coated LM delivers an enhanced reversible capacity of 202 mAh g−1 at 1 C (260 mA g−1) with excellent cycling stability and rate capability (94% capacity retention after 200 cycles and 144 mAh g−1 at 5 C). This work demonstrates that interfacial bonding between coating and bulk material is a successful strategy for the modification of LLO electrodes for the next-generation of high-energy Li-ion batteries. © 2019 Wiley-VCH Verlag GmbH & Co.
Introducing 4s–2p orbital hybridization to stabilize spinel oxide cathodes for lithium-ion batteries
(Wiley-VCH GmbH, 2022-04-25) Liang, GM; Olsson, E; Zou, JS; Wu, ZB; Li, JX; Lu, CZ; D'Angelo, AM; Johannessen, B; Thomsen, L; Cowie, BCC; Peterson, VK; Cai, Q; Pang, WK; Guo, ZP
Oxides composed of an oxygen framework and interstitial cations are promising cathode materials for lithium-ion batteries. However, the instability of the oxygen framework under harsh operating conditions results in fast battery capacity decay, due to the weak orbital interactions between cations and oxygen (mainly 3d–2p interaction). Here, a robust and endurable oxygen framework is created by introducing strong 4s–2p orbital hybridization into the structure using LiNi0.5Mn1.5O4 oxide as an example. The modified oxide delivers extraordinarily stable battery performance, achieving 71.4 % capacity retention after 2000 cycles at 1 C. This work shows that an orbital-level understanding can be leveraged to engineer high structural stability of the anion oxygen framework of oxides. Moreover, the similarity of the oxygen lattice between oxide electrodes makes this approach extendable to other electrodes, with orbital-focused engineering a new avenue for the fundamental modification of battery materials. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH - Open access.
A long cycle-life high-voltage spinel lithium-ion battery electrode achieved by site-selective doping
(John Wiley & Sons, Inc, 2020-03-23) Liang, GM; Wu, ZB; Didier, C; Zhang, WC; Cuan, J; Li, BH; Ko, KY; Hung, PY; Lu, CZ; Chen, YZ; Leniec, G; Kaczmarek, SM; Johannessen, B; Thomsen, L; Peterson, VK; Pang, WK; Guo, ZP
Spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode candidate for the next-generation high energy-density lithium-ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site-selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fdurn:x-wiley:14337851:media:anie202001454:anie202001454-math-0001 m structure. This site-selective doping not only suppresses unfavorable two-phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg-doped LNMOs exhibit extraordinarily stable electrochemical performance in both half-cells and prototype full-batteries with novel TiNb2O7 counter-electrodes. This work pioneers an atomic-doping engineering strategy for electrode materials that could be extended to other energy materials to create high-performance devices. © 2020 Wiley-VCH Verlag GmbH & Co
Non-stoichiometric Mn doping in olivine lithium iron phosphate: structure and electrochemical properties
(Australian Institute of Physics, 2011-02-02) Feng, C; Li, HH; Du, GD; Guo, ZP; Sharma, N; Peterson, VK; Li, HJ
LiFePO4 and [Li0.918(10)Fe0.01][Fe0.99Mn0.01]PO4 or 1% Mn-doped LiFePO4 were synthesized by the one-step rheological phase reaction method using inexpensive FePO4 as the main raw material. Synchrotron X-ray diffraction, neutron powder diffraction, and transmission electron microscopy were used to characterize LiFePO4 and Mn-doped LiFePO4. Particle sizes were found to be distributed in the range of 0.5 to 1 μm and the carbon-content in the as-prepared samples was around 2 wt%. Rietveld analysis suggests 1 % Mn-doping replaces 1 % Fe from the Fe (M2) site and places this fraction of Fe on the Li (M1) site. The first process on the M2 site is isovalent doping (Mn2+ for Fe2+), while the second process on M2 is supervalent doping (Fe2+ for Li+). The second process requires that Li vacancies exist for charge balance and our simultaneous refinements against neutron and synchrotron X-ray diffraction data indicate an amount of Li vacancies consistent with this requirement. This doping regime agrees with the observed enhancement of the electrochemical properties of the Mn-doped LiFePO4 compared to the undoped LiFePO4. The Mn-doped LiFePO4 cathodes exhibit higher capacity and better cycling performance than the pure LiFePO4.
Phase evolution and intermittent disorder in electrochemically lithiated graphite determined using in operando neutron diffraction
(American Chemical Society, 2020-03-24) Didier, C; Pang, WK; Guo, ZP; Schmid, S; Peterson, VK
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. © 2020 American Chemical Society
The promise of high-entropy materials for high-performance rechargeable Li-ion and Na-ion batteries
(Elsevier, 2023-12-20) Zheng, W; Liang, G; Liu, Q; Li, JX; Yuwono, JA; Zhang, S; Peterson, VK; Guo, ZP
Our growing dependence on rechargeable Li/Na-ion batteries calls for substantial improvements in the electrochemical performance of battery materials, including cathodes, anodes, and electrolytes. However, the performance enhancements based on traditional modification methods of elemental doping and surface coating are still far from the target of high-performance rechargeable batteries. Fortunately, the recent emergence of high-entropy materials preserving a stable solid-state phase for energy-related applications provides unprecedented flexibility and variability in materials composition and electronic structure, opening new avenues to accelerate battery materials development. This perspective first presents clear qualitative and quantitative definitions for high-entropy battery materials, as well as summarizes the enhancement mechanisms. Then, we comprehensively review state-of-the-art research progress and highlight key factors in the rational design of advanced high-entropy battery materials from both experimental and calculational aspects. Moreover, the challenges limiting the progress of this research are presented, alongside insights and approaches to address these issues at the research forefront. Finally, we outline potential directions for extending the future development of the high-entropy strategy to solve other critical issues in battery materials research. This perspective will guide researchers in their studies toward the development of high-performance rechargeable Li-ion and Na-ion batteries. © 2024 Elsevier Inc. - Open Archive
A robust coin-cell design for in situ synchrotron-based x-ray powder diffraction analysis of battery materials
(John Wiley & Sons, Inc, 2020-10-22) Liang, GM; Hao, JN; D'Angelo, AM; Peterson, VK; Guo, ZP; Pang, WK
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. © 2020 Wiley-VCH GmbH

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