The development of low-cost and long-lasting all-climate cathode materials for the sodium ion battery has been one of the key issues for the success of large-scale energy storage. One option is the ...utilization of earth-abundant elements such as iron. Here, we synthesize a NASICON-type tuneable Na
Fe
(PO
)
(P
O
)/C nanocomposite which shows both excellent rate performance and outstanding cycling stability over more than 4400 cycles. Its air stability and all-climate properties are investigated, and its potential as the sodium host in full cells has been studied. A remarkably low volume change of 4.0% is observed. Its high sodium diffusion coefficient has been measured and analysed via first-principles calculations, and its three-dimensional sodium ion diffusion pathways are identified. Our results indicate that this low-cost and environmentally friendly Na
Fe
(PO
)
(P
O
)/C nanocomposite could be a competitive candidate material for sodium ion batteries.
One major challenge in the field of lithium-ion batteries is to understand the degradation mechanism of high-energy lithium- and manganese-rich layered cathode materials. Although they can deliver 30 ...% excess capacity compared with today's commercially- used cathodes, the so-called voltage decay has been restricting their practical application. In order to unravel the nature of this phenomenon, we have investigated systematically the structural and compositional dependence of manganese-rich lithium insertion compounds on the lithium content provided during synthesis. Structural, electronic and electrochemical characterizations of Li
Ni
Mn
O
with a wide range of lithium contents (0.00 ≤ x ≤ 1.52, 1.07 ≤ y < 2.4) and an analysis of the complexity in the synthesis pathways of monoclinic-layered LiLi
Ni
Mn
O
oxide provide insight into the underlying processes that cause voltage fading in these cathode materials, i.e. transformation of the lithium-rich layered phase to a lithium-poor spinel phase via an intermediate lithium-containing rock-salt phase with release of lithium/oxygen.
High entropy oxides (HEOs) with chemically disordered multi-cation structure attract intensive interest as negative electrode materials for battery applications. The outstanding electrochemical ...performance has been attributed to the high-entropy stabilization and the so-called 'cocktail effect'. However, the configurational entropy of the HEO, which is thermodynamically only metastable at room-temperature, is insufficient to drive the structural reversibility during conversion-type battery reaction, and the 'cocktail effect' has not been explained thus far. This work unveils the multi-cations synergy of the HEO Mg
Co
Ni
Cu
Zn
O at atomic and nanoscale during electrochemical reaction and explains the 'cocktail effect'. The more electronegative elements form an electrochemically inert 3-dimensional metallic nano-network enabling electron transport. The electrochemical inactive cation stabilizes an oxide nanophase, which is semi-coherent with the metallic phase and accommodates Li
ions. This self-assembled nanostructure enables stable cycling of micron-sized particles, which bypasses the need for nanoscale pre-modification required for conventional metal oxides in battery applications. This demonstrates elemental diversity is the key for optimizing multi-cation electrode materials.
Herein, we introduce a 4.0 V class high‐voltage cathode material with a newly recognized sodium superionic conductor (NASICON)‐type structure with cubic symmetry (space group P213), Na3V(PO3)3N. We ...synthesize an N‐doped graphene oxide‐wrapped Na3V(PO3)3N composite with a uniform carbon coating layer, which shows excellent rate performance and outstanding cycling stability. Its air/water stability and all‐climate performance were carefully investigated. A near‐zero volume change (ca. 0.40 %) was observed for the first time based on in situ synchrotron X‐ray diffraction, and the in situ X‐ray absorption spectra revealed the V3.2+/V4.2+ redox reaction with high reversibility. Its 3D sodium diffusion pathways were demonstrated with distinctive low energy barriers. Our results indicate that this high‐voltage NASICON‐type Na3V(PO3)3N composite is a competitive cathode material for sodium‐ion batteries and will receive more attention and studies in the future.
A new NASICON‐type high‐voltage cathode material of Na3V(PO3)3N was synthesized and its electrochemical performance was improved by carbon matrix decoration. An in‐depth investigation of the material was performed through in situ XAS and XRD, and its 3D sodium pathways were clearly identified through DFT calculations.
Lithium‐ and manganese‐rich layered oxides (LMLOs, ≥ 250 mAh g−1) with polycrystalline morphology always suffer from severe voltage decay upon cycling because of the anisotropic lattice strain and ...oxygen release induced chemo‐mechanical breakdown. Herein, a Co‐free single‐crystalline LMLO, that is, LiLi0.2Ni0.2Mn0.6O2 (LLNMO‐SC), is prepared via a Li+/Na+ ion‐exchange reaction. In situ synchrotron‐based X‐ray diffraction (sXRD) results demonstrate that relatively small changes in lattice parameters and reduced average micro‐strain are observed in LLNMO‐SC compared to its polycrystalline counterpart (LLNMO‐PC) during the charge–discharge process. Specifically, the as‐synthesized LLNMO‐SC exhibits a unit cell volume change as low as 1.1% during electrochemical cycling. Such low strain characteristics ensure a stable framework for Li‐ion insertion/extraction, which considerably enhances the structural stability of LLNMO during long‐term cycling. Due to these peculiar benefits, the average discharge voltage of LLNMO‐SC decreases by only ≈0.2 V after 100 cycles at 28 mA g‐1 between 2.0 and 4.8 V, which is much lower than that of LLNMO‐PC (≈0.5 V). Such a single‐crystalline strategy offers a promising solution to constructing stable high‐energy lithium‐ion batteries (LIBs).
A Li+/Na+ ion‐exchange reaction is reported to synthesize the Co‐free single‐crystalline LiLi0.2Ni0.2Mn0.6O2 (LLNMO‐SC). In situ synchrotron‐based X‐ray diffraction and absorption spectroscopy are utilized to investigate the structural evolution of LLNMO‐SC and its polycrystalline counterpart (LLNMO‐PC) during electrochemical cycling. The origin of mitigated voltage decay in LLNMO‐SC is unraveled upon long‐term cycling.
Layered alkali-containing 3d transition-metal oxides are of the utmost importance in the use of electrode materials for advanced energy storage applications such as Li-, Na-, or K-ion batteries. A ...significant challenge in the field of materials chemistry is understanding the dynamics of the chemical reactions between alkali-free precursors and alkali species during the synthesis of these compounds. In this study, in situ high-resolution synchrotron-based X-ray diffraction was applied to reveal the Li/Na/K-ion insertion-induced structural transformation mechanism during high-temperature solid-state reaction. The in situ diffraction results demonstrate that the chemical reaction pathway strongly depends on the alkali-free precursor type, which is a structural matrix enabling phase transitions. Quantitative phase analysis identifies for the first time the decomposition of lithium sources as the most critical factor for the formation of metastable intermediates or impurities during the entire process of Li-rich layered LiLi0.2Ni0.2Mn0.6O2 formation. Since the alkali ions have different ionic radii, Na/K ions tend to be located on prismatic sites in the defective layered structure (Na2/3-xNi0.25Mn0.75O2 or K2/3-xNi0.25Mn0.75O2) during calcination, whereas the Li ions prefer to be localized on the tetrahedral and/or octahedral sites, forming O-type structures.
Structure changes of a mixture of alkali-free precursor and alkali species during the synthesis of layered Li-, Na-, or K-containing 3d transition-metal oxides (ATMOs) were monitored by in situ high-resolution synchrotron-based X-ray diffraction. The intermediate phases, contributing to the ATMO formation pathway, were directly observed, which provide valuable information for the rational design and synthesis of advanced layered oxides with desirable structural and chemical properties. Display omitted
•In situ high-resolution HT-sXRD techniques was used to unveil the Li/Na/K-ion insertion induced structural evolution during heating.•The dynamics of chemical reaction between alkali-free precursor and alkali species upon calcination were systematically investigated.•High-temperature lithiation reaction pathway strongly depends on the alkali-free precursor type.•Site preferences of Li/Na/K-ion leads to the formation of various types of layered structures.
In view of the requirements for high-energy lithium ion batteries (LIBs), hierarchically layered LiNi1/3Co1/3Mn1/3O2 (NCM111) cathode materials have been prepared using a hydroxide coprecipitation ...method and subsequent high-temperature solid-state reaction. The diffraction results show that the synthesized NCM111 has a well-defined layered hexagonal structure. The initial specific discharge capacity of a Li/NCM111 cell is 204.5 mAh g−1 at a current density of 28 mA g−1 between 2.7 and 4.8 V. However, the cell suffers from poor capacity retention over extended charge-discharge cycles. The structural evolution of NCM111 electrode during electrochemical cycling is carefully investigated by in situ high-resolution synchrotron radiation diffraction. It is found that the nanodomain formation of a layered hexagonal phase H3 and a cubic spinel phase after charging to voltages above 4.6 V is the main source for the structural collapse in c direction and the poor cycling performance. This process is accompanied by the removal of oxygen, the transition metal (TM) migration and the crack generation in the nanodomains of the primary particles. These results may help to better understand the structural degradation of layered cathodes in order to develop high energy density LIBs.
Highlights
The composite gel electrolyte with low tortuosity ion-conducting arrays (GPE/ICAs) exhibiting high room-temperature ionic conductivity (1.08 mS cm
−1
) was successfully prepared by ...directionally growing ice crystals and in-situ polymerization.
The stable and rapid Li
+
migration through ICAs in the GPE is proved by
6
Li solid-state nuclear magnetic resonance and synchrotron radiation X-ray diffraction combined with computer simulations.
Li/LiFePO
4
full cells using GPE/ICAs exhibit excellent cycle performance and high-capacity retention at wide temperature (0–60 °C), which has the potential towards all-weather practical solid-state batteries.
The rapid improvement in the gel polymer electrolytes (GPEs) with high ionic conductivity brought it closer to practical applications in solid-state Li-metal batteries. The combination of solvent and polymer enables quasi-liquid fast ion transport in the GPEs. However, different ion transport capacity between solvent and polymer will cause local nonuniform Li
+
distribution, leading to severe dendrite growth. In addition, the poor thermal stability of the solvent also limits the operating-temperature window of the electrolytes. Optimizing the ion transport environment and enhancing the thermal stability are two major challenges that hinder the application of GPEs. Here, a strategy by introducing ion-conducting arrays (ICA) is created by vertical-aligned montmorillonite into GPE. Rapid ion transport on the ICA was demonstrated by
6
Li solid-state nuclear magnetic resonance and synchrotron X-ray diffraction, combined with computer simulations to visualize the transport process. Compared with conventional randomly dispersed fillers, ICA provides continuous interfaces to regulate the ion transport environment and enhances the tolerance of GPEs to extreme temperatures. Therefore, GPE/ICA exhibits high room-temperature ionic conductivity (1.08 mS cm
−1
) and long-term stable Li deposition/stripping cycles (> 1000 h). As a final proof, Li||GPE/ICA||LiFePO
4
cells exhibit excellent cycle performance at wide temperature range (from 0 to 60 °C), which shows a promising path toward all-weather practical solid-state batteries.
Layered transition-metal oxide materials are ideal cathode candidates for sodium-ion batteries due to high specific energy, yet suffer severe interfacial instability and capacity fading owing to ...strongly nucleophilic surface. In this work, the interfacial stability of layered NaNi
1/3
Fe
1/3
Mn
1/3
O
2
cathode was effectively enhanced by electrolyte optimization. And the interfacial chemistry between the cathode and four widely used electrolytes (EC/DMC, EC/EMC, EC/DEC and EC/PC) was elucidated through experiments and theoretical calculations. The Na
+
solvation structures at cathode-electrolyte interface in all four electrolytes exhibited enhanced coordination due to high electron density and strong nucleophilicity of oxide surface, which promoted the electrolytes’ decomposition with decreased oxidation stability. Among them, the EC/DMC electrolyte showed the tightest solvation structure due to smaller molecular chains and stable electrochemistry, which derived an even and robust cathode electrolyte interphase. It effectively protected the cathode and facilitated the reversible Na
+
transport during long cycles, enabling the batteries with a high capacity retention of 83.3% after 300 cycles. This work provides new insights into the role of electrode surface characteristics in interface chemistry that can guide the design of advanced electrode and electrolyte materials for rechargeable batteries.
Polyanion‐type phosphate materials, such as M3V2(PO4)3 (M = Li/Na/K), are promising as insertion‐type negative electrodes for monovalent‐ion batteries including Li/Na/K‐ion batteries (lithium‐ion ...batteries (LIBs), sodium‐ion batteries (SIBs), and potassium‐ion batteries (PIBs)) with fast charging/discharging and distinct redox peaks. However, it remains a great challenge to understand the reaction mechanism of materials upon monovalent‐ion insertion. Here, triclinic Mg3V4(PO4)6/carbon composite (MgVP/C) with high thermal stability is synthesized via ball‐milling and carbon‐thermal reduction method and applied as a pseudocapacitive negative electrode in LIBs, SIBs, and PIBs. In operando and ex situ studies demonstrate the guest ion‐dependent reaction mechanisms of MgVP/C upon monovalent‐ion storage due to different sizes. MgVP/C undergoes an indirect conversion reaction to form Mg0, V0, and Li3PO4 in LIBs, while in SIBs/PIBs the material only experiences a solid solution with the reduction of V3+ to V2+. Moreover, in LIBs, MgVP/C delivers initial lithiation/delithiation capacities of 961/607 mAh g−1 (30/19 Li+ ions) for the first cycle, despite its low initial Coulombic efficiency, fast capacity decay for the first 200 cycles, and limited reversible insertion/deinsertion of 2 Na+/K+ ions in SIBs/PIBs. This work reveals a new pseudocapacitive material and provides an advanced understanding of polyanion phosphate negative material for monovalent‐ion batteries with guest ion‐dependent energy storage mechanisms.
Mg3V4(PO4)6/carbon composite shows large electrochemical difference for Li+ and Na+/K+ storage suggests different electrochemical mechanisms among Li+ and Na+/K+ storage. In operando studies demonstrate that Mg3V4(PO4)6/carbon undergoes an indirect conversion reaction for Li+ storage, while the material experiences a solid solution for Na+/K+ storage. This work reveals a new pseudocapacitive material Mg3V4(PO4)6/C and guest ion‐dependent energy storage mechanisms of Mg3V4(PO4)6/C.
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