Nickel‐rich layered lithium transition metal oxides (LiNi1−x−yCoxMnyO2 and LiNi1−x−yCoxAlyO2, x + y ≤ 0.2) are the most attractive cathode materials for the next generation lithium‐ion batteries for ...automotive application. However, they suffer from structural/interfacial instability during repeated charge/discharge, resulting in severe performance degradation and serious safety concerns. This work provides a comprehensive review about challenges and strategies to advance nickel‐rich layered cathodes specifically for harsh (high‐voltage, high‐temperature, and fast charging) operations. Firstly, the degradation pathways of nickel‐rich cathodes including surface/interface degradation, undesired cathode–electrolytes parasitic reactions, gas evolution, inter/intragranular cracking, and electrical/ionic isolation are discussed. Then, recent achievements in stabilizing the structure/interface of nickel‐rich cathodes via surface coating, cation/anion doping, composition tailoring, morphology engineering, and electrolytes optimization are summarized. Moreover, challenges and strategies to improve the performance of Ni‐rich cathodes at the electrode level are discussed. Outlook and perspectives to promote the practical application of nickel‐rich layered cathodes toward automotive application are provided as well.
This review is aimed at a comprehensive discussion on the challenges and strategies (material/electrode structures and interphase) to advance the application of Ni‐rich cathodes for harsh operation (high Ni content, high voltage, high temperature, and high rate).
Considering the natural abundance and low cost of sodium resources, sodium‐ion batteries (SIBs) have received much attention for large‐scale electrochemical energy storage. However, smart structure ...design strategies and good mechanistic understanding are required to enable advanced SIBs with high energy density. In recent years, the exploration of advanced cathode, anode, and electrolyte materials, as well as advanced diagnostics have been extensively carried out. This review mainly focuses on the challenging problems for the attractive battery materials (i.e., cathode, anode, and electrolytes) and summarizes the latest strategies to improve their electrochemical performance as well as presenting recent progress in operando diagnostics to disclose the physics behind the electrochemical performance and to provide guidance and approaches to design and synthesize advanced battery materials. Outlook and perspectives on the future research to build better SIBs are also provided.
Room temperature sodium‐ion batteries show great promise for large scale electrochemical energy storage application because of the low cost and large abundance of sodium resource. The progress and main challenges regarding the development of electrode, electrolytes, and advanced diagnostics are summarized with the aim of achieving a high energy density of over 400 Wh kg−1 on the cell level.
Electrolyte modulation simultaneously suppresses polysulfide the shuttle effect and lithium dendrite formation of lithium–sulfur (Li‐S) batteries. However, the sluggish S redox kinetics, especially ...under high S loading and lean electrolyte operation, has been ignored, which dramatically limits the cycle life and energy density of practical Li‐S pouch cells. Herein, we demonstrate that a rational combination of selenium doping, core–shell hollow host structure, and fluorinated ether electrolytes enables ultrastable Li stripping/plating and essentially no polysulfide shuttle as well as fast redox kinetics. Thus, high areal capacity (>4 mAh cm−2) with excellent cycle stability and Coulombic efficiency were both demonstrated in Li metal anode and thick S cathode (4.5 mg cm−2) with a low electrolyte/sulfur ratio (10 μL mg−1). This research further demonstrates a durable Li‐Se/S pouch cell with high specific capacity, validating the potential practical applications.
A rational combination of selenium‐doped sulfur cathode design with electrolyte modulation enables robust shuttle‐ and dendrite‐free cathode and anode chemistries. This strategy is demonstrated to be effective in achieving ultrastable Li‐S batteries even under high cathode loading and low electrolyte conditions with a pouch cell configuration.
Lithium reactivity with electrolytes leads to their continuous consumption and dendrite growth, which constitute major obstacles to harnessing the tremendous energy of lithium-metal anode in a ...reversible manner. Considerable attention has been focused on inhibiting dendrite via interface and electrolyte engineering, while admitting electrolyte-lithium metal reactivity as a thermodynamic inevitability. Here, we report the effective suppression of such reactivity through a nano-porous separator. Calculation assisted by diversified characterizations reveals that the separator partially desolvates Li
in confinement created by its uniform nanopores, and deactivates solvents for electrochemical reduction before Li
-deposition occurs. The consequence of such deactivation is realizing dendrite-free lithium-metal electrode, which even retaining its metallic lustre after long-term cycling in both Li-symmetric cell and high-voltage Li-metal battery with LiNi
Mn
Co
O
as cathode. The discovery that a nano-structured separator alters both bulk and interfacial behaviors of electrolytes points us toward a new direction to harness lithium-metal as the most promising anode.
The proper choice of nonprecious transition metals as single atom catalysts (SACs) remains unclear for designing highly efficient electrocatalysts for hydrogen evolution reaction (HER). Herein, ...reported is an activity correlation with catalysts, electronic structure, in order to clarify the origin of reactivity for a series of transition metals supported on nitrogen‐doped graphene as SACs for HER by a combination of density functional theory calculations and electrochemical measurements. Only few of the transition metals (e.g., Co, Cr, Fe, Rh, and V) as SACs show good catalytic activity toward HER as their Gibbs free energies are varied between the range of –0.20 to 0.30 eV but among which Co‐SAC exhibits the highest electrochemical activity at 0.13 eV. Electronic structure studies show that the energy states of active valence dz2 orbitals and their resulting antibonding state determine the catalytic activity for HER. The fact that the antibonding state orbital is neither completely empty nor fully filled in the case of Co‐SAC is the main reason for its ideal hydrogen adsorption energy. Moreover, the electrochemical measurement shows that Co‐SAC exhibits a superior hydrogen evolution activity over Ni‐SAC and W‐SAC, confirming the theoretical calculation. This systematic study gives a fundamental understanding about the design of highly efficient SACs for HER.
The origin of single atom catalytic activity for hydrogen evolution reaction is explored via mutual collaboration of computational prediction and experimental validation. It is found that single atom catalytic activity depends on their valence orbital states, showing excellent correlation with charge transfer and activity descriptors. This systematic study will open a new direction to design heterogeneous catalysts for hydrogen evolution reaction.
Abstract
Graphite, a robust host for reversible lithium storage, enabled the first commercially viable lithium-ion batteries. However, the thermal degradation pathway and the safety hazards of ...lithiated graphite remain elusive. Here, solid-electrolyte interphase (SEI) decomposition, lithium leaching, and gas release of the lithiated graphite anode during heating were examined by in situ synchrotron X-ray techniques and in situ mass spectroscopy. The source of flammable gas such as H
2
was identified and quantitively analyzed. Also, the existence of highly reactive residual lithium on the graphite surface was identified at high temperatures. Our results emphasized the critical role of the SEI in anode thermal stability and uncovered the potential safety hazards of the flammable gases and leached lithium. The anode thermal degradation mechanism revealed in the present work will stimulate more efforts in the rational design of anodes to enable safe energy storage.
Sustainable sodium‐ion batteries (SSIBs) using renewable organic electrodes are promising alternatives to lithium‐ion batteries for the large‐scale renewable energy storage. However, the lack of ...high‐performance anode material impedes the development of SSIBs. Herein, we report a new type of organic anode material based on azo group for SSIBs. Azobenzene‐4,4′‐dicarboxylic acid sodium salt is used as a model to investigate the electrochemical behaviors and reaction mechanism of azo compound. It exhibits a reversible capacity of 170 mAh g−1 at 0.2C. When current density is increased to 20C, the reversible capacities of 98 mAh g−1 can be retained for 2000 cycles, demonstrating excellent cycling stability and high rate capability. The detailed characterizations reveal that azo group acts as an electrochemical active site to reversibly bond with Na+. The reversible redox chemistry between azo compound and Na ions offer opportunities for developing long‐cycle‐life and high‐rate SSIBs.
SIB‐ling rivals: A new category of organic electrode material, azo compounds, exhibits one of the best performances in organic sodium‐ion batteries (SIBs). The extended π‐conjugated structure in the aromatic azo compound and strong adsorption toward Na+ ions by nitrogen atoms in the azo group enables the long cycle life and high‐rate performance of the azo compounds.
The separator, an ionic permeable and electronic insulating membrane between cathode and anode, plays a crucial role in the electrochemical and safety performance of batteries. However, commercial ...polyolefin separators not only suffer from inevitable thermal shrinkage at elevated temperature, but also fail to inhibit the hidden chemical crosstalk of reactive gases such as O2, leading to often reported thermal runaway (TR) and hence preventing large‐scale implementation of high‐energy‐density lithium‐ion batteries. Herein, a nanoporous non‐shrinkage separator (GS‐PI) is fabricated via a novel gel‐stretching orientation approach to eliminate TR. In situ synchrotron small angle X‐ray scattering during heating clearly shows that the as‐prepared thin GS‐PI separator exhibits superior mechanical tolerance at high temperature, thus effectively preventing internal short circuit. Meanwhile, the unique nanoporous structure design further blocks chemical crosstalk and the associated exothermic reactions. Accelerating rate calorimetry tests reveal that the practical 1 Ah LiNi0.6Co0.2Mn0.2O2 (NCM622)/graphite pouch cell using GS‐PI nanoporous separator show a maximum temperature rise (dT/dtmax) of only 3.7 °C s−1 compared to 131.6 °C s−1 in the case of Al2O3@PE macroporous separator. Moreover, despite the reduced pore size, the GS‐PI separator demonstrates better cycling stability than conventional Al2O3@PE separator at high temperature without sacrificing specific capacity and rate capability.
A non‐shrinkage nanoporous separator is designed for enhancing the safety of lithium‐ion battery through a novel gel‐stretching strategy. Both internal short circuit and chemical crossover within the battery are simultaneously prevented when the separator is employed. The results elucidate the underlying mechanism to ensure battery safety and highlight the design principles for advanced separators.
P2-type sodium manganese-rich layered oxides are promising cathode candidates for sodium-based batteries because of their appealing cost-effective and capacity features. However, the structural ...distortion and cationic rearrangement induced by irreversible phase transition and anionic redox reaction at high cell voltage (i.e., >4.0 V) cause sluggish Na-ion kinetics and severe capacity decay. To circumvent these issues, here, we report a strategy to develop P2-type layered cathodes via configurational entropy and ion-diffusion structural tuning. In situ synchrotron X-ray diffraction combined with electrochemical kinetic tests and microstructural characterizations reveal that the entropy-tuned Na
Mn
Ni
Cu
Mg
Ti
O
(CuMgTi-571) cathode possesses more {010} active facet, improved structural and thermal stability and faster anionic redox kinetics compared to Na
Mn
Ni
O
. When tested in combination with a Na metal anode and a non-aqueous NaClO
-based electrolyte solution in coin cell configuration, the CuMgTi-571-based positive electrode enables an 87% capacity retention after 500 cycles at 120 mA g
and about 75% capacity retention after 2000 cycles at 1.2 A g
.
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