Li‐rich cathode materials have attracted increasing attention because of their high reversible discharge capacity (>250 mA h g−1), which originates from transition metal (TM) ion redox reactions and ...unconventional oxygen anion redox reactions. However, many issues need to be addressed before their practical applications, such as their low kinetic properties and inefficient voltage fading. The development of cutting‐edge technologies has led to cognitive advances in theory and offer potential solutions to these problems. Herein, a recent in‐depth understanding of the mechanisms and the frontier electrochemical research progress of Li‐rich cathodes are reviewed. In addition, recent advances associated with various strategies to promote the performance and the development of modification methods are discussed. In particular, excluding Li‐rich Mn‐based (LRM) cathodes, other branches of the Li‐rich cathode materials are also summarized. The consistent pursuit is to obtain energy storage devices with high capacity, reliable practicability, and absolute safety. The recent literature and ongoing efforts in this area are also described, which will create more opportunities and new ideas for the future development of Li‐rich cathode materials.
The practical applications of Li‐rich cathode materials, especially Li‐rich Mn‐based (LRM) cathodes, are hindered by their inherent shortcomings. In this case, the recent understanding of complex reaction mechanisms, the novel modification methods, and the corresponding development trends are comprehensively reviewed. Additionally, other branches and the future opportunities of the Li‐rich cathode materials are also summarized.
VOPO4⋅x H2O has been proposed as a cathode for rechargeable aqueous zinc batteries. However, it undergoes significant voltage decay in conventional Zn(OTf)2 electrolyte. Investigations show the ...decomposition of VOPO4⋅x H2O into VOx in the electrolyte and voltage drops after losing the inductive effect from polyanions.PO43− was thus added to shift the decomposition equilibrium. A high concentration of cheap, highly soluble ZnCl2 salt in the electrolyte further prevents VOPO4⋅x H2O dissolution. The cathode shows stable capacity and voltage retentions in 13 m ZnCl2/0.8 m H3PO4 aqueous electrolyte, in direct contrast to that in Zn(OTf)2 where the decomposition product VOx provides most electrochemical activity over cycling. Sequential H+ and Zn2+ intercalations into the structure are revealed, delivering a high capacity (170 mAh g−1). This work shows the potential issue with polyanion cathodes in zinc batteries and proposes an effective solution using fundamental chemical principles.
The VOPO4⋅x H2O cathode undergoes decomposition and dissolution in rechargeable aqueous Zn batteries. A 13 m ZnCl2/0.8 m H3PO4 aqueous electrolyte is designed to inhibit its degradation, allowing stable capacity and voltage retentions over cycling. Sequential H+ and Zn2+ intercalations into the structure deliver a high capacity of 170 mAh g−1.
High‐nickel LiNi1−x−yMnxCoyO2 (NMC) and LiNi1−x−yCoxAlyO2 (NCA) are the cathode materials of choice for next‐generation high‐energy lithium‐ion batteries. Both NMC and NCA contain cobalt, an ...expensive and scarce metal generally believed to be essential for their electrochemical performance. Herein, a high‐Ni LiNi1−x−yMnxAlyO2 (NMA) cathode of desirable electrochemical properties is demonstrated benchmarked against NMC, NCA, and Al–Mg‐codoped NMC (NMCAM) of identical Ni content (89 mol%) synthesized in‐house. Despite a slightly lower specific capacity, high‐Ni NMA operates at a higher voltage by ≈40 mV and shows no compromise in rate capability relative to NMC and NCA. In pouch cells paired with graphite, high‐Ni NMA outperforms both NMC and NCA and only slightly trails NMCAM and a commercial cathode after 1000 deep cycles. Further, the superior thermal stability of NMA to NMC, NCA, and NMCAM is shown using differential scanning calorimetry. Considering the flexibility in compositional tuning and immediate synthesis scalability of high‐Ni NMA very similar to NCA and NMC, this study opens a new space for cathode material development for next‐generation high‐energy, cobalt‐free Li‐ion batteries.
A novel cobalt‐free high‐energy cathode material, high‐nickel LiNi1−x−yMnxAlyO2 (NMA), is reported, with desirable physical and electrochemical properties. Benchmarked against LiNi1−x−yMnxCoyO2 (NMC) and LiNi1−x−yCoxAlyO2 (NCA) of identical Ni content (89 mol%), NMA delivers attractive specific energy, rate capability, cyclability, and thermal stability. Morevoer, NMA offers immediate synthesis scalability without the constraint of a vulnerable cobalt supply chain.
Rechargeable aqueous batteries with Zn2+ as a working‐ion are promising candidates for grid‐scale energy storage because of their intrinsic safety, low‐cost, and high energy‐intensity. However, ...suitable cathode materials with excellent Zn2+‐storage cyclability must be found in order for Zinc‐ion batteries (ZIBs) to find practical applications. Herein, NaCa0.6V6O16·3H2O (NaCaVO) barnesite nanobelts are reported as an ultra‐stable ZIB cathode material. The original capacity reaches 347 mAh g−1 at 0.1 A g−1, and the capacity retention rate is 94% after 2000 cycles at 2 A g−1 and 83% after 10 000 cycles at 5 A g−1, respectively. Through a combined theoretical and experimental approach, it is discovered that the unique V3O8 layered structure in NaCaVO is energetically favorable for Zn2+ diffusion and the structural water situated between V3O8 layers promotes a fast charge‐transfer and bulk migration of Zn2+ by enlarging gallery spacing and providing more Zn‐ion storage sites. It is also found that Na+ and Ca2+ alternately suited in V3O8 layers are the essential stabilizers for the layered structure, which play a crucial role in retaining long‐term cycling stability.
A hydrated, monovalent‐ and divalent‐cations co‐pre‐inserted V3O8 layered structure, namely NaCa0.6V6O16·3H2O (NaCaVO), is synthesized and shows ultra‐stable and high‐rate Zn2+‐storage performance. Through a combined theoretical and experimental approach, the excellent performance is found to stem from the structural‐H2O‐enabled large gallery spacing and fast charge transfer kinetics along with Na+ and Ca2+ costabilized V3O8 layer structure.
Li2S/metal nanocomposites are synthesized via chemical conversion reactions, and their properties as cathode prelithiation additives have been investigated to offset the initial lithium loss in ...lithium‐ion batteries. The Li2S/Co nanocomposite shows good stability, and delivers a high “donor” lithium‐ion specific capacity of 670 mAh g−1 in the cutoff potential range of existing cathode materials in a carbonate‐based electrolyte.
Abstract
Potassium‐ion batteries are attracting great interest for emerging large‐scale energy storage owing to their advantages such as low cost and high operational voltage. However, they are still ...suffering from poor cycling stability and sluggish thermodynamic kinetics, which inhibits their practical applications. Herein, the synthesis of hierarchical K
1.39
Mn
3
O
6
microspheres as cathode materials for potassium‐ion batteries is reported. Additionally, an effective AlF
3
surface coating strategy is applied to further improve the electrochemical performance of K
1.39
Mn
3
O
6
microspheres. The as‐synthesized AlF
3
coated K
1.39
Mn
3
O
6
microspheres show a high reversible capacity (about 110 mA h g
−1
at 10 mA g
−1
), excellent rate capability, and cycling stability. Galvanostatic intermittent titration technique results demonstrate that the increased diffusion kinetics of potassium‐ion insertion and extraction during discharge and charge processes benefit from both the hierarchical sphere structure and surface modification. Furthermore, ex situ X‐ray diffraction measurements reveal that the irreversible structure evolution can be significantly mitigated via surface modification. This work sheds light on rational design of high‐performance cathode materials for potassium‐ion batteries.
Layered Li‐rich cathode materials with high reversible energy densities are becoming prevalent. However, owing to the activation of low‐potential redox couples and the progressively irreversible ...structural transformation caused by the local adjustment of transition‐metal ions in the intra/interlayer driven by anionic redox, continuous capacity degradation, and voltage decay emerge, thus greatly reducing the energy density and increasing the difficulty of battery system management. Herein, layered Li‐rich cathode materials with higher intralayer configuration entropy have more local structural diversity and higher distortion energy, resulting in superior local structural adaptability with no drastic redox couple evolution, major local structural adjustment, or obvious layered‐to‐spinel phase transition. Consequently, the energy retention of the entropy‐stabilization‐strategy‐enhanced Li‐rich cathode materials is almost twice that of a typical Li‐rich cathode material (Li1.20Mn0.54Ni0.13Co0.13O2, T‐LRM) after 3 months of cyclic testing. Moreover, when cycled at 1 C, the voltage degradation per cycle is less than 0.02%, that is, it results in a voltage loss of only 0.8 mV per cycle, which is excellent performance. This study paves the way for the development of Li‐rich cathode materials with stabilized intralayer atomic arrangements and high local structural adaptability.
Layered Li‐rich cathode materials with higher intralayer configuration entropy have more local structural diversity and higher distortion energy, resulting in superior local structural adaptability: no drastic redox couple evolution, major local structural adjustment, or obvious layered‐to‐spinel phase transition. This leads to high stability of the capacity and voltage, greatly enhancing energy retention.
Aqueous zinc-ion batteries (ZIBs) with low-priced, high-safety, and high synergistic efficiency have captured an ever-increasing amount of consideration and have been expected to be a promising ...choice to replace LIBs. However, the cathode materials of ZIBs reported have many shortcomings such as poor electron and zinc ion conductivity and complicated energy storage mechanisms. In this review, several typical cathode materials for ZIBs in recent years and their detailed energy storage mechanisms are summarized, and various improvement methods to enhance the electrochemical properties of ZIBs are briefly introduced. Eventually, the current problems and the expected development foregrounds of ZIBs are proposed.
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Although lithium-ion batteries (LIBs) have many advantages, they cannot satisfy the demands of numerous large energy storage industries owing to their high cost, low security, and low resource richness. Aqueous zinc-ion batteries (ZIBs) with low cost, high safety, and high synergistic efficiency have attracted an increasing amount of attention and are considered a promising choice to replace LIBs. However, the existing cathode materials for ZIBs have many shortcomings, such as poor electron and zinc ion conductivity and complex energy storage mechanisms. Thus, it is crucial to identify a cathode material with a stable structure, substantial limit, and suitability for ZIBs. In this review, several typical cathode materials for ZIBs employed in recent years and their detailed energy storage mechanisms are summarized, and various methods to enhance the electrochemical properties of ZIBs are briefly introduced. Finally, the existing problems and expected development directions of ZIBs are discussed.
An increase in the amount of nickel in LiMO2 (M = Ni, Co, Mn) layered system is actively pursued in lithium‐ion batteries to achieve higher capacity. Nevertheless, fundamental effects of Ni element ...in the three‐component layered system are not systematically studied. Therefore, to unravel the role of Ni as a major contributor to the structural and electrochemical properties of Ni‐rich materials, Co‐fixed LiNi0.5+xCo0.2Mn0.3–xO2 (x = 0, 0.1, and 0.2) layered materials are investigated. The results, on the basis of synchrotron‐based characterization techniques, present a decreasing trend of Ni2+ content in Li layer with increasing total Ni contents. Moreover, it is discovered that the chex.‐lattice parameter of layered system is not in close connection with the interslab thickness related to actual Li ion pathway. The interslab thickness increases with increasing Ni concentration even though the chex.‐lattice parameter decreases. Furthermore, the lithium ion pathway is preserved in spite of the fact that the c‐axis is collapsed at highly deintercalated states. Also, a higher Ni content material shows better structural properties such as larger interslab thickness, lower cation disorder, and smoother phase transition, resulting in better electrochemical properties including higher Li diffusivity and lower overpotential when comparing materials with lower Ni content.
For the Co‐fixed LiNixCoyMnzO2 layered system, an increase in nickel content creates favorable environments for lithium ion transport such as wider lithium ion channels, lower cation disorders, and smoother phase transitions, resulting in better electrochemical performance including rate capability and cycle life. More importantly, the lithium ion channels are preserved in spite of the fact that the c‐axis is collapsed.
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