The rapid growth in global electric vehicles (EVs) sales has promoted the development of Co-free, Ni-rich layered cathodes for state-of-the-art high energy-density, inexpensive lithium-ion batteries ...(LIBs). However, progress in their commercial use has been seriously hampered by exasperating performance deterioration and safety concerns. Herein, a robust single-crystalline, Co-free, Ni-rich LiNi0.95Mn0.05O2 (SC-NM95) cathode is successfully designed using a molten salt-assisted method, and it exhibits better structural stability and cycling durability than those of polycrystalline LiNi0.95Mn0.05O2 (PC-NM95). Notably, the SC-NM95 cathode achieves a high discharge capacity of 218.2 mAh g−1, together with a high energy density of 837.3 Wh kg−1 at 0.1 C, mainly due to abundant Ni2+/Ni3+ redox. It also presents an outstanding capacity retention (84.4%) after 200 cycles at 1 C, because its integrated single-crystalline structure effectively inhibits particle microcracking and surface phase transformation. In contrast, the PC-NM95 cathode suffers from rapid capacity fading owing to the nucleation and propagation of intergranular microcracking during cycling, facilitating aggravated parasitic reactions and rock-salt phase accumulation. This work provides a fundamental strategy for designing high-performance single-crystalline, Co-free, Ni-rich cathode materials and also represents an important breakthrough in developing high-safe, low-cost, and high-energy LIBs.
Robust single-crystalline Co-free Ni-rich LiNi0.95Mn0.05O2 (SC-NM95) cathode successfully designed by molten salt-assisted method exhibits the enhanced structural stability and cycling durability compared with that of polycrystalline LiNi0.95Mn0.05O2 (PC-NM95) cathode. Display omitted
•Single-crystalline Co-free Ni-rich LiNi0.95Co0.05O2 cathode was firstly designed and systematically explored.•The SC-NM95 cathode presents outstanding structural stability and cycling durability.•The performance degradations of PC-NM95 were attributed to the microcracking formation and structural transformations.•It provides insights into the fundamental design of high-performance single-crystalline Co-free Ni-rich cathodes.
The ever‐increasing energy density requirements in electric vehicles (EVs) have boosted the development of Ni‐rich layered oxide cathodes for state‐of‐the‐art lithium‐ion batteries. Nevertheless, the ...commercialization of polycrystalline Ni‐rich cathodes (PCNCs) is hindered by the severe performance degradation and safety concerns that are tightly related to its particle cracking during cycling. Single‐crystalline Ni‐rich cathodes (SCNCs) with eliminated grain boundaries and high mechanical strength have recently attracted extensive attention owing to their superior structural and cycling stability, which present high crack resistance during electrochemical operation. Various articles have focused on the trial‐and‐error synthesis and modifications of SCNCs, as well as the comparison of performances and mechanisms with PCNCs. However, there has been much less effort in systematic analysis and summary to reveal their key challenges, controversies, and the corresponding primary causes. In this review, the advantages and debates in structural and electrochemical properties of SCNCs over PCNCs are summarized to provide fundamental understanding of SCNCs. Then the current practical issues and challenges are comprehensively discussed from the viewpoints of both academia and industry, as well as the proposed modification strategies and underlying mechanisms for SCNCs. The outlook and perspectives are further given to facilitate the commercial applications of SCNCs in high‐performance EVs.
Single‐crystalline Ni‐rich cathodes (SCNCs) with high crack resistance have recently attracted extensive attention. This review summarizes the advantages and debates on structural and electrochemical properties of SCNCs, and comprehensively discusses the current practical issues and challenges from the perspectives of both academia and industry, as well as the proposed modification strategies and underlying mechanisms for SCNCs.
The extensive applications of spinel LiMn2O4 (LMO) are severely plagued by grievous capacity degradation and structural collapse, mainly ascribed to deleterious Jahn−Teller distortion and subsequent ...dissolution of Mn2+. Herein, highly stable LMO with atomic interlocking effect is rationally designed via engineering Al into the unoccupied 16c sites. The local coordination environment of the surficial MnO6 octahedron is reconstructed by robust Al−O band coherency, giving strengthened lattice oxygen skeleton and constraining heterophase evolution with the suppression of Jahn−Teller distortion, validated by theoretical calculations coupled with synchrotron X‐ray absorption spectrum. Concomitantly, with the occupation of Al in interstitial site, the migration of Mn is effectively restrained, directly observed by scanning transmission electron microscopy, leading to the inhibition of inactivation as well as dissolution loss of Mn. Resultantly, splendid long cycling stability of Al‐LMO after 1000 loops with only 0.019% capacity fading per cycle is presented. Given this, this elaborate study can provide an ingenious avenue for regulating the structure/interface chemistry architecture in electrode materials.
The highly stable LiMn2O4 with atomic interlocking effect is activated via engineering Al into the unoccupied 16c sites on surface, which is conducive to suppress Jahn−Teller distortion as well as heterophase evolution, and restrain the migration of Mn.
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•Electrochemical performances of LiMn2−xRuxO4 (x = 0, 0.01, 0.03, 0.05) cathodes are systematically studied.•The Ru-LMO cathode presents superior structural stability and cycling ...durability.•The robust crystal structure framework is effectively reconstructed based on d-p orbital hybridization design.•It inaugurates an explicit direction for rationally tuning the orbital hybridization for alkali metal batteries.
Spinel LiMn2O4 is a prevalent cathode material due to its environmental benignities and high operating voltage. Nevertheless, capacity attenuation and structural collapse are still inevitable, caused by the native Jahn–Teller distortion and spontaneous disproportionation of Mn3+. Hereby, LiMn2O4 cathode with stable crystallographic structure is rationally designed based on valence-bond theory with introduction of Ru dopant. The enhanced orbital hybridization between Mn 3d and O 2p is successfully achieved owing to the reinforcing band coherency of Mn–O aroused from the electrostatic interaction between Mn and Ru atoms. Notably, the robust crystal structure framework is effectively reconstructed, which is beneficial for ameliorating phase evolution and inhibiting structural degradation substantiated by the state-of-the-art synchrotron X-ray absorption spectroscopy and in-situ X-ray diffraction. Concomitantly, LiO4 tetrahedron is effectively weakened, further facilitating the rapid Li+ diffusion kinetics intensively confirmed by theoretical calculations and electrochemical tests. Remarkably, the as-designed Ru-doped LiMn2O4 manifests splendid long cycling stability, affording a respectable capacity retention of 88.2 % after 200 loops. Given this, the intriguing work might inaugurate an explicit direction for rationally tuning the orbital hybridization towards advanced electrodes in alkali metal batteries.
With ever‐increasing pursuit for high‐value output in recycling spent lithium‐ion batteries (LIBs), traditional recycling methods of cathodes tend to be obsolete because of the complicated ...procedures. Herein, we first upcycle spent polycrystal LiNi0.88Co0.095Al0.025O2 (S‐NCA) to high value‐added single‐crystalline and Li‐rich cathode materials through a simple but feasible LiOH‐Na2SO4 eutectic molten salt strategy. The in situ X‐ray diffraction technique and a series of paratactic experiments record the evolution process of upcycling and prove that excessive Li occupies the transition metal (TM) layers. Beneficial from the single‐crystalline and Li‐rich nature, the regenerated NCA (R‐NCA) exhibits remarkably enhanced electrochemical performances in terms of long‐term cyclability, high‐rate performance and low polarization. This approach can also be successfully extended to other cathode materials e.g., LiNixCoyMnzO2 (NCM) and mixed spent NCAs with varied degree of Li loss.
Direct upcycling of a spent Ni‐rich cathode (LiNi0.88Co0.095Al0.025O2, NCA) to a single‐crystalline and Li‐rich cathode is achieved for Li‐ion batteries in a binary LiOH‐Na2SO4 system. The regenerated NCA exhibits a remarkable electrochemical performance in terms of long‐term cyclability, high rate performance and low polarization. This strategy can be extended to other cathode materials e.g., LiNixCoyMnzO2 (NCM) and mixed spent NCAs with varied Li compositions.
Recent developments of transition metal selenides as potential anode materials for lithium-ion batteries (LIBs) have attracted much attention. In this work, NiSe2 nanosheets grown on carbon fiber ...cloth (denoted as NiS2 nanosheets/CFC) are successfully prepared via simple hydrothermal and subsequent annealing methods. When investigated as anode for LIBs, NiSe2 nanosheets/CFC exhibits high reversible capacities of 1196 mA h g−1 after 100 cycles at 0.1 A g−1, 811 mA h g−1 after 150 cycles at 0.5 A g−1, corresponding to superior capacity retention of 94%. Besides, a high-rate capability of 682 mA h g−1 at 2 A g−1 is also achieved. The excellent electrochemical performance of NiSe2 nanosheets/CFC is mainly derived from the good electrical conductivity of carbon fiber cloth (CFC), the increased active-surface area and fast Li+ diffusion caused by the nanosheets structure with particle packing. Therefore, NiSe2 nanosheets/CFC is anticipated to be a promising anode material for flexible Li-ion batteries.
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•NiSe2 nanosheets grown on CFC are successfully prepared.•NiSe2 nanosheets/CFC exhibits a high capacity of 1196 mA h g−1 after 100 cycles at 0.1 A g−1.•The excellent electrochemical performance is mainly due to the good conductivity and the nanostructure.
Robust single-crystalline Ni-rich cathodes with increasing Ni proportion, LiNi0.83Co0.11Mn0.06O2 (SC83), LiNi0.88Co0.06Mn0.06O2 (SC88), and LiNi0.95Co0.03Mn0.02O2 (SC95) were successfully designed ...with molten salt-assisted method, and the correlation between the Li+ storage properties, particle microcracking, surface phase transitions, and Ni fraction in the single-crystalline Ni-rich cathodes have been profoundly investigated.
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•-crystalline Ni-rich cathodes with increasing Ni proportion were designed with molten salt-assisted method.•The single-crystalline LiNi0.83Co0.11Mn0.06O2 cathode presents superior structural stability and cycling durability.•Performance degradations were attributed to the aggravated Li/Ni mixing and H2 ↔ H3 phase transition.•It provides approach for designing high-energy density and stable single-crystalline Ni-rich cathodes.
Further commercial development of polycrystalline Ni-rich layered cathode is severely hindered by the deep-rooted particle microcracking, mainly initiated among the randomly orientated grain boundaries of the primary particles. Herein, robust single-crystalline Ni-rich LiNi0.83Co0.11Mn0.06O2 (SC83) prepared by molten salt-assisted method shows the enhanced structure stability and cycling durability. It’s found that the particle microcracking is effectively removed for SC83 cathode during prolonged cycling helped with its eliminated grain boundaries and slight crystal shrinkage, leading to superior capacity retention of 92.8% after 100 cycles. Notably, the discharge capacity and energy density are effectively boosted with increasing Ni fraction majorly based on the more available Ni2+/Ni3+ redox, giving rise to high capacities of 211.2 and 219.4 mAh g−1 for LiNi0.88Co0.06Mn0.06O2 (SC88) and LiNi0.95Co0.03Mn0.02O2 (SC95) cathodes, respectively. However, the particle microcracking is progressively exacerbated owing to the aggravated Li/Ni mixing and H2 ↔ H3 phase transition with Ni proportion higher than or equal to 88% in SC cathodes, resulting in severe structure collapse and capacity fading during high-rate cycling, in which a poor capacity retention of 51.8% after 250 cycles at 5C is observed for single-crystalline SC95cathode. This work sheds light on the rational design of single-crystalline Ni-rich cathodes, and highlighted the trade-off between the energy density and cycling durability, facilitating the extensive applications of single-crystalline Ni-rich cathodes in high-performance electric vehicles (EVs).
Because of the high theoretical capability surpassing other anode materials, silicon (Si) has been regarded as the most potential anode material for the next-generation lithium-ion batteries (LIBs). ...In this work, the amorphous SiO2 precursors extracted from earth-abundant and silicon-rich clay mineral, kaolinite, have been applied to prepare Si nanosheets (k-Si) through a magnesiothermic reduction method. Benefiting from the special two-dimensional nanostructure, the problem caused by volume expansion can be greatly relieved. As an anode material of LIBs, the Si nanosheets deliver a high reversible specific capacity of 1909 mAh g−1 at a low current density of 0.2 A g−1 after 50 cycles, 1156 mAh g−1 at a high current density of 2 A g−1 after 500 cycles and excellent rate capability of 889 mAh g−1 at a current density of 4 A g−1, remarkably preceding the performance of Si material prepared by commercial SiO2 powders. The strategy paves a promising way to the efficient production of electrode materials from the natural minerals.
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•SiO2 nanosheets can be extracted from abundant and low-cost kaolinite.•Si nanosheets can be obtained with a high yield via magnesium thermal reaction.•High capacity and long cycling stability can be achieved.
In this work, one-dimensional (1D) needle-like porous FeCo2O4 nanowire arrays on flexible carbon cloth (CC) are successfully fabricated by a facile synthesis route and investigated as anode material ...for lithium ion batteries (LIBs). X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) have been applied to characterize the materials. The 1D FeCo2O4 nanowires provide a large surface area and enough space to accommodate volume changes. Besides, taking advantages of good conductivity from the CC substrate and the synergistic effect between Co and Fe ions, the integrated FeCo2O4 nanowire arrays/CC electrodes exhibits prominent lithium-storage performance with high reversible capacity of about 2101 mAh g−1 at 100 mA g−1 and outstanding capacity retention of 97.1% from 2 to 200 cycles, and retains high rate capacity of 876 mAh g−1 at 2 A g−1. Even cycled at higher current density of 1 A g−1, FeCo2O4 nanowire arrays/CC electrode still maintains stable reversible capacity of 1013.8 mAh g−1 after 350 cycles, corresponding to 78.3% of the second discharge capacity. Therefore, FeCo2O4 nanowire arrays/CC could be considered to be a promising candidate as anode material for flexible Li-ion batteries and future stretchable/bendable electronic devices.
One-dimensional needle-like porous FeCo2O4 nanowire arrays on flexible carbon cloth (CC) by a facile hydrothermal method and subsequent post-annealing treatment. FeCo2O4 nanowire arrays/CC exhibits outstanding lithium storage performance in terms of high reversible capacity, good cycling stability, and superior rate capability, which can be considered to be a promising candidate as anode material for flexible Li-ion batteries and future stretchable/bendable electronic devices. Display omitted
•FeCo2O4 nanowires/CC were synthesized via a facile hydrothermal reaction followed by annealing treatment.•FeCo2O4 nanowires/CC showed high capacity, superior capacity retention, and outstanding rate performance.•FeCo2O4 nanowires/CC could be applied to the flexible Li-ion batteries and wearable devices.
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