Material innovation on high‐performance Na‐ion cathodes and the corresponding understanding of structural chemistry still remain a challenge. Herein, we report a new concept of high‐entropy strategy ...to design layered oxide cathodes for Na‐ion batteries. An example of layered O3‐type NaNi0.12Cu0.12Mg0.12Fe0.15Co0.15Mn0.1Ti0.1Sn0.1Sb0.04O2 has been demonstrated, which exhibits the longer cycling stability (ca. 83 % of capacity retention after 500 cycles) and the outstanding rate capability (ca. 80 % of capacity retention at the rate of 5.0 C). A highly reversible phase‐transition behavior between O3 and P3 structures occurs during the charge‐discharge process, and importantly, this behavior is delayed with more than 60 % of the total capacity being stored in O3‐type region. Possible mechanism can be attributed to the multiple transition‐metal components in this high‐entropy material which can accommodate the changes of local interactions during Na+ (de)intercalation. This strategy opens new insights into the development of advanced cathode materials.
My brave phase: A high entropy oxide (HEO) cathode, containing nine additional components, the layered O3‐phase NaNi0.12Cu0.12Mg0.12Fe0.15Co0.15Mn0.1Ti0.1Sn0.1Sb0.04O2, delivers long cycling stabilities and high rate capability. As more than 60 % of the capacity is stored in the O3‐type region, the entropy stabilization of the O3‐phase gives the cycling stability and better rate performance.
The demand for electrical energy storage (EES) is ever increasing, which calls for better batteries. NASICON‐structured materials represent a family of important electrodes due to its superior ionic ...conductivity and stable structures. A wide range of materials have been considered, where both vanadium‐based and titanium‐based materials are recommended as being of great interest. NASICON‐structured materials are suitable for both the cathode and the anode, where the operation potential can be easily tuned by the choice of transition metal and/or polyanion group in the structure. NASICON‐structured materials also represent a class of solid electrolytes, which are widely employed in all‐solid‐state ion batteries, all‐solid‐state air batteries, and hybrid batteries. NASICON‐structured materials are reviewed with a focus on both electrode materials and solid‐state electrolytes.
NASICON‐structured materials exhibit great structural stability and fast ionic conductivity. More importantly, these materials can be used as cathodes, anodes, and solid electrolytes. In general, the interfacial resistance between a solid electrolyte and the electrodes in solid‐state batteries is large. However, if all‐NASICON solid‐state batteries can be fabricated, the interfacial resistance may be decreased because it can form a solid‐solution or composite between electrodes and electrolytes due to their similar structure.
The comprehensive performance of carbon anodes for Na‐ion batteries (NIBs) is largely restricted by their inferior rate capability and safety issues. Herein, a slope‐dominated carbon anode is ...achieved at a low temperature of 800 °C, which delivers a high reversible capacity of 263 mA h g−1 at 0.15C with an impressive initial Coulombic efficiency (ICE) of 80 %. When paired with the NaNi1/3Fe1/3Mn1/3O2 cathode, the reversible capacity at 6C is still 75 % of that at 0.15C, and 73 % of the capacity is retained after 1000 cycles at 3C. The enhanced Na storage performance could be attributed to the unique microstructure with randomly oriented short carbon layers and the relatively higher defect concentration. Given its robustness, such a low‐temperature carbonization strategy could also be applicable to other precursors and provide a new opportunity to design slope‐dominated carbon anodes for high safety, low‐cost NIBs with excellent ICE and superior rate capability.
Positive energy: The slope‐dominated carbon anode produced by the inverse low‐temperature strategy shows great potential for low‐cost and high‐safety Na‐ion batteries in terms of high specific capacity, impressive ICE, superior rate capability, and long cycle stability, without any doping, nano‐sizing, or pore‐creating procedures.
Engineering the structure and chemistry of solid electrolyte interface (SEI) on electrode materials is crucial for rechargeable batteries. Using hard carbon (HC) as a platform material, a correlation ...between Na+ storage performance, and the properties of SEI is comprehensively explored. It is found that a “good” SEI layer on HC may not be directly associated with certain kinds of SEI components, such as NaF and Na2O. Whereas, arranging nano SEI components with refined structures constructs the foundation of “good” SEI that enables fast Na+ storage and interface stability of HC in Na‐ion batteries. A layer‐by‐layer SEI on HC with inorganic‐rich inner layer and tolerant organic‐rich outer flexible layer can facilitate excellent rate and cycling life. Besides, SEI layer as the gate for Na+ from electrolyte to HC electrode can modulate interfacial crystallographic structures of HC with pillar‐solvent that function as “pseudo‐SEI” for fast and stable Na+ storage in optimal 1 m NaPF6‐TEGDME electrolytes. Such a layer‐by‐layer SEI combined with a “pseudo‐SEI” layer for HC enables an outstanding rate of 192 mAh g−1 at 2 C and stable cycling over 1100 cycles at 0.5 C. This study provides valuable guidance to improve the electrochemical performance of electrode materials through regulation of SEI in optimal electrolytes.
Building a high‐quality solid electrolyte interface (SEI) layer on electrode material is the key to the high performance of rechargeable batteries. A correlation between the SEI quality, that is, structure and chemistry, and the Na+ storage kinetics and mechanism in hard carbon material is demonstrated in Na‐ion batteries, which effectively guides improvement of battery performance through the engineering of the SEI layer.
All‐solid‐state polymer electrolytes (ASPEs) with excellent processivity are considered one of the most forward‐looking materials for large‐scale industrialization. However, the contradiction between ...improving the mechanical strength and accelerating the ionic migration of ASPEs has always been difficult to reconcile. Herein, a rational concept is raised of high‐entropy microdomain interlocking ASPEs (HEMI‐ASPEs), inspired by entropic elasticity well‐known in polymer and biochemical sciences, by introducing newly designed multifunctional ABC miktoarm star terpolymers into polyethylene oxide for the first time. The tailor‐made HEMI‐ASPEs possess multifunctional polymer chains, which induce themselves to assemble into micro‐ and nanoscale dynamic interlocking networks with high topological structure entropy. HEMI‐ASPEs achieve excellent toughness, considerable ionic conductivity, an appreciable lithium transference number (0.63), and desirable thermal stability (Td > 400 °C) for all‐solid‐state lithium metal batteries. The Li|HEMI‐ASPE‐Li|Li symmetrical cell shows a stable Li plating/stripping performance over 4000 h, and a LiFePO4|HEMI‐ASPE‐Li|Li full cell exhibits a high capacity retention (≈96%) after 300 cycles. This work contributes an innovative design concept introducing high‐entropy supramolecular dynamic networks for ASPEs.
A rational concept of high‐entropy microdomain interlocking all‐solid‐state polymer electrolytes is designed by introducing newly polymerized multifunctional ABC miktoarm star terpolymers into polyethylene oxide. The tailor‐made electrolyte shows advanced mechanical, electrochemical, and thermodynamic performances, stably enabling all‐solid‐state Li metal symmetrical cell cycles over 4000 h.
Sodium‐ion batteries (SIBs) have attracted more and more attention for scalable electrical energy storage due to the abundance and wide distribution of Na resources. However, the anode still remains ...a great challenge for the application of SIBs. Here the production of uniform hard carbon microtubes (HCTs) made from natural cotton through one simple carbonization process and their application as an anode are reported. The study shows that the electrochemical performance of the HCTs is seriously affected by the carbonization temperature due to the difference in their microstructure and heteroatomic content. The HCTs carbonized at 1300 °C deliver the highest reversible capacity of 315 mAh g−1 and good rate capability due to their unique tubular structure. This contribution not only provides a new approach for the preparation of hard carbon materials with unique tubular microstructure using natural inspiration, but it also deepens the fundamental understanding of the sodium storage mechanism.
A novel hard carbon material with microtube structure constructed from hollow fiber structure of cotton fiber by simple one‐step carbonization approach is presented. The electrochemical sodium storage difference of hard carbon microtubes with different carbonization temperature and the sodium storage mechanism are systematically investigated in this work.
Volumetric energy density is a critical but easily neglected index of lithium‐metal batteries (LMBs). Compared with gravimetric energy density, the volumetric energy density (VED) of LMBs is much ...more sensitive to the anode/cathode (A/C) ratio due to the low density of lithium (Li) metal and the volume expansion of the Li‐metal anode owing to its pulverization during cycles. Anode‐free LMBs (AF‐LMBs) have high theoretical VED due to the absence of an anode and high retention with relatively low cell expansion. Because Li plating highly depends on the mother substrate, Li plating on copper (Cu) substrates is more reversible and denser than that on Li substrates during cycling, which is beneficial for maintaining high volumetric capacity and efficient Li utilization. Therefore, considering that excess Li must be strictly limited to achieve competitive energy density, AF‐LMBs (with bare Cu foil as the anode current collector) for high‐volumetric‐density batteries are recommended.
The density of Li metal is low, so the abuse of Li foil in Li‐metal batteries (LMBs) can easily lead to the loss of their advantage in volumetric energy density over Li‐ion batteries. In addition, Li plating on a Li substrate is not as dense as that on a Cu substrate. Therefore, anode‐free LMBs are more worthy of recommendation.
Layered transition metal oxides NaxMO2 (M=transition metal) with P2 or O3 structure have attracted attention in sodium‐ion batteries (NIBs). A universal law is found to distinguish structural ...competition between P2 and O3 types based on the ratio of interlayer distances of the alkali metal layer d(O‐Na‐O) and transition‐metal layer d(O‐M‐O). The ratio of about 1.62 can be used as an indicator. O3‐type Na0.66Mg0.34Ti0.66O2 oxide is prepared as a stable anode for NIBs, in which the low Na‐content (ca. 0.66) usually undergoes a P2‐type structure with respect to NaxMO2. This material delivers an available capacity of about 98 mAh g−1 within a voltage range of 0.4–2.0 V and exhibits a better cycling stability (ca. 94.2 % of capacity retention after 128 cycles). In situ X‐ray diffraction reveals a single‐phase reaction in the discharge–charge process, which is different from the common phase transitions reported in O3‐type electrodes, ensuring long‐term cycling stability.
O3‐type Na0.66Mg0.34Ti0.66O2 oxide is prepared as a stable anode for sodium‐ion batteries (NIBs). This material delivers an available capacity of about 98 mAh g−1 within a voltage range of 0.4–2.0 V and exhibits a better cycling stability (ca. 94.2 % of capacity retention after 128 cycles). In situ XRD results reveal a single‐phase reaction, in contrast to the common phase transitions reported in O3‐type electrodes.
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