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.
Reversibly intercalating ions into host materials for electrochemical energy storage is the essence of the working principle of rocking-chair type batteries. The most relevant example is the graphite ...anode for rechargeable Li-ion batteries which has been commercialized in 1991 and still represents the benchmark anode in Li-ion batteries 30 years later. Learning from past lessons on alkali metal intercalation in graphite, recent breakthroughs in sodium and potassium intercalation in graphite have been demonstrated for Na-ion batteries and K-ion batteries. Interestingly, some significant differences proved to exist for the intercalation of Na
+
and K
+
into graphite compared with the Li
+
case. Such different host-guest interactions are unique depending on the host materials and electrolytes, which greatly contribute to a deeper understanding of intercalation-type electrode materials for next generation alkali metal ion batteries. This review summarizes significant advances from both experimental and theoretical calculations with a focus on comparing the intercalation of three alkali metal ions (Li
+
, Na
+
, K
+
) into graphite and aims to clarify the intimate host-guest relationships and the underlying mechanisms. New approaches developed to achieve favorable intercalation coupled with the challenges in this field are also discussed. We also extrapolate alkali metal ion intercalation in graphite to mono-/multi-valent ions in layered electrode materials, which will deepen the understanding of intercalation chemistry and provide guidance to explore new guests and hosts.
This review compares the intercalation behaviors of alkali metal ions in graphite, offers insight for the host-guest interaction mechanisms, and expands the intercalation chemistry of pure ions to complex anions, ion-solvent, and multivalent ions.
The ever-growing demand for advanced energy storage devices in portable electronics, electric vehicles and large scale power grids has triggered intensive research efforts over the past decade on ...lithium and sodium batteries. The key to improve their electrochemical performance and enhance the service safety lies in the development of advanced electrode, electrolyte, and auxiliary materials. Ionic liquids (ILs) are liquids consisting entirely of ions near room temperature, and are characterized by many unique properties such as ultralow volatility, high ionic conductivity, good thermal stability, low flammability, a wide electrochemical window, and tunable polarity and basicity/acidity. These properties create the possibilities of designing batteries with excellent safety, high energy/power density and long-term stability, and also provide better ways to synthesize known materials. IL-derived materials, such as poly(ionic liquids), ionogels and IL-tethered nanoparticles, retain most of the characteristics of ILs while being endowed with other favourable features, and thus they have received a great deal of attention as well. This review provides a comprehensive review of the various applications of ILs and derived materials in lithium and sodium batteries including Li/Na-ion, dual-ion, Li/Na-S and Li/Na-air (O
2
) batteries, with a particular emphasis on recent advances in the literature. Their unique characteristics enable them to serve as advanced resources, medium, or ingredient for almost all the components of batteries, including electrodes, liquid electrolytes, solid electrolytes, artificial solid-electrolyte interphases, and current collectors. Some thoughts on the emerging challenges and opportunities are also presented in this review for further development.
A comprehensive review of various applications of ionic liquids and derived materials in lithium and sodium batteries with an emphasis on recent advances.
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.
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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