Benefiting from a higher volumetric capacity (3833 mA h cm
−3
for Mg
vs.
2046 mA h cm
−3
for Li) and dendrite-free Mg metal anode, reversible Mg batteries (RMBs) are a promising chemistry for ...applications beyond Li ion batteries. However, RMBs are still severely restricted by the absence of high performance cathodes for any practical application. In this review, we provide a critical and rigorous review of Mg battery cathode materials, mainly reported since 2013, focusing on the impact of structure and composition on magnesiation kinetics. We discuss cathode materials, including intercalation compounds, conversion materials (O
2
, S, organic compounds), water co-intercalation cathodes (V
2
O
5
, MnO
2
etc.
), as well as hybrid systems using Mg metal anode. Among them, intercalation cathodes are further categorized by 3D (Chevrel phase, spinel structure
etc.
), 2D (layered structure), and 1D materials (polyanion: phosphate and silicate), according to the diffusion pathway of Mg
2+
in the framework. Instead of discussing every published work in detail, this review selects the most representative works and highlights the merits and challenges of each class of cathodes. Advances in theoretical analysis are also reviewed and compared with experimental results. This critical review will provide comprehensive knowledge of Mg cathodes and guidelines for exploring new cathodes for rechargeable magnesium batteries.
This paper provides a critical and rigorous review on Mg battery cathodes, focusing on the impact of structure and composition on magnesiation kinetics.
All‐solid‐state Li metal batteries have attracted extensive attention due to their high safety and high energy density. However, Li dendrite growth in solid‐state electrolytes (SSEs) still hinders ...their application. Current efforts mainly aim to reduce the interfacial resistance, neglecting the intrinsic dendrite‐suppression capability of SSEs. Herein, the mechanism for the formation of Li dendrites is investigated, and Li‐dendrite‐free SSE criteria are reported. To achieve a high dendrite‐suppression capability, SSEs should be thermodynamically stable with a high interface energy against Li, and they should have a low electronic conductivity and a high ionic conductivity. A cold‐pressed Li3N–LiF composite is used to validate the Li‐dendrite‐free design criteria, where the highly ionic conductive Li3N reduces the Li plating/stripping overpotential, and LiF with high interface energy suppresses dendrites by enhancing the nucleation energy and suppressing the Li penetration into the SSEs. The Li3N–LiF layer coating on Li3PS4 SSE achieves a record‐high critical current of >6 mA cm−2 even at a high capacity of 6.0 mAh cm−2. The Coulombic efficiency also reaches a record 99% in 150 cycles. The Li3N–LiF/Li3PS4 SSE enables LiCoO2 cathodes to achieve 101.6 mAh g−1 for 50 cycles. The design principle opens a new opportunity to develop high‐energy all‐solid‐state Li metal batteries.
According to the proposed principles for the suppression of dendrite formation, a Li3N–LiF composite that is thermodynamically stable and has high interface energy against Li metal is designed as an interlayer for dendrite‐free all‐solid‐state batteries. A Li3N–LiF layer coating on a Li3PS4 solid‐state electrolyte achieves a record‐high critical current of >6 mA cm−2 even at a high capacity of 6.0 mAh cm−2.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Due to the non-flammable nature of water-based electrolytes, aqueous lithium-ion batteries are resistant to catching fire. However, they are not immune to the risk of explosion, since the sealing ...structure adopted by current batteries limits the dissipation of heat and pressure within the cells. Here, we report a safe aqueous lithium-ion battery with an open configuration using water-in-salt electrolytes and aluminum oxide coated anodes. The design can inhibit the self-discharge by substantially suppressing the oxygen reduction reaction on lithiated anodes and enable good cycle performance over 1000 times. Our study may open a pathway towards safer lithium-ion battery designs.
Metallic zinc is an ideal anode due to its high theoretical capacity (820 mAh g
), low redox potential (-0.762 V versus the standard hydrogen electrode), high abundance and low toxicity. When used in ...aqueous electrolyte, it also brings intrinsic safety, but suffers from severe irreversibility. This is best exemplified by low coulombic efficiency, dendrite growth and water consumption. This is thought to be due to severe hydrogen evolution during zinc plating and stripping, hitherto making the in-situ formation of a solid-electrolyte interphase (SEI) impossible. Here, we report an aqueous zinc battery in which a dilute and acidic aqueous electrolyte with an alkylammonium salt additive assists the formation of a robust, Zn
-conducting and waterproof SEI. The presence of this SEI enables excellent performance: dendrite-free zinc plating/stripping at 99.9% coulombic efficiency in a Ti||Zn asymmetric cell for 1,000 cycles; steady charge-discharge in a Zn||Zn symmetric cell for 6,000 cycles (6,000 h); and high energy densities (136 Wh kg
in a Zn||VOPO
full battery with 88.7% retention for >6,000 cycles, 325 Wh kg
in a Zn||O
full battery for >300 cycles and 218 Wh kg
in a Zn||MnO
full battery with 88.5% retention for 1,000 cycles) using limited zinc. The SEI-forming electrolyte also allows the reversible operation of an anode-free pouch cell of Ti||Zn
VOPO
at 100% depth of discharge for 100 cycles, thus establishing aqueous zinc batteries as viable cell systems for practical applications.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
High-safety, low-cost, and high-volumetric-capacity rechargeable magnesium batteries (RMBs) are promising alternatives to lithium ion batteries. However, lack of high-power, high-energy, and stable ...cathodes for RMBs hinders their commercialization. Herein, an environmentally benign, low-cost, and sustainable covalent organic framework (COF) cathode for Mg storage is reported for the first time. It delivers a high power density of 2.8 kW kg–1, a high specific energy density of 146 Wh kg–1, and an ultralong cycle life of 3000 cycles with a very slow capacity decay rate of 0.0196% per cycle, representing one of the best cathodes to date. The comprehensive electrochemical analysis proves that triazine ring sites in the COF are redox centers for reversible reaction with magnesium ions, and the ultrafast reaction kinetics are mainly attributed to pseudocapacitive behavior. The high-rate Mg storage of the COF offers new opportunities for the development of ultrastable and fast-charge RMBs.
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Potassium-ion batteries (PIBs) have been considered as promising alternatives to lithium-ion batteries due to potassium's high natural abundance of 2.09 wt% ( vs. 0.0017 wt% for Li) and K/K + having ...a low redox potential of −2.93 V ( vs. −2.71 V for Na/Na + ). However, PIB electrodes still suffer huge challenges due to the large K-ion radius and slow reaction dynamics. Herein, we report a high-capacity Sb@CSN composite anode with Sb nanoparticles uniformly encapsulated by a carbon sphere network (CSN) for PIBs. First-principles computations and electrochemical characterization confirm a reversible sequential phase transformation of KSb 2 , KSb, K 5 Sb 4 , and K 3 Sb during the potassiation/depotassiation process. In a concentrated 4 M KTFSI/EC + DEC electrolyte, the Sb@CSN anode delivers a high reversible capacity of 551 mA h g −1 at 100 mA g −1 after 100 cycles with an extremely slow capacity decay of only 0.06% per cycle from the 10th to 100th cycle; when at a high current density of 200 mA g −1 , the Sb@CSN anode still maintains a capacity of 504 mA h g −1 after 220 cycles. The Sb@CSN anodes demonstrate one of the best electrochemical performances for all K-ion battery anodes reported to date. The exceptional performance of Sb@CSN should be attributed to the efficient encapsulation of small Sb nanoparticles in the conductive carbon network as well as the formation of a robust KF-rich SEI layer on the Sb@CSN anode in the concentrated 4 M KTFSI/EC + DEC electrolyte.
In carbonate electrolytes, the organic–inorganic solid electrolyte interphase (SEI) formed on the Li‐metal anode surface is strongly bonded to Li and experiences the same volume change as Li, thus it ...undergoes continuous cracking/reformation during plating/stripping cycles. Here, an inorganic‐rich SEI is designed on a Li‐metal surface to reduce its bonding energy with Li metal by dissolving 4m concentrated LiNO3 in dimethyl sulfoxide (DMSO) as an additive for a fluoroethylene‐carbonate (FEC)‐based electrolyte. Due to the aggregate structure of NO3− ions and their participation in the primary Li+ solvation sheath, abundant Li2O, Li3N, and LiNxOy grains are formed in the resulting SEI, in addition to the uniform LiF distribution from the reduction of PF6− ions. The weak bonding of the SEI (high interface energy) to Li can effectively promote Li diffusion along the SEI/Li interface and prevent Li dendrite penetration into the SEI. As a result, our designed carbonate electrolyte enables a Li anode to achieve a high Li plating/stripping Coulombic efficiency of 99.55 % (1 mA cm−2, 1.0 mAh cm−2) and the electrolyte also enables a Li||LiNi0.8Co0.1Mn0.1O2 (NMC811) full cell (2.5 mAh cm−2) to retain 75 % of its initial capacity after 200 cycles with an outstanding CE of 99.83 %.
An inorganic‐rich solid electrolyte interphase (SEI) has been constructed on Li metal to promote dense Li growth with a Coulombic efficiency of 99.55 % in the carbonate electrolyte. It was synthesized on the surface of the Li‐metal anode using concentrated LiNO3 in dimethyl sulfoxide (DMSO) as an additive in the FEC‐based electrolyte, which participates in the primary Li+ solvation shell and promotes the reduction of NO3− ions to form the inorganic‐rich SEI.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Grid-scale energy storage is essential for reliable electricity transmission and renewable energy integration. Redox flow batteries (RFB) provide affordable and scalable solutions for stationary ...energy storage. However, most of the current RFB chemistries are based on expensive transition metal ions or synthetic organics. Here, we report a reversible chlorine redox flow battery starting from the electrolysis of aqueous NaCl electrolyte and the as-produced Cl
is extracted and stored in the carbon tetrachloride (CCl
) or mineral spirit flow. The immiscibility between the CCl
or mineral spirit and NaCl electrolyte enables a membrane-free design with an energy efficiency of >91% at 10 mA/cm
and an energy density of 125.7 Wh/L. The chlorine flow battery can meet the stringent price and reliability target for stationary energy storage with the inherently low-cost active materials (~$5/kWh) and the highly reversible Cl
/Cl
redox reaction.
Layered metal oxides have been widely used as the best cathode materials for commercial lithium-ion batteries and are being intensively explored for sodium-ion batteries. However, their application ...to potassium-ion batteries (PIBs) is hampered because of the poor cycling stability and low rate capability due to the larger ionic size of K+ than of Li+ or Na+. Herein, a facile self-templated strategy was used to synthesize unique P2-type K0.6CoO2 microspheres that consist of aggregated primary nanoplates as PIB cathodes. The unique K0.6CoO2 microspheres with aggregated structure significantly enhanced the kinetics of the K+ intercalation/deintercation and also minimized the parasitic reactions between the electrolyte and K0.6CoO2. The P2-K0.6CoO2 microspheres demonstrated a high reversible capacity of 82 mAh g–1 at 10 mA g–1, high rate capability of 65 mAh g–1 at 100 mA g–1, and long cycle life (87% capacity retention over 300 cycles). The high reversibility of the P2-K0.6CoO2 full cell paired with a hard carbon anode further demonstrated the feasibility of PIBs. This work not only successfully demonstrates exceptional performance of P2-type K0.6CoO2 cathodes and microspheres K0.6CoO2∥hard carbon full cells, but also provides new insights into the exploration of other layered metal oxides for PIBs.
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Engineering a stable solid electrolyte interphase (SEI) is critical for suppression of lithium dendrites. However, the formation of a desired SEI by formulating electrolyte composition is very ...difficult due to complex electrochemical reduction reactions. Here, instead of trial-and-error of electrolyte composition, we design a Li-11 wt % Sr alloy anode to form a SrF2-rich SEI in fluorinated electrolytes. Density functional theory (DFT) calculation and experimental characterization demonstrate that a SrF2-rich SEI has a large interfacial energy with Li metal and a high mechanical strength, which can effectively suppress the Li dendrite growth by simultaneously promoting the lateral growth of deposited Li metal and the SEI stability. The Li–Sr/Cu cells in 2 M LiFSI-DME show an outstanding Li plating/stripping Coulombic efficiency of 99.42% at 1 mA cm–2 with a capacity of 1 mAh cm–2 and 98.95% at 3 mA cm–2 with a capacity of 2 mAh cm–2, respectively. The symmetric Li–Sr/Li–Sr cells also achieve a stable electrochemical performance of 180 cycles at an extremely high current density of 30 mA cm–2 with a capacity of 1 mAh cm–2. When paired with LiFePO4 (LFP) and LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes, Li–Sr/LFP cells in 2 M LiFSI-DME electrolytes and Li–Sr/NMC811 cells in 1 M LiPF6 in FEC:FEMC:HFE electrolytes also maintain excellent capacity retention. Designing SEIs by regulating Li-metal anode composition opens up a new and rational avenue to suppress Li dendrites.
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