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Lithium‐ion batteries with spinel Li4Ti5O12 materials as anode, which can offer fast charge times, high power output, superior safety, and long life, are considered to be a competitive choice for grid‐scale energy storage systems (ESS). Herein, a 10 Ah lithium–titanate battery with lithium cobalt oxide–lithium nickel cobalt manganese oxide dual‐phase cathode is developed and its application in 100 kWh‐level ESS is investigated. The 10 Ah single battery demonstrates a specific capacity of 79 Wh kg−1 with a high‐capacity retention rate of 91.8% after 1000 cycles at 55 °C and >80% capacity retention at 15 Ccell. The 125 kWh ESS shows an energy efficiency of 97.82% and 89.97% at 0.2 and 1.5 CSystem, respectively. Self‐discharge and constant power tests indicate that the battery system is stable, thus suitable for storing intermittent power from renewable sources such as solar and wind. The system's ability of smoothing the fluctuated power is confirmed by coordinating with a wind power system. [ABSTRACT FROM AUTHOR]

Rechargeable batteries based on multivalent cation (Mvn+, n>1) carriers are considered potentially low‐cost alternatives to lithium‐ion batteries. However, the high charge‐density Mvn+ carriers generally lead to sluggish kinetics and poor structural stability in cathode materials. Herein, we report an Mvn+ storage via intercalation pseudocapacitance mechanism in a 2D bivalve‐like organic framework featured with localized ligands. By switching from conventional intercalation to localized ligand‐assisted‐intercalation pseudocapacitance, the organic cathode exhibits unprecedented fast kinetics with little structural change upon intercalation. It thus enables an excellent power density of 57 kW kg−1 over 20000 cycles for Ca2+ storage and a power density of 14 kW kg−1 with a long cycling life over 45000 cycles for Zn2+ storage. This work may provide a largely unexploited route toward constructing a local dynamic coordination microstructure for ultrafast Mvn+ storage. [ABSTRACT FROM AUTHOR]

Lithium‐ion batteries commonly exhibit a gradual loss of Li‐storage capacity during operation and storage. However, they can also abruptly lose much of their capacity in a rollover fashion (i.e., "sudden death") under aggressive but practically relevant conditions, such as high‐voltage operation or cycling at elevated temperatures. Here the origin of rollover failure is investigated in high‐energy LiNi0.80Co0.15Al0.05O2‐graphite (NCA‐Gr) batteries cycled at 55 °C. A combined chemical, structural, and electrochemical studies revealed that severe Li plating at the anode surface is the major reason causing the capacity rollover. The Li plating at elevated temperature is triggered by temperature hotspots resulting from inhomogeneous Li‐ion flux, which is a thermodynamic‐driven mechanism different from the kinetically limited one at low temperature and/or under fast‐charging conditions. A Zr(OH)4‐coated, ion‐rectifying separator is further designed to enable an NCA‐Gr pouch cell with a stable cycle performance for 600 cycles and without a sudden death at 55 °C. [ABSTRACT FROM AUTHOR]

A series of Al-doped Li 1+x Ni 0.5 Al x Mn 1.5-x O 4 cathode materials for lithium ion batteries are successfully synthesized via a co-precipitation method. Raman spectroscopy studies reveal that the cation-disordered tends to increase with the content of Al. The data of X-ray photoelectron spectroscopy (XPS) depth profiles reveal that the inert Al 3+ ions segregates preferentially to the surface during the synthesis process. The results of the electrochemical tests suggest that the substitution of a small amount of Al has the ability to improve the rate capability of LiNi 0.5 Mn 1.5 O 4 spinel with conventional electrolytes. Especially, the Al-doped (x = 0.06) sample delivers a long cycle-life at high rate (20 C). The enhanced performance is attributed to the formation of Al-enriched surface, providing a more stable interface with the electrolyte at high voltage (∼4.7 V), along with the stabilization of the spinel structure with a disordering of the cations and improved Li-ion diffusion, based on results of the potentiostatic intermittent titration technique. [ABSTRACT FROM AUTHOR]

A new electrolyte based on fluorinated 3-(1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoropropane (F-EPE) solvent is studied in LiNi 0.5 Mn 1.5 O 4 /Li cells. The electrochemical stability of the electrolyte with 10% F-EPE is carried out by linear sweep voltammetry and electrochemical floating test. These results indicate that the electrolyte with F-EPE has an oxidation potential of more than 5.2 V vs. Li + /Li, which is higher than that without F-EPE and enlarges the oxidative window of electrolyte. A thin and uniform SEI layer is formed on the surface of LiNi 0.5 Mn 1.5 O 4 cathode by using electrolyte with F-EPE, leads to an improvement in the electrochemical performance, validated by charge-discharge tests, EIS, SEM, TEM, and XPS analysis. [ABSTRACT FROM AUTHOR]

The fluorine gradient-doped LiNi 0.5 Mn 1.5 O 4 spinels are synthesized by a facile one-step method and the effect of heat treatment on their structure, morphology, and electrochemical performance are investigated. The results show that introduction of fluorine leads to a larger lattice parameter and particle size, and the formation of F-enriched surface. Whereas at 400 °C, the fluorine gradient-doped LiNi 0.5 Mn 1.5 O 4 sample exhibits an improved long-term cycling stability and high rate performance, due to the suppression of the reaction between electrolyte and cathode, resulting in a decrease in the total resistance and the formation of a thin, uniform and smooth film on the surface. As a result of in situ XRD with charged pristine and the fluorine gradient-doped samples, the similar thermal-decomposition pathways from the charged spinel to the final NiMn 2 O 4 -type spinel structure with a small amount of NiMnO 3 and α-Mn 2 O 3 are observed. In addition, the disappearance temperature of the charged spinel structures is at about 280 °C for the fluorine gradient-doped sample, exhibiting an improved thermal stability of high voltage cathode material. These results show that fluorine gradient-doped LiNi 0.5 Mn 1.5 O 4 sample is a promising positive electrode material for high performance lithium ion batteries. [ABSTRACT FROM AUTHOR]