The progress in understanding and modifying LiMn2O4-based batteries from various aspects are systematically and comprehensively summarized in this review.

In this paper, tris(trimethylsilyl) phosphite (TMSP) and 1,3‐propanediolcyclic sulfate (PCS) are unprecedentedly prescribed as binary functional additives for treating the poor performances of high‐voltage (5 V‐class) LiNi0.5Mn1.5O4/MCMB (graphitic mesocarbon microbeads) Li‐ion batteries at both room temperature and 50 °C. The high‐voltage LiNi0.5Mn1.5O4/MCMB cell with binary functional additives shows a preponderant discharge capacity retention of 79.5% after 500 cycles at 0.5 C rate at room temperature. By increasing the current intensity from 0.2 to 5 C rate, the discharge capacity retention of the high‐voltage cell with binary functional additives is ≈90%, while the counterpart is only ≈55%. By characterizations, it is rationally demonstrated that the binary functional additives decompose and participate in the modification of solid–electrolyte interface layers (both electrodes), which are more conductive, protective, and resistant to electrolyte oxidative/reductive decompositions (accompanying active‐Li+ consuming parasitic reactions) due to synergistic effects. Specifically, the TMSP additive can stabilize LiPF6 salt and scavenge erosive hydrofluoric acid. More encouragingly, at 50 °C, the high‐voltage cell with binary functional additives holds an ultrahigh discharge capacity retention of 79.5% after 200 cycles at 1 C rate. Moreover, a third designed self‐extinguishing flame‐retardant additive of (ethoxy)‐penta‐fluoro‐cyclo‐triphosphazene (PFPN) is introduced for reducing the flammability of the aforementioned binary functional additives containing electrolyte.

We demonstrate a bacterial cellulose supported multifunctional polymer electrolyte for a 4.45 V-class LiCoO2 lithium metal battery.

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Lithium ion capacitors (LICs), which are hybrid electrochemical energy storage devices combining the intercalation/deintercalation mechanism of a lithium‐ion battery (LIB) electrode with the adsorption/desorption mechanism of an electric double‐layer capacitor (EDLC) electrode, have been extensively investigated during the past few years by virtue of their high energy density, rapid power output, and excellent cycleability. In this review, the LICs are defined as the devices with an electrochemical intercalation electrode and a capacitive electrode in organic electrolytes. Both electrodes can serve as anode or cathode. Throughout the history of LICs, tremendous efforts have been devoted to design suitable electrode materials or develop novel type LIC systems. However, one of the key challenges encountered by LICs is how to balance the sluggish kinetics of intercalation electrodes with high specific capacity against the high power characteristics of capacitive electrode with low specific capacitance. Herein, the developments and the latest advances of LIC in material design strategies and key techniques according to the basic scientific problems are summarized. Perspectives for further development of LICs toward practical applications are also proposed.

Blended‐salt electrolytes showing synergistic effects have been formulated by simply mixing several lithium salts in an electrolyte. In the burgeoning field of next‐generation lithium batteries, blended‐salt electrolytes have enabled great progress to be made. In this Review, the development of such blended‐salt electrolytes is examined in detail. The reasons for formulating blended‐salt electrolytes for lithium batteries include improvement of thermal stability (safety), inhibition of aluminum‐foil corrosion of the cathode current collector, enhancement of performance over a wide temperature range (or at a high or low temperature), formation of favorable interfacial layers on both electrodes, protection of the lithium metal anode, and attainment of high ionic conductivity. Herein, we highlight key scientific issues related to the formulation of blended‐salt electrolytes for lithium batteries.

Bi- and Na-substituted Ca3Co4O9 polycrystalline samples have been prepared using a hot-pressing technique and their thermoelectric properties were carefully studied in air from room temperature to 1000 K. The substitutions of Bi3+ and Na+ for Ca2+, as well as Bi3+ and Na+ double substitution, cause both the electrical conductivity (σ) and thermoelectric power (S) to increase simultaneously. The double substitution has also been demonstrated to be effective to decrease the thermal conductivity (κ). The dimensionless figure of merit ZT (=S2σT/κ) reaches 0.32 at 1000 K in the double-substituted sample.

plating/stripping. [7][8][9][10][11][12][13][14][15] As a result, LMB always suffer from rapid capacity deterioration and high safety risk, especially at high charge/discharge rates and over a wide temperature range (from subzero temperatures to high temperatures). Encouragingly, varied strategies have been devoted to explore the Li-dendrite growth mechanism and Li-metal protection. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Wherein, one of the most effective and feasible strategy in protecting Li metal is electrolyte optimization, such as developing ionic liquids, [16] dual-salt electrolytes with additives, [20] gel polymer electrolyte, [18,27,28] concentrated electrolytes, [9,[24][25][26]29,30] etc.Undoubtedly, wide temperature range high-energy LMBs are urgently demanded for special applications, such as carrying out special missions in polar areas, desert areas, snowy mountains region, and outer space. [31] However, the operation of LMBs over a wide temperature range is seldom reported because of the fact that it is a huge challenge to find a compromise between subzero temperature performances and high temperature performances. [31][32][33] At subzero temperatures, due to the significantly reduced Li + conductivity (increased viscosity) of electrolyte and simultaneously increased charge transfer resistances, the severe growth of Li dendrites will become more uncontrolled. [31,34] At high temperatures, the bottlenecks are thermal instability of conventional LiPF 6 salt, severe solid electrolyte interphase (SEI) layer destruction-reformation accompanied by severe gas evolution, and accelerated transition metal dissolution-migration-deposition. [31] Significantly, formulating an electrolyte will play a dominant role in enabling the wide temperature operation of LMBs.Dual-salt electrolyte systems adopting two thermally stable main lithium salts have been proposed to significantly enhance the performances of both LIBs and LMBs. [20,[33][34][35][36][37][38][39][40][41][42] For the wide temperature operation of LIBs, thermally stable lithium borates (such as lithium tetrafluoroborate (LiBF 4 ), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalate)borate (LiDFOB), etc.) dissolved in low melting point and high boiling point carbonatebased solvents (such as propylene carbonate (PC, T m = −48.8 °C, T b = 242 °C), ethyl methyl carbonate (EMC, T m = −53 °C, T b = 110 °C), etc.), have been investigated. [33][34][35][36][37][38] Recently, we have reviewed the potential application of functional lithium-borate salts in high performance lithium batteries, [43] and have successfully synthesized a bulky anion lithium trifluoro(perfluoro-tert-butyloxyl)borate (Li[(CF 3 ) 3 COBF 3 ], LiTFPFB), which exhibits high Li + conductivity and oxidation stability, as well as noncorrosivity to In this study, self-synthesized lithium trifluoro(perfluoro-tert-butyloxyl) borate (LiTFPFB) is combined with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) to formulate a novel 1 m dual-salt electrolyte, which contain...