Micro‐ and Mesoporous Carbide‐Derived Carbon–Selenium Cathodes for High‐Performance Lithium Selenium Batteries

Abstract

ion battery (LIB) chemistry. Such LIB cells offer signifi cantly higher energy density than lead-acid or nickel-metal hydride batteries and reasonably good cycle stability. [ 4 ] However there is a plenty of room for improvement in various aspects, such as cost, safety, energy density, power, thermal, and cycling stabilities. [ 5 ] One strategy to improve LIB is to employ higher capacity cathode materials and, in some cases, simultaneously replace graphite anodes with higher capacity Li electrodes. There has been a signifi cant research interest in the development of higher-specifi c-energy cathodes, particularly in identifying alternatives for the lithium cobalt oxide (LCO), NMC and NCA, which commonly offer capacity in the range from 150 to 200 mAh g -1 . The moderate energy density, insuffi cient safety characteristics and relativity high cost of these cathode materials are among the major motivations for investigating new cathode materials with higher energy density and competitive price. The lithium-sulfur (Li-S) cells have demonstrated promising energy density values, exceeding those of the high energy density LIBs. [ 6,7 ] However, the majority of Li-S cells exhibit relatively poor rate and cycle stability, which limit opportunities for their commercialization. One of the challenges is the dissolution of intermediate lithium polysulfi de species formed during cycling, which induces a shuttle phenomenon (low Coulombic effi ciency). Also, low intrinsic electric conductivity of S and largely insoluble low order lithium polysulfi des precipitation (such as Li 2 S, and Li 2 S 2 ) are also not desirable for power capability and cycling stability.The somewhat similar lithium-selenium (Li-Se) system in non-aqueous media was recently found to offer promising performances. [ 8 ] Selenium has high theoretical volumetric capacity of ≈3270 mAh cm -3 (not considering expansion upon lithiation) and moderately high theoretical gravimetric capacity of ≈678 mAh g -1 based on molecular weight of 78.96 g mol -1 and density of 4.82 g cm -3 . [ 9 ] High volumetric capacity is particularly attractive for both EV and electronic device applications considering battery packs shall be installed in the limited space. Challenges with Li-Se systems are fairly analogous to that of Li-S systems, including polyselenide dissolution during the cell operation and limited electronic conductivity (although an order of magnitude higher than in S). Only few research groups have reported characterizations of Li-Se systems, where they utilized porous carbon as a conductive framework to entrap Se. [ 10,11 ] This approach might be able to slightly reduce polyselenide dissolution and improve electrical conductivity of selenium Nanocomposites of selenium (Se) and ordered mesoporous silicon carbidederived carbon (OM-SiC-CDC) are prepared for the fi rst time and studied as cathodes for lithium-selenium (Li-Se) batteries. The higher concentration of Li salt in the electrolytes greatly improves Se utilization and cell cycle stability. Se-CDC shows signifi...

Selenium Embedded in Metal–Organic Framework Derived Hollow Hierarchical Porous Carbon Spheres for Advanced Lithium–Selenium Batteries

“…Issues occurred as S, Se cathode also has to face the poor cycle performance and low Coulombic efficiency (CE) caused by the dissolution of high-order polyselenides. [15][16][17] In order to modify the electrochemical properties of Li-Se cells, great efforts have been made as follows. Guo's group successfully encapsulated Se within a typical ordered mesoporous carbon in the form of cyclic Se 8 17 and hierarchically micro-/mesoporous carbon spheres.…”

In situ surface protection for enhancing stability and performance of conversion-type cathodes

“…2(a), right]. 22,39 Besides S, the chalcogenides (Li 2 S, Se, Li 2 Se, Te, and Li 2 Te) are similarly suffering from dissolution of intermediate reaction products (polychalcogenides) in electrolytes, 23,28,[39][40][41][42][43][44] which results in capacity loss, shuttle, and formation of insulating layers. [21][22][23]43,45 Similar to Li-chalcogen batteries, recent studies on various MHs also reported serious challenges of metal and halide dissolution during electrochemical conversion reactions.…”

“…As such, if cathode dissolution and unfavorable interactions between active materials and electrolyte are avoided, conversion cathodes should be able to show very long cycle stability in cells. [16][17][18][19][20][21][22][23][24][25][26][46][47][48][49][50] The in situ CEI protection on the surface of the conversion cathodes has a promise to overcome such challenges as shown in Fig. 3(b).…”

“…the CEI should ideally be formed at the potentials below that of the Li extraction from the cathode at the first cycle. In this sense, a large first cycle overpotential commonly observed in conversion cathodes 11,13,[16][17][18]23,27,28,39,41,48,[60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78] is beneficial, as it provides more freedom to select electrolyte compositions with suitable oxidation/reduction potentials [ Fig. 4(a)].…”

Novel 3-D network SeS /NCPAN composites prepared by one-pot in-situ solid-state method and its electrochemical performance as cathode material for lithium-ion battery

“…Zeng et al [28] confined Se in the matrix of porous carbon nanofibers (PCNFs), which can deliver a reversible capacity of 516 mAh/g after 900 cycles without any capacity loss at 0.5 A/g and 306 mAh/g at 4 A/g. Lee et al [29] prepared nanocomposites of Se and ordered mesoporous silicon carbide-derived carbon (OM-SiC-CDC), whose the discharge capacity in 7 M electrolyte retained approximately 96.4 % of its initial capacity (around 420 mAh/g). Li et al [30] confined Se in metal complex-derived porous carbon (Se/MnMC-B), which exhibited a capacity of 580 mAh/g after 1000 cycles at 1C.…”