With the increasing demand for efficient and economic energy storage, Li-S batteries have become attractive candidates for the next-generation high-energy rechargeable Li batteries because of their high theoretical energy density and cost effectiveness. Starting from a brief history of Li-S batteries, this Review introduces the electrochemistry of Li-S batteries, and discusses issues resulting from the electrochemistry, such as the electroactivity and the polysulfide dissolution. To address these critical issues, recent advances in Li-S batteries are summarized, including the S cathode, Li anode, electrolyte, and new designs of Li-S batteries with a metallic Li-free anode. Constructing S molecules confined in the conductive microporous carbon materials to improve the cyclability of Li-S batteries serves as a prospective strategy for the industry in the future.
The lithium-sulfur battery holds a high theoretical energy density, 4-5 times that of today's lithium-ion batteries, yet its applications have been hindered by poor electronic conductivity of the sulfur cathode and, most importantly, the rapid fading of its capacity due to the formation of soluble polysulfide intermediates (Li(2)S(n), n = 4-8). Despite numerous efforts concerning this issue, combatting sulfur loss remains one of the greatest challenges. Here we show that this problem can be effectively diminished by controlling the sulfur as smaller allotropes. Metastable small sulfur molecules of S(2-4) were synthesized in the confined space of a conductive microporous carbon matrix. The confined S(2-4) as a new cathode material can totally avoid the unfavorable transition between the commonly used large S(8) and S(4)(2-). Li-S batteries based on this concept exhibit unprecedented electrochemical behavior with high specific capacity, good cycling stability, and superior rate capability, which promise a practicable battery with high energy density for applications in portable electronics, electric vehicles, and large-scale energy storage systems.
A Li3PO4 solid electrolyte interphase (SEI) layer is demonstrated to be stable in the organic electrolyte, even during the Li deposition/dissolution process. Thus, the Li-conducting Li3PO4 SEI layer with a high Young's modulus can effectively reduce side reactions between Li metal and the electrolyte and can restrain Li dendrite growth in lithium-metal batteries during cycling.
High-quality Prussian blue crystals with a small number of vacancies and a low water content show high specific capacity and remarkable cycle stability as cathode materials for Na-ion batteries.
Lithium metal is one of the most attractive anode materials for electrochemical energy storage. However, the growth of Li dendrites during electrochemical deposition, which leads to a low Coulombic efficiency and safety concerns, has long hindered the application of rechargeable Li-metal batteries. Here we show that a 3D current collector with a submicron skeleton and high electroactive surface area can significantly improve the electrochemical deposition behaviour of Li. Li anode is accommodated in the 3D structure without uncontrollable Li dendrites. With the growth of Li dendrites being effectively suppressed, the Li anode in the 3D current collector can run for 600 h without short circuit and exhibits low voltage hysteresis. The exceptional electrochemical performance of the Li-metal anode in the 3D current collector highlights the importance of rational design of current collectors and reveals a new avenue for developing Li anodes with a long lifespan.
Employing small sulfur molecules as the active cathode component for room-temperature Na-S batteries, reveals a novel mechanism that is verified for the batteries' electrochemistry. The sulfur cathode enables a complete two-electron reaction to form Na2 S, bringing a tripled specific capacity and an increased specific energy compared with traditional high-temperature Na-S batteries. At the same time, it offers better cycling stability endowing the batteries with a longer lifespan.
sources into large-scale grids, inexpensive, efficient, and fast-responding electrical energy storage (EES) systems are essential to store the off-peak energy and releasing the stored energy during the onpeak period. Among various EES systems, rechargeable batteries represent one of the most competitive technologies because of their high conversion efficiency and environmental friendliness. [1][2][3][4] For stationary EES systems, batteries with low cost, high safety, high rate capability, and long cycle stability are highly desired.Lithium (Li)-ion batteries (LIBs) have achieved great success in the market of portable electronics and electric vehicles since their commercialization by Sony Company in 1991. However, the shortage of Li resources in nature gives rise to a concern about its sustainable development in grid scale. Compared with Li, sodium resource has rich natural abundance in the earth crust and a worldwide distribution, consequently leading to a low price of sodium-based raw materials (e.g., the cost of Na 2 CO 3 is about 25-30 times lower than that of Li 2 CO 3 ). Besides, sodium has a suitable redox potential (E 0 (Na + /Na) = −2.71 V versus standard hydrogen electrode (SHE), 0.3 V above that of Li + /Li) and similar physical and chemical properties with lithium. [5,6] Therefore, rechargeable sodium-ion batteries (SIBs), which have a similar "rockingchair" working principle of LIBs, are emerging as an appealing choice as alternatives for LIBs. Note that it is difficult for SIBs to bypass LIBs in terms of energy densities because of the much higher weight of Na and lower standard electrochemical potential. [7][8][9][10] Nevertheless, the use of low-cost materials, including inexpensive Na-based raw materials and Al current collectors for both cathodes and anodes in SIBs, could significantly reduce the cost. In this case, SIBs could be applied where cost-effectiveness rather than energy density is the most critical issue, e.g., in the field of large-scale EES. As a result, sodiumbased electroactive materials are enjoying renewed interest especially for very low cost systems for grid storage. [11,12] Given that cathode materials are the key component that determines energy density and cost, tremendous efforts have been devoted to exploring suitable positive electrode materials with high reversible capacity, rapid Na ions insertion/extraction, and good cycling stability in the past few years. [13,14] A broad range of compounds, including layered oxides, polyanionic frameworks, hexacyanoferrates, and organics, haveThe increasing demand for replacing conventional fossil fuels with clean energy or economical and sustainable energy storage drives better battery research today. Sodium-ion batteries (SIBs) are considered as a promising alternative for grid-scale storage applications due to their similar "rockingchair" sodium storage mechanism to lithium-ion batteries, the natural abundance, and the low cost of Na resources. Searching for appropriate electrode materials with acceptable electrochemical perfor...
Germanium is a promising high-capacity anode material for lithium ion batteries, but it usually exhibits poor cycling stability because of its huge volume variation during the lithium uptake and release process. A double protection strategy to improve the electrode performance of Ge through the use of Ge@C core-shell nanostructures and reduced graphene oxide (RGO) networks has been developed. The as-synthesized Ge@C/RGO nanocomposite showed excellent cycling performance and rate capability in comparison with Ge@C nanoparticles when used as an anode material for Li ion batteries, which can be attributed to the electronically conductive and elastic RGO networks in addition to the carbon shells and small particle sizes of Ge. The strategy is simple yet very effective, and because of its versatility, it may be extended to other high-capacity electrode materials with large volume variations and low electrical conductivities.
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