Sulfurized polyacrylonitrile (SPAN) is a very stable and promising sulfur-based cathode material for high energy density lithium-sulfur (Li-S) batteries, which can circumvent the polysulfides dissolution issue. However, the stress concentration caused by volume change in SPAN cathodes is relatively significant but is rarely focused on. It is widely reckoned that the binder plays a key role in buffering the stress induced by electrode materials and hence maintains the integrity of electrodes. Nevertheless, the understanding of the actual effect of binders to SPAN cathodes from the aspect of mechanics remains to be deepened. Here, the optical fiber Bragg grating (FBG) is implanted into SPAN cathode films to in situ evaluate the electrochemo-mechanical behaviors by using four different binders. The internal strain evolution of SPAN cathodes is affected by multiple factors of adhesion and mechanical properties of different binders. It is found that the SPAN cathode using poly(acrylic acid) (PAA) binder with outstanding mechanical properties experiences the largest strain change but the electrochemical performance is even better under high sulfur loading. Furthermore, the strain evolution is monitored under high sulfur loading condition and how the sulfur loading affects the signals of the built-in FBG sensors is tried to figure out.

Silicon (Si) anode has attracted broad attention because of its high theoretical specific capacity and low working potential. However, the severe volumetric changes of Si particles during the lithiation process cause expansion and contraction of the electrodes, which induces a repeatedly repair of solid electrolyte interphase, resulting in an excessive consuming of electrolyte and rapid capacity decay. Clearly known the deformation and stress changing at mu epsilon resolution in the Si-based electrode during battery operation provides invaluable information for the battery research and development. Here, an in operando approach is developed to monitor the stress evolution of Si anode electrodes via optical fiber Bragg grating (FBG) sensors. By implanting FBG sensor at specific locations in the pouch cells with different Si anodes, the stress evolution of Si electrodes has been systematically investigated, and Delta sigma/areal capacity is proposed for stress assessment. The results indicate that the differences in stress evolution are nested in the morphological changes of Si particles and the evolution characteristics of electrode structures. The proposed technique provides a brand-new view for understanding the electrochemical mechanics of Si electrodes during battery operation. The integration of optical sensors within pouch cells containing different Silicon (Si) anodes has facilitated a comprehensive analysis of the stress evolution exhibited by them. The results demonstrate that the differences in stress evolution are nested in the morphological of Si particles and thecharacteristics of electrode structures. These findings offer fresh insights into the electrochemical mechanics of Si-based electrodes. image

Silicon is widely recognized as an ideal anode material due to its high specific capacity, low lithiation potential, high abundance, and environmental friendliness. Nevertheless, the immense volume expansion during the lithiation leads to pulverization of silicon particles, which causes electrode failure with a rapid capacity decay. Herein, the polymerized 1, 3‐dioxolane (PDOL) electrolyte is used to stabilize the micro‐silicon Si anode via in situ polymerization route. The conformality of the quasi‐solid electrolyte suppresses the pulverization of the Si microparticles (SiMPs) effectively and thus alleviates the capacity decay. The SiMPs/PDOL anode shows an excellent initial CE of 97.5% and maintains a reversible capacity of 1837.1 mAh g−1 at 500 mA g−1 after 100 cycles. The Si/PDOL/LiFePO4 full cells also exhibit a stable cycling performance with a capacity retention of 76.3% after 300 cycles. This work provides a new and easy path for the practical application of silicon anode at low cost.

As a promising cathode material in sodium-ion batteries, Prussian blue (PB) suffers from humid sensitivity during electrode manufacturing, which leads to structural and electrochemical instability. Herein, we design a moisture-proof Prussian blue via surface modification of hydrophobic octadecylamine (ODA) chains with a thickness of similar to 6 nm. The hydrophobic Prussian blue (PB@TA@ODA) exhibits excellent sodium storage performance, owing to its high stability in humid environments. After exposure to a humid environment for 7 days, PB@TA@ODA-7D can provide a reversible capacity of 145 mAh g(-1) at 1 C and deliver 94 mAh g(-1) at 30 C. After 100 cycles at 1 C, it still retains 111 mAh g(-1). Further investigations show that the hydrophobic ODA chains can protect PB from H2O attacking the high-spin Fe, thus maintaining structural stability in a humid environment. The hydrophilic strategy proposed in this work can effectively promote the processability of PB in electrode manufacturing, which is crucial for its practical application in sodium-ion batteries.

The instability of the solid-liquid interface is a crucial problem of the silicon (Si) anode, which seriously affects the performance of the battery. Therefore, constructing an artificial interface for silicon (Si) anodes is an effi-cient way to restrain the volume expansion and reduce the side reactions. Herein, we develop a poly(acryloni-trile)-Sulfur (PAN-S) based artificial solid-electrolyte interphase (SEI) film on Si, which significantly improves the cycling and rate performance owing to its mechanical strength and ion transport ability. The PAN-S coated silicon anode exhibits outstanding electrochemical performance, which shows a good cycle life of 1370 mAh g-1 capacity retained after 500 cycles at 0.5C (1C = 4000 mA g-1) and outstanding rate performance of 1103 mAh g-1 retained at 4C. This work provides a facile surface engineering strategy for designing electrode mate-rials with significant volume expansion and poor electrochemical kinetics.

The pore structure of hard carbon has an important influence on its sodium storage performance. Herein, pitch‐derived hard carbons with different pore structures have been prepared via the combination of physical activation and vapor carbon coating. It reveals that the open pores favor the slope capacity while the closed pores can promote the plateau capacity, which consolidates the pore‐filling mechanism of hard carbon during the sodium storage in the plateau region. HC1400‐5 h@PP with rich closed micropores can deliver a reversible specific capacity of 299.1 mAh g−1 with initial Coulombic efficiency of 81.1%. The plateau capacity accounts for 66.6% of the total capacity. Ex situ Raman and galvanostatic intermittent titration investigations show that there exists an energy barrier for the Na deposition in the closed pores, leading to the rapid decay of plateau capacity at a high current density.

Iron hexacyanoferrate (FeHCF) is a promising cathode material for sodium-ion batteries. However, FeHCF always suffers from a poor cycling stability, which is closely related to the abundant vacancy defects in its framework. Herein, post-synthetic and in-situ vacancy repairing strategies are proposed for the synthesis of high-quality FeHCF in a highly concentrated Na4Fe(CN)6 solution. Both the post-synthetic and in-situ vacancy repaired FeHCF products (FeHCF-P and FeHCF-I) show the significant decrease in the number of vacancy defects and the reinforced structure, which can suppress the side reactions and activate the capacity from low-spin Fe in FeHCF. In particular, FeHCF-P delivers a reversible discharge capacity of 131 mAh g-1 at 1 C and remains 109 mAh g-1 after 500 cycles, with a capacity retention of 83%. FeHCF-I can deliver a high discharge capacity of 158.5 mAh g-1 at 1 C. Even at 10 C, the FeHCF-I electrode still maintains a discharge specific capacity of 103 mAh g-1 and retains 75% after 800 cycles. This work provides a new vacancy repairing strategy for the solution synthesis of high-quality FeHCF.

Silicon is the most widely used anode material for high-energy lithium-ion batteries because of its high capacity and abundant reserves. Nevertheless, the huge volume change of silicon during cycling can cause severe structural damage and instability of the solid electrolyte interphase (SEI), thus leading to rapid capacity fading and poor Coulombic efficiency. Herein, an S-containing artificial SEI layer (S-ARSEI) was designed on the silicon surface via the nucleophilic reaction between polysulfides and ester electrolyte, which greatly alleviates its volume expansion and improves the Li+ transport. The silicon anode coated by an S-ARSEI layer maintains a reversible specific capacity of 1387 mA h g-1 at 0.5 C after 500 cycles with a capacity retention of 70%. It also exhibits an excellent rate performance of 1200 mA h g-1 at 2 C. This work provides a new design of an S-containing SEI layer for the volume expansion electrodes for the secondary batteries.

Lithium loss during the initial charge process inevitably reduces the capacity and energy density of lithium-ion batteries. Cathode additives are favored with respect to their controllable prelithiation degree and scalable application; however, the insulating nature of their delithiation products retards electrode reaction kinetics in subsequent cycles. Herein, we propose a prelithiation separator by modifying a commercial separator with a Li2S/Co nanocomposite to compensate for the initial capacity loss. The Li2S/Co coating layer extracts active lithium ion during the charge process and shows a delithiation capacity of 993 mA h g-1. When paired with a LiFePO4|graphite full cell, the reversible capacity is increased from 112.6 to 150.3 mA h g-1, leading to a 29.5% boost in the energy density. The as-prepared pouch cell also demonstrates a stable cycling performance. The excellent electrochemical performance and the scalable production of the prelithiation separator reveal its great potential in lithium-ion battery industry application.

Lithium-sulfur (Li−S) batteries are regarded as one of the most promising next-generation energy storage systems due to their high theoretical energy density and low material cost. However, the conventional ether-based electrolytes of Li−S batteries are extremely flammable and have high solubility of lithium polysulfides (LiPS), resulting in a high safety risk and a poor life cycle. Herein, we report an ether/carbonate co-solvent fluorinated electrolyte with a special solvation sheath of Li+, which can prevent the formation of dissoluble long-chain LiPS of the sulfur cathode, restrict Li dendrite growth at the anode side, and show fire resistance in combustion experiments. As a result, the proposed Li−S batteries with 70 wt% sulfur content in its cathode deliver stable life cycle, low self-discharge ratio, and intrinsic safety. Therefore, the unique passivation characteristics of the designed fluorinated electrolyte break several critical limitations of the traditional “liquid phase”-based Li−S batteries, offering a facile and promising way to develop long-life and high-safety Li−S batteries.

Herein, the coordination-induced increase in the electron density of fused C6 rings in MOFs as high performance anode materials for Li+ ion batteries is described. Zn-PTCA is able to deliver a high specific capacity of 700 mA h g-1 at 50 mA g-1 and exhibits excellent cycle performance over 1100 cycles and good rate capability.

Porous CoP3@PPy microcubes are synthesized from the cubic Co3[Co(CN)6]2precursors followed by PPy coating. When used as anode material for lithium ion batteries, a large specific capacity of 1310 mAh g−1 can be obtained for CoP3@PPy composite at 100 mA g−1, and retains 650 mAh g−1 after 220 cycles at 500 mA g−1. Even at high current density of 4000 mA g−1, the CoP3@PPy composite still maintains a reversible capacity as high as 800 mAh g−1. When matched with LiFePO4 for full battery, a high capacity of 540 mAh g−1 can be obtained at 100 mA g−1 after 100 cycles. The improved lithium storage performance of CoP3@PPy is ascribed to the unique porous structure of CoP3 microcubes and the homogeneous PPy buffer/conducting layers, which can alleviate the giant volume changes and facilitate fast charge transfer during the lithiation/delithiation process.

Lithium sulfide (Li2S) provides a promising route for lithium storage due to high theoretical specific capacity (1166 mAh g(-1)). The electrochemical performance of Li2S can be significantly enhanced by forming Li2S-carbon composites with the introduction of carbon. However, the complex synthesis method of Li2S carbon composites restrains the large-scale productivity. Herein, we propose a facile route to prepare carbon coated Li2S-carbon nanotube composites (Li2S@C-CNT) via spray drying and heat treatment, which is a low-cost and large-scale method for facile synthesis of Li2S-carbon composites. For the Li2S@C-CNT composites, Li2S nanoparticles are contacted with surrounding particles due to the 3D CNTs framework. The novel construction not only suppresses the diffusion of polysulfides during cycling, but also remarkably accelerates the transport of electron and ion, resulting in a high specific capacity (1100 mAh g(-1)) and good cycling performance. The rational designed architecture and good electrochemical performance of Li2S@C-CNT will pave the avenue for realizing high energy density of Li2S-based batteries. (C) 2018 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Lithium sulfide (Li2 S) is a promising cathode material with high capacity, which can be paired with nonlithium metal anodes such as silicon or tin so that the safety issues caused by the Li anode can be effectively avoided. However, the Li2 S full cell suffers from rapid capacity degradation due to the dissolution of intermediate polysulfides. Herein, a Li2 S/Si full cell is designed with a Li2 S cathode incorporated by titanium nitride (TiN) polysulfide immobilizer within parallel hollow carbon (PHC). This full cell delivers a high initial reversible capacity of 702 mAh gLi2S -1 (1007 mAh gsulfur -1 ) at 0.5 C rate and excellent cyclability with only 0.4% capacity fade per cycle over 200 cycles. The long cycle stability is ascribed to the strong polysulfide anchor effect of TiN and highly efficient electron/ion transport within the interconnected web-like architecture of PHC. Theoretical calculations, self-discharge measurements, and anode stability experiments further confirm the strong adsorption of polysulfides on the TiN surface. The present work demonstrates that the flexible Li2 S cathode and paired Si anode can be used to achieve highly efficient Li-S full cells.

Hard carbons have received considerable attention as anode materials for sodium‐ion batteries (SIBs). However, it is still a challenge to improve the plateau capacity and initial coulombic efficiency (ICE) of hard carbons. Herein, a facile vapor carbon‐coating method is used to modify the surface structure of carbon spheres (CS) via the pyrolysis of polypropylene (PP), aiming to seal the exposed pores through a high‐quality carbon layer. CS@2%PP exhibits highly improved sodium storage performance compared to that of the pristine CS, which delivers a plateau capacity of 220 m Ah g−1 and an ICE of 81%. Further investigations show that the improved sodium storage performance of CS@2%PP can be mainly attributed to the reduced structural defects on the surface, lower specific surface area (11.5 m2 g−1), and increased closed pores (12.5%) via carbon coating. The results prove that the surface vapor carbon coating is a facile route to improve the plateau capacity and ICE of hard carbon anodes in SIBs.

Si/Cu3Si@C composites encapsulated in CNTs network (SCC-CNTs) were synthesized via the combination of ball-milling and CVD methods. SCC-CNTs consist of conductive Cu3Si, amorphous carbon layer, cross-linked CNTs, and the etched pores, which can play the synergistic effects on the improvement of electronic conductivity and Li+ diffusion. The volume expansion of Si anode is also suppressed during the electrochemical process. The SCC-CNTs composites demonstrate a remarkably improved electrochemical performance compared with pure Si, which can deliver a discharge capacity of 2 171 mAh·g−1 at 0.4 A·g−1 with ICE of 85.2%, and retain 1 197 mAh· g−1 after 150 cycles. This work provides a facile approach to massively produce the high-performance Si-based anode materials for next-generation LIBs.

Micron‐sized Si particles are successfully coated by TiN and N‐doped hard carbon (NC) via the combination of the solution method and the tape‐casting method. The double‐coated Si@TiN@NC electrode exhibits excellent electrochemical stability and rate capability, which delivers a reversible capacity of 1024 mAh g−1 at a current density of 4 A g−1 after 550 cycles, corresponding to a capacity retention of 85%. Even at 8 A g−1, the capacity still maintains 1087 mAh g−1. Further investigation shows that the electrochemical enhancement of Si@TiN@NC is mainly attributed to the buffering effect of NC, and the excellent electronic conductivity and mechanical stability of TiN. The TiN@NC double‐layer coating structure provides a new strategy for the design of high‐performance silicon anode in lithium ion batteries (LIBs). Furthermore, the tape‐casting method is a promising way to massively produce silicon‐based composites.

Porous hard carbons are synthesized via carbonizing lotus stems with naturally hierarchical structures. The hard carbon carbonized at 1400 degrees C (LS1400) delivers a total capacity 350 mAh g(-1) in the current density of 100 mA g(-1) and a plateau capacity of 250 mAh g(-1). Even cycled at 100 mA g(-1) after 450 cycles, the capacity still retains 94%. Further investigation shows that the sodium storage of LS carbons involves Na+ adsorption in the defect sites, Na+ insertion and Na metal deposition in the closed pores. However, the Na metal deposition in closed pores mainly contribute to the plateau capacity, leading to the excellent sodium storage performance of LS1400 with a large closed pore ratio of 66%. The results show that the intrinsic structure of natural biomass can inspire us to design hard carbon with large closed pore ratio as excellent anode for sodium ion batteries.

Silicon based anode materials with high specific capacity, low voltage plateau, environmental friendliness and abundant resources, are expected to replace graphite for the next generation lithium-ion batteries with high energy density. However, the conductivity of silicon is poor. Even worse, the huge volume change of Si during charge/discharge process can result in large electrochemical polarization, material pulverization, SEI film reconstitution, low coulombic efficiency and continuous capacity fading. However, silicon and carbon composites can combine their advantages of high capacity and excellent electronic conductivity, forming an anode with stable structure, good cycle stability and high capacity. This paper reviews the research progress of Si/C composite in the structural design, preparation process and electrochemical performance from the view of different dimensions of silicon (SiNPs, SiNTs/ SiNWs, SiNFs, Bulk Si), and the Si/C composite materials for future research are also prospected.

We demonstrate the availability of Fe7Se8 as anode for sodium-ion batteries (SIBs) for the first time. A Fe7Se8 nanocomposite encapsulated by nitrogen-doped carbon layers (Fe7Se8@NC) has been fabricated via a facile thermal method using Prussian Blue as precursor, and its sodium storage mechanisms and extraordinary activation process during cycling are revealed for comprehensive understanding of its reaction process. It shows that the sodium storage mechanisms of Fe7Se8 can be affected by the activation process, especially in the charge process. As SIB anode material, the Fe7Se8@NC exhibits an outstanding electrochemical performance with a reversible discharge capacity of 367mAhg−1 at 500mAg−1. Even at 2000mAg−1, the capacity can retain 251mAhg−1. Moreover, the Fe7Se8@NC shows excellent cyclability, which maintains the capacity up to 339mAhg−1 at 1000mAg−1 after 1200 cycles. The results demonstrate that Fe7Se8@NC is a promising anode material for SIBs.