Search

Micro-sized silicon anodes can significantly increase the energy density of lithium-ion batteries with low cost. However, the large silicon volume changes during cycling cause cracks for both organic-inorganic interphases and silicon particles. The liquid electrolytes further penetrate the cracked silicon particles and reform the interphases, resulting in huge electrode swelling and quick capacity decay. Here we resolve these challenges by designing a high-voltage electrolyte that forms silicon-phobic interphases with weak bonding to lithium-silicon alloys. The designed electrolyte enables micro-sized silicon anodes (5 µm, 4.1 mAh cm−2) to achieve a Coulombic efficiency of 99.8% and capacity of 2175 mAh g−1 for >250 cycles and enable 100 mAh LiNi0.8Co0.15Al0.05O2 pouch full cells to deliver a high capacity of 172 mAh g−1 for 120 cycles with Coulombic efficiency of >99.9%. The high-voltage electrolytes that are capable of forming silicon-phobic interphases pave new ways for the commercialization of lithium-ion batteries using micro-sized silicon anodes. Micro-sized silicon are promising anode materials due to low-cost and high-energy, yet their application is hindered by inaccessible electrolytes. Here, the authors report sulfolane-based electrolytes that form silicon-phobic interphases and enable high-voltage pouch cells to achieve superior cycle life. [ABSTRACT FROM AUTHOR]

Water‐in‐salt electrolytes (WISE) have largely widened the electrochemical stability window (ESW) of aqueous electrolytes by formation of passivating solid electrolyte interphase (SEI) on anode and also absorption of the hydrophobic anion‐rich double layer on cathode. However, the cathodic limiting potential of WISE is still too high for most high‐capacity anodes in aqueous sodium‐ion batteries (ASIBs), and the cost of WISE is also too high for practical application. Herein, a low‐cost 19 m (m: mol kg−1) bi‐salts WISE with a wide ESW of 2.8 V was designed, where the low‐cost 17 m NaClO4 extends the anodic limiting potential to 4.4 V, while the fluorine‐containing salt (2 m NaOTF) extends the cathodic limiting potential to 1.6 V by forming the NaF–Na2O–NaOH SEI on anode. The 19 m NaClO4–NaOTF–H2O electrolyte enables a 1.75 V Na3V2(PO4)3∥Na3V2(PO4)3 full cell to deliver an appreciable energy density of 70 Wh kg−1 at 1 C with a capacity retention of 87.5 % after 100 cycles. [ABSTRACT FROM AUTHOR]

With high energy density and improved safety, rechargeable battery chemistries with a zinc (Zn) metal anode offer promising and sustainable alternatives to those based on lithium metal or lithium‐ion intercalation/alloying anode materials; however, the poor electrochemical reversibility of Zn plating/stripping, induced by parasitic reactions with both aqueous and non‐aqueous electrolytes, presently limits the practical appeal of these systems. Although recent efforts in rechargeable Zn metal batteries (RZMBs) have achieved certain advancements in Zn metal reversibility, as quantified by the Coulombic efficiency (CE), a standard protocol for CE has not been established, and results across chemistries and systems are often conflicting. More importantly, there is still an insufficient understanding regarding the critical factors dictating Zn reversibility. In this work, a rigorous, established protocol for determining CE of lithium metal anodes is transplanted to the Zn chemistry and is used for systematically examining how a series of factors including current collector chemistry, current density, temperature, and the upper voltage limit during stripping affect the measured reversibility of different Zn electrolytes. With support from density functional theory calculations, this standardized Zn CE protocol is then leveraged to identify an important correlation between electrolyte solvation strength toward Zn2+ and the measured Zn CE in the corresponding electrolyte, providing new guidance for future development and evaluation of Zn electrolytes. [ABSTRACT FROM AUTHOR]

Aqueous Zn batteries are promising energy‐storage devices. However, their lifespan is limited by irreversible Zn anodes owing to water decomposition and Zn dendrite growth. Here, we separate aqueous electrolyte from Zn anode by coating a thin MOF layer on anode and filling the pores of MOF with hydrophobic Zn(TFSI)2‐tris(2,2,2‐trifluoroethyl)phosphate (TFEP) organic electrolyte that is immiscible with aqueous Zn(TFSI)2–H2O bulk electrolyte. The MOF encapsulated Zn(TFSI)2‐TFEP forms a ZnF2‐Zn3(PO4)2 solid electrolyte interphase (SEI) preventing Zn dendrite and water decomposition. The Zn(TFSI)2‐TFEP@MOF electrolyte protected Zn anode enables a Zn||Ti cell to achieve a high average Coulombic efficiency of 99.1 % for 350 cycles. The highly reversible Zn anode brings a high energy density of 210 Wh kg−1 (of cathode and anode mass) and a low capacity decay rate of 0.0047 % per cycle over 600 cycles in a Zn||MnO2 full cell with a low capacity ratio of Zn:MnO2 at 2:1. [ABSTRACT FROM AUTHOR]

Synthesis of silicon/carbon (Si/C) composites from biomass resources could enable the effective utilization of agricultural products in the battery industry with economical as well as environmental benefits. Herein, a simplified process was developed to synthesize Si/C from biomass, by using a low‐cost agricultural byproduct "rice husk (RH)" as a model. This process includes the calcination of RH for SiO2/C and the reduction of SiO2/C by Al in molten salts at a moderate temperature. This process does not need the removal of carbon before thermal reduction of SiO2, which is thought to be necessary to avoid the formation of SiC at elevated temperatures. Thus, carbon derived from biomass can be directly used for Si/C composites for anode materials. The resultant Si/C shows a high reversible capacity of 1309 mAh g−1 and long cycle life (300 cycles). This research advocates a new and simplified strategy for the synthesis of RH‐based biomass‐derived Si/C, which is beneficial for low‐cost, environmentally friendly, and green energy storage applications. [ABSTRACT FROM AUTHOR]

Zn metal has been regarded as the most promising anode for aqueous batteries due to its high capacity, low cost, and environmental benignity. Zn anode still suffers, however, from low Coulombic efficiency due to the side reactions and dendrite growth in slightly acidic electrolytes. Here, the Zn plating/stripping mechanism is thoroughly investigated in 1 m ZnSO4 electrolyte, demonstrating that the poor performance of Zn metal in mild electrolyte should be ascribed to the formation of a porous by‐product (Zn4SO4(OH)6·xH2O) layer and serious dendrite growth. To suppress the side reactions and dendrite growth, a highly viscoelastic polyvinyl butyral film, functioning as an artificial solid/electrolyte interphase (SEI), is homogeneously deposited on the Zn surface via a simple spin‐coating strategy. This dense artificial SEI film not only effectively blocks water from the Zn surface but also guides the uniform stripping/plating of Zn ions underneath the film due to its good adhesion, hydrophilicity, ionic conductivity, and mechanical strength. Consequently, this side‐reaction‐free and dendrite‐free Zn electrode exhibits high cycling stability and enhanced Coulombic efficiency, which also contributes to enhancement of the full‐cell performance when it is coupled with MnO2 and LiFePO4 cathodes. [ABSTRACT FROM AUTHOR]

Abstract: Electrolytes that are able to reversibly deposit/strip Mg are crucial for rechargeable Mg batteries. The most studied complex electrolytes based on Lewis acid‐base chemistry are expensive, difficult to be synthesized, and show limited anodic stability. Conventional electrolytes using simple salts such as Mg(TFSI)2 can be readily synthesized, but Mg deposition/stripping in these simple salt electrolytes is accompanied by a large overpotential due to the formation of a surface layer on the Mg metal with a low Mg ion conductivity. Here the overpotential for Mg deposition/stripping in a simple salt, Mg(TFSI)2‐1,2‐dimethoxyethane (DME), electrolyte is significantly reduced by adding a small concentration of iodine (≤50 × 10−3 m) as an additive. Mechanism studies demonstrate that an Mg ion conductive solid MgI2 layer is formed on the surface of the Mg metal and acts as a solid electrolyte interface. With the Mg(TFSI)2‐DME‐I2 electrolyte, a very small voltage hysteresis is achieved in an Mg‐S full cell. [ABSTRACT FROM AUTHOR]

Abstract: Sustainable sodium‐ion batteries (SSIBs) using renewable organic electrodes are promising alternatives to lithium‐ion batteries for the large‐scale renewable energy storage. However, the lack of high‐performance anode material impedes the development of SSIBs. Herein, we report a new type of organic anode material based on azo group for SSIBs. Azobenzene‐4,4′‐dicarboxylic acid sodium salt is used as a model to investigate the electrochemical behaviors and reaction mechanism of azo compound. It exhibits a reversible capacity of 170 mAh g−1 at 0.2C. When current density is increased to 20C, the reversible capacities of 98 mAh g−1 can be retained for 2000 cycles, demonstrating excellent cycling stability and high rate capability. The detailed characterizations reveal that azo group acts as an electrochemical active site to reversibly bond with Na+. The reversible redox chemistry between azo compound and Na ions offer opportunities for developing long‐cycle‐life and high‐rate SSIBs. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIB) have potential for large scale renewable energy storage due to geopolitical abundance of Na. However, the high capacity Na-ion anodes still suffer from poor cycling stability and low Coulombic efficiency (CE). Herein, uniform Sn 4 P 3 @C spheres were synthesized by a facile aerosol spray-pyrolysis-phosphidation method. By tuning the electrolyte, a reversible capacity of ~ 800 mAh/g with an extremely low capacity decay rate of 0.09% per cycle was achieved with a record-high initial CE (> 90%) and high cyclic CE (~ 99.9%). The Sn 4 P 3 @C in the stable ether-based electrolyte shows the highest accumulated cycling capacities in the reported SIB anodes. [ABSTRACT FROM AUTHOR]

Aluminum metal is a promising anode material for next generation rechargeable batteries owing to its abundance, potentially dendrite-free deposition, and high capacity. The rechargeable aluminum/sulfur (Al/S) battery is of great interest owing to its high energy density (1340 Wh kg−1) and low cost. However, Al/S chemistry suffers poor reversibility owing to the difficulty of oxidizing AlS x. Herein, we demonstrate the first reversible Al/S battery in ionic-liquid electrolyte with an activated carbon cloth/sulfur composite cathode. Electrochemical, spectroscopic, and microscopic results suggest that sulfur undergoes a solid-state conversion reaction in the electrolyte. Kinetics analysis identifies that the slow solid-state sulfur conversion reaction causes large voltage hysteresis and limits the energy efficiency of the system. [ABSTRACT FROM AUTHOR]

A new super-concentrated aqueous electrolyte is proposed by introducing a second lithium salt. The resultant ultra-high concentration of 28 m led to more effective formation of a protective interphase on the anode along with further suppression of water activities at both anode and cathode surfaces. The improved electrochemical stability allows the use of TiO2 as the anode material, and a 2.5 V aqueous Li-ion cell based on LiMn2O4 and carbon-coated TiO2 delivered the unprecedented energy density of 100 Wh kg−1 for rechargeable aqueous Li-ion cells, along with excellent cycling stability and high coulombic efficiency. It has been demonstrated that the introduction of a second salts into the 'water-in-salt' electrolyte further pushed the energy densities of aqueous Li-ion cells closer to those of the state-of-the-art Li-ion batteries. [ABSTRACT FROM AUTHOR]

The sulfur-based cathode materials suffer severely from poor cycling stability and low utilization, incurred by their stepwise reaction mechanism that generates polysulfide intermediates and the subsequent irreversible losses. In this work, those issues are significantly relieved by entrapping sulfur species in carbon host rich in oxygen functionalities. Sulfur species in such C/S composite are highly stabilized by their interaction with oxygen, and can deliver a reversible capacity of 508 mAh/(g of S) for 2000 cycles when coupled with Li, representing the best cycling stability up to date. More interestingly, extra capacity can be accessed by simply prelithiating the oxygen-stabilized C/S composites down to 0.6 V for a few cycles, which enables a high capacity of 1621 mAh/(g of S) that eventually stabilizes at 820 mAh/(g of S) for 600 cycles. The mechanism for this electrochemical activation process is investigated with both spectroscopic and electrochemical techniques, which reveal that the inactive sulfur bonded to oxygen is liberated in the initial deep lithiation precycles and becomes electrochemically active. The oxygen-stabilized sulfur can also be coupled with Na anode to form Na/S cell, confirming that the formation of S−O interaction in C/S composite generates promising sulfur-based cathode materials for Li-S and Na-S batteries. [ABSTRACT FROM AUTHOR]

Although the theoretical capacity of silicon is ten times higher than that of graphite, the overall electrode capacity of Si anodes is still low due to the low Si loading and heavy metal current collector. Here, a novel flexible 3D Si/C fiber paper electrode synthesized by simultaneously electrospraying nano-Si-PAN (polyacrylonitrile) clusters and electrospinning PAN fibers followed by carbonization is reported. The combined technology allows uniform incorporation of Si nanoparticles into a carbon textile matrix to form a nano-Si/carbon composite fiber paper. The flexible 3D Si/C fiber paper electrode demonstrate a very high overall capacity of ≈1600 mAh g-1 with capacity loss less than 0.079% per cycle for 600 cycles and excellent rate capability. The exceptional performance is attributed to the unique architecture of the flexible 3D Si/C fiber paper, i.e., the resilient and conductive carbon fiber network matrix, carbon-coated Si nanoparticle clusters, strong adhesion between carbon fibers and Si nanoparticle clusters, and uniform distribution of Si/C clusters in the carbon fiber frame. The scalable and facile synthesis method, good mechanical properties, and excellent electrochemical performance at a high Si loading make the flexible 3D Si/C fiber paper batteries extremely attractive for plug-in electric vehicles, flexible electronics, space exploration, and military applications. [ABSTRACT FROM AUTHOR]

Abstract: Well dispersed chestnut-like Cd2Ge2O6 (CGO) and Cd2Ge2O6/reduced graphene oxide (CGO/RGO) nanocomposites are successfully prepared via a facile one-pot hydrothermal method and characterized as novel lithium storage materials for the first time. Electrochemical characterization of lithiation/delithiation of the CGO/RGO nanocomposites reveals a large capacity of 943mAhg−1 for the first cycle and a capacity retention of 721mAhg−1 even after 100 cycles. The superior electrochemical performance of the CGO/RGO nanocomposites electrode compared to the pure CGO electrode can be attributed to the well dispersed RGO which enhances the electronic conductivity and accommodate the volume change during the lithium storage process. [Copyright &y& Elsevier]

The electrochemical performance of mesoporous carbon (C)/tin (Sn) anodes in Na-ion and Li-ion batteries is systematically investigated. The mesoporous C/Sn anodes in a Na-ion battery shows similar cycling stability but lower capacity and poorer rate capability than that in a Li-ion battery. The desodiation potentials of Sn anodes are approximately 0.21 V lower than delithiation potentials. The low capacity and poor rate capability of C/Sn anode in Na-ion batteries is mainly due to the large Na-ion size, resulting in slow Na-ion diffusion and large volume change of porous C/Sn composite anode during alloy/dealloy reactions. Understanding of the reaction mechanism between Sn and Na ions will provide insight towards exploring and designing new alloy-based anode materials for Na-ion batteries. [ABSTRACT FROM AUTHOR]

A disk pressed from commercial SnO2 powder, sandwiched between two nickel screen current collectors, was used as a lithium-ion secondary anode. Its electrochemical lithium insertion–extraction behavior was investigated by galvanostatic charge–discharge and galvanostatic intermittent titration (GITT) using a microcurrent on one current collector. The trans-electrode voltage was measured to monitor the transmissive resistance across the SnO2 electrode during the discharge–charge process. Special electrochemical impedance spectroscopy (EIS) protocols were used to investigate the kinetic and transmissive impedances during initial lithium insertion. Protocol B or C EIS, described in the text, give the local transmissive impedance near the operating current collector, while Protocol B′ or C′ give the local transmissive impedance near the other current collector. The use of special EIS protocols showed that the inner transmissive impedance near the operating current collector side is higher than that near the other current collector. [Copyright &y& Elsevier]

The wide applications of rechargeable batteries require state‐of‐the‐art batteries that are sustainable (abundant resource), tolerant to high‐temperature operations, and excellent in delivering high capacity and long‐term cycling life. Due to the scarcity and uneven distribution of lithium, it is urgent to develop alternative rechargeable batteries. Herein, an organic compound, azobenzene‐4,4′‐dicarboxylic acid potassium salts (ADAPTS) is developed, with an azo group as the redox center for high performance potassium‐ion batteries (KIBs). The extended π‐conjugated structure in ADAPTS and surface reactions between ADAPTS and K‐ions enable the stable charge/discharge of K‐ion batteries even at high temperatures up to 60 °C. When operated at 50 °C, ADAPTS anode delivers a reversible capacity of 109 mAh g−1 at 1C for 400 cycles. A reversible capacity of 77 mAh g−1 is retained at 2C for 1000 cycles. At 60 °C, the ADAPTS‐based KIBs deliver a high capacity of 113 mAh g−1 with 81% capacity retention at 2C after 80 cycles. The exceptional electrochemical performance demonstrates that ADAPTS is a promising electrode material for high‐temperature KIBs. An organic anode based on an azo group as the redox center is designed and synthesized for high temperature potassium‐ion batteries. The surface reaction‐controlled mechanism between the azo compound and K‐ions enables superior electrochemical performance of K‐ion batteries with an operating temperature up to 60 °C. [ABSTRACT FROM AUTHOR]

A novel bismuth-carbon composite, in which bismuth nanoparticles were anchored in a nitrogen-doped carbon matrix (Bi@NC), is proposed as anode for high volumetric energy density lithium ion batteries (LIBs). Bi@NC composite was synthesized via carbonization of Zn-containing zeolitic imidazolate (ZIF-8) and replacement of Zn with Bi, resulting in the N-doped carbon that was hierarchically porous and anchored with Bi nanoparticles. The matrix provides a highly electronic conductive network that facilitates the lithiation/delithiation of Bi. Additionally, it restrains aggregation of Bi nanoparticles and serves as a buffer layer to alleviate the mechanical strain of Bi nanoparticles upon Li insertion/extraction. With these contributions, Bi@NC exhibits excellent cycling stability and rate capacity compared to bare Bi nanoparticles or their simple composites with carbon. This study provides a new approach for fabricating high volumetric energy density LIBs. [ABSTRACT FROM AUTHOR]

• Li 3 VO 4 nanoparticles in porous N-doped carbon are synthesized. • Porous N-doped carbon is derived from melamine and citric acid. • Porous N-doped carbon and Li 3 VO 4 nanoparticles together give superior performances. • This composite exhibits a capacity of 236.6 mAh g−1 after 1000 cycles at 4.0 A g−1. • This composite coupled with LiCoO 2 as full cells are examined. Li 3 VO 4 nanoparticles in N-doped carbon with porous structure are synthesized using supermolecular aggregates formed by melamine and citric acid as the nitrogen source, via a dry-freezing process, followed with a calcination. Nitrogen doping enhances the interaction between Li 3 VO 4 and carbon, reduces the charge-transfer resistance over the interface, and restrains the pulverization and aggregation upon cycling. The design of porous structure accelerates the permeation of electrolyte and increases the contact between active materials and electrolyte. The synergistic effects between N-doped carbon and porous structure significantly improve the electrochemical performances. Thus, this composite delivers a capacity of 405.1 mAh g−1 at 0.1 A g−1 or 199.9 mAh g−1 at 10.0 A g−1 within 0.2–3.0 V. After 1000 cycles at 4.0 A g−1, the specific capacity is still kept as 236.6 mAh g−1. By pairing with commercial LiCoO 2 , this composite delivers a high energy density of 195.05 Wh kg−1 total at 70.52 W kg−1 total , and 94.06 Wh kg−1 total at 3.9 kW kg−1 total. [ABSTRACT FROM AUTHOR]

Abstract: A porous silicon–carbon anode on a lightweight carbon fiber current collector is reported here for lithium-ion batteries. This Si–C anode was synthesized through a one-step carbonization of a Si-poly(acrylonitrile-co-methyl acrylate) precursor, which was directly deposited on a carbon fiber mat. The carbon fiber curent collector allows higher loading of active materials, resulting in high energy to mass and area ratios. The obtained Si–C electrode demonstrated superior overall capacity, cyclability, and rate capacity. [Copyright &y& Elsevier]

Lithium-ion capacitors, as a hybrid electrochemical energy storage device, realize high specific energy and power density within one device, thus attracting extensive attention. Here, hierarchically porous Li 3 VO 4 /C nanocomposite is prepared by a solvo-thermal reaction, followed with a post-annealing process. This composite has macropores at the center and mesopores in the wall, thus effectively promoting electrolyte penetration and structure stability upon cycling simultaneously. Compared to mesoporous Li 3 VO 4 , the enhanced rate capability and specific capacity of hierarchically porous Li 3 VO 4 /C indicate the synergistic effect of mesopores and macropores. Inspired by these results, this composite is coupled with mesoporous carbon (CMK-3) for lithium-ion capacitors, generating a specific energy density of 105 Wh kg −1 at a power density of 188 W kg −1 . Even if the power density increases to 9.3 kW kg −1 , the energy density still remains 62 Wh kg −1 . All these results demonstrate the promising potential of hierarchically porous Li 3 VO 4 in lithium ion capacitors. [ABSTRACT FROM AUTHOR]

Nano-Sn/C composites are ideal anode materials for highenergyand power density Li-ion batteries. However, because of the low meltingpoint of Sn and the tendency of grain growth, especially during hightemperature carbonization, it has been a significant challenge tocreate well-dispersed ultrasmall Sn nanoparticles within a carbonmatrix. In this paper, we demonstrate an aerosol spray pyrolysis technique,as a facile and scalable method, to synthesize a nano-Sn/C compositewith uniformly dispersed 10 nm nano-Sn within a spherical carbon matrix.The discharge capacity of nano-Sn/C composite sphere anodes maintainsthe initial capacity of 710 mAh/g after 130 cycles at 0.25 C. Thenano-Sn/C composite sphere anodes can provide ∼600 mAh/g evenat a high rate of 20 C. To the best of our knowledge, such high rateperformance for Sn anodes has not been reported previously. The exceptionalperformance of the nano-Sn/C composite is attributed to the uniquenano-Sn/C structure: (1) carbon matrix offers mechanical support toaccommodate the stress associated with the large volume change ofnano-Sn, thus alleviating pulverization; (2) the carbon matrix preventsSn nanoparticle agglomeration upon prolonged cycling; and (3) carbonnetwork provides continuous path for Li ions and electrons insidethe nano-Sn/C composite spheres. [ABSTRACT FROM AUTHOR]

Abstract: A patterned core–shell tin (Sn) nanorod anode is fabricated by pulse electrodeposition of Sn onto a self-assembled Tobacco Mosaic Virus (TMV) structured nickel current collector. Pulse electrodeposition onto the virus assembled 3D electrode surfaces produces homogenous Sn coatings with significant void space to accommodate the large volume change associated with Sn lithiation. The TMV enabled 3D Sn anodes shows high capacity retention of 560 mAh g−1 after 100 cycles with the average capacity fading rate of 0.4% per cycle. The high electronic conductivity of Sn, short diffusion length for Li-ions, and large interface between Sn nano-rods and electrolyte greatly enhance the rate performance of the TMV enabled Sn anodes. [Copyright &y& Elsevier]

Abstract: A patterned 3D Si anode is fabricated by physical vapor deposition of n-type Si on a self-assembled TMV1cys-structured nickel current collector. The combination of the large surface area conferred by the virus-enabled 3D Ni/TMV1cys current collector with the high electric conductivity of n-type Si rods results in excellent cyclic stability and rate capability for the core-shell n-type Si/Ni/TMV1cys anodes. Electrochemical impedance spectroscopy reveals that the high electronic conductivity of n-type Si significantly reduces charge transfer resistance, thus even at high current densities the capacity of the n-type Si is increased to almost 630mAh/g compared to undoped Si. [Copyright &y& Elsevier]

Abstract: The effects of carbonization process and carbon nanofiber/nanotube additives on the cycling stability of silicon–carbon composite anodes were investigated by monitoring the impedance evolution during charge/discharge cycles with electrochemical impedance spectroscopy (EIS). Three types of Si–C anodes were investigated: the first type consisted of Si nanoparticles incorporated into a network of carbon nanofibers (CNFs) and multi-walled carbon nanotubes (MWNTs), with annealed polymer binder. The second type of Si–C anodes was prepared by further heat treatment of the first Si–C anodes to carbonize the polymer binder. The third Si–C anode was as same as the second one except no CNFs and MWNTs being added. Impedance analysis revealed that the carbonization process stabilized the Si–C anode structure and decreased the charge transfer resistance, thus improving the cycling stability. On the other hand, although the MWNTs/CNFs additives could enhance the electronic conductivity of the Si–C anodes, the induced inhomogeneous structure decreased the integrity of the electrode, resulting in a poor long term cycling stability. [Copyright &y& Elsevier]