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The energy density presents the core competitiveness of lithium (Li)-ion batteries. In conventional Li-ion batteries, the utilization of the gravimetric/volumetric energy density at the electrode level is unsatisfactory (

The electrochemical utilization of organic electrode materials (OEMs) is highly dependent on an excess amount of inactive carbon at the expense of low packing density and energy density. In this work, the challenges by substituting inactive carbon with electronic conductive inorganic cathode (ECIC) materials, which are endowed with high electronic conductivity to transport electrons for redox reactions of the whole electrodes, high ion-storage capacity to act as secondary active materials, and strong affinity with OEMs to inhibit their dissolution, are addressed. Combining representative ECICs (TiS2 and Mo6 S8 ) with organic electrode materials (perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and hexaazatrinaphthalene (HATN)) simultaneously achieves high capacity, low porosity, lean electrolyte, and thus high energy density. High gravimetric and volumetric energy densities of 153 Wh kg-1 and 200 Wh L-1 are delivered with superior cycling stability in a 30 mA h-level Li/PTCDA-TiS2 pouch cell. The proof-of-concept of organic-ECIC electrodes is also successfully demonstrated in monovalent Na, divalent Mg, and trivalent Al batteries, indicating their feasibility and generalizability. With the discovery of more ECIC materials and OEMs, it is anticipated that the proposed organic-ECIC system can result in further improvements at cell level to compete with transition metal-based Li-ion batteries.

Nickel-rich layered LiNi0.8Co0.1Mn0.1O2 is a promising cathode material due to its high specific capacity. However, commercial application of this material is impeded by its rapid capacity degradation associated with structural instability. In this work, 0.5–2 mol% Nb5+ doped LiNi0.8Co0.1Mn0.1O2 cathode material is prepared by heat treatment of a mixture of stoichiometric amounts of nano-sized Nb2O5 powders, co-precipitated NixMn1-x(OH)2 precursors, and LiOH·H2O. The results show that Nb5+ doping significantly improves the cycling properties of LiNi0.8Co0.1Mn0.1O2 cathode material and that the optimal Nb5+ content in the structure is 1 mol%. Under a voltage range of 2.75–4.3 V, 1 mol% Nb5+ doped LiNi0.8Co0.1Mn0.1O2 cathode material shows an initial discharge capacity of 180.2 mAh/g at 0.1C, with a capacity retention of 96.9% for subsequent 300 cycles at 1C at room temperature. In contrast, bare LiNi0.8Co0.1Mn0.1O2 shows a capacity retention of only ~79.8% under the same conditions, with an initial specific discharge capacity of 184.9 mAh/g. The improvement in cycling performance is attributed to stabilization of the layered structure by Nb5+, mitigated migration of Ni2+ to the Li layer, improved lithium diffusion kinetics and reduced lattice expansion/shrinkage during cycling. Stabilization of the layered structure by Nb5+ doping is further reflected by the observation of fewer cracks in cathode electrodes after prolonged cycling.

A non-sintered method with toothpaste electrode for improving electrode ionic conductivity and reducing interface impedance is introduced in solid-state rechargeable batteries. At 70 °C, this novel solid-state battery can deliver a capacity of 80 mAh g–1 in a voltage range of 2.5–3.8 V at 0.1C rate using layered oxide Na0.66Ni0.33Mn0.67O2, Na-β″-Al2O3 and sodium metal as cathode, electrolyte and anode, respectively. Moreover, the battery shows a superior stability and high reversibility, with a capacity retention of 90% after 10 000 cycles at 6C rate and a capacity of 79 mAh g–1 is recovered when the current rate is returned to 0.1C. Furthermore, a very thick electrode with active material mass loading of 6 mg cm–2 also presents a reasonable electrochemical performance. These results demonstrate that this is a promising approach to solve the interface problem and would open a new route in designing the next generation solid-state battery.

Solid polymer electrolytes (SPEs) would be promising candidates for application in high-energy rechargeable lithium (Li) batteries to replace the conventional organic liquid electrolytes, in terms of the enhanced safety and excellent design flexibility. Herein, we first report novel perfluorinated sulfonimide salt-based SPEs, composed of lithium (trifluoromethanesulfonyl)(n-nonafluorobutanesulfonyl)imide (Li[(CF3SO2)(n-C4F9SO2)N], LiTNFSI) and poly(ethylene oxide) (PEO), which exhibit relatively efficient ionic conductivity (e.g., 1.04 × 10–4 S cm–1 at 60 °C and 3.69 × 10–4 S cm–1 at 90 °C) and enough thermal stability (>350 °C), for rechargeable Li batteries. More importantly, the LiTNFSI-based SPEs could not only deliver the excellent interfacial compatibility with electrodes (e.g., Li-metal anode, LiFePO4 and sulfur composite cathodes), but also afford good cycling performances for the Li|LiFePO4 (>300 cycles at 1C) and Li–S cells (>500 cycles at 0.5C), in comparison with the conventional LiTFSI (Li[(C...

Energy storage technologies are the core technology for smooth integration of renewable energy into the grid. Among which sodium-ion batteries show great promise due to the potential low cost originated from the abundant resources and wide distribution of sodium. However, the anode still remains great challenge for the commercialization of sodium-ion batteries. Here we report a pyrolyzed anthracite (PA) anode material with superior low cost and high safety through one simple carbonization process. The PA anode material shows promising sodium storage performance demonstrated by prototype pouch cells with a practical energy density of 100 Wh kg −1 , good rate and cycling performance. Furthermore, the high safety of pouch cells with PA anode was also proved by a series of safety experiments. These desirable properties of the PA anode can meet the requirements for practical applications and pave the way for the industrial production of low-cost and high-safety sodium-ion batteries for large-scale electrical energy storage.

Sodium-ion batteries (SIBs), a promising substitute for lithium-ion batteries (LIBs), are considered to have potential to be employed in large-scale energy storage systems with lower cost and enhanced safety as primary concerns. Solid polymer electrolyte (SPE) based SIBs will better meet these demands because of their good flame-resistance and excellent flexibility, compared with conventional organic liquid electrolyte based SIBs. Here, we describe an SPE composed of sodium bis(fluorosulfonyl)imide (NaFSI) and poly(ethylene oxide) (PEO). The NaFSI/PEO (molar ratio of EO/Na+ = 20) blended polymer electrolyte exhibits a low glass transition temperature (i.e., 37.9 oC), relatively high ionic conductivity (i.e., ~4.1 × 104 S cm1 at 80 oC), and enough electrochemical and thermal stability for application in SIBs. Most importantly, the NaFSI/PEO blended polymer electrolyte displays excellent interfacial stability with Na metal in Na/Na cells and good cycling performance in prototype cells with Na0.67Ni0.33Mn0.67O2 (NNM) as cathode material. All these properties make NaFSI based solid polymer electrolytes promising candidates for use in SIBs.

A new family of hydrophobic ionic liquids (ILs) based on a super-delocalized perfluorinated sulfonimide anion, namely (trifluoromethyl( S -trifluoromethylsulfonylimino)sulfonyl)(trifluoromethylsulfonyl)imide ([CF 3 SO( NSO 2 CF 3 ) 2 ] − , [sTFSI] − ), with various oniums, including imidazolium, quaternary ammonium, pyrrolidinium and piperidinium, have been prepared and characterized. Their physical and electrochemical properties are extensively characterized, and comparatively studied with those based on a lesser delocalized analogue, bis(trifluoromethanesulfonyl) imide ([(CF 3 SO 2 ) 2 N] − , [TFSI] − ), in terms of thermal properties, density, viscosity, ionic conductivity, and electrochemical stability. These new [sTFSI]-based ILs show low glass transitions (between −95 and −81 °C), relatively low viscosities (36–120 cP at 25 °C), good thermal stabilities ( T d > 400 °C), and wide electrochemical windows. Particularly, the viscosities are generally lower for the [sTFSI]-based ILs than for the corresponding [TFSI]-based ones, due to better charge delocalization and higher degrees of freedoms for [sTFSI] − vs. [TFSI] − . It is found that the [sTFSI] − anion is more resistant toward oxidation, but less resistant toward reduction than the [TFSI] − one, suggesting that replacement of a O group in [TFSI] − with a strong electron-withdrawning CF 3 SO 2 N = group increase both the reductive and oxidative potential. The coulombic efficiencies of Li deposition/stripping on Ni electrode are comparable in the [sTFSI]- and [TFSI]-based ionic liquid electrolytes; however, Li/LiFePO 4 cell using the [sTFSI]-based ionic liquid electrolyte shows more stable cycling performance than that using the [TFSI]-based one, which would be attributable to the improved anodic stability of the [sTFSI] − anion and stable electrode/electrolyte interphases formed on Li anode.

Lithium (fluorosulfonyl)(n-nonafluorobutanesulfonyl)imide [Li[(FSO2)(n-C4F9SO2)N] (LiFNFSI)] is investigated as a conducting salt, which can form a relatively stable solid-electrolyte-interphase film in concentrated ether electrolyte to achieve favorable protection for lithium metal anodes. Li|Cu and Li|Li cells with concentrated LiFNFSI-based electrolyte have been demonstrated to display high average Coulombic efficiency (≈97%) and excellent cycling stability (over 1,000 h) of metallic lithium anodes, compared to concentrated lithium bis(trifluoromethanesulfonyl)imide [Li[N(SO2CF3)2] (LiTFSI)]-based electrolyte. The morphologies and compositions of the lithium–metal anode surface are also comparatively analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Moreover, superior electrochemical performance in the concentrated LiFNFSI-based electrolyte for Li|LiFePO4 cells is also presented herein. These results indicate that concentrated LiFNFSI-based electrolyte is a pr...

Spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) exhibits two different Ni/Mn arrangements, i.e., the Ni/Mn ordered P4 3 32 phase and disordered Fd-3m phase. It has been found that the Ni/Mn disorder is correlated with the formation of oxygen vacancies, nevertheless the underlying mechanism remains unclear. Density functional theory (DFT) calculations show that formation of 1:3 ordered Ni 2+ and Mn 4+ ions is energetically favorable compared to the disordered Ni 3+ and Mn 3+ ions caused by Ni aggregation in the stoichiometric P4 3 32 phase. However, in oxygen deficient LiNi 0.5 Mn 1.5 O 4− δ , the oxygen vacancies tend to diminish the valence discrepancy between the Ni aggregated and the ordered P4 3 32 phases, making the former energetically competitive and consequently resulting in the disordered Ni/Mn distribution. Understanding the origin of Ni/Mn disorder also sheds light on the cation doping effect. Calculations show that Mg 2+ ion tends to replace Ni 2+ ion in ordered P4 3 32 phase, and maintaining the Ni/Mn order. By contrast, Al doping promotes the Ni/Mn disorder, as Al 3+ ion prefers to substitute for Ni 3+ and Mn 3+ ions emerged in Ni/Mn disordered structure. Our findings rationalize the experimental observations, and further reveal that Ni/Mn arrangement could be controlled by adjusting the electronic structure of spinel LNMO system.

A novel single lithium-ion (Li-ion) conducting polymer electrolyte is presented that is composed of the lithium salt of a polyanion, poly[(4-styrenesulfonyl)(trifluoromethyl(S-trifluoromethylsulfonylimino)sulfonyl)imide] (PSsTFSI(-)), and high-molecular-weight poly(ethylene oxide) (PEO). The neat LiPSsTFSI ionomer displays a low glass-transition temperature (44.3 °C; that is, strongly plasticizing effect). The complex of LiPSsTFSI/PEO exhibits a high Li-ion transference number (tLi (+) =0.91) and is thermally stable up to 300 °C. Meanwhile, it exhibits a Li-ion conductivity as high as 1.35×10(-4) S cm(-1) at 90 °C, which is comparable to that for the classic ambipolar LiTFSI/PEO SPEs at the same temperature. These outstanding properties of the LiPSsTFSI/PEO blended polymer electrolyte would make it promising as solid polymer electrolytes for Li batteries.

A novel single lithium-ion (Li-ion) conducting polymer electrolyte composed of lithium poly[(4-styrenesulfonyl)(fluorosulfonyl)imide] (LiPSFSI) and poly(ethylene oxide) (PEO) exhibits a high Li-ion transference number (tLi+ = 0.90) and sufficient electrochemical stability for use in Li batteries. The ionic conductivities of the LiPSFSI/PEO blended polymer electrolytes are higher than those of the lithium poly(4-styrenesulfonate) (LiPSS)/PEO electrolyte and are comparable to those of the lithium poly[(4-styrenesulfonyl)(trifluoromethanesulfonyl)imide] (LiPSTFSI)/PEO electrolyte in the temperature range of 25–90 °C. More importantly, the complex of LiPSFSI/PEO exhibits excellent interfacial compatibility with the Li metal electrode compared to both those of the LiPSS/PEO and LiPSTFSI/PEO electrolytes.

Metallic tin (Sn) used as anode material for lithium ion batteries has long been proposed, but its low temperature electrochemical performance has been rarely concerned. Here, a Sn/C composite with nano-Sn embedded in expanded graphite (Sn/EG) is synthesized. The nano-Sn particles (∼30 nm) are uniformly distributed in the interlayers of expanded graphite forming a tightly stacked layered structure. The electrochemical performance of the Sn/EG, particularly at low temperature, is carefully investigated compared with graphite. At -20 °C, the Sn/EG shows capacities of 200 mAh g −1 at 0.1C and 130 mAh g −1 at 0.2C, which is much superior to graphite ( −1 ). EIS measurements suggest that the charge transfer impedance of the Sn/EG increases less rapidly than graphite with decreasing temperatures, which is responsible for the improved low temperature electrochemical performance. The Li-ion chemical diffusion coefficients of the Sn/EG obtained by GITT are an order of magnitude higher at room temperature than that at -20 °C. Furthermore, the Sn/EG exhibits faster Li-ion intercalation kinetics than graphite in the asymmetric charge/discharge measurements, which shows great promise for the application in electric vehicles charged at low temperature.

Due to the abundance of sodium in nature, sodium-ion batteries (SIBs) have attracted widespread attention. Numerous intercalated cathode materials have already been reported, but fewer intercalated anode materials are known. Among these materials, most anodes suffer from low coulombic efficiency and the dendritic growth of sodium due to the lower sodiated voltages (below 1.0 V). To improve the safety performance of batteries, exploring new anode materials which have higher sodiated voltage above 1.0 V is very important. Herein, a series of novel intercalated anode materials, ATiOPO4 (A = NH4, K, Na), is introduced for SIBs at the first time. Preparation of NaTiOPO4 by a traditional solid-state reaction is difficult. So we first synthesized NH4TiOPO4 (NTP) by a simple hydrothermal reaction, KTiOPO4 (KTP) and NaTiOPO4 (NaTP) were each prepared by ion exchange with the respective nitrate. These samples were investigated by electrochemical discharge/charge which showed average sodiated voltages of 1.45 V (NTP), 1.4 V (KTP) and 1.5 V (NaTP); respectively. In situ XRD results indicated that a two-phase reaction mechanism accompanies electrochemical Na insertion/extraction in NaTP. These anode materials are potential candidates for developing SEI-free and high safety SIBs.

Carbonaceous materials hold the most promising application among all anode materials for sodium-ion batteries (SIBs) because of the high storage capacity and good cycling stability. However, the high cost and the low initial Coulombic efficiency limit their further commercialization. Herein, an amorphous carbon material was fabricated through direct pyrolysis of low-cost pitch and phenolic resin at heat treatment temperatures between 1200 and 1600 °C. The electrochemical performances of the amorphous carbon were systematically investigated in SIBs with inexpensive Al foil as current collector and environmentally benign aqueous sodium alginate as binder. By optimizing the carbonization temperature and precursor, we achieved an initial Coulombic efficiency of 88% – the highest reported so far for carbon-based anodes in SIBs with a high reversible capacity of 284 mA h g − 1 and excellent cycling performance. It was found that both the carbonization temperature and the mass ratio of pitch to phenolic resin have significant impact on the local structure of amorphous carbon, which leads to various electrochemical behaviors. When coupled with an air-stable O3-Na 0.9 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 cathode, the full cell shows excellent electrochemical performance with an initial Coulombic efficiency of 80%, a good cycling stability and an energy density of 195 Wh/kg. This contribution provides a new approach for the development of low-cost sodium-ion batteries.

Achieving high ionic conductivity in solid electrolytes and reducing the interfacial resistance between solid electrolytes and electrode materials are considered to be one of the biggest challenges in developing solid-state batteries. The integration of the high ionic conductivity of inorganic ceramics and the flexibility of organic polymers was attempted to yield a solvent-free ceramic/polymer composite solid electrolyte for Na batteries for the first time. The composite solid electrolytes exhibit a Na+ ion conductivity as high as 2.4 mS cm−1 at 80 °C. Meanwhile, this composite membrane is thermally stable up to 150 °C and maintains the flexibility of polymer electrolytes. The solid-state Na3V2(PO4)3/CPE/Na battery using this ceramic/polymer composite electrolyte exhibits an initial reversible capacity of 106.1 mA h g−1 and excellent cycle performance with negligible capacity loss over 120 cycles.

Sodium-ion batteries (SIBs) are a promising candidate for grid electricity storage due to their potential low cost. The development of anode materials is a crucial step to promote the commercialization of SIBs, and amorphous carbon materials are likely to be the most promising alternatives among all proposed anode materials. However, the cost of the reported carbon materials is still very high due to the expensive precursors and their low carbon yield. Here, we report an amorphous carbon (AC) material made from low cost pitch. The amorphous carbon material with an amazing high carbon yield of 57% was achieved by utilizing the emulsification interaction between pitch and lignin to suppress the graphitization of pitch during the carbonization. The effects of heat-treatment temperatures and the pitch/lignin mass ratios on the morphology, microstructure and the electrochemical performance of AC were systematically investigated. By optimizing experimental conditions, we achieved one representative AC with a suitable morphology and microstructure, which exhibits promising performances with a high reversible capacity of 254 mA h g−1, a high initial coulombic efficiency of 82% and excellent cycling stability. This is the first demonstration that the pitch can be successfully applied in fabricating amorphous carbon anode materials for SIBs with superior low cost and high performance.

The utilization of renewable energies has become increasingly urgent for the sustainable development of our society. Energy storage systems are essential in order to efficiently use these energies. Sodium-ion batteries (SIBs) show bright prospect in the application for energy storage markets due to the potential low cost originating from unlimited sources and wide distribution of Na. However, the anode remains a great challenge in the industrialization of SIBs. Hard carbon holds the most promising future among all reported anodes; however, there are still two main shortcomings such as high cost and low initial coulombic efficiency, which limit its application. Here, we report a hard carbon material derived from an abundant and abandoned biomass of corn cobs (HCC) using a simple carbonization method. The HCC shows excellent sodium storage performance with a reversible capacity of ca. 300 mA h g−1, a high initial coulombic efficiency of 86% and good cycling stability. A prototype sodium-ion battery was prepared to prove the application prospect using HCC1300 as the anode and Na0.9[Cu0.22Fe0.30Mn0.48]O2 as the cathode, exhibiting a high energy density of 207 W h kg−1 and a long cycle life. These excellent properties demonstrate that HCC is a potential candidate as an anode material for sodium-ion battery application.

Electrolytes compatible with lithium metal (Li) anode and cathode materials are regarded as one of the most crucial components toward the practical deployment of rechargeable lithium metal batteries (RLMBs). Herein, we report a highly salt-concentrated electrolyte (SCE) comprising lithium bis(fluorosulfonyl)imide (LiFSI) and 1,3-dioxolane (DOL)-based ether solvents for stable cycling of 4-V-class rechargeable Li cells. The selective addition of 1,8-diazabicyclo(5.4.0)undec‑7-ene (DBU) is capable of suppressing the ring-opening polymerization of DOL. The resulting LiFSI-DOL-based SCE shows excellent chemical stability (150 days), good anodic stability (ca. 5.0 V vs. Li/Li+), and decent ionic conductivity (1.3 mS cm−1) at room temperature. Using the LiFSI-DOL-based SCE, the Li || Cu cells exhibit dendrite-free Li deposition/dissolution processes with high Coulombic efficiencies (> 99%), and the Li || LiNi1/3Mn1/3Co1/3O2 cell shows good capacity retention (81% after 400 cycles). These results strongly suggest the feasibility of the LiFSI-DOL-based SCE as electrolyte for 4-V-class RLMBs.

Solid polymer electrolytes (SPEs), comprising lithium fluorinated sulfonimide including Li[(FSO2)(RFSO2)N] (RF = n-CmF2m+1, m = 0 (LiFSI), 1 (LiFTFSI), 2 (LiFPFSI), and 4 (LiFNFSI)) and Li[(CF3SO2)2N] (LiTFSI) as conducting salt and poly(ethylene oxide) (PEO) as polymer matrix, are utilized for investigating the impact of anionic structure of lithium salt on the performances of rechargeable lithium metal (Li) batteries (RLMBs), through comparing their fundamental physical properties, including ionic conductivity and anodic stability, and electrochemical performances for Li || Li and Li || LiFePO4 cells. It is found that the cycling stabilities of both the Li anode and LiFePO4 cathode are highly dependent on the structure of fluorinated imide anion. The cycling stabilities for both the Li || Li and Li || LiFePO4 cells with Li[(FSO2)(RFSO2)N] systematically outperfom those with LiTFSI at 0.2 mA cm−2 and 80 °C (i.e., being increased in the order of LiTFSI

The thermodynamic instability of the layered structure and severe side reactions with liquid carbonate electrolytes have been considered as the key obstacles for the practical application of LiCoO2 (LCO) at voltages of above 4.5 V (versus Li/Li+). Here, we have developed a facile wet-mixing synthetic method which can realize thin and uniform surface coating of aluminum doped zinc oxide (AZO) on LCO particles. The half-cells employing the AZO modified LCO display excellent 4.5 V cycle performance with the discharge capacity retention of 80% after 650 cycles and superior rate capability of 8C capacity of 100 mAh g−1. Combined with surface structure characterizations and bond valence calculations, it is revealed that the stabilized surface and superior kinetic properties contribute to the performance enhancement of AZO modified LCO at 4.5 V. This work demonstrates AZO a suitable coating material for surface protection of cathode materials for high-voltage applications. The preparation method developed in this work is also suitable for mass production and applicable to fabrication of other types of battery materials.

Spinel cathode materials (e.g., LiMn

The high-voltage spinel LiNi0.5Mn1.5O4 cathode material suffers from the rapid degradation of electrochemical cycling performance at elevated temperatures, which prevents its successful commercialization. Herein, we show that coating the surface of this material with Ta2O5, which has high resistance against hydrofluoric acid (HF) attack, is an effective way to improve its electrochemical cycling performance. A Ta2O5-coated LiNi0.5Mn1.5O4 half-cell shows a capacity retention of ∼93% and a Coulombic efficiency of ∼98% after 100 cycles at 55 °C, compared to the corresponding values of ∼76% and ∼95% measured for the bare LiNi0.5Mn1.5O4 half-cell. The detailed structural analysis of the Ta2O5-coated LiNi0.5Mn1.5O4 shows that a small amount of Ta5+ ions diffuse into the 16c site on the cathode surface during the coating process, as directly observed by Cs corrected scanning transmission electron microscopy. The modification of the LiNi0.5Mn1.5O4 surface with Ta5+, together with the residual Ta2O5 coating, stabi...

Most technologically important electrode materials for lithium-ion batteries are essentially lithium ions plus a transition-metal oxide framework. However, their atomic and electronic structure evolution during electrochemical cycling remains poorly understood. Here we report the in situ observation of the three-dimensional structural evolution of the transition-metal oxide framework in an all-solid-state battery. The in situ studies LiNi0.5Mn1.5O4 from various zone axes reveal the evolution of both atomic and electronic structures during delithiation, which is found due to the migration of oxygen and transition-metal ions. Ordered to disordered structural transition proceeds along the , , directions and inhomogeneous structural evolution along the direction. Uneven extraction of lithium ions leads to localized migration of transition-metal ions and formation of antiphase boundaries. Dislocations facilitate transition-metal ions migration as well. Theoretical calculations suggest that doping of lower valence-state cations effectively stabilize the structure during delithiation and inhibit the formation of boundaries., Here, with the state-of-the-state electron microscope, the authors report three-dimensional atomic-scale observation of LiNi0.5Mn1.5O4 from various directions, revealing unprecedented insight into the evolution of both atomic and electronic structures during delithiation.

Recently, increasing attention has been paid to the newly emerging area of sodium-ion batteries, as a promising supplement for lithium-ion batteries. Although many cathode materials have been proposed, most of these have limitations for practical applications, such as a low capacity or a poor cycling performance. Here, sodium-deficient O3-Na0.9[Ni0.4Mn x Ti0.6−x ]O2 (where x 5 0.1–0.6, abbreviated as NNMT-9415, 9424, 9433, 9442, 9451, and 9460, respectively) materials are introduced, which can be used as the cathode in sodium-ion batteries. Among these materials, the electrochemical behavior of materials with x 5 0.4 and 0.3 is the highest with a higher capacity and better cycling property than the other materials. These can deliver an initial capacity of about 120 mA h g21 in a voltage range of 2.5–4.2 V with a negligible capacity loss even after 100 cycles. The rate capabilities of 82% and 64% at 1 C and 2 C current rates, respectively, are also satisfactory. The good cycling performance and high capacity make these two materials potential candidates as the cathode material for sodium-ion batteries.

Lithium salt with a super-delocalized imide anion, namely (trifluoromethane( S -trifluoromethanesulfonylimino)sulfonyl) (trifluoromethanesulfonyl)imide ([CF 3 SO(=NSO 2 CF 3 ) 2 ] − ), [sTFSI] − ), has been prepared and studied as conducting salt for Li-ion cells. The fundamental physicochemical and electrochemical properties of neat Li[sTFSI] and its carbonate-based liquid electrolyte have been characterized with various chemical and electrochemical tools. Li[sTFSI] shows a low melting point at 118 °C, and is thermally stable up to 300 °C without decomposition on the spectra of differential scanning calorimetry-thermogravimetry-mass spectrometry (DSC-TG-MS). The electrolyte of 1.0 M (mol dm −3 ) Li[sTFSI] in ethylene carbonate (EC)/ethyl-methyl-carbonate (EMC) (3:7, v/v) containing 0.3% water does not show any hydrolytic decomposition on the spectra of 1 H and 19 F NMR, after storage at 85 °C for 10 days. The conductivities of 1.0 M Li[sTFSI]-EC/EMC (3:7, v/v) are slightly lower than those of Li[(CF 3 SO 2 ) 2 N] (LiTFSI), but higher than those of Li[(C 2 F 5 SO 2 ) 2 N] (LiBETI). The electrochemical behavior of Al foil in the Li[sTFSI]-based electrolyte has been investigated by using cyclic voltammetry and chronoamperometry, and scanning electron microscope (SEM). It is illustrated that Al metal does not corrode in the high potential region (3–5 V vs. Li/Li + ) in the Li[sTFSI]-based electrolyte. On Pt electrode, the Li[sTFSI]-based electrolyte is highly resistant to oxidation (ca. 5 V vs. Li/Li + ), and is also resistant to reduction to allow Li deposition and stripping. The applicability of Li[sTFSI] as conducting salt for Li-ion cells has been tested using graphite/LiCoO 2 cells. It shows that the cell with Li[sTFSI] displays better cycling performance than that with LiPF 6 .

A prototype rechargeable sodium-ion battery using an O3-Na0.90[Cu0.22 Fe0.30 Mn0.48]O2 cathode and a hard carbon anode is demonstrated to show an energy density of 210 W h kg(-1) , a round-trip energy efficiency of 90%, a high rate capability (up to 6C rate), and excellent cycling stability.

Silicon is the most promising anode material for the next generation high-performance lithium ion batteries. However, its commercial application is hindered by its poor performance due to the huge volume change during cycling. Although two-dimensional silicon-based materials show significantly improved performance, flexible synthesis of such materials is still a challenge. In this work, silicon-based nanosheets with a multilayer structure are synthesized for the first time by a topochemical reaction. The morphology and oxidation state of these nanosheets can be controlled by appropriate choice of reaction media and oxidants. Benefiting from the hierarchical structure and ultrathin size, when the silicon-based nanosheets are employed as anodes they exhibit a charge (delithiation) capacity of 800 mAh/g after 50 cycles with a maximum coulombic efficiency of 99.4% and good rate performance (647 mAh/g at 1 A/g). This work demonstrates a novel method for preparing nanosheets not only for lithium ion batteries but also having various potential applications in other fields, such as catalysts, electronics and photonics.

The alkali-ion storage in spinel lithium titanate (Li4Ti5O12) is comprehensively investigated in this work. In Li4Ti5O12, Na storage is more dependent on the particle size compared to Li storage. Electrochemical results show a Na-storage capacity from 150 to 16 mAh g−1, with increasing particle size from 50 to 500 nm, whereas the Li-storage capacity appears to be independent of particle size. The Na-storage rate capability in Li4Ti5O12 is much worse than that of Li, probably because of the sluggish Na+ diffusion in Li4Ti5O12. Ab initio molecular dynamics simulations also indicate that this can be attributed to the slow diffusion kinetics of Na+ in spinel Li4Ti5O12.

Si–Cu–Ti thin films with Cu 3 Si nanowires on the surface and voids in the Cu layer are fabricated for the first time by magnetron sputtering combined with atomic layer deposition (ALD) of alumina. The formation of the surface Cu 3 Si nanowires is strongly dependent on the thickness of the coated alumina and cooling rate of the thin films during annealing. The maximum coverage of the surface Cu 3 Si nanowires is obtained with an alumina thickness of 2 nm and a cooling rate of 1 °C min −1 . The electrode based on this thin film shows an excellent capacity retention of more than 900 mAh g −1 and a high columbic efficiency of more than 99% after 100 cycles. The improvement of the electrochemical performance of Si–Cu–Ti thin film electrode is attributed to the surface Cu 3 Si nanowires which reduce the polarization and inhomogeneous lithiation by formation of a surface conductive network, in addition to the alleviation of volume expansion of Si by voids in the Cu layer during cycling.

Cr-based cathode materials for Li-ion batteries have attracted significant attentions due to the feature of multiple electron transfer. The origin of the poor electrochemical inactivity of LiCrO2 has not been clarified for decades. Here an irreversible phase transformation from the layered to the rock-salt structure is observed at atomic scale in partially electrochemical delithiated LiCrO2: Cr ions migrate from Cr layers into Li layers in the surface regions. The Cr ions at Li layers in the surface regions could block extraction of lithium from the interior regions. Density functional theory (DFT) calculations confirm that Cr ions in Li layers can stabilize the structure in the Li-poor area, but the diffusion energy barrier of Li ions will be greatly increased. It is proposed accordingly that the surface phase transformation and the blocking of diffusion channel are the main origin for the poor electrochemical reactivity of LiCrO2. Such a surface blocking phenomenon may be a common origin for inactivity of some cathode materials, in which cation mixing become significant after initial delithiation. In addition, Cr ions in LiCrO2 are oxidized only from Cr3+ to Cr4+ during electrochemical delithiation, instead of Cr6+ as usually expected, based on synchrotron X-ray absorption spectra (XAS) studies.

Sodium-ion batteries (SIBs) are expected to be a promising commercial alternative to lithium-ion batteries (LIBs) for large-scale and low-cost electrical energy storage applications in the near future. Despite this, the absence of a suitable negative electrode material hinders their development. In this contribution, we synthesized monodispersed hard carbon spherules (HCS) from an abundant biomass of sucrose, and investigated the influence of the carbonization temperature on the microstructure and electrochemical performance. The initial coulombic efficiency of the HCS was increased to 83% by coating its surface with soft carbon through the pyrolysis of toluene. Interestingly, the plateau capacity at the low potential region increased with increasing carbonization temperature. The HCS carbonized at 1600 °C showed the highest plateau capacity (220 mA h g−1) and excellent cycling performance with a capacity retention of 93% after 100 cycles. When coupled with an air-stable P2-Na2/3Ni1/3Mn2/3O2 positive electrode, the full cell exhibited a high initial coulombic efficiency of 76%, a mean operating voltage of 3.5 V and excellent cycling performance. The theoretical energy density of this system was estimated to be 200 W h kg−1. These promising properties are believed to be close to the level required for practical applications.

Stabilization of the atomic-level surface structure of LiMn

Distorted surface regions (5-6 nm) with an unusual layered-like structure on LiMn

Low cost, highly efficient and safe devices for energy storage have long been desired in our society. Among these devices, electrochemical batteries with alkali metal anodes have attracted worldwide attention. However, the practical application of such systems is limited by dendrite formation and low cycling efficiency of alkali metals. Here we report a class of liquid anodes fabricated by dissolving sodium metal into a mixed solution of biphenyl and ethers. Such liquid anodes are highly safe and have a low redox potential of 0.09 V versus sodium, exhibiting a high conductivity of 1.2 × 10−2 S cm−1. When coupled with polysulfides dissolved in dimethyl sulfoxide as the cathode, a battery is demonstrated to sustain over 3,500 cycles without measureable capacity loss at room temperature. This work provides a base for exploring a family of liquid anodes for rechargeable batteries that potentially meet the requirements for grid-scale electrical energy storage., Ideal energy storage technologies should be efficient, safe and cost-effective. Here, the authors make progress by using dissolved sodium metal in a solution of biphenyl and ethers as a liquid anode for rechargeable sodium beta-alumina batteries.

Application of high-voltage spinel LiNi0.5Mn1.5O4 cathode material is the closest and the most realistic approach to meeting the midterm goal of lithium-ion batteries for electric vehicles (EVs) and plug-in hybrid electric vehicles (HEVs). However, this application has been hampered by long-standing issues, such as capacity degradation and poor first-cycle Coulombic efficiency of LiNi0.5Mn1.5O4 cathode material. Although it is well-known that the structure of LiNi0.5Mn1.5O4 into which Li ions are reversibly intercalated plays a critical role in the above issues, performance degradation related to structural changes, particularly in the first cycle, are not fully understood. Here, we report detailed investigations of local atomic-level and average structure of LiNi0.5Mn1.5O4 during first cycle (3.5–4.9 V) at room temperature. We observed two types of local atomic-level migration of transition metals (TM) ions in the cathode of a well-prepared LiNi0.5Mn1.5O4//Li half-cell during first charge via an aberrati...

Binary electrolytes, comprising of lithium bis(fluorosulfonyl) imide (LiFSI) and ionic liquids (ILs) of N -methyl- N -propylpiperidinium bis(fluorosulfonyl) imide (PI 13 FSI) with various concentrations of LiFSI (i.e., LiFSI/PI 13 FSI in 0.05:1, 0.1:1, 0.2:1, 0.5:1, 0.8:1 and 1:1, by mole) have been investigated as electrolyte for Li-ion cells, in terms of phase behavior, thermal stability, density, viscosity, ionic conductivity, lithium-ion transference number, and electrochemical behaviors on Al, Pt, Ni, and composite natural graphite electrodes, with particular attention to the effect of concentration of LiFSI in PI 13 FSI on these properties. The stability of Al in the high potential region (3.0–5.0 V vs. Li/Li + ) has been confirmed in these electrolytes using cyclic voltammetry, chronoamperometry and SEM morphology. The anodic stability of these electrolytes on Pt electrode has been little affected by addition of LiFSI. Li deposition/stripping on Ni electrode shows low columbic efficiencies ( − anions and PI 13 + cations. Reduction of FSI − anions for forming solid electrolyte interphase (SEI) films on the graphite is observed at ca. 2.0 V (vs. Li/Li + ), followed by intercalation of Li + ions and IL cations into graphite in these electrolytes at the first cathodic scan in CV measurements. The performances of SEI films formed on the graphite highly depend on the concentration of LiFSI, and a stable Li-ion conducting SEI film can only be formed in the electrolyte containing a high concentration of LiFSI. Li/natural graphite cell using LiFSI-PI 13 FSI (1:1, by mole) as electrolyte displays high specific capacities (> 360 mAh g −1 ) and columbic efficiencies (> 99%) after conditioning, except for a large irreversible capacity (139 mAh g −1 ) observed at the first cycle. Analyses of XPS and electrochemical impedance spectra reveal that a stable Li-ion conducting SEI film, mainly comprising reduction products of FSI − anions (e.g., LiF, LiOH, Li 2 SO 3 , and species containing NSO 2 -, FSO 2 -, and N − ), has been formed on the graphite.

The binary eutectic mixture of lithium bis(fluorosulfonyl)imide (LiFSI) and potassium bis(fluorosulfonyl)imide (KFSI) with a molar ratio of x(LiFSI): x(KFSI) = 0.41: 0.59 has been investigated as molten salt electrolyte for natural graphite/LiFePO4 lithium-ion cells at 80 degrees C. The electrochemical performances of the Li/natural graphite, Li/LiFePO4, and natural graphite/LiFePO4 cells using this molten salt electrolyte have been evaluated, in terms of cycling performances and electrochemical impedance spectra (EIS) at 80 degrees C. Both the Li/natural graphite and Li/LiFePO4 cells show good cycling performances. The initial specific capacities after conditioning for the natural graphite and LiFePO4 electrodes are 353 and 150 mAh g(-1), respectively, and the corresponding capacity retention rates are 98% and 97%, respectively, after 100 cycles at 80 degrees C, except for a large irreversible capacity (162 mAh g(-1)) observed for the natural graphite at the first cycle for forming solid electrolyte interface (SEI) film. The natural graphite/LiFePO4 lithium-ion cell using this molten salt electrolyte shows a low capacity in the range of 71-86 mAh g(-1), due to the large irreversible capacity (71 mAh g(-1)) at the first cycle, but it shows a good cycleability after the first cycle, and provides a specific capacity of 71 mAh g(-1) after 100 cycles at 80 degrees C. The variations of cycling performances of these cells can be well correlated with their impedance evolution with cycling. (C) 2014 Elsevier Ltd. All rights reserved.

New solid polymer electrolytes (SPEs) comprising of lithium bis(fluorosulfonyl)imide (LiFSI) and high molecular weight poly(ethylene oxide) (PEO, Mv = 5 × 106 g mol−1) have been prepared and characterized, and are comparatively studied with the representative SPEs, Li[N(SO2CF3)2] (LiTFSI)/PEO, at a molar ratio of EO/Li+ = 20. Their physicochemical properties have been investigated in terms of phase transition behavior, ionic conductivity, lithium-ion transference number (tLi+), electrochemical stability, and with particular attention to the interfacial behavior between lithium electrode and SPEs. It has been demonstrated that the ionic conductivities of LiFSI/PEO electrolyte are higher than those of LiTFSI/PEO one above 60 °C, and exceeds 10−3 S cm−1 at 80 °C. The interface resistances of Li symmetric cell (Li metal | polymer electrolytes | Li metal) using LiFSI/PEO electrolyte are much lower than those using LiTFSI/PEO. The Li/LiFePO4 cell using LiFSI/PEO electrolyte exhibits good cycling performance at 80 °C. These outstanding properties of the LiFSI/PEO electrolyte make it attractive as SPEs for Li battery.

Surface dissolution of manganese is a long-standing issue hindering the practical application of spinel LiMn2O4 cathode material, while few studies concerning the crystal structure evolution at the surface area have been reported. Combining X-ray photoelectron spectroscopy, electron energy loss spectroscopy, scanning transmission electron microscopy, and density functional theory calculations, we investigate the chemical and structural evolutions on the surface of a LiMn2O4 electrode upon cycling. We found that an unexpected Mn3O4 phase was present on the surface of LiMn2O4 via the application of an advanced electron microscopy. Since the Mn3O4 phase contains 1/3 soluble Mn2+ ions, formation of this phase contributes significantly to the Mn2+ dissolution in a LiMn2O4 electrode upon cycling. It is further found that the Mn3O4 appears upon charge and disappears upon discharge, coincident with the valence change of Mn. Our results shed light on the importance of stabilizing the surface structure of cathode m...

Lithium metal with high theoretical specific capacity (3860 mAh/g) and the lowest electrochemical potential (−3.04 V vs standard hydrogen electrode) has been considered as the most promising anode material for next-generation rechargeable batteries. Since lithium readily reacts with most organic solvents, complete replacement of conventional electrolytes with solid electrolyte has attracted much attention. However, in solid-state lithium batteries uncontrollable lithium dendrites growth and large interface fluctuations during lithium plating/stripping still happens, leading to short circuit or capacity fading. This study employs Neutron Depth Profile (NDP), a unique tool with high sensitivity and high spatial resolution for lithium detection in solid device, to investigate the lithium plating behavior in Li|Li6.4La3Zr1.4Ta0.6O12 (LLZTO)|Ti solid-state battery with three-dimensional (3D) Ti electrode. The experiments, together with theoretical modeling, show that the majority of lithium can be deposited in the void space of the Ti 3D electrode which largely diminishes solid electrolyte/electrode interface degradation and suppresses lithium dendrite growth as well. This research demonstrates that a negative electrode with efficiently designed 3D framework can not only undertake the huge volume expansion during lithium plating but also regulate lithium deposition behavior to inhibit Li dendrite growth.