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Aqueous Li-ion batteries (ALIBs) are regarded as promising large-scale energy storage technology because of their intrinsic safety and cost-effectiveness. However, because of the “cathodic challenge” encountered using aqueous electrolytes, the choice of anode material is restricted to candidates having relatively high redox potential and low capacity, thus resulting in low energy density. In this communication, we report a TiO2 B anode for ALIBs that has low lithiation potential (∼1.6 V in nonaqueous electrolytes and ∼1.8 V in aqueous electrolytes), high capacity (∼200 mAh/g), and high structural stability. When the TiO2 B anode is paired with spinel LiMn2O4, the LiMn2O4//TiO2 B full cell can deliver high capacity (194.5 mAh/g, based on the anode mass) and high energy density (150 Wh/kg, based on the total electrode mass). Furthermore, a full cell employing this anode displays superior cycling performance with a high capacity retention of 76% after 400 cycles at 1 C, this is attributed to the structural stability of the TiO2 B nanowires and the wide electrochemical stability window of the Water-in-Salt (WIS) electrolyte. It is anticipated that the TiO2 B anode can provide a new option for constructing high-energy ALIBs.

Cobalt-free LiNiO2 cathode materials offer a higher energy density at a lower cost than high Co-containing cathode materials. However, Ni(OH)2 precursors for LiNiO2 cathodes are traditionally prepared by the coprecipitation method, which is expensive, complex, and time-consuming. Herein, we report a fast, facile, and inexpensive electrolysis process to prepare a Ni(OH)2 precursor, which was mixed with LiOH/LiNO3 salts to obtain a LiNiO2 cathode material. A combination of advanced characterization techniques revealed that the LiNiO2 cathode material prepared in this way exhibited an excellent layered structure with negligible Li/Ni site mixing and surface structural distortion. Electrochemical cycling of the LiNiO2 cathode material showed an initial discharge capacity of 235.2 mA h/g and a capacity retention of 80.2% after 100 cycles (at 1 C) between 2.75 and 4.3 V. The degradation of the cycling performance of the LiNiO2 cathode material was mainly attributed to the formation of a surface solid-electrolyte interface and a ∼5 nm rock salt-like structure, while the bulk structure of the cathode after cycling was generally stable.

The reactivity of garnet solid electrolytes toward humid air hinders their practical application despite their attractive, superior properties such as high Li+ conductivity and wide electrochemical window. Sealing garnets with organic solvents can not only prevent them from reacting with humid air but also render them compatible with other processing technologies. Therefore, the chemical and structural stability of garnets in organic solvents must be studied. In this study, we selected several commonly used organic solvents with different representative functional groups to investigate their stability with garnets and reaction mechanisms. The experiments and theoretical calculations revealed that all of the solvents reacted with garnets through Li-H exchange, and solvent acidity determined the reaction strength. Furthermore, the solvent acidity was closely correlated to the functional groups connected to H atoms, which can affect charge distribution. Solvents or the tautomer of the solvents with hydroxyl groups such as alcohol, acetone, and N-methyl pyrrolidone, which are relatively more acidic, can lead to a violent reaction with changes in the lattice parameters of garnets. Ether compounds and saturated aliphatic hydrocarbons with relatively low acidity are highly stable against garnets. The proposed reaction mechanisms and rules may help in selecting appropriate solvents for different applications of garnets.

The lack of appropriate cathodes is restraining the advances of Mg batteries. Crystalline cathode materials suffer from sluggish reaction kinetics and low-capacity delivery. The finite type of crystalline structure further confines the rational design of cathode materials. Herein, we proposed amorphization and anion enrichment as a brand-new strategy to not only enhance the solid-state ion diffusion and provide more ion-storage sites in amorphous structure but also contribute to the local transfer of multiple electrons through the additional anionic redox centers. Accordingly, a series of amorphous titanium polysulfides (a-TiS x , x = 2, 3, and 4) were designed, which significantly outperformed their crystalline counterparts and achieved a highly competitive energy density of ∼260 Wh/kg. The unique Mg2+ storage mechanism involves the dissociation/formation of S-S bonds and changes in the coordination number of Ti, namely, a mixture of conversion and intercalation reaction, accompanied by the joint cationic (Ti) and anionic (S) redox-rich chemistry. Our proposed amorphous and redox-rich design philosophy might provide an innovative direction for developing high-performance cathode materials for multivalent-ion batteries.

Anode-free lithium metal batteries can maximize the energy density at the cell level. However, without the Li compensation from the anode side, it faces much more challenging to achieve a long cycling life with a competitive energy density than Li metal-based batteries. Here, we prolong the lifespan of an anode-free Li metal battery by introducing Li-rich Li2 [Ni0.8 Co0.1 Mn0.1 ]O2 into the cathode as a Li-ions extender. The Li2 [Ni0.8 Co0.1 Mn0.1 ]O2 can release a large amount of Li-ions during the first charging process to supplement the Li loss in the anode, then convert into NCM811, thus extending the lifespan of the battery without the introduction of inactive elements. By the benefit of Li-rich cathode and high reversibility of Li metal on Cu foil, the anode-free pouch cells enable to achieve 447 Wh kg-1 energy density and 84 % capacity retention after 100 cycles in the condition of limited electrolyte addition (E/C ratio of 2 g Ah-1 ).

Summary Oxygen activity in highly delithiated LiCoO2 is critical to fully utilizing the energy density of this high-tap-density cathode but still lacks a clear understanding. In this work, we combined the results of several experimental techniques, especially resonant inelastic X-ray scattering (RIXS) and neutron pair distribution function (NPDF) analysis, together with theoretical calculations to study this topic. Our results conclude that oxygen redox takes place globally in the lattice, rather than forming localized dimerization as previously thought. RIXS results directly reveal the reversible oxygen redox, and NPDF results show that the O–O pair distance is considerably shortened in the highly delithiated LiCoO2. Theoretical calculations indicate that no O–O bonding is formed in LiCoO2, in sharp contrast to the lithium-rich system in which O–O bonding does form. These results provide the rationale for achieving a reversible deep delithiation and high energy density for LiCoO2-based electrodes.

The commercialization of rechargeable Li metal batteries is hindered by dendrite growth and volumetric variation. Herein, we report a Li-rich dual-phase Li-Cu alloy with built-in 3D conductive skeleton to replace conventional planar Li anode. The Li-Cu alloy is simply prepared by fusion of Li and Cu metals at a relatively low-temperature of 500 °C, followed by a cooling process where phase-segregation leads to metallic Li phase distributed in the network of LiCux solid solution phase. Different from the common Li alloy, the electrochemical alloying reaction between Li and Cu metals is not observed. Therefore, the lithiophilic LiCux nanowires guides conformal plating of Li and the porous framework provides superior dimensional stability for the anode. This unique ferroconcrete-like structure of Li-Cu alloy enables dendrite-free Li plating for an expanded cycling lifetime. Constructing a new type of Li alloy with in situ formed electrochemically inactive framework is a promising and easily scaled-up strategy toward practical application of Li metal anodes.

All-solid-state batteries have been considered as the ultimate solution for energy storage systems with high energy density and high safety. However, the obvious solid-solid contact and the interface stability issues pose great challenges to the construction of all-solid-state batteries with practically usable performances. Here, we discover that the heat-initiated polymerization of vinylene carbonate (VC) and the simultaneous incorporation of cathode electrolyte interphase (CEI) forming additive lithium difluoro(oxalato)borate (LiDFOB) can synergistically promote the formation of a high-voltage stable and low resistant interface layer between the cathode and solid electrolyte. A poly(ethylene oxide) PEO-based all-solid-state lithium battery (ASSLB) employing the LiCoO2 cathode electrode modified through such an in-situ CEI strategy demonstrates superior 4.2 ​V cycle stability, with a discharge capacity retention of 71.5% after 500 cycles. Besides, the accelerating rate calorimetry (ARC) test reveals that the cell displays extraordinary safety performance with no distinct thermal runaway below 350 ​°C. This work demonstrates an effective interface engineering strategy that can promise the formation of electrochemically and thermally stable cathode/solid electrolyte interface which is essential for the stable and safe operation of ASSLBs. Moreover, the validation of stable cycling of PEO-based ASSLBs at high voltages may encourage the efforts on further optimizations of interface engineering processes as well as large-scale fabrication, as the improvement of the energy-densities of PEO-based ASSLBs will be of paramount significance for practical applications.

Sn anode materials with high specific capacity are an appealing alternative to graphite for next-generation advanced lithium-ion batteries. However, poor electrochemical performance originating from fracture and pulverization due to the enormous volume changes during lithium alloying/dealloying hinders their commercial applications. Here, we propose the synthesis of a novel 3D structured Sn anode material by a facile method: heat treatment of nanosized SnO2 spheres in a tube furnace with a flowing mixed atmosphere of C2H2/Ar at 400 °C. After the heat treatment, the nanosized SnO2 spheres convert into pure Sn bulk material (~20 μm), which consists of Sn nanowires (~50 nm in diameter and several microns in length). This unique 3D structure with sufficient voids between the nanowires effectively mitigates the volume expansion of Sn bulk material and ensures good electrical contact between the anode material and conducting additives. As a consequence, the 3D structured Sn anode material exhibits a specific reversible capacity of ~600 mA h/g and no significant capacity degradation (compared with that of the 20th cycle) over 500 cycles at 0.2 C.

Structural design plays an essential role in the energy density of wearable batteries. Although various flexible materials have been developed to substitute traditional rigid components, current we...

The carbon-conducting additive-induced degradation of the cycling performance of lithium-ion batteries needs to be carefully controlled, particularly at a high operating voltage and elevated temperature. Herein, we report the investigation of surface coating with 2–3 nm of Al2O3, TiO2 and Ta2O5 oxides on Super P carbon black via atomic layer deposition. Detailed step potential tests revealed that after storage in EC/DMC electrolyte for 14 days at 55 °C, the stability of Ta2O5-coated Super P was the highest compared with those of Al2O3- and TiO2-coated counterparts. This result is attributed to Ta2O5 acting as a HF barrier, which mitigates the oxidation of electrolyte on the surface of Super P, as observed by XPS, thus showing less deposition of carbonate species. Further experiments showed that the surface of the Ta2O5 coating layer was stable, while the Al2O3 and TiO2 coating layers were completely dissolved in dilute HF after storage for 12 h Ta2O5-coated Super P was verified in a LiNi0.5Mn1.5O4 half-cell charged to 4.9 V at 55 °C. The results showed that with Ta2O5-coated Super P as the conducting additive, the half-cell exhibited an improved coulombic efficiency of 99.5%, compared with 98.3% for the pristine Super P.

The soft carbon precursor pitch, featured with low-cost and easy-availability, is regarded as a very promising candidate for the synthesis of carbonaceous anode. However, the Na-storage performance of pitch-derived carbon is strongly hindered by its highly graphitized structure, which mainly comes from the reordering during the fusion-state carbonization. To prevent the graphitization, herein, we propose an in-situ Mg(NO3)2·6H2O solidification strategy to convert the fusion-state to solid-state carbonization. The oxygen species and solid products generated from the decomposition of Mg(NO3)2·6H2O can retard the melting and reordering of pitch, thus tailoring the microstructure. The optimal sample displays outstanding overall performances in both half- and full-cells, with ~3-fold increase in capacity. Particularly, the carbon yield is significantly increased from 61% to 92% because less organic molecules can escape. The understandings gained in this work not only offer insights to adjust the carbonization process, but also provide solutions to obtain highly disordered carbon anodes from soft carbon precursors.

Summary All-solid-state lithium-metal batteries are regarded as promising next-generation battery systems. While thermal runaway in conventional Li-ion batteries is known to cause safety hazards, the thermal issues posed by highly reactive metallic lithium (Li) with non-flammable ceramic solid electrolytes (SEs) have been less studied but are critical for the safety of all-solid-state Li-metal batteries. Here, we quantify the thermal stability of four prevalent oxide SEs with metallic Li using the accelerating rate calorimeter (ARC). Thermal runaway is observed during ARC tests for four widely used SEs when contacting with Li, while no obvious heat releases from garnet with Li. The oxygen generation from SEs at elevated temperatures is found to be responsible for the thermal runaway with Li. Our results indicate potential safety issues in all solid-state batteries (ASSBs) brought by highly reactive metallic Li and oxygen from SEs at increased temperatures, emphasizing the need for investigating thermal safety issues in ASSBs.

Successfully commercialized poly(ethylene oxide) (PEO)-based solid polymer batteries (SPBs) are expected to continuously play a key role in the next generation of high-energy density lithium-ion ba...

Nowadays, cost-efficient and high-power energy storage technologies are urgently required for extensive integration of intermittent wind and solar renewable energy. Complying with the simplification and acceleration principle, we designed a fast-charge Al organic battery in which ionic diffusion in anode materials and through the solid electrolyte interphase (SEI) process is simplified while the generation of charge-carrier ions at the cathode/anode interface and ion diffusion in cathode materials are accelerated. A prototype based on 2,3,5,6-tetraphthalimido-p-benzoquinone (TPBQ)–Al was successfully demonstrated with 100 mA h pouch cells displaying superior power capability, high energy density and excellent cycling stability. Moreover, extensive characterizations and DFT calculations predict the crystal structure and simulate the precise reaction pathway corresponding to the thermodynamic redox potential of TPBQ and consolidate our proposed AlCl2+ electrochemical surface-coordination and storage mechanism. We believe that our design philosophy by simplifying and accelerating kinetics would provide guidance for tailoring fast and affordable energy storage systems.

Owing to its unique structure, Chevrel phase (CP) is a promising candidate for applications in rechargeable multivalent (Mg and Al) batteries. However, its wide applications are severely limited by...

Layered oxides are one of the most promising cathode materials for sodium ion batteries (NIBs), however, the relatively low working voltage hinders the increase of energy density thus limiting the application scenarios of NIBs. Here we prepared and investigated a series of Sn4+ substituted Na0.67Ni0.33Mn0.67-xSnxO2 (x = 0.10, 0.20, 0.30, 0.33) and found that Sn-substitution can induce three effects: promoting O3-stack formation, smoothing the voltage profile and increasing the working voltage to ∼3.6 V. This study would enrich the knowledge of Sn-substitution and give guide to the better design of high-voltage cathode materials for NIBs.

LiCoO2 is a dominant cathode material for lithium-ion (Li-ion) batteries due to its high volumetric energy density, which could potentially be further improved by charging to high voltages. However, practical adoption of high-voltage charging is hindered by LiCoO2’s structural instability at the deeply delithiated state and the associated safety concerns. Here, we achieve stable cycling of LiCoO2 at 4.6 V (versus Li/Li+) through trace Ti–Mg–Al co-doping. Using state-of-the-art synchrotron X-ray imaging and spectroscopic techniques, we report the incorporation of Mg and Al into the LiCoO2 lattice, which inhibits the undesired phase transition at voltages above 4.5 V. We also show that, even in trace amounts, Ti segregates significantly at grain boundaries and on the surface, modifying the microstructure of the particles while stabilizing the surface oxygen at high voltages. These dopants contribute through different mechanisms and synergistically promote the cycle stability of LiCoO2 at 4.6 V. LiCoO2 is a widely used cathode material in Li-ion batteries for applications such as portable electronics. Here, the authors report multiple-element doping to enable stable cycling of LiCoO2 at high voltages that are not yet accessible with commercial Li-ion batteries.

In this paper, we report a facile method for the in situ deposition of a thin solid electrolyte layer on the surface of anode materials, which can significantly improve the rate capability and reduce the time for reaching capacity maximum. The thin solid electrolyte layer (∼8 nm) is formed by adding a small amount of LiNO3 into the anode materials; the added LiNO3 decomposes irreversibly into Li3N and LiNxOy on the surface of the anode materials during the first cycle, facilitating fast diffusion of lithium ions and limiting the formation of the surface electrolyte interface films. This is verified by adding LiNO3 into graphite half-cells which shows a fast activation process at high current density: in particular, the charge capacity reaches its maximum after only ∼30 and ∼40 cycles at 170 and 340 mA g−1, respectively, compared to ∼50 and ∼80 cycles for the graphite half-cell. Furthermore, the LiNO3 additive results in high capacity retention at high C-rates, with a value of 82.4% at 680 mA g−1, compared with 22.4% for the graphite half-cell. The facile and low-cost method reported here is expected to be readily applicable to other electrode materials for high-performance lithium-ion batteries.

Aqueous K-ion batteries (AKIBs) are promising candidates for grid-scale energy storage due to their inherent safety and low cost. However, full AKIBs have not yet been reported due to the limited availability of suitable electrodes and electrolytes. Here we propose an AKIB system consisting of an Fe-substituted Mn-rich Prussian blue KxFeyMn1 − y[Fe(CN)6]w·zH2O cathode, an organic 3,4,9,10-perylenetetracarboxylic diimide anode and a 22 M KCF3SO3 water-in-salt electrolyte. The cathode achieves 70% capacity retention at 100 C and a lifespan of over 10,000 cycles due to the mitigation of phase transitions by Fe substitution. Meanwhile, the electrolyte can help decrease the dissolution of both electrodes owing to the lack of free water. The AKIB exhibits a high energy density of 80 Wh kg−1 and can operate well at rates of 0.1–20 C and over a wide temperature range (−20 to 60 °C). We believe that our demonstration could pave the way for practical applications of AKIBs for grid-scale energy storage. Intensive efforts are underway towards developing battery-based grid-scale storage technologies. Here, the authors report an aqueous K-ion battery that offers many attractive advantages over various battery alternatives.

Recently, sodium-ion batteries (SIBs), regarded as promising supplements for lithium-ion batteries (LIBs), especially in the large-scale energy storage field, are attracting more and more attention. However, the limited suitable cathode materials hinder the wide commercialization of SIBs. Given this aspect, in this work, a new layered oxide with 4d metal Tin was synthesized and investigated as cathode material for SIBs. Two optimized sodium-deficient O3-Na0.9Ni0.45Sn0.55O2 and O3-Na0.9Ni0.4Mn0.1Sn0.5O2 were selected for comprehensive investigation, both of which exhibited high operating voltage of around 3.45 V with smooth charge/discharge curves. In comparison, O3-Na0.9Ni0.4Mn0.1Sn0.5O2 shows a higher reversible capacity (65 mA h/g, 0.1 C), better rate capability and cycling stability than that of O3-Na0.9Ni0.45Sn0.55O2 (50 mA h/g, 0.1 C), indicating that a small amount of Mn-substitution can improve the electrochemical performance. This work presents a new possibility of discovering potential cathode candidates by exploring the Tin-based layered oxides.

The comprehensive performance of carbon anodes for Na-ion batteries (NIBs) is largely restricted by their inferior rate capability and safety issues. Herein, a slope-dominated carbon anode is achieved at a low temperature of 800 °C, which delivers a high reversible capacity of 263 mA h g-1 at 0.15C with an impressive initial Coulombic efficiency (ICE) of 80 %. When paired with the NaNi1/3 Fe1/3 Mn1/3 O2 cathode, the reversible capacity at 6C is still 75 % of that at 0.15C, and 73 % of the capacity is retained after 1000 cycles at 3C. The enhanced Na storage performance could be attributed to the unique microstructure with randomly oriented short carbon layers and the relatively higher defect concentration. Given its robustness, such a low-temperature carbonization strategy could also be applicable to other precursors and provide a new opportunity to design slope-dominated carbon anodes for high safety, low-cost NIBs with excellent ICE and superior rate capability.

High capacity cation-disordered Li-rich oxides not only enlarge the chemical design space of cathode materials, but also play an important role in promoting the development of high energy density Li-ion batteries. However, there are still some issues, such as capacity degradation, that impede their practical applications. In-depth understanding of the structure and mechanisms in cation-disordered Li-rich oxides is favorable for their further performance optimization. Herein, taking the new designed high capacity (~ 280 mA h/g) disordered Li1.2Ti0.35Ni0.35Nb0.1O1.8F0.2 as a model compound, we meticulously study its structure evolution and electrochemical reaction mechanisms upon cycling by combination of first principles calculation, synchrony X-ray diffraction (SXRD), X-ray pair distribution function (XPDF), X-ray absorption spectroscopy (XAS), in situ XRD, and Neutron powder diffraction (NPD) et al. The excellent structure stability and robust anions framework of cation-disordered Li-rich oxides are experimentally demonstrated. Meanwhile, the high capacity mechanisms rely on the simultaneous cations and anions redox reactions and the capacity degradation mechanism induced by oxygen loss upon cycling are also proposed. Based on these revelations, the optimization strategy and potential applications of cation-disordered Li-rich oxides are further proposed.

The lithium metal anode (LMA) instability at deep cycle with high utilization is a crucial barrier for developing lithium (Li) metal batteries, resulting in excessive Li inventory and electrolyte demand. This issue becomes more severe in capacity-type lithium-sulfur (Li-S) batteries. High-concentration or localized high-concentration electrolytes are noted as effective strategies to stabilize Li metal but usually lead to a high electrolyte density (>1.4 g mL-1 ). Here we propose a bifunctional fluorinated silane-based electrolyte with a low density of 1.0 g mL-1 that not only is much lighter than conventional electrolytes (≈1.2 g mL-1 ) but also form a robust solid electrolyte interface to minimize Li depletion. Therefore, the Li loss rate is reduced over 4.5-fold with the proposed electrolyte relative to its conventional counterpart. When paired with onefold excess LMA at the electrolyte weight/cell capacity (E/C) ratio of 4.5 g Ah-1 , the Li-S pouch cell using our electrolyte can survive for 103 cycles, much longer than with the conventional electrolyte (38 cycles). This demonstrates that our electrolyte not only reduces the E/C ratio but also enhances the cyclic stability of Li-S batteries under limited Li amounts.

Amorphous anion-rich materials would offer a previously unexplored solution for high-capacity Al-ion storage., The strong electrostatic interaction between Al3+ and close-packed crystalline structures, and the single-electron transfer ability of traditional cationic redox cathodes, pose challenged for the development of high-performance rechargeable aluminum batteries. Here, to break the confinement of fixed lattice spacing on the diffusion and storage of Al-ion, we developed a previously unexplored family of amorphous anion-rich titanium polysulfides (a-TiSx, x = 2, 3, and 4) (AATPs) with a high concentration of defects and a large number of anionic redox centers. The AATP cathodes, especially a-TiS4, achieved a high reversible capacity of 206 mAh/g with a long duration of 1000 cycles. Further, the spectroscopy and molecular dynamics simulations revealed that sulfur anions in the AATP cathodes act as the main redox centers to reach local electroneutrality. Simultaneously, titanium cations serve as the supporting frameworks, undergoing the evolution of coordination numbers in the local structure.

Spinel cathode materials (e.g., LiMn2O4 and LiNi0.5Mn1.5O4) with strongly bonded surface coatings are desirable for delivering improved electrochemical performance in long-term cycling. Here, we report that the introduction of bridging ions such as Fe and Co, which can diffuse into both the spinel cathode materials and Li3PO4, the latter is found to cover the spinel surface in the form of dense and uniform particles (∼2-3 nm). Detailed structural analysis of the surface reveals that the bridging ions diffuse into the 16c site of the spinel structure to form ion-doped spinel cathode materials, which contribute to the formation of strong bonds between the surface and Li3PO4, possibly via spinel-(surface bridging ions)-Li3PO4 bonds. The critical role of the surface bridging ions is further investigated by heating the as-formed Li3PO4-coated spinel cathode materials (with bridging ions) to high temperatures, resulting in further diffusion of bringing ions from the surface to the interior of the spinel materials and consequently depletion of the surface spinel-(surface bridging ions)-Li3PO4 bonds. This leads to the gradual growth of surface Li3PO4 particles (∼20 nm) and the exposure of the spinel surface.

Garnet-type solid-state electrolytes (SSEs) are considered to be a good choice for solid-state batteries, yet the interfacial issues with metallic Li limit their applications. Herein, we propose an ultrasimple and effective strategy to enhance the interfacial connection between garnet SSEs and Li metal just by drawing a graphite-based soft interface with a pencil. Both experimental analysis and theoretical calculations confirm that the reaction between the graphite-based interfacial layer and metallic lithium forms a lithiated connection interface with good lithium-ionic and electronic conductivity. Compared to the reported interfacial materials, the graphite provides a soft interface with better ductility and compressibility. With improvement by this soft interface, the impedance of symmetric Li cells significantly decreases and the cell cycle is stable for over 1000 h. Moreover, a solid-state battery with Li-metal anode, ternary NCM523 cathode, and treated-garnet SSEs is fabricated and displays excellen...

High-voltage spinel LiNi0.5Mn1.5O4 cathode materials typically exhibit a perfect octahedral morphology; i.e., only the {111} planes are observed. However, a truncated octahedral morphology is sometimes observed with the appearance of both the {100} planes and the {111} planes. The underlying mechanism of this morphological transformation is unclear. CS corrected scanning transmission electron microscopy (STEM) techniques were used to study LiNi0.5Mn1.5O4 samples lifted by a focused ion beam (FIB) to determine the atomic-level crystal and electronic structures of the octahedral and truncated octahedral morphologies. STEM images directly show that the appearance of the {100} planes in the truncated octahedral particles of LiNi0.5Mn1.5O4 is closely associated with the atomic-level migration of Ni and Mn ions in the surface region. The STEM electron energy loss spectroscopy (EELS) confirms the presence of oxygen-deficient and Ni-rich areas, particularly in the region close to the newly formed {100} planes. Th...

Stabilization of the atomic-level surface structure of LiMn2O4 with Al3+ ions is shown to be significant in the improvement of cycling performance, particularly at a high temperature (55 °C) and high voltage (5.1 V). Detailed analysis by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy, etc. reveals that Al3+ ions diffuse into the spinel to form a layered Li(Alx,Mny)O2 structure in the outmost surface where Al3+ concentration is the highest. Other Al3+ ions diffuse into the 8a sites of spinel to form a (Mn3-xAlx)O4 structure and the 16d sites of spinel to form Li(Mn2-xAlx)O4. These complicated surface structures, in particular the layered Li(Alx,Mny)O2, are present at the surface throughout cycling and effectively stabilize the surface structure by preventing dissolution of Mn ions and mitigating cathode-electrolyte reactions. With the Al3+ ions surface modification, a stable cycle performance (∼78% capacity retention after 150 cycles) and high Coulombic efficiency (∼99%) are achieved at 55 °C. More surprisingly, the surface-stabilized LiMn2O4 can be cycled up to 5.1 V without significant degradation, in contrast to the fast capacity degradation found in the unmodified case. Our findings demonstrate the critical role of ions coated on the surface in modifying the structural evolution of the surface of spinel electrode particles and thus will stimulate future efforts to optimize the surface properties of battery electrodes.

Organic materials, especially the carbonyl compounds, are promising anode materials for room temperature sodium-ion batteries owing to their high reversible capacity, structural diversity as well as eco-friendly synthesis from bio-mass. Herein, we report a novel anthraquinone derivative, C14H6O4Na2 composited with carbon nanotube (C14H6O4Na2-CNT), used as an anode material for sodium-ion batteries in ether-based electrolyte. The C14H6O4Na2-CNT electrode delivers a reversible capacity of 173 mAh g−1 and an ultra-high initial Coulombic efficiency of 98% at the rate of 0.1 C. The capacity retention is 82% after 50 cycles at 0.2 C and a good rate capability is displayed at 2 C. Furthermore, the average Na insertion voltage of 1.27 V vs. Na+/Na makes it a unique and safety battery material, which would avoid Na plating and formation of solid electrolyte interface. Our contribution provides new insights for designing developed organic anode materials with high initial Coulombic efficiency and improved safety capability for sodium-ion batteries.

Mixed silicon and carbon (Si–C) materials with high capacity are ideal candidates for the substitution of graphite or other carbon anodes in lithium-ion batteries. However, the low coulombic efficiency of the Si–C anode in the first cycle due to the formation of a solid electrolyte interphase and the consumption of active lithium have hindered its commercial applications. Here, we report using Li2S as a prelithiation material to compensate for the loss of active lithium in the first cycle and, consequently, to enhance the specific energy of lithium-ion batteries. The Si–C anode has an initial discharge specific capacity of ∼738 mA h g−1 and a charge specific capacity of ∼638 mA h g−1. The prelithiation material with a core–shell structure is prepared by mixing Li2S, Ketjenblack (KB) and poly(vinylpyrrolidone) (PVP) in anhydrous ethanol, which shows a high irreversible capacity of ∼1084 mA h g−1. The effect of the compensation of lost active lithium is verified via a LiFePO4 (Li2S)/Si–C full cell, which exhibits not only a high specific capacity but also a stable cycling performance. The specific energy of the LiFePO4 (Li2S)/Si–C full cell shows a remarkable increase compared to the LiFePO4/Si–C full cell, exhibiting ∼13.4%, ∼26.7%, ∼65.0% and ∼110.2% more specific energy after the 1st, 10th, 100th and 200th cycle, respectively.

The formation of Li dendrites is effectively inhibited by utilizing a small amount of polysulfide (1 to 2 mM Li2Sx, 2 ≤ x ≤ 8) in a conventional carbonate electrolyte to introduce a significant amount of polyethylene oxide (PEO)-like polymers into solid-electrolyte interphase (SEI) films. The polysulfide added likely acts as a catalyst rather than an additive, which is not consumed during repeated charging/discharging cycles. Thus the stability of Li-metal batteries during prolonged cycling is remarkably improved.

Solid electrolytes with high ionic conductivity and excellent electrochemical stability are of prime significance to enable the application of solid-state batteries in energy storage and conversion. In this study, solid composite polymer electrolytes (CPEs) based on sodium bis(trifluorosulfonyl) imide (NaTFSI) and poly (ethylene oxide) (PEO) incorporated with active ceramic filler (NASICON) are reported for the first time. With the addition of NASICON fillers, the thermal stability and electrochemical stability of the CPEs are improved. A high conductivity of 2.8 mS/cm (at 80 °C) is readily achieved when the content of the NASICON filler in the composite polymer reaches 50 wt%. Furthermore, Na 3 V 2 (PO 4 ) 3 /CPE/Na solid-state batteries using this composite electrolyte display good rate and excellent cycle performance.

Lithium-ion batteries with graphite as the anode consume ∼10% of the active lithium from the cathode to form a solid electrolyte interphase layer during the first cycle, resulting in a reduced reversible capacity. Here, we report using Li2S as a cathode pre-lithiation material to compensate for the loss of active lithium and, consequently, enhance the specific energy of lithium-ion batteries. A Li2S material with a core-shell structure is prepared by mixing Li2S, Ketjenblack (KB) and poly(vinylpyrrolidone) (PVP) in anhydrous ethanol, and the material shows a specific charge capacity of ∼1053 mAh g−1 (631 mAh g−1 based on the total weight of cathode pre-lithiation materials, binders and conductive additives). The ability of this material to compensate for active lithium is investigated by coating a typical cathode LiFePO4 as an example, with the core-shell Li2S/KB/PVP via a simple and non-toxic coating method. Our results show that the LiFePO4 (Li2S)/graphite full cell exhibits a specific discharge capacity of 146.7 mAh g−1 in the first cycle, which is the same as the specific discharge capacity of the LiFePO4 half cell. XPS analysis reveals Li2S decomposes into lithium ions and sulfur with release of electrons in the first charge. Such a successful extraction of the active lithium from Li2S results in excellent cycling performance with increased specific energy.

Distorted surface regions (5–6 nm) with an unusual layered-like structure on LiMn2O4 cathode material were directly observed after it was cycled (3–4.9 V), indicating a possible spinel-to-layered structural transformation. Formation of these distorted regions severely degrades LiMn2O4 cathode capacity. As we attempt to get a better understanding of the exact crystal structure of the distorted regions, the structural transformation pathways and the origins of the distortion are made difficult by the regions’ nanoscopic size. Inspired by the reduction of Mn4+ to Mn3+ in surface electronic structures that might be associated with oxygen loss during cycling, we further investigated the atomic-level surface structure of LiMn2O4 by heat-treatments between 600 and 900 °C in various atmospheres, finding similar surface spinel-to-layered structural transformation only for LiMn2O4 heat-treated in argon atmosphere for a few minutes (or more). Controllable and measurable oxygen loss during heat-treatments result in M...

According to the working principle of Lithium ion batteries, a perfect coating layer should not only be a lithium ion conductor but also an electronic conductor. In this work, the layered cathode material LiNi1/3Mn1/3Co1/3O2 was modified by a dual functional coating layer created from the Li-ion conductor Li2SiO3 and electronic conductor carbon. It was found that the modified LiNi1/3Mn1/3Co1/3O2 showed outstanding electrochemical performance after being coated with an appropriate content of Li2SiO3&C. Particularly, at the high current density of 5C (1C = 160 mA/g), the LiNi1/3Mn1/3Co1/3O2 coated with Li2SiO3&C could still deliver a discharge capacity of 96 mAh/g after 500 cycles with a capacity retention of 89.62%. In comparison, the pristine only delivered a discharge capacity of 71 mAh/g after 450 cycles. Furthermore, our strategy is convenient and universal, it can also be applied to other layered cathode materials to ameliorate their electrochemical properties.

Batteries with lithium metal anodes are promising because of lithium’s high energy density. However, the growth of Li dendrites on the surface of the Li electrode in a liquid electrolyte during cycling reduces the safety and cycle performance of batteries, hindering their commercial application. In this work, we observe for the first time a smooth and dendrite-free Li deposition with a vertically grown, self-aligned, and highly compact columnar structure formed during cycling in a mixed carbonate–ether electrolyte. The stable microsized (∼10 μm in diameter and ∼20 μm in length) Li deposits are aligned in arrays on the surface of the Li electrode. The columnar Li deposits still exhibit a dendrite-free morphology and a compact structure after 200 cycles at a current density of 1 mA/cm2 and a 1.5 mAh/cm2 cycling capacity in a mixed carbonate–ether electrolyte. This work shows an optimiztic outlook for Li batteries with liquid electrolytes.

Detailed investigation of the influence of surface modification using a typical oxide (TiO2) on the electrochemical cycling performance of LiNi0.5Mn1.5O4 at room temperature (25 °C) and elevated temperature (55 °C) is reported. This spinel cathode material is commonly surface-modified with various metal oxides to improve its electrochemical cycling performance in lithium ion batteries. However, the underlying mechanisms of such a treatment, with respect to the surface crystal structure and chemistry evolution, have remained unclear. Bare-LiNi0.5Mn1.5O4 and TiO2-modified LiNi0.5Mn1.5O4 both show excellent cycling performance, i.e. almost no capacity retention and ∼99% coulombic efficiency for 150 cycles, at room temperature. However, at 55 °C the latter shows significantly better electrochemical cycling performance, with 93% capacity retention and ∼96% coulombic efficiency for 100 cycles, than the former with 70% capacity retention and ∼93% coulombic efficiency. Via advanced electron microscopy techniques, we observed that titanium ions migrated into the surface region of LiNi0.5Mn1.5O4 during the surface modification process at high temperature and reconstructed the (1–3 nm) surface spinel structure into a rocksalt-like structure and the subsurface (several nanometers) into a pseudo-rocksalt-like structure. The reconstruction of the surface and subsurface of the LiNi0.5Mn1.5O4 spinel cathode material mitigates not only the migration of Mn ions from the bulk into the electrolyte but also the formation of a solid state electrolyte interface, which plays a critical role in the improvement of electrochemical cycling performance at elevated temperatures.

To improve the safety of sodium (Na) batteries, we first report a new solid polymer electrolyte (SPE), composed of sodium (fluorosulfonyl)(n-nonafluorobutanesulfonyl)imide (Na[(FSO2)(n-C4F9SO2)N], NaFNFSI) and poly(ethylene oxide) (PEO), which is prepared by a facile solution-casting method. The NaFNFSI/PEO (EO/Na+ = 15) blended polymer electrolyte exhibits a relatively high ionic conductivity of 3.36 × 10−4 S cm−1 at 80 °C, sufficient thermal stability (>300 °C) and anodic electrochemical stability (≈4.87 V vs. Na+/Na) for application in solid-state Na batteries. Most importantly, the NaFNFSI-based SPE can not only deliver excellent chemical and electrochemical stability with Na metal, but can also display good cycling and current-rate performances for the Na|SPE|NaCu1/9Ni2/9Fe1/3Mn1/3O2 cell. All of these outstanding properties would make the NaFNFSI-based SPE promising as a candidate for application in solid-state Na batteries.

Layering the charge Layered metal oxides such as lithium cobalt oxide have attracted great attention for rechargeable batteries. In lithium cells, only the octahedral structure forms, but in sodium cells, trigonal prismatic structures are also possible. However, there is a lack of understanding about how to predict and control the formation of each structure. Zhao et al. used the simple properties of ions, namely their charge and their radius appropriately weighted by stoichiometry, to determine whether sodium in the interlayers between the transition metal or other ion-oxide layers remain octahedral rather than switching over to trigonal prismatic coordination. Science , this issue p. 708

Lattice-oxygen redox (l-OR) has become an essential companion to the traditional transition-metal (TM) redox charge compensation to achieve high capacity in Li-rich cathode oxides. However, the understanding of l-OR chemistry remains elusive, and a critical question is the structural effect on the stability of l-OR reactions. Herein, the coupling between l-OR and structure dimensionality is studied. We reveal that the evolution of the oxygen-lattice structure upon l-OR in Li-rich TM oxides which have a three-dimensional (3D)-disordered cation framework is relatively stable, which is in direct contrast to the clearly distorted oxygen-lattice framework in Li-rich oxides which have a two-dimensional (2D)/3D-ordered cation structure. Our results highlight the role of structure dimensionality in stabilizing the oxygen lattice in reversible l-OR, which broadens the horizon for designing high-energy-density Li-rich cathode oxides with stable l-OR chemistry.

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...