Discharge Potential Research Articles

Influence of operating conditions on the desalination performance of a symmetric pre-conditioned Ti3C2Tx-MXene membrane capacitive deionization system

Introduction of new nanomaterials with conductivity, salt adsorption capacity (SAC) and rate (SAR) exceeding that of carbon electrodes may greatly improve capacitive deionization of water. However, those materials show a different electrochemical behavior, which must be studied and optimized for practical use. Here, effects of operating conditions on desalination performance of pre-conditioned Ti3C2Tx-MXene-based electrodes in a symmetric membrane capacitive deionization (MCDI) system were investigated. Specifically, influences of discharge potential, half-cycle length (HCL), and flow rate were systematically studied. Results showed different degrees of performance dependence on operating conditions. For instance, lower discharge potentials increased SAC and SAR by 152%. However, longer HCL increased SAC by 32% while decreasing SAR by 54%. Finally, faster flow rates decreased both SAC and SAR by 20%. Desalination performances of symmetric pre-conditioned MXene and activated carbon cloth (ACC) electrodes were gravimetrically and volumetrically compared in MCDI system. Pre-conditioned MXene electrodes gravimetrically performed 30% lower than ACC due to their notably higher density. Yet, pre-conditioned MXene electrodes volumetrically outperformed ACC by 162%. Results suggest that although MXenes offer high electrochemical activity and hydrophilicity, making them promising candidates for CDI applications, the strong dependence of desalination performance of MXenes on operating conditions requires in-depth understanding and warrants further research.

High‐Performance Platinum‐Perovskite Composite Bifunctional Oxygen Electrocatalyst for Rechargeable Zn–Air Battery

AbstractConstructing highly active electrocatalysts with superior stability at low cost is a must, and vital for the large‐scale application of rechargeable Zn–air batteries. Herein, a series of bifunctional composites with excellent electrochemical activity and durability based on platinum with the perovskite Sr(Co0.8Fe0.2)0.95P0.05O3−δ (SCFP) are synthesized via a facile but effective strategy. The optimal sample Pt‐SCFP/C‐12 exhibits outstanding bifunctional activity for the oxygen reduction reaction and oxygen evolution reaction with a potential difference of 0.73 V. Remarkably, the Zn–air battery based on this catalyst shows an initial discharge and charge potential of 1.25 and 2.02 V at 5 mA cm−2, accompanied by an excellent cycling stability. X‐ray photoelectron spectroscopy, X‐ray absorption near‐edge structure, and extended X‐ray absorption fine structure experiments demonstrate that the superior performance is due to the strong electronic interaction between Pt and SCFP that arises as a result of the rapid electron transfer via the PtOCo bonds as well as the higher concentration of surface oxygen vacancies. Meanwhile, the spillover effect between Pt and SCFP also can increase more active sites via lowering energy barrier and change the rate‐determining step on the catalysts surface. Undoubtedly, this work provides an efficient approach for developing low‐cost and highly active catalysts for wider application of electrochemical energy devices.

Three-dimensional porous pitch-derived carbon coated Si nanoparticles-CNT composite microsphere with superior electrochemical performance for lithium ion batteries

Although silicon has attracted attention as a promising anode material for lithium ion batteries due to its high theoretical capacity and relatively low discharge potential, the issue of large volume expansion and contraction during its de-/alloying reaction with Li has resulted in the development of nanostructured electrode design and coating methods using suitable carbon sources to improve the stability of the electrode. Pitch is regarded as an attractive carbon coating source owing to its mesophase characteristics, high mechanical strength, and electrical conductivity. In this study, three-dimensional porous pitch-derived carbon coated Si nanoparticles-carbon nanotube (Si-CNT@PC) composite microspheres were successfully synthesized by spray pyrolysis and a following pitch infiltration process. Uniformly distributed Si nanoparticles, acid-treated multiwall CNTs, and polystyrene (PS) nanobeads enabled the formation of porous structured Si-CNT composite microspheres by spray pyrolysis. Uniform infiltration of pitch dissolved in tetrahydrofuran followed by a carbonization process resulted in Si-CNT@PC microspheres. The uniquely structured Si-CNT@PC microspheres exhibited superior electrochemical properties compared with Si-CNT microspheres not coated with carbon. The synergetic effects of carbon-coated Si nanoparticles, macroporous structure formed by decomposition of PS nanobeads, and the CNT backbone resulted in excellent lithium-ion storage performance of Si-CNT@PC microspheres. The discharge capacities of Si-CNT and Si-CNT@PC at a current density of 1 A g−1 for the 200th cycle were 51 and 1209 mA h g−1, respectively.

(Co,Fe)3O4 Decorated Nitrogen‐Doped Carbon Nanotubes in Nano‐Composite Gas Diffusion Layers as Highly Stable Bifunctional Catalysts for Rechargeable Zinc‐Air Batteries

Abstract(Co,Fe)3O4 nanoparticles are decorated onto N‐doped carbon nanotubes at room temperature through a simple mixing process and are simultaneously deposited within a porous gas diffusion layer (GDL) by an impregnation technique. The (Co,Fe)3O4 nanoparticles are identified as the spinel phase through transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy (XPS) analysis. The composite GDL is used as the air electrode for Zn‐air batteries and shows excellent performance as a bifunctional catalyst with initial discharge and charge potentials of 1.19 V and 2.00 V, respectively, at 20 mA cm−2. Cycling performance of the impregnated electrode compares favourably with benchmark Pt‐RuO2 catalysts at both 10 mA cm−2 and 20 mA cm−2. The (Co,Fe)3O4/N‐CNT impregnated GDL had a final discharge/charge efficiency of 58.5 % after 100 h (200 cycles) of bifunctional cycling at 10 mA cm−2, which is superior to that of Pt‐RuO2 (55.3 % efficiency). The cycling efficiency for (Co,Fe)3O4/N‐CNT impregnated GDL at 20 mA cm−2 is also better than that for Pt−Ru (53.5 % vs 41.3 % after 50 h (100 cycles)). The result is a simple and easily scalable one‐pot electrode synthesis method for high performing bi‐functional air electrodes for Zn‐air batteries.

Electrochemical behavior of Mg-Al-Zn-Ga-In alloy as the anode for seawater-activated battery

The effect of indium alloying on the corrosion and discharge behaviors of Mg-Al-Zn-Ga alloys is investigated via materials characterization, immersion test and electrochemical methods. The results indicate that indium alloying can effectively modify the distribution of intermetallic phases in Mg matrix via promoting the segregation of Al in the form of Mg17Al12 in matrix. The addition of indium can effectively activate Mg-Al-Zn-Ga alloy evidenced by increased hydrogen evolution volume and weight loss, negative shift of corrosion and discharge potentials, increase of corrosion current density, decrease of polarization resistance and promoted Faradic efficiency. Nonetheless, excessive indium alloying (2.0 wt.%) would strikingly deteriorate the electrochemical performance of Mg-Al-Zn-Ga anode due to the exorbitant active effect. The Mg-6 wt.%Al-3 wt.%Zn-1 wt.%Ga-1 wt.%In in as-cast state with acceptable corrosion rate and desirable discharge performance is a low cost, non-toxic and well-performance magnesium alloy, which is a promising anode materials for seawater-activated batteries.

Synthesis of 1,4-benzoquinone dimer as a high-capacity (501 mA h g−1) and high-energy-density (>1000 Wh kg−1) organic cathode for organic Li-Ion full batteries

The organic cathodes with high specific capacity are highly desirable to fabricate high-specific-energy-density organic Li-ion full cells. Herein, we initially propose the long-term plan for the systematic synthesis of the oligomer family of 1,4-benzoquinone (BQ), which can possess theoretical specific capacity above 500 mA h g−1. As a start, the dimer of 1,4-benzoquinone (2,2′-bis-(1,4-benzoquinone), BBQ) is synthesized, which can realize the specific capacity of 501 mA h g−1 and the average discharge potential of ~2.5 V (vs. Li+/Li). Even facing the dissolution problem, BBQ can deliver average specific capacities of ~190 mA h g−1 during 3000 cycles at 500 mA g−1 and ~120 mA h g−1 during 8000 cycles at 2 A g−1 in Li-ion half cells. Afterwards, the all-organic Li-ion full cells are fabricated by using the reduced state (Li4TP) of lithium terephthalate (Li2TP) as the starting anode and BBQ as the starting cathode. Delightfully, the resulting Li4TP-BBQ Li-ion full cells can realize the specific capacity of 316 mA h g−1cathode in the 1st cycle (500 mA g−1). Meanwhile, average specific capacities of ~98 mA h g−1 during 1000 cycles can be fulfilled (500 mA g−1). The results of the Li4TP-BBQ Li-ion full cells are among the best all-organic Li-ion full batteries reported to date.

Nitrogen-Doped Graphene-Buffered Mn2 O3 Nanocomposite Anodes for Fast Charging and High Discharge Capacity Lithium-Ion Batteries.

Mn2 O3 is a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity and low discharge potential. However, low electronic conductivity and capacity fading limits its practical application. In this work, Mn2 O3 with 1D nanowire geometry is synthesized in neutral aqueous solutions by a facile and effective hydrothermal strategy for the first time, and then Mn2 O3 nanoparticle and nitrogen-doped reduced graphene oxide (N-rGO) are composited with Mn2 O3 nanowires (Mn2 O3 -GNCs) to enhance its volume utilization and conductivity. When used as an anode material for LIBs, the Mn2 O3 -GNCs exhibit high reversible capacity (1350 mAh g-1 ), stable cycling stability, and good rate capability. Surprisingly, the Mn2 O3 -GNC electrodes can also show fast charging capability; even after 200 cycles (charge: 10 A g-1 ; discharge: 0.5 A g-1 ), its discharge capacity can also keep at ≈500 mAh g-1 . In addition, the Mn2 O3 -GNCs also have considerable full cell and supercapacitor performance. The excellent electrochemical performances can be ascribed to the N-rGO network structure and 1D nanowire structure, which can ensure fast ion and electron transportation.

A Method for Estimating Urban Flood-Carrying Capacity Using the VIS-W Underlying Surface Model: A Case Study from Wuhan, China

In 2016, 192 cities, including Wuhan, Nanjing, and Jiujiang, suffered from severe flooding, which raised social and government concerns in China. This paper proposes a method based on the underlying surface to estimate the urban flood-carrying capacity. First, water is extended into the underlying surface vegetation-impervious surface-soil (VIS) model to form the vegetation-impervious surface-soil and water (VIS-W) model. Second, the watershed is delimitated using a digital elevation model (DEM). Third, the natural water system’s storage capacity, including rivers, lakes, and puddles, is estimated. Using the rainfall–runoff hydrology model and the VIS-W model, the storing ability, the receiving ability, the discharge potential, and the emergency of pumping outward are assessed to derive the final flood-carrying capacity. Finally, the result is compared with data on the waterlogging points collected in July 2016 during a flood and waterlogging event in Wuhan. It is found that 84% of waterlogging points are located in the “weak” or “normal” areas, and 16% are located in the “strong” areas. Additionally, 99% of total waterlogging points are located upstream, based on the stream extracted by the DEM. This phenomenon indicates that Wuhan can mitigate flood disasters by fully utilizing the natural water system storage capacity to corporate the city’s drainage schedule.

Ab initio molecular dynamics study of SiO2 lithiation

Li-ion batteries (LIBs) are sought to meet the demand for high energy storage applications. Due to its high specific charge capacity and low discharge potential, SiO2 is a promising candidate material for LIBs anodes. To design high performance anodes and coating materials using SiO2, understanding the structural transformation and Li-ion kinetics in different structural forms of SiO2 is essential. Here, we performed ab initio molecular dynamics to study the lithiation mechanism for crystalline and amorphous SiO2 and the effect of surface termination to elucidate the lithiation process of conversion oxides and contribute to the development of future LIBs.

Redox Polymers as Electrode-Active Materials for Batteries

Organic cathode materials are promising candidates for a new generation of ‘green batteries’, since they have low toxicity and can be produced from renewable resources or from petroleum. This review shows that organic redox polymers can show excellent battery performance regarding cycling stability and rate capability, and attractive specific capacities are accessible. Radical polymers and redox polymers based on heteroaromatics demonstrate superior rate capabilities and cycling stabilities at fast C-rates as well as high discharge potentials of 3–4 V versus Li/Li+, while quinone- or imide-based polymers deliver high specific capacities of up to 260 mAh g−1 with stable cycling at moderate C-rates and lower discharge potentials. This review article highlights the underlying design principles showcasing selected examples of well-performing redox polymers.

Hierarchical Ni2P nanosheets anchored on three-dimensional graphene as self-supported anode materials towards long-life sodium-ion batteries

Transition metal phosphides have reached tremendous inspiration as electrode materials for sodium-ion batteries (SIBs) due to high specific capacity and low discharge potential. However, the pulverization of electrode structure during cycling is still a key factor that restricts the further development of SIBs. Herein, unique hierarchical Ni2P nanosheets/three-dimensional graphene (3DG) composite with stable structure is successfully prepared. The effects of pH on the morphology and properties of the as-prepared Ni2P are studied. When pH value is 4, the hierarchical Ni2P/3DG interdigitated networks remain higher specific capacity (313.5 mA h g−1 at 100 mA g−1 for 100 cycles) and better rate properties (155.4 mA h g−1 at 1 A g−1 after 1000 cycles). Moreover, full cells consisting of Ni2P/3DG anode and Na3V2(PO4)3 cathode are assembled and characterized. The enhanced sodium storage can be attributed to the unique structure and high conductivity of 3DG. The hierarchical structure can effectively buffer volume expansion, prevent structure pulverization and keep intimate contact between Ni2P and electrolyte. Besides, 3DG provides fast and continuous long-distance electron transportation. These results demonstrate the hierarchical Ni2P/3DG nanocomposite electrode can be a potential choice for sodium ion storage.

Sub-10 nm SnO2/Fe3O4/graphene nanosheets: Nanocatalysis to improve initial coulombic efficiency for lithium storage

SnO2 is considered as an ideal substitute for graphite anode in lithium ion batteries since it has a four-fold theoretical capacity and low discharge potential. However, the poor transformation from Sn/Li2O to SnO2 due to sluggish kinetic results in a low initial Coulombic efficiency (ICE) of only 52.4%. At the same time, the intrinsically low ionic/electronic conductivity and high volume swings during charge/discharge processes seriously limit its long-term stability and high-rate performance. Different from traditional strategies, nanotechnology and composite, this work prepares sub-10 nm SnO2/Fe3O4/graphene nanosheets with controllable Fe/Sn atomic ratios through a hydrothermal method to study the nanocatalytic effect of Fe on improving the ICE. The component, structure and lithium storage performance of the samples, with varied Sn/Fe ratios, are systematically investigated. The sample with Sn/Fe of 1.31 shows a high ICE of 70.9% (considering the negative effect of huge solid/electrolyte interface films, this value is quite high) and an outstanding reversible capacity of 1048 mA h g−1 after 800 cycles at the current density of 200 mA g−1. The valence states of Sn and Fe before and after cycling are analyzed by X-ray photoelectron spectroscopy. Our findings offer new evidence for electrochemical catalytic conversion mechanism for lithium storage and highlight opportunities to boost the energy storage capability of the fourth main group compounds.

Thermodynamic Perspective on Co-Intercalation Behavior of Li/Mg Dual Cations in Intercalation Cathode Materials

Post Li-ion batteries using multivalent ions, such as Mg2+, Ca2+, Zn2+, have attracted much attention in recent years, but developing appropriate intercalation cathode materials for these multivalent cations remains a difficult task due to the sluggish solid-phase diffusion behavior, which is usually caused by the strong coulomb interaction between multivalent cations with the ionic cathode hosts. As an attempt to solve this problem, we proposed a new battery technology, which is referred to as Li-Mg dual-cation batteries.[1-2] The Li-Mg dual-cation batteries possess a so-called “rocking-chair”-type structure, where Li ion and Mg ion are involved in each half-cell reaction simultaneously. When exploring the characteristics of these batteries, we found an interesting phenomenon that Mg intercalation usually shows higher discharge potential in Li-Mg dual-cation electrolyte than in Mg single-cation electrolyte. The increase of discharge potential (i.e. decrease of the overpotential for Mg intercalation) strongly suggests that the co-existing Li ion is helpful to promote the Mg intercalation with cathode hosts. To elucidate what causes this phenomenon, we performed the first-principles calculations[3-4] with the Nudged Elastic Band (NEB) method[5] to estimate the activation energy of Mg cation migration in cathode hosts that are discharged in Li or Mg single-cation and Li-Mg dual-cation electrolytes and finally revealed a facilitating mechanism for the solid-phase diffusion of Mg cation.[6] In this presentation, we give a comprehensive explanation on the co-intercalation behavior of Li ion and Mg ion in Li-Mg dual-cation batteries, especially from a thermodynamic perspective. This work advances the fundamental understanding of ionic conduction phenomena of multivalent cations, which is indispensable for developing future energy storage devices. [1] T. Ichitsubo, S. Okamoto, T. Kawaguchi, Y, Kumagai, F. Oba, S. Yagi, N. Goto, T, Doi, E. Matsubara, J. Mater. Chem. A 3, 10188(2015). [2] H. Li, T. Ichitsubo, S. Yagi, E. Matsubara, J. Mater. Chem. A 5, 3534(2017). [3] P. E. Blöchl, Phys. Rev. B 50, 17953(1994). [4] J. P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 77, 3865(1996). [5] G. Henkelman, B. P. Uberuaga, H. Jónsson, J. Chem. Phys. 113, 9901(2000). [6] H. Li, N. L. Okamoto, T. Hatakeyama, Y, Kumagai, F. Oba, T. Ichitsubo, Adv. Energy Mater. 8, 1801475(2018).

π‐Conjugation Enables Ultra‐High Rate Capabilities and Cycling Stabilities in Phenothiazine Copolymers as Cathode‐Active Battery Materials

AbstractIn recent years, organic battery cathode materials have emerged as an attractive alternative to metal oxide–based cathodes. Organic redox polymers that can be reversibly oxidized are particularly promising. A drawback, however, often is their limited cycling stability and rate performance in a high voltage range of more than 3.4 V versus Li/Li+. Herein, a conjugated copolymer design with phenothiazine as a redox‐active group and a bithiophene co‐monomer is presented, enabling ultra‐high rate capability and cycling stability. After 30 000 cycles at a 100C rate, >97% of the initial capacity is retained. The composite electrodes feature defined discharge potentials at 3.6 V versus Li/Li+ due to the presence of separated phenothiazine redox centers. The semiconducting nature of the polymer allows for fast charge transport in the composite electrode at a high mass loading of 60 wt%. A comparison with three structurally related polymers demonstrates that changing the size, amount, or nature of the side groups leads to a reduced cell performance. This conjugated copolymer design can be used in the development of advanced redox polymers for batteries.

Exploring the Effect of Strong Complexing Agents As Electrolyte Additives on Anode Performance in Mg-Air Primary Batteries

Mg-air primary batteries have drawn increasing attention recently due to their low cost, safety, and high theoretical specific power density. However, high self-corrosion rate and anode fouling during discharge (mainly due to the formation of Mg(OH)2/MgO) lead to particularly lower delivered voltage and utilization efficiency. Modification of the battery electrolyte chemistry plays a crucial role in tackling these shortcomings and improving battery performance. Remarkable enhancements to the Mg anode’s performance by addition of group of organic complexing agents in the Mg-air battery electrolyte has recently been reported [1]. In this study, the effect of two strong organic complexing agents (i.e. disodium 4,5-dihydroxy-1,3-benzenedisulfonate(Tiron) and Nitrilotriacetic acid(NTA)) as additives to the Mg-air battery electrolyte was investigated. Commercially pure magnesium with relatively high Fe impurity level (i.e. 220ppm) has been chosen as the anode material in order to have a better understanding of the interaction of the complexing agents with pure Mg and the common Fe impurity. Half-cell measurements were conducted to evaluate the discharge performance of the anode in the presence of the complexing agents. The electrochemical and corrosion behavior were studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve. The morphology of the anode surface after discharge was investigated by scanning electron microscope (SEM). The results indicate that strong complexing agents can remarkably improve the discharge potential by activating the Mg anode surface and mitigating the high cathodic activity stemmed from Fe impurities. A possible downside of adding strong complexing agents is the tendency to accelerate the corrosion rate of the Mg anode. However, tuning the complexing agent concentration in the electrolyte can significantly improve the utilization efficiency at the expense of a slight decrease in the battery delivered voltage. [1] D. Höche, S.V. Lamaka, B. Vaghefinazari, T. Braun, R.P. Petrauskas, M. Fichtner, M.L. Zheludkevich, Performance boost for primary magnesium cells using iron complexing agents as electrolyte additives, Scientific Reports, 8 (2018).

Bifunctional catalysts of CoNi nanoparticle-embedded nitrogen-doped carbon nanotubes for rechargeable Zn–air batteries

It is essentially important to improve the performance of Zn–air batteries by studying bifunctional catalysts for oxygen evolution reactions (OER) and oxygen reduction reactions (ORR) with low-cost, high-efficiency and high-stability properties. Here, CoNi nanoparticles embedded in the bamboo-like N-doped carbon tubes (CoxNiy@NC) were synthesized, where the optimized catalyst of Co2Ni1@NC exhibits superior bifunctional electrocatalytic activity, showing a low overpotential of 300 mV under the current density of 10 mA cm−2 for OER and a large limiting current density of 3.76 mA cm−2 under 0.40 V for ORR in an alkaline solution. In addition, the Co2Ni1@NC also shows excellent electrocatalytic activity in acidic and neutral solutions. Importantly, primary Zn–air batteries based on Co2Ni1@NC affords an excellent specific capacity of 834 mAh/gZn with a discharge potential of 1.25 V at 5 mA cm−2. A rechargeable Zn–air battery assembled with Co2Ni1@NC shows excellent cycling stability, where the first discharge and charge voltages reach 1.21 and 2.00 V under 1 mA cm−2, respectively. This finding provides a simple synthesis approach, which allows one to construct bifunctional catalysts based on metal@NC for future energy conversion and storage devices.

Li‐Breathing Air Batteries Catalyzed by MnNiFe/Laser‐Induced Graphene Catalysts

AbstractThe development of efficient bifunctional catalysts for oxygen reduction and evolution reactions (ORR and OER) is important in the development of rechargeable metal–O2 (air) batteries. Here, a straightforward synthesis of highly efficient bifunctional OER/ORR catalysts MnNiFe/LIG (M111/LIG and M311/LIG where the numbers reflect the relative molar ratio of Mn, Ni, and Fe species) is presented through a facile re‐lasing method. The MnNiFe/LIG shows promising performance in Li–O2 and Li–air batteries without the presence of a redox mediator. The Li–O2 battery with M311/LIG catalysts is reliably discharged and charged for 150 cycles while the discharge potential slightly increases by 0.24 V. The Li‐breathing air battery with M311/LIG catalyst is stable during 350 cycles while the Li‐breathing air battery with M111/LIG catalyst is stable for ≈300 cycles. The function of the M111/LIG and M311/LIG catalysts in the Li–O2 batteries and the influence of the catalysts on the discharge and decomposition products are also investigated. This study promotes further development in carbon–metal oxide composite cathode catalysts for metal–air batteries and underscores the efficacy of laser‐induced graphene for electrode fabrications.

Activated Carbon-Decorated Spherical Silicon Nanocrystal Composites Synchronously-Derived from Rice Husks for Anodic Source of Lithium-Ion Battery.

The nanocomposites of activated-carbon-decorated silicon nanocrystals (AC<nc-Si>AC) were synchronously derived in a single step from biomass rice husks, through the simple route of the calcination method together with the magnesiothermic reduction process. The final product, AC<nc-Si>AC, exhibited an aggregated structure of activated-carbon-encapsulated nanocrystalline silicon spheres, and reveals a high specific surface area (498.5 m2/g). Owing to the mutualization of advantages from both silicon nanocrystals (i.e., low discharge potential and high specific capacity) and activated carbon (i.e., high porosity and good electrical conductivity), the AC<nc-Si>AC nanocomposites are able to play a substantial role as an anodic source material for the lithium-ion battery (LIB). Namely, a high coulombic efficiency (97.5%), a high discharge capacity (716 mAh/g), and a high reversible specific capacity (429 mAh/g after 100 cycles) were accomplished when using AC<nc-Si>AC as an LIB anode. The results advocate that the simultaneous synthesis of biomass-derived AC<nc-Si>AC is beneficial for green energy-storage device applications.

Ultrahigh-energy-density fluorinated calcinated macadamia nut shell cathodes for lithium/fluorinated carbon batteries

Lithium/fluorinated carbon (Li/CFx) batteries are widely applied in various industries because of the high energy densities of CFx compounds. However, incompatibility between high degrees of fluorination and the electrochemical activity of C–F bonds limits further improvements of the energy densities of CFx cathodes. Here, calcined macadamia nut shell is fluorinated with F2 gas below 300 °C. The products deliver specific capacities exceeding 900 mAh g−1, associated with discharge potentials exceeding 3.0 V (vs. Li/Li+). The product fluorinated at 280 °C achieves an unprecedented maximum energy density of 2585 W h kg−1, surpassing the present maximum theoretical energy density of commercial (CF)n (2185 W h kg−1). Its electrochemical properties presumably originate from the complete destruction of the periodic crystalline lattice in the basal plane, which substantially alters the electron distribution within the C–F bonds. This study presents a new approach for designing exceptionally high-energy-density CFx compounds for lithium primary batteries using an accessible and inexpensive raw material.

Li–Ti Cation Mixing Enhanced Structural and Performance Stability of Li‐Rich Layered Oxide

AbstractLi‐rich layered metal oxides are one type of the most promising cathode materials in lithium‐ion batteries but suffer from severe voltage decay during cycling because of the continuous transition metal (TM) migration into the Li layers. A Li‐rich layered metal oxide Li1.2Ti0.26Ni0.18Co0.18Mn0.18O2 (LTR) is hereby designed, in which some of the Ti4+ cations are intrinsically present in the Li layers. The native Li–Ti cation mixing structure enhances the tolerance for structural distortion and inhibits the migration of the TM ions in the TMO2 slabs during (de)lithiation. Consequently, LTR exhibits a remarkable cycling stability of 97% capacity retention after 182 cycles, and the average discharge potential drops only 90 mV in 100 cycles. In‐depth studies by electron energy loss spectroscopy and aberration‐corrected scanning transmission electron microscopy demonstrate the Li–Ti mixing structure. The charge compensation mechanism is uncovered with X‐ray absorption spectroscopy and explained with the density function theory calculations. These results show the superiority of introducing transition metal ions into the Li layers in reinforcing the structural stability of the Li‐rich layered metal oxides. These findings shed light on a possible path to the development of Li‐rich materials with better potential retention and a longer lifespan.