The structural stability and electrochemical performance of boron substituted fluorinated graphite as a Li ion batteries cathode material are studied by first principles calculations. The results show that boron substituted fluorinated graphite BC3F4 possesses excellent structural stability, good electrical and ionic conductivities. Unexpectedly, the average Li intercalation voltage of LiBC3F4 is up to 4.44 V, which is much larger than that of LiBCF2. The average voltage of LiBC3F4 is even larger than that of common commercial transition metal oxides cathodes, indicating that LiBC3F4 is a breakthrough of transition metal-free high voltage cathode materials. By comparing the Fermi level, we found the Fermi level of LiBC3F4 is 1.38 eV lower than that of LiBCF2, leading to the decrease of the electron filling energy for the Li intercalation and forming much higher voltage. Moreover, LiBC3F4 shows small volume expansion and high energy density. LiBC3F4 is a promising high voltage cathode material for Li ion batteries. Finally, by calculating the evolution of Li intercalation voltage and Fermi level during the discharging process, a linear correlation between the Fermi level and Li intercalation voltage has been found.
Layered LiMO2 (M = Ni, Co, Mn, and Al mixture) cathode materials used for Li-ion batteries are reputed to be highly reactive through their surface, where the chemistry changes rapidly when exposed to ambient air. However, conventional electron/spectroscopy-based techniques or thermogravimetric analysis fails to capture the underlying atom-scale chemistry of vulnerable Li species. To study the evolution of the surface composition at the atomic scale, here we use atom probe tomography and probed the surface species formed during exposure of a LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode material to air.…
Finding proper electrocatalysts capable of efficient catalyzing both ORR and OER is of great importance for metal-air batteries. With increasing inclination towards structural and flexible devices, developing a high-performance self-standing air-cathode is highly demanded and challenging, as most of oxygen catalysts are powder and need to be further processed. Here, we construct highly bifunctional air catalyst from macroscopic CNT fibers (CNTf) through direct CVD spinning followed by hydrothermal method. The electrocatalytic properties of the samples were tuned by altering nitrogen-doping and…
This article reviews the development of cathode materials for secondary lithium ion batteries since its inception with the introduction of lithium cobalt oxide in early 1980s. The time has passed and numerous cathode materials are designed and developed to realize not only the enhanced capacity but also the power density simultaneously. However, there are numerous challenges such as the cyclic stability of cathode materials, their structural and thermal stability, higher operating voltage together with high ionic and electronic conductivity for efficient ion and charge transport during chargin…
Rechargeable Zn batteries with aqueous electrolytes have been considered as promising alternative energy storage technology, with various advantages such as low cost, high volumetric capacity, environmentally friendly, and high safety. However, a lack of reliable cathode materials has largely pledged their applications. Herein, we developed a machine learning (ML) based approach to predict cathodes with high capacity (>150 mAh/g) and high voltage (>0.5V). We screened over ~130,000 inorganic materials from the Materials Project database and applied the crystal graph convolutional neural network…
Mg batteries utilizing a Mg metal anode with a high-voltage intercalation cathode define a potential pathway toward energy storage with high energy density. However, the realization of Mg batteries is plagued by the instability of existing electrolytes against the Mg-metal anode and high-voltage cathode materials. One viable solution to this problem is the identification of protective coating materials that could effectively separate the distinct chemistries of the metal-anode and the cathode materials from the electrolyte. Using first-principles calculations we map the electrochemical stabili…
We discuss how x-ray Compton scattering spectra can be used for investigating the evolution of electronic states in cathode materials of Li batteries under the lithiation/delithiation process. In particular, our analysis of the Compton spectra taken from polycrystalline LixCoO2 samples shows that the spectra are dominated by the contribution of the O-2p redox orbital. We identify a distinct signature of d-orbital delocalization, which is tied directly to the conductivity of the material, providing a descriptor based on Compton spectra for monitoring the lithiation range with improved conductiv…
Searching for efficient and high-performance cathode materials for rechargeable magnesium ion batteries (RMBs) is urgent for exploring sustainable energy technologies. However, the majority of cathode materials for RMBs usually suffer from low rate capacity and inferior cycle performance caused by structure collapse. Herein, ternary CuCo$_2$S$_4$/Cu$_7$S$_4$ composites with nano-sized are first synthesized by a facile solvothermal method in this work and the magnesium ion storage behavior is discussed when applied in the cathode for RMBs. Electrochemical results demonstrate that the nanosphere…
A new nanofibrous material, consisting of a conductive carbon core and an external layer made of vanadium oxide, has been studied as a cathode for aluminium-ion batteries. The material enables a mixed-ion intercalation mechanism, resulting in the alternating insertion of $\text{Al}^{3+}$ and $\text{AlCl}_4^-$ in the $\text{V}_2\text{O}_5$ and carbon layers, respectively. This is a highly desirable feature for cathode materials which may increase the energy density of future batteries by optimising the utilisation of the electrolyte.
We report the synthesis, physical properties and electrochemical performance of Zn substituted Na$_{0.44}$Mn$_{1-x}$Zn$_x$O$_2$ ($x=$ 0 -- 0.02) nanostructures as cathode in Na-ion batteries for energy storage applications. These samples stabilize in the orthorhombic structure and the morphology is found to be slab like with 100 -- 200~nm width and few micrometer of length. The resistivity measurements show highly insulating nature for all the samples, where the activation energy decreases with increasing Zn concentration indicating more defect levels in the band gap. The cyclic voltammogram (…
Sc is the lightest transition metal that could help to achieve the goal of high theoretical capacity. Hence, we here explored the performance of ScS_{2} monolayer as a cathode material for alkali-ion batteries (Li, Na, K) and other multi-valent metal-ion batteries (Mg, Al). Previous studies on ScS_{2} have focused only on the fundamental electronic and magnetic properties of the ScS_{2} monolayer, but not on its possible applications. Our first-principles calculations show that 2D ScS_{2} is able to deliver a large theoretical capacity of 491.36 mAh g^{-1} for alkali-ions and 324.29 mAh g^{-1}…
Na-ion batteries (NIBs), which are recognized as a next-generation alternative technology for energy storage, still suffer from commercialization constraints due to the lack of low-cost, high-performance cathode materials. Since our first discovery of Cu$^{3+}$/Cu$^{2+}$ electrochemistry in 2014, numerous Cu-substituted/doped materials have been designed for NIBs. However for almost ten years, the potential of Cu$^{3+}$/Cu$^{2+}$ electrochemistry has been grossly underappreciated and normally regarded as a semielectrochemically active redox. Here, we re-synthesized P2-Na$_{2/3}$[Cu$_{1/3}$Mn$_…
Interfaces are ubiquitous in Li-ion battery electrodes, occurring across compositional gradients, regions of multiphase intergrowths, and between electrodes and solid electrolyte interphases or protective coatings. However, the impact of these interfaces on Li energetics remains largely unknown. In this work, we calculated Li intercalation-site energetics across cathode interfaces and demonstrated the physics governing these energetics on both sides of the interface. We studied the olivine/olivine-structured LixFePO4/LixMPO4 (x=0 and 1, M=Co, Ti, Mn) and layered/layered-structured LiNiO2/TiO2 …
The polyanionic compound Na2MnSiO4 is regarded as one of the promising cathode materials for Na-ion batteries due to good specific capacity with its attractive prospect of utilization of two electrons in the redox processes. So, in this study, we have performed the thermodynamic and electronic structure analysis of Na2MnSiO4 using first principles density functional theory calculations. The intermediate ground state configurations for Na2MnSiO4of Na de-intercalation were found using the cluster expansion method and are used to obtain the 0 K voltage profile as a function of Na concentration. T…
Four different forms of carbon: activated carbon (AC) from human hair, AC from hemp fibers, a carbon fullerene extract consisting of C$_{60}$ and C$_{70}$ fullerene (CFEx) and Super-P carbon black were tested and compared as cathodes for non-aqueous aluminium-ion batteries (AIBs). These materials differ in their general structure, porosity and morphology. Fullerenes display a crystalline structure, whereas hemp fibers, Super-P and hair are amorphous in nature. Of all materials, AC obtained from hair recorded the highest specific capacity after 50 cycles at 103 mAh g$^{-1}$ with a Coulombic eff…
Following the successful utilization of LiFePO4 as a novel cathode material for rechargeable lithium batteries, interest and efforts have grown in the research of another olivine structured material LiMnPO4 due to its higher operating potential voltage and energy density. However, high rate performance for LiMnPO4-based cathode materials has been challenging due to its extremely low electrical and ionic conductivities. Here, we develop a synthesis of Fe-doped LiMnPO4 (LiMn0.75Fe0.25PO4) nanorods directly bonded on graphene sheets (reduced from graphene oxide) to render LiMn0.75Fe0.25PO4 nanoro…
It is well known that the spatial distribution of the carbon-binder domain (CBD) offers a large potential to further optimize lithium-ion batteries. However, it is challenging to reconstruct the CBD from tomographic image data obtained by synchrotron tomography. In the present paper, we consider several approaches to segment 3D image data of two different cathodes into three phases, namely active material, CBD and pores. More precisely, we focus on global thresholding, a local closing approach based on EDX data, a k-means clustering method, and a procedure based on a neural network that has be…
In this work, the structural stability and the electronic properties of LiNiBO 3 and LiFe x Ni (1-x) BO 3 are studied using first principle calculations based on density functional theory. The calculated structural parameters are in good agreement with the available theoretical data. The most stable phases of the Fe substituted systems are predicted from the formation energy hull generated using the cluster expansion method. The 66% of Fe substitution at the Ni site gives the most stable structure among all the Fe substituted systems. The bonding mechanisms of the considered systems are discus…
We present theoretical analysis on why and how rechargeable metal-air type batteries can be made significantly safer and more practical by utilizing CO2/oxalate conversions instead of O2/peroxide or O2/hydroxide ones, in the positive electrode. Metal-air batteries, such as the Li-air one, may have very large energy densities, comparable to that of gasoline, theoretically allowing for long range all-electric vehicles. There are, however, still significant challenges, especially related to the safety of their underlying chemistries, the robustness of their recharging and the need of supplying hi…
Composite materials achieved by including transition-metal oxides with different structures and morphologies in sulfur are suggested as scalable cathodes for high-energy lithium-sulfur (Li-S) batteries. The composites contain 80 wt.% sulfur and 20 wt.% of either MnO2 or TiO2, leading to a sulfur content in the electrode of 64 wt.% and revealing a reversible, fast, and lowly polarized conversion process in the cell with limited interphase resistance. The S-TiO2 composite exhibits an excellent rate capability between C/10 and 2C, and a cycle life extended over 400 cycles at 2C, owing to the effe…
Li-ion rechargeable batteries have enabled the wireless revolution transforming global communication. Future challenges, however, demands distributed energy supply at a level that is not feasible with the current energy-storage technology. New materials, capable of providing higher energy density are needed. Here we report a new class of lithium-ion batteries based on a graphene ink anode and a lithium iron phosphate cathode. By carefully balancing the cell composition and suppressing the initial irreversible capacity of the anode, we demonstrate an optimal battery performance in terms of spec…
Conversion cathode materials are gaining interest for secondary batteries due to their high theoretical energy and power density. However, practical application as a secondary battery material is currently limited by practical issues such as poor cyclability. To better understand these materials, we have developed a pseudo-two-dimensional model for conversion cathodes. We apply this model to FeS2 - a material that undergoes intercalation followed by conversion during discharge. The model is derived from the half-cell Doyle-Fuller-Newman model with additional loss terms added to reflect the con…
Many successful battery electrodes are based on 2D-layered materials. We have studied aluminium-ion batteries using molybdenum dichalcogenides: \ce{MoS2}, \ce{MoSe2} and MoSSe as active cathode materials. The batteries showed clear discharge voltage plateaus in the ranges 1.6 - 1.4 V for \ce{MoS2} and \ce{MoSe2}, and 0.6 - 0.5 V for MoSSe. \ce{MoS2} and \ce{MoSe2} have similar crystal structures, interestingly we found that \ce{MoSe2} performed better than \ce{MoS2}. MoSSe exhibited a higher specific capacity over \ce{MoS2} and \ce{MoSe2}, but the energy density was lower than \ce{MoSe2} at a …
It is well-known that the microstructure of electrodes in lithium-ion batteries strongly affects their performance. Vice versa, the microstructure can exhibit strong changes during the usage of the battery due to aging effects. For a better understanding of these effects, mathematical analysis and modeling has turned out to be of great help. In particular, stochastic 3D microstructure models have proven to be a powerful and very flexible tool to generate various kinds of particle-based structures. Recently, such models have been proposed for the microstructure of anodes in lithium-ion energy a…
Li-O$_2$ batteries (LOB) performance degradation ultimately occurs through the accumulation of discharge products and irreversible clogging of the porous electrode during the cycling. Electrode binder degradation in the presence of reduced oxygen species can result in additional coating of the conductive surface, exacerbating capacity fading. Herein, we establish a facile method to fabricate free-standing, binder-free electrodes for LOBs in which multi-wall carbon nanotubes (MWCNT) form cross-linked networks exhibiting high porosity, conductivity, and flexibility. These electrodes demonstrate …
Crystal structures play a vital role in determining materials properties. In Li-ion cathodes, the crystal structure defines the dimensionality and connectivity of interstitial sites, thus determining Li-ion diffusion kinetics. While a perfect crystal has infinite structural coherence, a class of recently discovered high-capacity cathodes, Li-excess cation-disordered rocksalts, falls on the other end of the spectrum: Their cation sublattices are assumed to be randomly populated by Li and transition metal ions with zero configurational coherence based on conventional X-ray diffraction, such that…
Vacancy-induced Modification of Electronic Band Structure of LiBO$_{2}$ Material as Cathode Surface Coating of Lithium-ion Batteries
University of Missouri（密苏里大学）；University of Missouri Research Reactor (MURR)（密苏里大学研究反应堆中心）；Escuela de Física, Universidad Pedagógica y Tecnológica de Colombia（哥伦比亚教育技术大学物理学院）
Potassium-ion ($\rm K$-ion) rechargeable batteries; considered to be lucrative low-cost battery options for large-scale and capacious energy storage systems, have been garnering tremendous attention in recent years. However, due to the scarcity of cathode materials that can condone the reversible re-insertion of the large $\rm K$-ions at feasible capacities, the viability of $\rm K$-ion batteries has been greatly undercut. In this paper, we explore a potential cathode material in the $\rm K_2O$-$\rm Fe_2O_3$-$\rm MnO_2$ ternary phase system, that not only demonstrates reversible $\rm K$-ion re…
Using a new class of (BH4)- substituted argyrodite Li6PS5Z0.83(BH4)0.17, (Z = Cl, I) solid electrolyte, Li-metal solid-state batteries operating at room temperature have been developed. The cells were made by combining the modified argyrodite with an In-Li anode and two types of cathode: an oxide, LixMO2 (M = 1/3Ni, 1/3Mn, 1/3Co; so called NMC) and a titanium disulfide, TiS2. The performance of the cells was evaluated through galvanostatic cycling and Alternating Current AC electrochemical impedance measurements. Reversible capacities were observed for both cathodes for at least tens of cycles…
Understanding the reactions in M-O2 cells (M = Li or Na) is of great importance for further advancement of this promising technology. Computational modelling can be helpful along this way, but an adequate approach is needed to model such complex systems. We propose a new scheme for modelling processes in M-O2 cells, where reference energies are obtained from high-level theory, CCSD(T), while the interactions of reaction intermediates with catalyst surfaces are extracted from computationally less expensive DFT. The approach is demonstrated for the case of graphene-based surfaces as model cataly…
Ultrahigh energy density batteries based on alpha-Li_xBN2 (1<x<3) positive electrode materials are predicted using density functional theory calculations. The utilization of the reversible LiBN2 + 2 Li+ + 2 e- -> Li3BN2 electrochemical cell reaction leads to a voltage of 3.62 V (vs Li/Li$^{+}$), theoretical energy densities of 3251 Wh/kg and 5927 Wh/L, with capacities of 899 mAh/g and 1638 mAh/cm3, while the cell volume of alpha-Li3BN2 changes only 2.8% per two-electron transfer. These values are far superior to the best existing or theoretically designed intercalation or conversion-based posi…
Multivalent batteries are an energy storage technology with the potential to surpass lithium-ion batteries, however their performance has been limited by the low voltages and poor solid-state ionic mobility of available cathodes. A computational screening approach to identify high-performance multivalent intercalation cathodes among materials that do not contain the working ion of interest has been developed which greatly expands the search space that can be considered for materials discovery. This approach has been applied to magnesium cathodes as a proof of concept and four resulting candida…
The world is at the cusp of a new era where pivotal importance is being attached to the development of sustainable and high-performance energy storage systems. Potassium-ion batteries are deemed not only as cheap battery candidates, but also as the penultimate high-voltage energy storage systems within the monovalent-cation chemistries. However, their performance and sustainability are undermined by the lack of suitable electrolytes for high-voltage operation particularly due to the limited availability of cathode materials. Here, the potential of ionic liquids based on potassium bis(trifluoro…
Lithium-metal batteries employing concentrated glyme-based electrolytes and different cathode chemistries are herein evaluated in view of a safe use of the highly energetic alkali-metal anode. Indeed, diethylene-glycol dimethyl-ether (DEGDME) and triethylene-glycol dimethyl-ether (TREGDME) dissolving lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium nitrate (LiNO3) in concentration approaching the solvents saturation limit are used in lithium batteries employing either a conversion sulfur-tin composite (S:Sn 80:20 w/w) or a Li+ (de-)insertion LiFePO4 cathode. Cyclic voltammetry (…
Covalent functionalization is a way to tune the electrochemical properties of hexagonal boron nitride (h-BN) monolayers. The wide band gap insulator h-BN may become metallic conductor upon functionalization with strong oxidants, such as fluorosulfonyl radicals ($\cdot$OSO$_2$F), as known since 1978 [N. Bartlett et al., J. Chem. Soc. Chem. Comm. {\bf 5}, 200 (1978)], with electrical conductivity of 1.5 S/cm [C. Shen et al., J. Solid State Chem. {\bf 147}, 74 (1999)] that greatly surpasses commercial cathode material Li$_{x}$CoO$_{2}$ while retaining excellent ionic conductivity. Functionalized …
We report the electrochemical performance of nanostructures of Na$_{0.66}$V$_4$O$_{10}$ as cathode material for rechargeable batteries. The Rietveld refinement of room temperature x-ray diffraction pattern shows the monoclinic phase with C2/m space group. The cyclic voltammetry curves of prepared half-cells exhibit redox peaks at ~3.1 and 2.6~V, which are due to two-phase transition reaction between V$^{5+/4+}$ and can be assigned to the single step deintercalation/intercalation of Na-ion. We observe a good cycling stability with specific discharge capacity (measured vs. Na$^+$/Na) between 80 …
Improved Electrochemical Performance and Diffusion kinetics by Boron-doping in Na$_{0.66}$Mn$_{0.8}$Fe$_{0.2}$O$_{2}$ Layered Cathodes for Sodium-Ion Batteries
Indian Institute of Technology Delhi（印度德里理工学院）；Hindu College, University of Delhi（德里大学印度教学院）；Indian Institute of Technology Delhi-Abu Dhabi（印度德里理工学院阿布扎比分校）
We prepared Na$_x$TO$_2$ (T = Mn, Co) nanostructures to use as cathode material in Na-ion batteries. The Rietveld refinement of x-ray diffraction data confirms the hexagonal symmetry. Scanning and transmission electron microscopy measurements show hexagonal and rod-shape morphology for T = Co and Mn, respectively. The magnetic measurements indicate the presence of variable oxidation states of Mn/Co ions, but no long range ordering till 5~K. We find that the Na$_{0.6}$MnO$_2$ is highly insulating whereas Na$_{0.7}$CoO$_2$ is semiconducting in nature. The conduction in Na$_{0.7}$CoO$_2$ takes pl…
Mg batteries with oxide cathodes have the potential to significantly surpass existing Li-ion technologies in terms of sustainability, abundance, and energy density. However, Mg intercalation at the cathode is often severely hampered by the sluggish kinetics of Mg$^{2+}$ migration within oxides. Here we report a combined theoretical and experimental study addressing routes to identify cathode materials with an improved Mg-ion mobility. Using periodic density functional theory calculations, Mg$^{2+}$ migration in oxide spinels has been studied, revealing key features that influence the activatio…
