High-energy Cathode Materials Research Articles

Chemical Desodiation, Na/Mg Ion-Exchange and Mg Rechargeable Battery Cathode Properties in NaMn1/2Ni1/2O2

1. Introduction In recent years, Mg rechargeable batteries have been studied instead of Li ion batteries to advance their energy densities and to reduce their costs. The layered rock salt structure has excellent battery characteristics in Na and Li ion batteries. Therefore, the layered rock-salt materials are also expected as high energy cathode materials in Mg rechargeable batteries [1]. However, since a (Li or Na)/Mg ion-exchange method has not yet been established, the present study examined to exchange the Na+/Mg2+ based on the soft chemical approach and to desodiate from NaMn1/2Ni1/2O2. We performed the crystal structure analysis and electrochemical measurements for the ion-exchanged and the desodiated NaMn1/2Ni1/2O2 to reveal whether these procedures were available method to synthesis the Mg rechargeable battery cathode materials. 2. Experimental NaMn1/2Ni1/2O2 was synthesized as the precursor for ion-exchange or desodiation via the coprecipitation method [2]. A molten salt or a reflux methods using organic solution were examined as the Na/Mg ion-exchange method. The phases and metal compositions of the synthesized samples were identified by XRD and ICP-AES, respectively. The valence states of the transition metals were evaluated by XAFS (BL14B2, SPring-8). The crystal structure analysis using the Rietveld method was performed for synchrotron XRD patterns (BL19B2, SPring-8). For electrochemical desodiation, the electrode consisted of NaMn1/2Ni1/2O2 : conductive carbon (Super C65) : binder (PTFE) = 5 : 5 : 1 and the metal Li as the negative electrode were assembled to the electrochemical cell, where the 1.0 mol/L LiPF6/EC:DMC (1:2 vol ratio) electrolyte was used. The cell was charged to 4.8 V at room temperature and then disassembled to extract the desodiated cathode in Ar atmosphere. The chemical desodiation was performed by using NO2BF4 oxidizer in the same manner as in the previous report [1]. The Mg battery cathode properties of the synthesized materials were measured using a three-electrode cell (Toyo System), with 1.0 mol/L Mg(TFSA)2/Triglyme as the electrolyte and AZ31 as anode and a Ag wire as reference electrode at 90 °C. 3. Results and Discussion The XRD showed that the precursor was assigned as a hexagonal system (R-3m). It was clarified that an unknown phase was formed after the ion exchange using the molten salt regardless the washing methods. In the ion exchange by reflux, when Mg(NO3)2・6H2O or MgCl2・6H2O was used as the Mg source, the product was attributed as a cubic system (Fm-3m). When MgBr2 was used as the Mg source, the (003) plane shifted to a lower angle. In chemical desodiation, XRD pattern of chemically desodiated Na1-xMn1/2Ni1/2O2 was similar to previously desodiated one by about 1.0 pfu [2]. The metal composition of the precursor was confirmed to be NaMn1/2Ni1/2O2 by ICP-AES. In the ion exchange due to reflux, when Mg(NO3)2・6H2O was used as the Mg source, Na and Mg were removed by washing, and in the case of using MgCl2・6H2O, it was insoluble in various acids. The valences of Mn and Ni decreased from XANES, suggesting that some Na ions were exchanged for Mg ions. In the charge/discharge test, since the theoretical capacity in electrochemical desodiation was achieved, the most of Na must be desodiated. In the discharge test of the Mg rechargeable battery, the initial discharge capacity was 100 mAh/g was obtained, it decreased to about 20 mAh/g after the 2nd cycle. The initial discharge capacity was 250 mAh/g as a result. In chemical desodiation, it was possible to obtain 210 mAh/g, and then to maintain the discharge capacity of 140 mAh/g for 5 cycles (Fig. 1). The capacity of chemically desodiated material was clearly improved compared with the electrochemically desodiated one. 4. Conclusion When MgI2 was used as the reducing agent, MgBr2 was used as the Mg source, and ethanol was used as the solvent, it was clarified that some Na/Mg ion-exchange may have occurred. In the electrochemically desodiated, and the initial high discharge capacity exhibited 250 mAh/g at room temperature. In the chemical desodiation, about 0.8 pfu desodiation and the initial discharge capacity of 209 mAh/g were obtained. It was revealed that the discharge capacity of about 140 mAh/g could be maintained for 5 cycles. Therefore, it is considered that the layered NaMn1/2Ni1/2O2 can be utilized as a cathode material for Mg rechargeable batteries by desodiation or ion-exchange. Acknowledgement This work was supported by JST ALCA-SPRING Grant Number JPMJAC1301, References 1) N. Ishida, S. Ando, N. Kitamura, Y. Idemoto, Solid State Ionics, 343, 115080 (2019).2) S. Komaba, N. Yabuuchi, T. Nakayama, A. Ogata, T. Ishikawa, I. Nakai, Inorg. Chem., 51, 6211-6220 (2012) Figure 1

Minerals As Electrode Materials for Ca-Based Rechargeable Batteries: Evaluation of the Pyroxene, Garnet, Melilite and Double Carbonate Groups

Rechargeable lithium-ion batteries dominate the consumer electronics and electric vehicle markets. However, concerns on Li availability have prompted the development of alternative high energy density electrochemical energy storage systems. Rechargeable batteries based on a Ca metal anode can exhibit advantages in terms of energy density, safety and cost. The development of rechargeable Ca metal batteries requires the identification of suitable high specific energy cathode materials. This work focuses on Ca-bearing minerals because they represent stable and abundant compounds. Suitable minerals should contain a transition metal able of being reversibly reduced and oxidized, which points to several major classes of silicates and carbonates. A recent work [1] discusses their electrode characteristics based on crystal chemistry analysis and density functional theory (DFT) calculations. The results indicate that upon Ca deintercalation, compounds such as pyroxene, garnet and double carbonate minerals could display high theoretical energy densities (ranging from 780 to 1500 Wh/kg) with moderate structural modifications. As a downside, DFT calculations indicate a hampered Ca mobility in their crystal structures with energy barriers for Ca migration exceeding 2 eV. More recent investigations found a lower energy barrier of 1 eV in the group of melilite with formula Ca2MSi2O7, where Ca ions are in a square antiprism coordination polyhedron and M is a transition metal ion in tetrahedral coordination.Acknowledgements: Authors are grateful for financial support from European Union H2020-FETOPEN funded project CARBAT-766617.[1] Torres, Luque, Tortajada, Arroyo-de Dompablo, Scientific Reports 9, 9644 (2019).

(Invited) High Throughput Atomic Layer Deposition Manufacturing Processes for Improved Batteries

Commercial adoption of EVs requires that we overcome consumer angst around battery range by enabling fast charge and increasing specific capacity, while also significantly decreasing cost ($/kWh). Achieving these objectives requires higher voltage and higher charge rate operation of high capacity cathodes and anodes and process intensification to minimize processing costs. The major challenge of high-capacity cathode materials paired with low-cost graphite anodes is their propensity for transition metal dissolution and crossover, and gas generation, which stems from electrochemical decomposition of the electrolyte solvent at electrode-electrolyte interfaces. This is exacerbated by increased voltage operation which not only requires voltage tolerant electrode materials and high voltage electrolytes but also requires advanced separators that minimize leakage current and maintain safe utilization under the more reactive conditions of high voltage (>4.5V vs Li+/Li). Equally destructive, fast charge operation adds rapid structural changes and cracking of both the cathode and anode materials due to rapid de-intercalation, transport, and intercalation of lithium ions from the cathode to the anode. Forge Nano has demonstrated that atomic layer deposition (ALD) is effective at maintaining the structural integrity of high energy cathode materials at charge rates up to 6C and up to 4.6V top of charge with greater than twice the lifetime under accelerated conditions. Advanced nanoengineered surface treatments on anodes, particularly ionically conductive coatings, also prevent lithium plating and mitigate anode degradation during fast charge. ALD is a platform technology that has been widely demonstrated as a laboratory method to modify interfaces to the benefit of a breadth of applications. While ALD is ubiquitous throughout the semiconductor industry, ALD is not yet widely accepted for modification of high surface area materials and few have demonstrated ALD on powder manufacturability. This talk highlights the impacts of ALD when applied to cathodes anodes and separators on battery performance, the various methods for scaling these ALD coatings to meet battery manufacturing requirements and the net pack-cost savings of ALD integration.

Heterostructured Nickel-Rich LiNi0.91Co0.05Mn0.04O2 cathode Materials via Exfoliation-Restacking of Anionic Clay

Nickel-rich layered lithium transition-metal oxides, LiNi1−xMxO2 (M = transition metal, x < 2), have been under intense investigation as high-energy cathode materials for rechargeable lithium batteries because of their high specific capacity and relatively low cost. However, the commercialization of nickel-rich oxides has been severely hindered by their intrinsic poor thermal stability at the fully charged state and insufficient cycle life, especially at elevated temperatures. Here, the surface of a nickel-rich layered cathode particles was modified with anionic clay via an exfoliation and restacking route. The nickel-rich layered cathode particles and anionic clay are well-matched with each other regarding electrostatic interactions, allowing the two inorganics to spontaneously self-assemble when mixed with each other in aqueous media. The electron energy loss spectroscopy profile demonstrated a very thin coating layer around 2.5 nm beyond the Ni boundary originating from the cathode particles. The resulting material displayed suppressed gas evolutions as well as thermal and electrochemical properties, which both theoretical and experimental results showed were due to homogenous passivation via a thin coating layer. The cylindrical-type 18650 cell was tested for longer cycles and at an elevated temperature (45 °C) in order to accelerate the side reactions between the active cathode materials and the electrolyte. The prepared cathode material had discharge capacities of 233 mAh/g at 0.2 C and 82.4 % capacity retention after 300 cycles, which showed much improved retention compared to non-surface modified particles (71.0 %). In addition, amount of transition metal dissolution that occurred after cycling, which is strongly related to degradation of cell performances when using Ni-rich cathode materials. Reducing of metal dissolution was successfully achieved by modifying the surface on the cathode material particles and dissolution of Ni ions was dramatically reduced by a factor of 8 compared to non-surface modified particles. Figure 1

A comprehensive understanding of the anionic redox chemistry in layered oxide cathodes for sodium-ion batteries

Sodium-ion batteries (SIBs) have demonstrated great application prospects in large-scale energy storage systems and low-speed electric vehicles due to the cost effectiveness and abundant resources. Layered transition-metal oxides are recognized as one of the most attractive sodium-ion storage cathode candidates by virtue of their high compositional diversity, environmental friendliness, ease of synthesis, and promising theoretical capacities. The practicability, however, is still limited by the fact that the energy densities of most Na-storage layered oxide cathodes solely using the conventional cationic redox are not comparable to those of the lithium-ion storage counterparts. Recently, the strategy of activating anionic redox (O2−/O n −) which is popular in Li-rich layered materials has been successfully applied in oxide cathodes of SIBs to promote the energy density to a new level. It is interesting to note that excess Na is not the prerequisite to induce anionic redox in sodium oxides, indicating a new mechanism underlying Na-ion materials. Herein, the latest advances on the anionic redox chemistry in layered oxide cathodes for SIBs, including the fundamental theories, triggering strategies, and applicable cathode materials, are comprehensively reviewed. Moreover, the challenges (mainly O2 release) facing anionic redox are discussed, and the possible remedies are outlined for future developments toward a highly reversible oxygen usage. We believe that this review can provide a valuable guidance for the exploration of high-energy layered oxide cathode materials of SIBs.

Nax(Cu–Fe–Mn)O2 system as cathode materials for Na-ion batteries

Sodium-ion containing layered metal oxides have shown excellent performances as a high-energy cathode material for sodium-ion batteries. However, the role of 3d metal cations as well as their interactions in this materials system have not been well understood, which also limits their performance improvement. In this study, we systematically investigated the electrochemical behaviors and the roles of metal cations of layered Na x (Cu–Fe–Mn)O 2 system with variable 3d transition metal elemental compositions. We observed three apparent phenomena. Firstly, a strong co-relationship between the pristine valence state of manganese (Mn) and the reversible capacity was observed, with the highest reversible capacity reaching 190 mA h g −1 for the composition (i.e., Na 0.75 (Cu 0.1 Fe 0.1 Mn 0.8 )O 2 ) with the lowest pristine valence state of Mn. Secondly, it was observed that the average potential of the Na x (Cu–Fe–Mn)O 2 system decreased with the increase of iron (Fe) composition. Thirdly, adding a proper amount of copper (Cu) was found to promote the rate performance and cyclability of the electrode material. To understand the underlying mechanism for such composition-dependent electrochemical behavior, we characterized the capacity of the electrode as a function of potential evolution and analyzed its relationship with the interactions between the metal cations. Interestingly, we found the variation in the Mn/Fe ratio could result in shifts in the redox potentials of Fe 3+ /Fe 4+ and Mn 3+ /Mn 4+ couples, which might be associated with superexchange interaction and Jahn-Teller effect. These findings shed light on design of new layered metal oxides for batteries with improved performances. • A cation composition diagram was developed to investigate a layered Na x (Cu–Fe–Mn)O 2 system. • A highest reversible capacity of 190 mA h g −1 was delivered by a composition of Na 0.75 (Cu 0.1 Fe 0.1 Mn 0.8 )O 2 . • Superexchange interaction and Jahn-Teller effect are proposed to explain the shifts of the redox potentials of Fe 3+ /Fe 4+ and Mn 3+ /Mn 4+ couples.

Insights into the Ti4+ doping in P2-type Na0.67Ni0.33Mn0.52Ti0.15O2 for enhanced performance of sodium-ion batteries

Due to the sodium abundance and availability, sodium-ion batteries (SIBs) have the potential to meet the worldwide growing demand of electrical energy storage. P2-type sodium transition-metal layer oxides with a high energy density are considered as the most promising cathode materials for SIBs. We present here a detailed study of the enhanced rate capability and cyclic stability of the Ti-doped Na0.67Ni0.33Mn0.67O2 cathode material. The combined analysis of ex-situ X-ray absorption fine structure (XAFS) spectroscopy, aberration-corrected high resolution transmission electron microscopy (AB-HRTEM) and X-ray diffraction (XRD) show that the strong Ti–O bond in the transition metal layers stabilizes the local structure, destroy the Na+-vacancy ordering and arrest the irreversible multiphase transformation that occurs during the intercalation/deintercalation process. Actually, Na0.67Ni0.33Mn0.52Ti0.15O2 exhibits a reversible capacity of 89.6 mA h g−1 even at 5 C, an excellent cyclability with 88.78 % capacity retention after 200 cycles at 0.5 C. This study provides a better understanding in optimization of the design of high-energy cathode materials based on titanium doped layered oxides for SIBs.

Exceptionally high-energy tunnel-type V1.5Cr0.5O4.5H nanocomposite as a novel cathode for Na-ion batteries

Abstract We report a tunnel-type V1.5Cr0.5O4.5H/carbon-nanotube (T-VCr/C) nanocomposite as a new high-energy cathode material for sodium-ion batteries. Structural analyses using Rietveld refinement and bond-valence-energy landscape analysis based on X-ray diffraction reveal the Na+ diffusion paths and possible atomic sizes of Na+ in the V1.5Cr0.5O4.5H structure. Through combined studies using first-principles calculations and various experimental techniques, we confirm that the T-VCr/C nanocomposite delivers a large specific capacity of ~306 mAh g−1, corresponding to 2 mol Na+ de/intercalation at 15 mA g−1, with an average operation voltage of ~2.5 V (vs. Na+/Na) in the voltage range of 1.0–4.0 V based on reversible V3+/V4+ and Cr3+/Cr4+ redox reactions. Even at 900 mA g−1, the T-VCr/C nanocomposite retains a specific capacity of ~214.9 mAh g−1, corresponding to ~70.2% of the capacity measured at 15 mA g−1. Furthermore, over 100 cycles at 300 mA g−1, the T-VCr/C nanocomposite exhibits capacity retention of ~77.1% compared with the initial capacity. Operando/ex-situ X-ray diffraction and X-ray absorption spectroscopy analyses reveal the small structural change of NaxV1.5Cr0.5O4.5H (0 ≤ x ≤ 2) during Na+ de/intercalation based on V4+/V3+ and Cr4+/Cr3+ redox reaction, leading to the outstanding electrochemical performance of the T-VCr/C nanocomposite.

Morphology, microstructure, and phase states in selective laser sintered lithium ion battery cathodes

• Bulk LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) is made by binder-free selective laser sintering. • Single-track morphology is used to refine processing and produce 3D samples. • Three-dimensional (3D) samples are porous with micron sized grains. • 3D samples exhibit both layered (R-3 m) and rock salt (Fm-3 m) structures. Fabrication of high-energy cathode materials with complex geometries is necessary to enable high-power density in next-generation lithium ion batteries (LIBs). Ceramic three-dimensional (3D) printing techniques are one possible avenue to achieve high performance. Current ceramic 3D-printing methods often suspend the electrochemically active cathode powder in binders that require substantial rheological development to enable printability and secondary binder removal processes to ensure degradation does not occur during electrochemical cycling. In this study, the need for binder additives is circumvented by employing the laser-based 3D-printing technique, selective laser sintering (SLS), for direct fabrication of 3D lithium nickel cobalt aluminum oxide (NCA) cathodes. Thermal stress and part distortion are mitigated by using in-situ substrate heating while operating the 1.07 μm fiber laser in q-switched continuous mode. A parametric single-track study is performed to refine the process parameters for the layer-by-layer selective laser sintering of bulk 3D NCA samples. These bulk 3D samples are porous with 2−3 μm grains and exhibit a dual phase state, including the layered structure (with symmetry R-3 m) and rock salt structure (Fm-3 m). The retention of the electrochemically active layered structure in these samples is promising for the development of binder-free, 3D-printed cathodes for LIBs with enhanced power density.

P2-type Fe and Mn-based Na0.67Ni0.15Fe0.35Mn0.3Ti0.2O2 as cathode material with high energy density and structural stability for sodium-ion batteries

P2-type layered cathode materials containing Fe and Mn have attracted much attention due to their elemental abundance, low costs and high reversible capacities, and most related work have focused on attaining cathodes with extremely high reversible capacity. However, the extremely high capacity usually leads to several disadvantages, including extremely wide voltage range, fast capacity fading upon cycling, and inappropriate initial Coulombic efficiency. This work investigates P2-type Na0.67Ni0.15Fe0.35Mn0.5O2 (NFM) and Na0.67Ni0.15Fe0.35Mn0.3Ti0.2O2 (NFMT) as high-energy cathode materials by elevating average operating voltage with Ni2+/Ni4+ and Fe3+/Fe4+ redox couples but limiting (de)sodiation in the voltage of 2.0–4.4 V to obtain an medium reversible capacity. NFMT has high energy density of 471 Wh kg−1 with reversible capacity of 157.2 mAh g−1 and average operating voltage of 3.0 V. NFMT also has an initial Coulombic efficiency of 98.8% and a capacity retention of 85.1% after 50 cycles at 20 mA g−1 (0.1C), better than those of some high-capacity P2-type Fe and Mn-based cathodes, showing great potential for future practical application in the sodium full cells. Ti4+ ion acts as pillar ion in the fully charged NFMT cathode, effectively suppressing thickness reduction of the MO2 slab, volume shrinkage of the cathode, and thus inhibiting P2–O2 phase transition at high voltage, which contribute to the improvement of the structural and cycling stability P-type oxides.

Role of Redox-Inactive Transition-Metals in the Behavior of Cation-Disordered Rocksalt Cathodes.

Owing to the capacity boost from oxygen redox activities, Li-rich cation-disordered rocksalts (LRCDRS) represent a new class of promising high-energy Li-ion battery cathode materials. Redox-inactive transition-metal (TM) cations, typically d0 TM, are essential in the formation of rocksalt phases, however, their role in electrochemical performance and cathode stability is largely unknown. In the present study, the effect of two d0 TM (Nb5+ and Ti4+ ) is systematically compared on the redox chemistry of Mn-based model LRCDRS cathodes, namely Li1.3 Nb0.3 Mn0.4 O2 (LNMO), Li1.25 Nb0.15 Ti0.2 Mn0.4 O2 (LNTMO), and Li1.2 Ti0.4 Mn0.4 O2 (LTMO). Although electrochemically inactive, d0 TM serves as a modulator for oxygen redox, with Nb5+ significantly enhancing initial charge storage contribution from oxygen redox. Further studies using differential electrochemical mass spectroscopy and resonant inelastic X-ray scattering reveal that Ti4+ is better in stabilizing the oxidized oxygen anions (On - , 0 < n < 2), leading to a more reversible O redox process with less oxygen gas release. As a result, much improved chemical, structural and cycling stabilities are achieved on LTMO. Detailed evaluation on the effect of d0 TM on degradation mechanism further suggests that proper design of redox-inactive TM cations provides an important avenue to balanced capacity and stability in this newer class of cathode materials.

High Energy Polyanion Cathode for K-Ion Batteries: KVPO4F

The development of high-energy cathode materials is crucial for the commercialization of emerging K-ion batteries (KIBs). While layered potassium-transition-metal-oxides (K x MO2, M=transition metals) have been investigated as potential cathodes, they have two intrinsic challenges. First, most of the K-layered oxides have K-poor composition (x<1.0 in K x MO2) and it leads practical difficulty of realizing KIBs because all the K ions should come from the cathode in a rocking-chair KIB.[1-6] Second, K-layered oxides have too high a voltage slope, resulting in low specific capacity and average voltage. Both the problems are attributable to much stronger K+-K+ interaction than Na+-Na+ and Li+-Li+ in the layered oxide structure.[2, 4] In contrast, polyanion cathodes can be better alternatives because 3-dimensional arrangement of K ions in their frameworks can significantly reduce the strength of effective interaction between K ions. As a result, polyanion cathodes can have K-rich (or K-stoichiometric) composition and high working voltage.In this work, we demonstrate that KVPO4F, a polyanion compound, is a high-energy cathode of KIBs. The KVPO4F cathode delivers a reversible capacity of ~105 mAh g−1 with an average voltage of ~4.3 V (vs. K/K+) (Figure 1), which is the highest among the K-cathodes developed up to date.[7] The specific energy (a gravimetric energy) of KVPO4F reaches ~450 Wh kg−1. Ex-situ X-ray diffraction characterization and ab-initio calculations demonstrate reversible multiple phase transitions of K x VPO4F during electrochemical cycling. K x VPO4F goes through various intermediate phases at x = 0.75, 0.625, and 0.5 upon K extraction and reinsertion. We further explain the role of oxygen substitution in KVPO4+xF1−x: the oxygenation of KVPO4F leads to an anion-disordered structure which prevents the formation of K+/vacancy orderings without electrochemical plateaus and hence to a smoother voltage profile.

Binder- and conductive additive-free laser-induced graphene/LiNi1/3Mn1/3Co1/3O2 for advanced hybrid supercapacitors

Hybrid supercapacitors have recently emerged as next-generation energy storage devices that bridge the gap between supercapacitors and lithium-ion batteries. However, developing high energy cathodes that maintain long-term cycle stability and a high rate capability for real applications remains a significantly challenging issue. Herein, we report a facile synthesis method for a laser-scribed graphene/LiNi1/3Mn1/3Co1/3O2 (LSG/NMC) composite for high energy cathode materials for use in hybrid supercapacitors. LSG/NMC composites exhibit not only a high capacitance of up to 141.5 F/g but also an excellent capacitance retention of 98.1% after 1000 cycles at a high current density of 5.0 A/g. The introduction of an NMC spacer between the LSG layers provides an enlarged interspace that can act as an efficient channel for additional storage sites and rapid access. In addition, we further confirmed that hybrid supercapacitors using LSG/NMC cathodes and H2T12O25 anodes with an AlPO4/carbon hybrid coating layer (H-HTO) deliver a remarkable energy density of ~123.5 Wh/kg, power density of ~14074.8 W/kg, and a long-term cycle stability of 94.6% after 20,000 cycles. This work demonstrates that our proposed material can be considered a strong cathode candidate for next-generation hybrid supercapacitors.

Dielectric Polarization in Inverse Spinel-Structured Mg2 TiO4 Coating to Suppress Oxygen Evolution of Li-Rich Cathode Materials.

High-energy Li-rich layered cathode materials (≈900 Wh kg-1 ) suffer from severe capacity and voltage decay during cycling, which is associated with layered-to-spinel phase transition and oxygen redox reaction. Current efforts mainly focus on surface modification to suppress this unwanted structural transformation. However, the true challenge probably originates from the continuous oxygen release upon charging. Here, the usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li-rich material is reported, using Mg2 TiO4 as a proof-of-concept material. The creation of a reverse electric field in surface layers effectively restrains the outward migration of bulk oxygen anions. Meanwhile, high oxygen-affinity elements of Mg and Ti well stabilize the surface oxygen of Li-rich material via enhancing the energy barrier for oxygen release reaction, verified by density functional theory simulation. Benefited from these, the modified Li-rich electrode exhibits an impressive cyclability with a high capacity retention of ≈81% even after 700 cycles at 2 C (≈0.5 A g-1 ), far superior to ≈44% of the unmodified counterpart. In addition, Mg2 TiO4 coating greatly mitigates the voltage decay of Li-rich material with the degradation rate reduced by ≈65%. This work proposes new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high-energy-density rechargeable batteries.

Encapsulation of Na4MnV(PO4)3 in robust dual-carbon framework rendering high-energy, durable sodium storage

Na4MnV(PO4)3 (NMVP) is a green, cheap, and high-energy cathode material for sodium-ion batteries. However, the low electrical conductivity severely limits its sodium storage performance. Herein, we report the spray-drying synthesis of robust and highly conductive reduced graphene oxide/amorphous carbon framework encapsulated NMVP (NMVP@rGO/AC) composite microspheres. The unique dual-carbon encapsulation architecture enables the NMVP@rGO/AC a high specific capacity (100 mAh g−1 at 100 mA g−1) with durable cyclability (capacity retention of 77.5% for 500 cycles). In situ XRD measurements reveal the reversible extraction/insertion of Na+ via unique solid-solution and two-phase reactions during de-sodiation/sodiation processes. This work provides a versatile platform for the construction of rGO/AC dual-carbon encapsulated active materials for electrochemical energy storage.

Battery Materials Technology Trends and Market Drivers for Automotive Applications

With the electric vehicle (EV) market set to grow rapidly over the coming years, the industry faces a challenging ramp-up of volume and material performance demands. From the current trend towards high-energy high-nickel cathode materials, driven in-part by consumer range anxiety, to the emergence of solid-state and beyond lithium-ion technologies, herein we review the changing requirements for active materials in automotive Li-ion battery (LIB) applications, and how science and industry are set to respond.

Localized Surface Doping for Improved Stability of High Energy Cathode Materials

Localized Surface Doping for Improved Stability of High Energy Cathode Materials

Stabilizing Li-rich layered cathode materials by nanolayer-confined crystal growth for Li-ion batteries

Li-rich layered oxides have aroused much interest in high-energy cathode materials for Li-ion batteries (LIBs). However, they still come with significant challenges of appreciable voltage decay and hysteresis upon cycling. Microstructure and surface are considered to be crucial for the stabilization of high-capacity Li-rich layered oxide cathode. In this work, we report the controlled synthesis of unique Li-rich layered nanobelts through nanolayer-confined crystal growth. The unique one-dimensional Li1.2Mn0.54Co0.13Ni0.13AlxO2 nanostructures and reconstruction of spinel phase domains may not only offer fast Li-ion diffusion pathways, but inhibit the structural collapse and mitigate the voltage decay upon discharge/charge cycling. The cathode made of Li1.2Mn0.54Co0.13Ni0.13AlxO2 layered/spinel nanobelts exhibits enhanced rate capability and long-term cyclability. An initial discharge capacity of 283.5 mA h g−1 at 0.1 C and the capacity retention of 88.1% over 100 cycles at 1 C are achieved. This work may pave an avenue toward nanostructuring and surface engineering of electrode materials and practical applications of high-energy-density LIBs.

Dopant Distribution in Co-Free High-Energy Layered Cathode Materials

The practical implementation of Co-free, LiNiO2-derived cathodes has been prohibited by their poor cycle life and thermal stability, resulting from the structural instability, phase transformations...

Advances in the Cathode Materials for Lithium Rechargeable Batteries.

The accelerating development of technologies requires a significant energy consumption, and consequently the demand for advanced energy storage devices is increasing at a high rate. In the last two decades, lithium-ion batteries have been the most robust technology, supplying high energy and power density. Improving cathode materials is one of the ways to satisfy the need for even better batteries. Therefore developing new types of positive electrode materials by increasing cell voltage and capacity with stability is the best way towards the next-generation Li rechargeable batteries. To achieve this goal, understanding the principles of the materials and recognizing the problems confronting the state-of-the-art cathode materials are essential prerequisites. This Review presents various high-energy cathode materials which can be used to build next-generation lithium-ion batteries. It includes nickel and lithium-rich layered oxide materials, high voltage spinel oxides, polyanion, cation disordered rock-salt oxides and conversion materials. Particular emphasis is given to the general reaction and degradation mechanisms during the operation as well as the main challenges and strategies to overcome the drawbacks of these materials.