High Power Cathode Material Research Articles

Boosting the intrinsic kinetics of lithium vanadium phosphate via an electrochemically active cross-link framework

The monoclinic lithium vanadium phosphate Li3V2(PO4)3 (LVP) is considered a promising cathode for lithium-ion batteries (LIBs) due to its high working voltage (>4.0 V, vs. Li+/Li) and high theoretical specific capacity (197 mAh g−1). However, the electrochemical procedure accompanied by three-electron reactions in LVP has proven challenging due to the complexity or asymmetry of the reaction pathways, thus limiting its wide application. Herein, an electrochemically active cross-link framework of LVP, LiFe0.3Mn0.7PO4 (LFMP) and graphene are successfully synthesized by an in situ catalytic process, which enables stable cycling and high-rate capabilities up to 4.8 V (vs. Li+/Li). Graphene-like carbon can be formed in situ with VOx as the catalyst and polyvinyl alcohol as the carbon source, and LFMP also inhibits the growth of LVP particles, allowing rapid Li+ and electron transport in the cathodes. Both in situ and ex situ X-ray diffraction prove that the cross-link framework efficiently smooths the lattice mismatch and achieves highly reversible structural phase transitions. The prepared 0.9LVP·0.1LFMP is able to provide a superior rate capability of 123 mAh g−1 at 20 C. After 150 cycles, the 0.9LVP·0.1LFMP shows 97.4 % capacity retention even under a voltage of 4.8 V (vs. Li+/Li). This work develops a new strategy for the future design of high-voltage and high-power cathode materials for LIBs.

Enhancing Orbital Interaction in Spinel LiNi0.5Mn1.5O4 Cathode for High-Voltage and High-Rate Li-Ion Batteries.

High voltage cobalt-free spinel LiNi0.5Mn1.5O4 (LNMO) is well organized as a high-power cathode material for lithium (Li)-ion batteries, however, the weak interaction between the 3d orbital of the transition metal (TM) ions and the 2p orbital of oxygen (O) leads to the instability of crystal structural, hindering the long-term stable cycling of LNMO cathode especially at high temperatures. Here, a design strategy of orbital interaction is initiated to strengthen TM 3d-O 2p framework in P-doped LNMO (P-LNMO) by choosing phytic acid as P dopant, which can realize more uniform doping compared to regular phosphate. The results show that the enhancement of TM 3d-O 2p orbital interaction in P-LNMO can suppress the Jahn-Teller effect and subsequent dissolution of Mn, as well as lowers the energy barrier for Li ion insertion/extraction kinetics. As a result, superior electrochemical performances including high discharge capacity, stable cycling behavior and enhanced rate capability of P-LNMO are obtained. Significantly, the P-LNMO pouch cell shows great cycling stability with 97.4% capacity retention after 100 cycles.

Improving electrochemical performance of spinel-type Ni/Mn-based high-voltage cathode material for lithium-ion batteries via La-F co-doping combined with in-situ integrated perovskite LaMnO3 coating layer

Spinel-type LiNi0.5Mn1.5O4 (LNMO) can provide high-voltage and high theoretical specific capacity as cathode material for lithium-ion batteries (LIBs), thereby LNMO is particularly suitable for electric/hybrid electric vehicles that require high power. Unfortunately, both serious structural deformation derived from the Jahn-Teller effect of Mn3+ and decomposition of electrolyte during repetitive charge/discharge processes at high operating potential result in fast capacity fade. In this work, lanthanum and fluorine co-doping LiNi0.5La0.01Mn1.49O3.97F0.03 (LF-LNMO) is proposed to eliminate its inherent defects. Fluorine can suppress Jahn-Teller effect of Mn3+ by reducing the generation of Mn3+; La3+ ions in LF-LNMO play a role in solidly riveting atoms together in the structure, and LaMnO3 coating layer acts as a physical protection barrier suppressing adverse side reactions that may damage battery performance. Thanks to the synergistic effect derived from structural modification of F−, the pinning effect of La3+ ions, and LaMnO3 surface coating interface reconstruction, the LF-LNMO cathode provides the best cycling performance and rate performance among all investigated electrode materials. Such as, LF-LNMO cathode can provide 64.02% capacity retention after the 1000th cycle at 500 mA g−1 and 30 °C, which is much higher than that (25.56%) of the undoped LiNi0.5Mn1.5O4 (P-LNMO). Besides, LF-LNMO electrode also behaves the excellent high-temperature cycling performance. This work provides a new strategy enhancing structural stability of spinel-type Ni/Mn-based oxide and would motivate us to further devise and prepare high power cathode materials for LIBs.

Role of Conducting Polymer in Aqueous Zinc Ion Batteries

Owing to high safety and low cost, aqueous rechargeable zinc-ion batteries (ZIBs) is currently a major research topic. In this study, we propose the microwave-assisted hydrothermal synthesis of polypyrrole (PPy)-coated Na1.1V3O7.9 (P-NVO) nanorods for the first time as a highenergy and high-power cathode material for ZIBs. The highly conductive PPy surface-coating layer is significant to enhance the electronic conductivity and Zn2+ diffusion kinetics, leading to utilize the V3+/V4+/V5+ multiple redox reactions of the NVO cathode in ZIBs. Compared to the NVO cathode, therefore, the P-NVO cathode offers higher discharge capacity, power capability and cycling stability; in particular, PPy coating triggers the full theoretical capacity of the NVO cathode (527 mAh g- 1 with ~ 3 mol Zn insertion per formula unit) and directly reflects a superior energy density of 408 Wh kg-1. Even at a high current density of 6000 mA g- 1, the P-NVO cathode sustains 1000 cycles with almost 100% capacity retention. Galvanostatic intermittent titration technique, cyclic voltammetry, in situ X-ray diffraction, and ex situ X-ray absorption near edge structure analyses are combined to verify the superior Zn2+ storage mechanism of the P-NVO cathode.

Triggering the theoretical capacity of Na1.1V3O7.9 nanorod cathode by polypyrrole coating for high-energy zinc-ion batteries

The exploration of advanced cathode materials for aqueous rechargeable zinc-ion batteries (ZIBs) is currently a major research topic. In this study, we propose the microwave-assisted hydrothermal synthesis of polypyrrole (PPy)-coated Na1.1V3O7.9 (P-NVO) nanorods for the first time as a high-energy and high-power cathode material for ZIBs. The highly conductive PPy surface-coating layer is significant to enhance the electronic conductivity and Zn2+ diffusion kinetics, leading to utilize the V3+/V4+/V5+ multiple redox reactions of the NVO cathode in ZIBs. Compared to the NVO cathode, therefore, the P-NVO cathode offers higher discharge capacity, power capability and cycling stability; in particular, PPy coating triggers the full theoretical capacity of the NVO cathode (527 mAh g−1 with ∼ 3 mol Zn insertion per formula unit) and directly reflects a superior energy density of 408 Wh kg−1. Even at a high current density of 6000 mA g−1, the P-NVO cathode shows unprecedented cycling stability over 1100 cycles without capacity loss. Galvanostatic intermittent titration technique, cyclic voltammetry, in situ X-ray diffraction, and ex situ X-ray absorption near edge structure analyses are combined to verify the superior Zn storage mechanism of the P-NVO cathode.

Zeolite-Templated Carbon as a Stable, High Power Magnesium-Ion Cathode Material.

One strategy to overcome the slow kinetics associated with electrochemical magnesium ion storage is to employ a permanently porous, capacitive cathode material together with magnesium metal as the anode. This strategy has begun to be employed, for example, using framework solids like Prussian blue analogues or porous carbons derived from metal-organic frameworks, but the cycling stability of an ordered, bottom-up synthesized,three-dimensional carbon framework toward magnesiation and demagnesiation in a shuttle-type battery remains unexplored. Zeolite-templated carbons (ZTCs) are a class of ordered porous carbonaceous framework materials with numerous superlative properties relevant to electrochemical energy storage. Herein, we report that ZTCs can serve as high-power cathode materials for magnesium-ion hybrid capacitors (MHCs), exhibiting high specific capacities (e.g., 113 mA h g-1 after 100 cycles) with an average discharge voltage of 1.44 V and exceptional capacity retention (e.g., 76% after 200 cycles). ZTC-based MHCs meet or exceed the gravimetric energy densities of state-of-the-art batteries functioning on the Mg2+ shuttle, while simultaneously displaying far superior rate capabilities (e.g., 834 W kg-1 at 600 mA g-1).

O3-type layer-structured Na0.8[Ni1/5Fe1/5Co1/5Mn1/5Ti1/5]O2 as long life and high power cathode material for sodium-ion batteries

O3-type layer-structured Na0.8[Ni1/5Fe1/5Co1/5Mn1/5Ti1/5]O2 (denoted as N0.8NFCMTO) has been investigated as a new cathode material for Na-ion batteries. The N0.8NFCMTO cathode delivers an initial discharge capacity of 107 mAhg−1 with excellent cycling stability of over 90% capacity retention after 100 cycles. This material delivers comparable capacity to that of previously reported layered cathode materials with multi-transition metal elements while showing an excellent rate capability and stable long cycle life. Synchrotron-based in situ X-ray diffraction and ex situ X-ray absorption spectroscopy investigations combined with quantitative refinement analysis reveal the reversible structural changes and charge compensation mechanism during sodium extraction/insertion, which is associated with the excellent cycling stability of the N0.8NFCMTO electrode.

Porous LiMn2O4 Nano-Microspheres as Durable High Power Cathode Materials for Lithium Ion Batteries

Porous LiMn2O4 spheres was easily fabricated with MnCO3 spheres and MnO2 as precursors and characterized in terms of structure and performance as the cathode of a lithium ion battery. The presence of pores with the average size of about 50 nm throughout the whole LiMn2O4 microspheres was confirmed by scanning electron microscope (SEM) and N2 adsorption-desorption measurements. The electrochemical tests show that the synthesized product has smaller electrochemical polarization, faster Li-ion intercalation kinetics and higher electrochemical stability. It exhibits excellent rate capability and cyclic stability: delivering a reversible discharge capacity of 71 mA h g−1 at a 5 C rate and yielding a capacity retention of over 92% at a rate of 0.5 C after 100 cycles. The superior performance of the synthesized product is attributed to its special structure: porous secondary spheres particles consisting of primary single-crystalline nanoparticles. The nanoparticle reduces the path of Li-ion diffusion and increases the reaction sites for lithium insertion/extraction, the pores provide room to buffer the volume changes during charge-discharge and the single crystalline nanoparticle endows the spinel with the best stability. Taking the excellent electrochemical performance and facile synthesis into consideration, the presented porous LiMn2O4 spheres could be a competitive candidate cathode material for high-performance lithium-ion batteries.

Scalable Room-Temperature Synthesis of Multi-shelled Na3(VOPO4)2F Microsphere Cathodes

Summary The large-scale application of rechargeable batteries in electric vehicles and energy-storage systems is still hindered by their high cost, particularly from the active materials. Here we proposed a concept of integration of extraction-separation and materials-preparation to further reduce the materials' cost. The power of this concept was demonstrated by the large-scale room-temperature synthesis (150 g per batch) of multi-shelled Na3(VOPO4)2F microspheres based on in situ generated bubbles as soft templates. The as-prepared Na3(VOPO4)2F shows superior rate capability with discharge capacity of 81 mAh g−1 at 15 C current rate and capacity retention of 70% after 3,000 cycles. Ex situ UV-vis was first employed to characterize the variation of oxidation state for vanadium during the charging and discharging process. This is the first report of a rapid and facile large-scale room-temperature controllable synthesis of Na3(VOPO4)2F microspheres, and this approach could be extended to synthesize other similar compounds.

Na+/Vacancy Disordered P2-Na0.67Co1-xTixO2: High-Energy and High-Power Cathode Materials for Sodium Ion Batteries.

Although sodium ion batteries (NIBs) have gained wide interest, their poor energy density poses a serious challenge for their practical applications. Therefore, high-energy-density cathode materials are required for NIBs to enable the utilization of a large amount of reversible Na ions. This study presents a P2-type Na0.67Co1-xTixO2 (x < 0.2) cathode with an extended potential range higher than 4.4 V to present a high specific capacity of 166 mAh g-1. A group of P2-type cathodes containing various amounts of Ti is prepared using a facile synthetic method. These cathodes show different behaviors of the Na+/vacancy ordering. Na0.67CoO2 suffers severe capacity loss at high voltages due to irreversible structure changes causing serious polarization, while the Ti-substituted cathodes have long credible cycleability as well as high energy. In particular, Na0.67Co0.90Ti0.10O2 exhibits excellent capacity retention (115 mAh g-1) even after 100 cycles, whereas Na0.67CoO2 exhibits negligible capacity retention (<10 mAh g-1) at 4.5 V cutoff conditions. Na0.67Co0.90Ti0.10O2 also exhibits outstanding rate capabilities of 108 mAh g-1 at a current density of 1000 mA g-1 (7.4 C). Increased sodium diffusion kinetics from mitigated Na+/vacancy ordering, which allows high Na+ utilization, are investigated to find in detail the mechanism of the improvement by combining systematic analyses comprising TEM, in situ XRD, and electrochemical methods.

High Power Cathode Material Na4VO(PO4)2 with Open Framework for Na Ion Batteries

High Power Cathode Material Na₄VO(PO₄)₂ with Open Framework for Na Ion Batteries

Unravelling the growth mechanism of hierarchically structured Ni1/3Co1/3Mn1/3(OH)2 and their application as precursors for high-power cathode materials

A hydroxide co-precipitation method is used to synthesize transition metal hydroxide (Ni1/3Co1/3Mn1/3(OH)2), which is the precursor for layer-structured LiNi1/3Co1/3Mn1/3O2. The optimum pH range for the preparation of Ni1/3Co1/3Mn1/3(OH)2 using a continuous stirred-tank reactor is calculated by taking into account the underlying chemical equilibria. The entire growth process of the Ni1/3Co1/3Mn1/3(OH)2 particles is investigated by monitoring the structure, morphology, particle size distribution, and tap density as a function of the reaction time. The results confirm that the co-precipitation reaction in the presence of ammonia started with the formation of crystal nuclei and (001) plane dominated nanosheets. The reaction ended with spherical and dense hydroxide precursors. The crystal growth mechanism was interpreted during the co-precipitation process, which involved the quick nucleation of primary particles followed by its slow aggregation and crystallization. The electrochemical properties of the final cathode materials with different morphologies are also studied. The results show that the electrochemical performances of the final LiNi1/3Co1/3Mn1/3O2 are strongly affected by the hierarchical structure of Ni1/3Co1/3Mn1/3(OH)2.

Improved Rate Capability By Dynamic Crystal Structure Change of Co-Substituted LiFePO4 with Reduced Lattice Mismatch

For the practical use of Lithium-ion battery in electric vehicles, the rate capability should be more improved. Although LiFePO4 is wildly known as the high power cathode materials, the large mismatch between LiFePO4 and FePO4 might still disturb the further improvement of the rate capability. Because the huge volume change during the phase transition require the large activation energy, the suppression of the crystal structure change is one of attracted design principle for cathode materials. Recently, Nishijima et al have reported that Zr-substitution in LiFePO4 eliminates the volume change between LiFePO4 and FePO4 and the cyclability of the doped LiFePO4 is drastically improved[1]. In this study, we investigate the rate capability of the Zr-dopoed LiFePO4. Moreover the phase transition behavior is examined by using operando X-ray diffraction measurements. LiFePO4, called hereafter undoped LFP, and Li(Fe0.95Zr0.05)(P0.9Si0.1)O4, called Zr-doped LFP, were synthesized by the solid solution method in the same manner as reported[1]. The crystal structure of the prepared samples were analyzed by X-ray diffraction (XRD) which were performed at beamline BL02B2, SPring-8 with a wavelength of 0. 699292(4) Å using a Debye-Scherrer camera and an imaging plate detector. The electrodes for the electrochemical tests were prepared by mixing 80% active material, 10% carbon black, and 10% polyvinylidene fluoride (PVDF) with 1-methyl-2-pyrrolidinone solvent. The slurry was then casted onto an Al foil current collector. 1 M LiPF6 in a 3:7 volume ratio of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) was used as the electrolyte. Li foil was used as a counter electrode. operando time-resolved XRD measurements were performed at SPring-8 with a wavelength of 0.619862(2) Å using a 1D detector, Mythen. All the peaks of XRD pattern of the both prepared powder samples are indexed to orthorhombic Pnma space group and any impurity is not observed. The calculated lattice volume of Zr-doped LFP is almost similar to that of undoped LFP. SEM measurements indicate that the particle size of both undoped LFP and Zr-doped LFP is approximately 100 nm. The rate capability of Zr-doped LFP is improved compared with undoped LFP. At 10 C rate, 110 mAh/g is still acquired in Zr-doped LFP, while the capacity of undoped LFP is decreased to 90 mAh/g. The polarization of the discharge profile is also suppressed by Zr substitution. Operando time-resolved XRD measurements reveal that the expansion of solid solution reaction of LiFePO4 and FePO4end-members in nonequilibrium condition. REFERENCES [1] Nishijima, M.; Ootani, T.; Kamimura, Y.; Sueki, T.; Esaki, S.; Murai, S.; Fujita, K.; Tanaka, K.; Ohira, K.; Koyama, Y.; Tanaka, I., Nat. Commun. 5, 4553 (2014).

A123's High Power and High Energy Li-Ion Chemistry Development for Vehicle Electrification

A123 has traditionally been a lithium-ion phosphate (LFP) focused company, providing state-of-the-art, high power solutions with excellent safety for low voltage automotive applications. This focus continues to result in the development of unique LFP synthesis and crystal structure doping processes to further enhance low temperature performance. In an effort to produce safe, high-energy density cells utilizing nickel-rich NCM cathodes and large capacity anode materials, A123 is implementing the same crystal level doping and surface coating approach that has been effective for low voltage material development. This presentation topic is therefore focused on the high power cathode material development that has resulted in Lithium Ion Starter Batteries (LiSBs) with cold crank capabilities that surpass lead acid batteries and high energy advancements at the material and cell levels in order to achieve energy densities approaching 300 Wh/kg and 600 Wh/L for EV applications.

Graphene wrapped ordered LiNi0.5Mn1.5O4 nanorods as promising cathode material for lithium-ion batteries

LiNi0.5Mn1.5O4 nanorods wrapped with graphene nanosheets have been prepared and investigated as high energy and high power cathode material for lithium-ion batteries. The structural characterization by X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy indicates the LiNi0.5Mn1.5O4 nanorods prepared from β-MnO2 nanowires have ordered spinel structure with P4332 space group. The morphological characterization by scanning electron microscopy and transmission electron microscopy reveals that the LiNi0.5Mn1.5O4 nanorods of 100–200 nm in diameter are well dispersed and wrapped in the graphene nanosheets for the composite. Benefiting from the highly conductive matrix provided by graphene nanosheets and one-dimensional nanostructure of the ordered spinel, the composite electrode exhibits superior rate capability and cycling stability. As a result, the LiNi0.5Mn1.5O4-graphene composite electrode delivers reversible capacities of 127.6 and 80.8 mAh g−1 at 0.1 and 10 C, respectively, and shows 94% capacity retention after 200 cycles at 1 C, greatly outperforming the bare LiNi0.5Mn1.5O4 nanorod cathode. The outstanding performance of the LiNi0.5Mn1.5O4-graphene composite makes it promising as cathode material for developing high energy and high power lithium-ion batteries.

Lithium-ion transport through a tailored disordered phase on the LiNi0.5 Mn1.5 O4 surface for high-power cathode materials.

The phase control of spinel LiNi0.5 Mn1.5 O4 was achieved through surface treatment that led to an enhancement of its electrochemical properties. Li(+) diffusion inside spinel LiNi0.5 Mn1.5 O4 could be promoted by modifying the surface structure of LiNi0.5 Mn1.5 O4 through phosphidation into a disordered phase (Fd3m) that allows facile Li(+) transport. Phosphidated LiNi0.5 Mn1.5 O4 showed a significantly enhanced electrochemical performance, even at high rates exceeding 10 C, demonstrating that the improved kinetics (related to the amount of Mn(3+) ) can render LiNi0.5 Mn1.5 O4 competitive as a high-power cathode material for electric vehicles and hybrid electric vehicles.

Insight into Designing High-Energy, High-Power Cathode Material for Lithium Ion Batteries

This work reports a physical mixture aswell as an integrated composite structure (ICS) of lithium-excess layered oxides and high voltage spinel oxides. With respect to physical mixture (PM), the improvement has shown in cycling retention. Different synthesis routes would result in drastically different properties in the composite case. The optimized composite, in comparison with the non-optimized one, both energy density and the power density have increased. The optimized composite could deliver 125 mAh/g capacity after 200 cycles at a rate of 1.2 C. Thework here provides some new insights into how to design better cathode materials for lithium ion batteries. © The Author(s) 2014. Published by ECS.

ChemInform Abstract: Recent Advances in Sodium Intercalation Positive Electrode Materials for Sodium Ion Batteries

AbstractReview: 61 refs.

Self-supported, binder-free 3D hierarchical iron fluoride flower-like array as high power cathode material for lithium batteries

We present a tactful and advanced architecture design of self-supported, binder-free 3D hierarchical iron fluoride flower-like array directly growing on Ti foil by a solvothermal approach. The probable growth mechanism of the 3D microflower is explored. The advantages of the porous 3D hierarchical nanostructure materials endow a stable capacity of 123mAhg−1 at 3C rate, and a good rate capability of 101mAhg−1 at a high current density of 2Ag−1 (10C). The superior electrochemical performance can be ascribed to the synergistic effect of charge transfer expressway, high specific surface area and porous hierarchical structure for electrolyte penetration deriving from the unique porous 3D hierarchical structure. The superior electrochemical performance combined with the unique structure of the FeF3·0.33H2O flower-like array demonstrates its great potential of being utilized as the cathode material in high rate battery application.

Improving the Stability of LiNi0.5Mn1.5O4 As a High-Power Cathode Material for Li-Ion Batteries By MgO Coating

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