Lithium-ion Cathode Materials Research Articles

Electrolytic recovery of metals from lithium battery cathodes in moisture-tolerant molten hydroxide salt

Lithium-ion battery recycling offers an opportunity to develop innovative technologies to close the loop on the battery materials cycle and increase the resilience of the battery supply chain. Here we demonstrate a two-step pyroelectrochemical method for producing mixed-metals from lithium-ion cathodes in a molten hydroxide salt. Mixed metal oxides in the form of insoluble lithium-ion cathode materials of LiNi0.6Mn0.2Co0.2O2 (NMC622) and spent lithium-ion battery materials (black mass) were electrochemically reduced to a soluble form and dissolved into a molten hydroxide salt bath. Electrochemical characterization of the process salt indicated accumulation of dissolved transition metals in the salt. A separate cathode was used to produce alloys of Ni, Mn, and Co electrochemically from the dissolved lithium-ion cathode materials. Characterization by scanning electron microscopy fitted with an energy dispersive X-ray spectrometer showed transition metals present in the cathode materials were recovered at the separate cathode. This approach represents a scalable, low temperature pyroelectrochemical process that can potentially reduce the cost and close the loop of battery cathode recycling.

Oxygen Dimerization as a Defect-Driven Process in Bulk LiNiO2.

To explore the possibility of oxygen dimerization-particularly, the formation of molecular oxygen-like species-in the bulk of LiNiO2 lithium ion cathode materials at high states of charge, we conduct a redox-product structure search inspired by recent methodological developments for point-defect structure prediction. We find that (1) delithiated Li1-x NiO2 (x = 1) has good kinetic stability toward decomposition into molecular oxygen and reduced transition-metal oxides but (2) defects can act as nucleation sites for oxygen dimerization. These results help reconcile conflicting reports on the formation of bulk molecular oxygen in LiNiO2 and other nickel-rich cathode materials, highlighting the role of defect chemistry in driving the bulk degradation of these compounds.

Cation doping for enhanced layer spacing and electrochemical performance in Li-rich Mn-based lithium-ion cathode materials

Lithium-rich manganese-based cathode materials offer promising research avenues owing to their high capacity. This study delved into the impact of cation doping on Li1.2Ni0.13Co0.13Mn0.54O2(LNCMO). A range of layered Li1.2BXNi0.13Co0.13Mn0.54O2 (LNCMOxB, B = Ca, Na, Al) cathode materials were produced utilizing calcium, sodium, and aluminum chloride as dopants. Combining these elements with the lithium-rich materials improves the capacity retention of the positive electrode and mitigates voltage decay. X-ray diffraction analysis, Rietveld structural refinement, SEM, and XPS verified the inclusion of Ca, Na, and Al in the synthesized samples. Electrochemical analysis revealed that the LNCMO-0.01Na sample, possessing the largest dopant radius, exhibited favorable cyclic stability at 0.2C. Conversely, the LNCMO-0.01Al sample, featuring the smallest doped cation radius, demonstrated superior rate performance. Specifically, after 30 cycles at varying rates, the capacity reached 170 mAh·g−1 at 0.2C. The LNCMO-0.007Ca sample exhibited the highest residual capacity, maintaining 151.4 mAh·g−1 after 100 cycles at 0.2C. Doping Li sites in Li1.2Ni0.13Co0.13Mn0.54O2 materials with appropriately sized divalent cations significantly enhances their overall electrochemical performance. This enhancement is attributed to ion doping within the Li and TM layers, expediting the diffusion kinetics of Li ions, and augmenting ion and electronic conductivity. Investigating the doping modification of lithium-rich manganese-based oxide microspheres is instrumental in advancing positive electrode materials for lithium-ion batteries, aiming for increased specific capacity and more stable material structures.

Ti-Doped Co-Free Li1.2Mn0.6Ni0.2O2 Cathode Materials with Enhanced Electrochemical Performance for Lithium-Ion Batteries

Cobalt-free manganese-based lithium-rich layered oxides (LLOs) have garnered research attention as prospective lithium-ion cathode materials owing to their large specific capacity and low price. However, their large-scale application is hindered by their low Coulombic efficiency, poor cycling performance, voltage attenuation, and structural phase transition. To address these issues, the LLO structure is modified via Ti doping at the manganese site herein. Ti-doped Li1.2Mn0.6−xTixNi0.2O2 (x = 0, 0.03, 0.05, 0.10, and 0.15) is prepared using the high-temperature solid-state method. The Ti-doped Li1.2Mn0.6Ni0.2O2 is calculated via first principles. The results show that Ti4+ doping improves the cycle stability and rate performance of Li1.2Mn0.6Ni0.2O2. Electrochemical test results show that the sample exhibits enhanced electrochemical performance when the Ti doping amount is 0.05. The discharge specific capacity at 0.1C is 210.4 mAh·g−1, which reaches 191.1 mAh·g−1 after 100 cycles, with a capacity retention rate of 90.7%. This study proves the feasibility of using cheap cobalt-free LLOs as cathode materials for LIBs and provides a novel system for exploiting low-cost and high-performance cathode materials.

Neutron imaging the spatial progression of chemical oxidation of lithium-ion cathode material in a packed bed reactor

Emerging electrochemical systems relevant to energy applications including redox targeted flow batteries rely on chemical redox of solid electroactive materials using dissolved redox couples. One configuration to facilitate contact between the redox shuttles and solid material which is volume efficient is a packed bed reactor. While methods have been reported to assess the overall progression by analysis of the packed bed reactor effluent, herein analysis of the spatial progression of the chemical redox will be reported. Combination of neutron and x-ray tomography enabled assessing the pore and particle structure in the packed bed reactor and the spatial homogeneity of the reaction at different overall extents of conversion of the reactor bed. These characterization tools provide methods to probe the chemical redox processes occurring within the reactor environment.

Pyrochlore-Type Iron Hydroxy Fluorides as Low-Cost Lithium-Ion Cathode Materials for Stationary Energy Storage.

Pyrochlore-type iron (III) hydroxy fluorides (Pyr-IHF) are appealing low-cost stationary energy storage materials due to the virtually unlimited supply of their constituent elements, their high energy densities and fast Li-ion diffusion. However, the prohibitively high cost of synthesis and cathode architecture currently prevent their commercial use in low-cost Li-ion batteries. Herein, we present a facile and cost-effective dissolution-precipitation synthesis of Pyr-IHF from soluble iron (III) fluoride precursors. High capacity retention by synthesized Pyr-IHF of > 80% after 600cycles at a high current density of 1Ag-1 was obtained, without elaborate electrode engineering. Operando synchrotron X-ray diffraction guided the selective synthesis of Pyr-IHF such that different water contents could be tested for their effect on the rate capability. Li-ion diffusion was found to occur in the 3D hexagonal channels of Pyr-IHF, formed by corner-sharing FeF6-x (OH)x octahedra. This article is protected by copyright. All rights reserved.

Amorphous nickel fluorosulfate cathode achieving a high-capacity by an additional electrochemical reaction mechanism

Although lithium-ion cathode materials with crystal structure are extensively applied, many intrinsic problems are inevitable, such as the low capacity ascribed to the need to sacrifice a large amount of active Li to maintain the crystal structure, and the spontaneous irreversible phase transition of the crystal during the cycles, which will lead to the deterioration or even inactivation of the crystal structure, resulting in poor cyclic stability of the crystal material. Herein, an amorphous nickel fluorosulfate cathode material (a-LNSF) is fabricated by a simple mechanical ball grinding method and compared with the electrochemical properties of LNSF with crystal structure. Comparing with LNSF, a-LNSF exhibits a high discharge specific capacity of 238.5 mAh/g at a current density of 0.1 C, and the specific capacity is still 118.3 mAh/g under a high current density of 10 C. Moreover, the capacity retention ratio is 85.7 % after 300 cycles at the current density of 1 C. a-LNSF achieves satisfactory electrochemical properties attributed to its inherently advantages of the amorphous structure. Theoretical calculations coupled with experiments to further explore the reason of superior electrochemical properties of a-LNSF, and an additional electrochemical reaction mechanism for capacity accumulation were discovered. Interestingly, the directional reversible migration of F-ions (stemming from the a-LNSF) between bulk material and carbon nanotubes is accompanied by the process of charge and discharge, the C-F ionic bonds with excellent reversibility and electronic conductivity are formed to improve the comprehensive electrochemical properties of a-LNSF during the charge/discharge processes.

Exploring Heterogeneous Kinetics in Redox-Mediated Energy Storage

Electrochemical energy storage technologies typically rely on heterogenous electron transfer reactions at current collectors and concurrent chemical reactions that generate or consume ions at the electrode in order to balance charge. These reactions are often volumetrically-limited, at the device level, by the available surface area for electron transfer reactions and associated mass transport of reactants or by the form factor of the chemical compounds, frustrating development and/or limiting utility. Flow batteries partially address this limitation by using soluble charge-redox couples paired with “inert” electrodes rather than a composite electrode packed with solid charge-storage materials.1 The use of dissolved redox active species, combined with flow, imparts greater design flexibility albeit at the expense of energy density. To this end, a combination of these approaches can be considered, where redox species transport charge between an “inert” electrode and a spatially-separated, high-capacity material by leveraging redox-mediated processes in a flow battery architecture.2 Redox-mediated energy storage systems leverage the high energy density of solid materials in combination with the modularity of solution-based flow systems. They operate by sacrificing a portion of the cell voltage towards a reaction between the soluble redox species and the solid material, which allows the cell capacity to be primarily determined by the amount of solid material used.3,4 By leveraging electrochemical reaction engineering principles, optimization of redox-mediated systems can enable flow batteries with energy densities that approach those of closed-form rechargeable batteries. Despite potential benefits, the introduction of spatially and temporally distinct chemical reactions also complicates battery design and operation, requiring careful consideration of solid-solution reactant combinations, reaction conditions, and system architecture. Herein, we investigate several redox-mediated reactions geared toward energy-dense flow battery systems, specifically focusing on lithium-storing positive electrode materials in combination with different soluble redox couples, in both aqueous and non-aqueous systems. Using in-situ voltammetry complemented by supporting measurements (thermogravimetric analysis, XRD), we characterize reactant materials during and after use in a redox-mediated system. We will also present theoretical considerations for the choice of reactants and solid-state materials for energy storage. Finally, experimental methods for characterizing such systems both in situ and operando will be discussed. The principles applied in experimental characterization of these systems are more broadly applicable to the mediated energy storage design space, and will inform future workflows for their study. Acknowledgements This work was funded by the Skoltech – MIT Next Generation Program. CTM would like to gratefully acknowledge support from the National Defense Science and Engineering Graduate fellowship, under the advisement of the Office of Naval Research. N.J.M and B.J.N gratefully acknowledge the NSF Graduate Research Fellowship Program under Grant Number 1122374. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. We also gratefully acknowledge support from the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. References (1) Aneke, M.; Wang, M. Energy Storage Technologies and Real Life Applications – A State of the Art Review. Applied Energy 2016, 179, 350–377. https://doi.org/10.1016/j.apenergy.2016.06.097.(2) Huang, Q.; Wang, Q. Next-Generation, High-Energy-Density Redox Flow Batteries. ChemPlusChem 2015, 80 (2), 312–322. https://doi.org/10.1002/cplu.201402099.(3) Huang, Q.; Li, H.; Grätzel, M.; Wang, Q. Reversible Chemical Delithiation/Lithiation of LiFePO 4 : Towards a Redox Flow Lithium-Ion Battery. Phys. Chem. Chem. Phys. 2013, 15 (6), 1793–1797. https://doi.org/10.1039/C2CP44466F.(4) Gupta, D.; Koenig, G. M. Analysis of Chemical and Electrochemical Lithiation/Delithiation of a Lithium-Ion Cathode Material. J. Electrochem. Soc. 2020, 167 (2), 020537. https://doi.org/10.1149/1945-7111/ab6bbf.

Surface-Modification of Doping and Coating Li1.2Ni0.2Co0.08Mn0.52O2 as a Long Life Cathode Material of Lithium-Ion Battery by Sodium Salt Treatment

Lithium-rich layered oxides are considered to be the most promising next-generation lithium-ion cathode materials due to their high specific capacity and energy density. However, its commercialization is limited due to its poor cycling stability and severe voltage decay. A NaH2PO4 molten salt treatment is designed, which simultaneously realizes Na+ doping and phosphate coating to improve the defects of lithium-rich materials. Sodium dihydrogen phosphate is of good contact with lithium-rich materials in the process of high temperature melting to facilitate surface sodium doping which is conducive to stabilizing the surface structure through lithium-sodium exchange. At the same time, the phosphate coating produced by lithium-sodium exchange and dehydration on the outer surface of the material can effectively inhibit the corrosion of the electrolyte. The modified material obtained by the synergistic effect of doping and coating has a capacity of 262.4 mAh·g−1 at 0.1 C and 169.6 mAh·g−1 at 5 C, the capacity retention rate of 73.6% after 500 cycles, and the voltage decay is significantly improved. A simple and effective method for improving the electrochemical performance of Li-rich layered materials is provided.

The influence of different drying methods on the properties of LiNi0.5Mn1.5O4 material

It was precisely because LiNi[Formula: see text]Mn[Formula: see text]O4 cathode material had many advantages, including high voltage, high power, no pollution, low cost, etc., that it became a research hotspot for lithium-ion cathode materials. Although LiNi[Formula: see text]Mn[Formula: see text]O4 has a three-dimensional Li[Formula: see text] diffusion channel, there are still some problems that lead to capacity decay and reduced cycling stability, limiting its commercial application. In this paper, the LiNi[Formula: see text]Mn[Formula: see text]O4 cathode material was prepared by the freezing precipitation method. We studied the effects of different drying methods, such as blast drying, water bath drying and freeze-drying on the structure, morphology and electrochemical properties of LiNi[Formula: see text]Mn[Formula: see text]O4 cathode materials. The study found that the LiNi[Formula: see text]Mn[Formula: see text]O4 cathode material prepared by the precipitation-freeze-drying method had a complete crystal form, a stable structure and no LixNi[Formula: see text]O impurity peak. The SEM image showed that the particles were smaller and had a smooth surface. The initial discharge-specific capacity at 0.1[Formula: see text]C was 105.2[Formula: see text]mAh⋅g[Formula: see text]. After 50 cycles, its specific discharge capacity was 99.4[Formula: see text]mAh⋅g[Formula: see text] and the capacity retention rate was 94.5%. Compared with LiNi[Formula: see text]Mn[Formula: see text]O4 materials prepared by other methods, it had better electrochemical performance.

Roll-to-roll solvent-free manufactured electrodes for fast-charging batteries

Roll-to-roll solvent-free manufactured electrodes for fast-charging batteries

Ultrathin V6O13 nanosheets assembled into 3D micro/nano structured flower-like microspheres for high-performance cathode materials of Li-ion batteries

Benefiting from its unique high theoretical capacity and energy density, V6O13 is considered an outstanding cathode candidate. Nevertheless, the lithium ions will form LixV6O13 when embedded in V6O13, resulting in volume expansion and crystal structure instability. For that reason, the construction of three-dimensional nanostructures is an awfully serviceable method to resolve the above problems. Herein, we adopt a green and convenient hydrothermal method to synthesize three-dimensional microsphere structure composed of nanoflakes, and flower-like V6O13 microspheres are synthesized by adjusting the concentration of nitric acid (HNO3). Meanwhile, the formation mechanism of flower-like V6O13 microspheres is investigated by controlling the hydrothermal reaction time and the concentration of HNO3. As a lithium-ion cathode material, flower-like V6O13 microspheres show an initial discharge specific capacity of up to 368.1 mAh/g at a current density of 0.1 A/g. There was still a discharge specific capacity of up to 313.1 mAh/g after 50 charge/discharge cycles, with a capacity retention rate of 85.1%. The flower-like V6O13 microsphere electrode also combines an excellent rate performance with a satisfactory cycling stability, which achieves a cycle retention rate of 80.2% even after 200 charge/discharge cycles, and an initial discharge specific capacity of 216.9 mA/g even at a high current density of 1 A/g. The results show that, benefitting from its large specific surface area and robust three-dimensional structure, the flower-like V6O13 microsphere electrode material exhibits excellent cycling performance, and the lithium-ion batteries which use it as the cathode material perform equally well in terms of high capacity and high rate.

Understanding the limits to short-range order suppression in many-component disordered rock salt lithium-ion cathode materials

Exploring suppression of short-range order in many-component Li-ion disordered rock salt cathodes, we discover capacity enhancement is tightly linked to excess Li and fluorine content, directing improved compositional design.

Development Status and Trend of Lithium Ion Cathode Materials

Driven by carbon peaking and carbon neutrality goals and market demand, China’s new energy vehicles have entered a stage of rapid development, which has led to significant changes in the industry of power battery cathode materials and its market pattern. This paper introduces the classification, advantages and disadvantages, and application scenarios of lithium ion cathode materials and focuses on the market status and industrial pattern of lithium iron phosphate cathode materials and ternary cathode materials before discussing the future industrial development trend.

Linking Thermal Runaway and Cycling Degradation of Lithium-Ion Batteries Using Multi-Scale X-Ray Imaging

To meet the increasing energy demands of portable devices and electric vehicles, high-nickel lithium-ion cathode materials with the general formula Li(NixMnyCoz)O2 (NMCXYZ) have been extensively researched. Currently, NMC811 is used commercially due to its high capacity and low cobalt content. However, capacity fade is still a prominent issue, with a variety of degradation mechanisms responsible. Of particular interest is secondary particle cracking, where the stress-strain effect of c-parameter expansion in the NMC crystal lattice leads to fractures. Boundaries between the primary particle grain that make up the secondary particle structure act as nucleation points for particle cracking. The exposed surface then reacts with the liquid electrolyte, leading to oxygen evolution and capacity loss. Single-crystal materials have shown promise as a method of improving cycle life, as the lack of agglomerated primary grains appear to make the monocrystalline particles more resilient to the mechanical strain of expansion during charging1.In parallel with the cycle life concerns, attention over battery safety continues to increase as instances of catastrophic battery failure are publicised across the world. While the specific steps that lead to battery thermal runaway have been extensively researched, the safety and thermal stability of degraded cells remains a scarcely investigated topic2. To that end, the goal of this work is to characterise the safety properties of different NMC morphologies, and study how charge-discharge cycling affects the thermal stability of these materials.In this work, we have combined accelerating rate calorimetry (ARC) with lab-based, post-mortem macro, micro and nano X-ray CT to observe the influence of cell structure on thermal runaway of NMC811 pouch cells with single-crystal and polycrystalline cathode materials in both the pristine and aged state. The results presented show that when pristine, the larger surface area of single-crystal materials provides more reaction sites and leads to a lower self-heating onset and thermal runaway initiation temperature compared to polycrystalline, suggesting a lower thermal stability. However, as polycrystalline particles break up during thermal runaway, the fragments create fresh surface to react with the electrolyte and continue the series of exothermic reactions, leading to a higher peak temperature. Macro-CT has revealed how the wound jellyroll structure of the cell focuses the force of the explosion through the flat sides of the cells, possibly increasing the likelihood of failure propagation. It has also been observed that the polycrystalline materials show a greater material ejection out from the centre of the cell, reinforcing the findings from the ARC investigations that although polycrystalline cells are more thermally stable initially, the peak temperatures produced during catastrophic failure are higher due to particle fracture. Micro and nano-CT are used to probe this idea further, revealing that polycrystalline particles show significant damage and fracturing during failure, whereas single-crystal materials remain largely intact.Both polycrystalline and single-crystal morphologies were cycled to 80% capacity retention, with EIS and diagnostic cycles used to identify prevalent degradation modes for both particle structures. As previously found, the single-crystal cells showed superior cycle life to the polycrystalline materials3. The same combination of ARC and X-ray CT was then applied to aged cells, where it was found that aged cells show lower thermal stability than their pristine counterparts.Overall, this work aims to build understanding of the interplay between material structure, safety and degradation of nickel-rich cathodes, with the goal of informing future material development to produce batteries that are safer throughout their lifetimes. G. Qian et al., Energy Storage Mater., 27, 140–149 (2020) https://doi.org/10.1016/j.ensm.2020.01.027.X. Feng et al., Energy Storage Mater., 10, 246–267 (2018) https://doi.org/10.1016/j.ensm.2017.05.013.D. Ren et al., eTransportation, 2, 100034 (2019) https://doi.org/10.1016/j.etran.2019.100034.

Anti-corrosion effect of insulating firebrick coated with CA6 in the calcination of lithium-ion cathode materials

The anti-corrosion properties of calcium hexaluminate (CA6) during the roasting of Li(NixCoyMnz)O2 (LNCM) materials have been investigated by means of specific experimental setups and test methods to verify its feasibility as an adiabatic insulation material for the roasting kiln of LNCM materials. Mullite insulating firebrick currently in industrial use was coated with CA6 (labelled M-CA6) and corrosion tests were carried out. The corrosion tests were carried out at different additions of corrosion sources, roasting temperatures, number of cycles of corrosion experiments. And the materials before and after corrosion characterized by the X-ray diffraction and scanning electron microscopy to determine the influence of different corrosion conditions on the interactions between M-CA6 and LNCM materials. In addition, The corrosion resistance of calcium CA6 and the feasibility of its application in practical industry was identified by characterising and comparing the high-temperature creep properties of the materials. The results of the laboratory scale experiments confirmed that M-CA6 was more resistant to LNCM than mullite insulating firebrick, and confirmed the feasibility and superiority of using CA6 as a lining insulation for LNCN kilns.

The Role of Gas Evolution in Particle Surface Cracking in Nickel-Rich Lithium-Ion Cathode Materials

Nickel-rich layered oxide cathode materials (LiNixTM(1-x)O2 where x > 0.8) are of great interest because they offer increased capacity compared to current commercial materials while maintaining compatibility with supply chain and production processes already in place. However, recent studies have shown that these materials in their current form are unsuitable for commercial applications due to the accelerated degradation caused by replacing more stable transition metals with the relatively unstable nickel. While various strategies have already been proposed to mitigate this issue, the fundamental degradation mechanism still needs to be better understood to inform the design of the next generation of nickel-rich cathode materials. In this work, differential electrochemical mass spectrometry (DEMS) is combined with titration mass spectrometry (TiMS) to measure gases evolved in a lithium half-cell during cycling as well as surface species which evolve gas upon addition of strong acid to an extracted cathode. Along with qualitative observations of particle cracking by scanning electron microscopy (SEM), these results reveal correlations between particle cracking, electrolyte reactivity, and carbonate oxidation and deposition on the changing cathode surface in nickel-rich cathode materials.

(Digital Presentation) Understanding the Impact of High-Nickel Cathode Microstructure on Battery Safety and Cycling Performance

To meet the increasing energy demands of portable devices and electric vehicles, high-nickel lithium-ion cathode materials with the general formula Li(NixMnyCoz)O2 (NMC) have been extensively researched. Currently NMC811 is used commercially for high-energy applications. The energy density of NMC also comes with concerns over cycle life and safety1,2. To improve the cycle life of NMC-based cells, single-crystal materials have recently gained attention to tackle the particle cracking issues found in polycrystalline cathodes3. However, for successful introduction to the lithium-ion battery market, inherent safety over a material’s lifetime also needs to be proven. Failure and degradation mechanisms both need to be fully understood to improve the stability of future cathode materials. Abusive testing, such as overheating, overcharge and nail penetration, has been used in conjunction with in-situ and ex-situ X-ray computed tomography (CT) 3D imaging to perform post-mortem studies and understand the relationship between thermal failure and cathode microstructure4,5. However, the interplay between safety characteristics, microstructural properties and material degradation remains unclear.This work first aims to compare the safety performance of polycrystalline and single-crystal NMC811 in 200 mAh pouch cells. Accelerating rate calorimetry (ARC) with a heat-wait-search (HWS) technique is used to heat cells and determine the onset of self-heating, onset of thermal runaway and the peak thermal runaway temperature. Laboratory-based pre- and post-mortem in-situ and ex-situ X-ray CT is also used for non-destructive imaging at multiple length scales to determine how failure propagates through the cells and the impacts on the electrodes and microstructure. Pouch cells containing polycrystalline and single-crystal NMC811 cathode and graphite anode are electrochemically cycled to induce material degradation. EIS measurements and diagnostic cycles are performed to identify prevalent degradation modes in both types of cathode materials. Finally, the same ARC and X-ray CT characterisations are performed on the aged cells to determine how degradation and changes to the material structure affect the safety performance in high-nickel cathode materials.The results of this work will improve the current understanding of capacity fade in high-nickel cathodes and the safety behaviour over the lifetime of a battery cell. This information can then be used to inform future materials development and strategies for mitigating thermal runaway in batteries. References L. Ma, M. Nie, J. Xia, and J. R. Dahn, J. Power Sources, 327, 145–150 (2016).H. J. Noh, S. Youn, C. S. Yoon, and Y. K. Sun, J. Power Sources, 233, 121–130 (2013).J. Langdon and A. Manthiram, Energy Storage Mater., 37, 143–160 (2021).D. Patel, J. B. Robinson, S. Ball, and D. J. L. Brett, (2020).D. P. Finegan et al., Phys. Chem. Chem. Phys., 18, 30912–30919 (2016).

Synthesis of high-density olivine LiFePO4 from paleozoic siderite FeCO3 and its electrochemical performance in lithium batteries

The lithium-ion cathode material olivine LiFePO4 (LFP) has been synthesized for the first time from natural paleozoic iron carbonate (FeCO3). The ferrous carbonate starting material consists of the mineral siderite at about 92 wt. % purity. Because FeCO3 has divalent iron, the reaction with lithium dihydrogen phosphate (LiH2PO4) provides a unique method to develop iron-(II) containing LFP in an inert atmosphere. Since siderite FeCO3 is a common mineral that can be directly mined, it may, therefore, provide an inexpensive route for the production of LFP. After carbon-coating, the LFP yields a capacity in the range of 80–110 mAh g−1LFP (in one chosen specimen sample), which is lower than commercially available LiFePO4 (150–160 mAh g−1LFP). However, the tap density of LFP derived from siderite is noticeably high at 1.65 g cm−3. The material is likely to be improved with powder purification, nanosized processing, and more complete carbon-coating coverage with increased optimization.

Improved rate performance of nanoscale cross-linked polyacrylonitrile-surface-modified LiNi0.8Co0.1Mn0.1O2 lithium-ion cathode material with ion and electron transmission channels.

LiNi0.8Co0.1Mn0.1O2 (NCM811) has attracted extensive attention due to its high energy density. Particularly, the Li-Ni mixing phenomenon and interfacial side reactions contribute to the rate and cycling performance of NCM811. Cross-linked polyacrylonitrile (cPAN) has certain electrical conductivity and is considered a competitive coating material. In this study, NCM811@cPAN was successfully prepared by wet chemical and heat treatments. The formation process of cPAN systematically analyzed by physical structure tests and microscopic morphological analysis demonstrates that cPAN existed on the surface of NCM811. The electrochemical results demonstrate that NCM811@cPAN has high initial coulombic efficiency (98.14% at 0.1C), good cycle stability and rate performance (222.30 mA h g-1 at 0.5C). The uniform and continuous nano cPAN coating helped avoid direct contact between NCM811 and the electrolyte, enhancing its interfacial stability. Moreover, cPAN exhibited certain electronic conductivity and generated a spinel structure, enhancing the diffusion rate of e- and Li+. Therefore, the electrochemical performance of NCM811 can be improved. This method and the coating material provide an effective strategy for the surface modification of other cathode materials used in Li-ion batteries.