Spinel Cathode Research Articles

Enhanced electrochemical performance of MoO3-coated LiMn2O4 cathode for rechargeable lithium-ion batteries

LiMn2O4 (LMO) spinel cathode materials are modified with MoO3 coating synthesized using a simple wet chemical method. The surface modified samples show much better capacity retention than pristine LMO. In specially, 3 wt% MoO3 coated sample (LMO/M3) exhibit superior rate specific capacity with 110, 90 and 75 mAhg−1 at 5, 7 and 10 C, respectively. In addition, after 900 cycles at a current of 2 C, a capacity retention of 69.1% was achieved for LMO/M3, which is higher than the 39.6% for the pristine LMO. The enhancements of the electrochemical performance can be largely attributed to the stabilization of the cathode structure by suppressing the manganese dissolution in the electrolyte and in favor for Li+ ion diffusion after MoO3 coating.

A SiOx‐Based Anode in a High‐Voltage Lithium‐Ion Battery

AbstractA novel synthetic procedure for the preparation of a SiOx‐based nanocomposite, involving gelification of resorcinol‐formaldehyde and tetraethyl orthosilicate, is reported. The composite is characterized as an anode material in a lithium‐ion battery. The micrometric, amorphous material has a characteristic nanostructured configuration and shows an electrochemical process involving both the alloying of Li−Si and the insertion of Li into the hard carbon matrix. The electrode reveals in a lithium half‐cell a relatively low impedance and a reversible capacity ranging from 650 mAh g−1, at the lower current, to 400 mAh g−1 at high current regimes, with a cycle life extending to 200 cycles. The anode is combined with a high‐voltage LiNi0.5Mn1.5O4 spinel cathode in a 4.3 V lithium‐ion battery delivering a capacity of about 115 mAh g−1 and operating at the high rate of 5C. The suitable synthesis pathway, the low cost and the promising electrochemical behavior suggest the nanocomposite anode for application in high‐performance lithium‐ion battery.

Low-Temperature Carbon Coating of Nanosized Li1.015Al0.06Mn1.925O4 and High-Density Electrode for High-Power Li-Ion Batteries.

Despite their good intrinsic rate capability, nanosized spinel cathode materials cannot fulfill the requirement of high electrode density and volumetric energy density. Standard carbon coating cannot be applied on spinel materials due to the formation of oxygen defects during the high-temperature annealing process. To overcome these problems, here we present a composite material consisting of agglomerated nanosized primary particles and well-dispersed acid-treated Super P carbon black powders, processed below 300 °C. In this structure, primary particles provide fast lithium ion diffusion in solid state due to nanosized diffusion distance. Furthermore, uniformly dispersed acid-treated Super P (ASP) in secondary particle facilitates lower charge transfer resistance and better percolation of electron. The ASPLMO material shows superior rate capability, delivering 101 mAh g-1 at 300 C-rate at 24 °C, and 75 mAh g-1 at 100 C-rate at -10 °C. Even after 5000 cycles, 86 mAh g-1 can be achieved at 30 C-rate at 24 °C, demonstrating very competitive full-cell performance.

Preparation of High Performance LiNi0.5Mn1.5O4 Materials and Metal Doping

Preparation of High Performance LiNi0.5Mn1.5O4 Materials and Metal Doping Tao Zhanga, b, Jing Maoa, b , *, Kehua Daid, c, Yuchun Zhaid, Guosheng Shaoa, b, Ruimin Qiaoe, Wanli Yange, Gao Liuc,* aSchool of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002, China bInternational Joint Research Laboratory for Low-Carbon & Environmental Materials of Henan Province, Zhengzhou University, Zhengzhou 450002, China cEnergy Storage and Distributed Resource Division, Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA dSchool of Materials and Metallurgy, Northeastern University, Shenyang 110004, China eAdvanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA * Corresponding author. Email: Maojing@zzu.edu.cn The LiMn1.5Ni0.5O4 (LNMO) with spinel structure is a promising cathode material candidate for next generation lithium-ion batteries for EV, HEV, energy storage, etc., for its high working voltage of ~4.7 V and capacity of ~130 mAh g−1 1-7. A PVP (polyvinylpyrrolidone)-assisted gel combustion method developed by our group is used to synthesize LiNi0.5Mn1.5O4 materials with high rate and cycling performance. The as-prepared LiNi0.5Mn1.5O4 delivered 132.9 mAh g−1, 130.2 mAh g−1, 128.1 mAh g−1 and 124.5 mAh g−1 at rates of 1 C, 5 C, 10 C and 15 C, respectively, and demonstrated excellent capacity retentions of 97.3% after 200 cycles with 1 C rate at room temperature. To further improve the performance, Cr-doped, Nb-doped and Co-doped LNMO are synthesized with same method. Cr-doping and light Nb-doping (LiNb0.02Ni0.49Mn1.49O4) improve the rate performance of LNMO. The Li+ chemical diffusion coefficient at different SOC suggests both Cr and light Nb doping fasten Li+ diffusion in LNMO particles. The impedance spectras show both R SEI and R ct are reduced by Cr and light Nb doping. The cycling performance is improved by Cr or Nb doping, and Cr-doping increases both coulombic efficiency and energy efficiency of LNMO at 1C cycling. The LiCr0.1Ni0.45Mn1.45O4 remains 94.1% capacity after 500 cycles at 1C, during the cycling the coulombic efficiency and energy efficiency keeps over 99.7% and 97.5%, respectively. The LiCo0.1Ni0.45Mn1.45O4 has much better rate capability while its specific capacity at C/5 is 10% lower than that of LNMO. At 15C rate, their specific capacities are closed, and the LiCo0.1Ni0.45Mn1.45O4 delivers 86.2% capacity relative to C/5, and this value for LNMO is only 77.0%. The D Li+ values of LiCo0.1Ni0.45Mn1.45O4 are 1~2 times higher than that of LNMO in most SOC region. The LiCo0.1Ni0.45Mn1.45O4 shows very excellent cycling performance, which is the best value compared with literatures. After 1000 cycles, the LiCo0.1Ni0.45Mn1.45O4 still delivers 94.1% capacity. Moreover, its coulombic efficiency and energy efficiency keep at 99.84% and over 97.3% during 1C cycling, respectively. [1] Manthiram, A.; Chemelewski, K.; Lee, E.-S., A Perspective on the High-Voltage LiMn1.5Ni0.5O4 Spinel Cathode for Lithium-Ion Batteries. Energy Environ. Sci. 2014, 7 (4), 1339-1350. [2] Hassoun, J.; Lee, K.-S.; Sun, Y.-K.; Scrosati, B., An Advanced Lithium Ion Battery Based on High Performance Electrode Materials. J. Am. Chem. Soc. 2011, 133 (9), 3139-3143. [3] Santhanam, R.; Rambabu, B., Research Progress in High Voltage Spinel LiNi0.5Mn1.5O4 Material. J. Power Sources 2010, 195 (17), 5442-5451. [4] Hu, M.; Pang, X.; Zhou, Z., Recent Progress in High-Voltage Lithium Ion Batteries. J. Power Sources 2013, 237, 229-242. [5] Kim, J. H.; Pieczonka, N. P.; Yang, L., Challenges and Approaches for High-Voltage Spinel Lithium-Ion Batteries. Chemphyschem 2014, 15 (10), 1940-1954. [6] Amine, K.; Tukamoto, H.; Yasuda, H.; Fujita, Y., Preparation and Electrochemical Investigation of LiMn2-xMexO4 (Me: Ni, Fe, and x = 0.5, 1) Cathode Materials for Secondary Lithium Batteries. J. Power Sources 1997, 68 (2), 604-608. [7] Zhong, Q. M.; Bonakdarpour, A.; Zhang, M. J.; Gao, Y.; Dahn, J. R., Synthesis and Electrochemistry of LiNixMn2-xO4. J. Electrochem. Soc. 1997, 144 (1), 205-213.

Comparative Studies on Interfacial Kinetics of Ordered and Disordered Spinel LiNi0.5Mn1.5O4

The charge-discharge behavior of LiNi0.5Mn1.5O4, having both the ordered and disordered spinel structures, had been investigated by several research groups [1–5]. However, there are discrepancies with regard to the suitability of the disordered or ordered spinel for better battery performance [3–5]. It is also not clearly understood whether the rate performance of the material is limited by bulk transport properties or interfacial charge transfer reaction kinetics. The purpose of the present work is to elucidate the role of the electrochemical charge transfer kinetics at the electrode/electrolyte interface of Li1-xNi0.5Mn1.5O4 in determining the rate performance of the spinel cathode. The measurements have been carried out on additive free sintered dense plate in order to exclude any extrinsic effect. The exchange current density at the electrode/electrolyte interface is found to be continuously increased with increasing the degree of delithiation for ordered phase (~0.21-6.5mA/cm2) at (x=0.01-0.60), in contrast the disordered phase exhibits gradually decrease of exchange current density in the initial delithiation at the 4V plateau regime (x=0.01-0.04) and again monotonously increases (0.65-6.8mA/cm2) with further delithiation at (x=0.04-0.60). The ionic diffusivity of ordered and disordered phase is found to be ~5x10-10cm2s-1 and ~10-9cm2s-1, respectively, and does not vary much with the degree of delithiation. From the obtained results it appears that the chemical diffusivity during electrochemical use is limited by lithium transport, but is fast enough over the entire state-of-charge range to allow charge/discharge of micron-scale particles at practical C-rates. References K. Amine, H. Tukamoto, H. Yasuda and Y. Fujita, J. Electrochem. Soc., 143, 1607 (1996).Q. M. Zhong, A. Bonakdarpour, M. J. Zhang, Y. Gao and J. R. Dahn, J. Electrochem. Soc., 144, 205 (1997).H. F. Xiang, X. Zhang, Q. Y.Jin, C. P. Zhang, C. H. Chen and X. W. Ge, J. Power Sources, 183, 355 (2008).H. M. Wu, I. Belharouak, H. Deng, A. Abouimrane, Y. K. Sun and K. Amine, J. Electrochem. Soc., 156, A1047 (2009).J. Hassoun, S. Panero, P. Reale and B. Scrosati, Adv. Mater., 21, 4807 (2009).

Effect of Fluoroethylene Carbonate in the Electrolyte for LiNi0.5Mn1.5O4 Cathode in Lithium-ion Batteries

Fluoroethylene carbonate (FEC) was studied as an additive for the electrolyte in lithium ion batteries with the LiNi0.5Mn1.5O4 (LNMO) spinel cathode operating at a high potential beyond 4.7 V (vs. Li/Li+). It was found that the FEC additive was electrochemically active for the 1st charge cycle on the LNMO cathode. The presence of a large amount of FEC (more than 40 vol%) in the electrolyte caused severe side reactions with abnormally long voltage plateaus. In contrast, when the electrolyte contained less than 30 vol% FEC , the surface of the LNMO cathode was stabilized by the formation of the solid-electrolyte interphase (SEI), leading to improved cyclability. However, the resistance from the SEI limited the rate capability because of sluggish lithium transportation through the SEI and electronic insulation between the particles in the electrode. Keywords: LNMO, Electrolyte, High potential electrode, FEC

Part I: Electronic and ionic transport properties of the ordered and disordered LiNi0.5Mn1.5O4 spinel cathode

Abstract Here, we report on the electronic and ionic conductivity and diffusivity of the ordered (P4332) and disordered ( F d 3 ¯ m ) LiNi0.5Mn1.5O4 spinel material, which have been determined by using ion and electron blocking cell configurations as a function of lithium concentration and temperature. The disordered phase exhibits about fifteen-time higher electronic conductivity than the ordered phase at room temperature in the lithiated state. Upon delithiation, the electronic conductivity of the ordered LiNi0.5Mn1.5O4 phase increases and reaches the same levels observed for the disordered phase. The ionic conductivity and diffusivity of LiNi0.5Mn1.5O4, in the ordered and disordered forms, are in the range of ∼1 × 10−9 S/cm and ∼5 × 10−9 cm2/s, respectively. Both phases exhibit similar activation energies for the ionic conductivity and diffusivity, i.e. 0.70 ± 0.2eV and 0.74 ± 0.2eV, respectively. It can be concluded from the obtained results that the electrochemical performance of LiNi0.5Mn1.5O4, whether ordered or disordered, is limited by lithium transport, but is fast enough to allow charge/discharge of micron-scale particles at practical C-rates.

Comprehensive Enhancement of Nanostructured Lithium-Ion Battery Cathode Materials via Conformal Graphene Dispersion.

Efficient energy storage systems based on lithium-ion batteries represent a critical technology across many sectors including consumer electronics, electrified transportation, and a smart grid accommodating intermittent renewable energy sources. Nanostructured electrode materials present compelling opportunities for high-performance lithium-ion batteries, but inherent problems related to the high surface area to volume ratios at the nanometer-scale have impeded their adoption for commercial applications. Here, we demonstrate a materials and processing platform that realizes high-performance nanostructured lithium manganese oxide (nano-LMO) spinel cathodes with conformal graphene coatings as a conductive additive. The resulting nanostructured composite cathodes concurrently resolve multiple problems that have plagued nanoparticle-based lithium-ion battery electrodes including low packing density, high additive content, and poor cycling stability. Moreover, this strategy enhances the intrinsic advantages of nano-LMO, resulting in extraordinary rate capability and low temperature performance. With 75% capacity retention at a 20C cycling rate at room temperature and nearly full capacity retention at -20 °C, this work advances lithium-ion battery technology into unprecedented regimes of operation.

A New CuO-Fe2 O3 -Mesocarbon Microbeads Conversion Anode in a High-Performance Lithium-Ion Battery with a Li1.35 Ni0.48 Fe0.1 Mn1.72 O4 Spinel Cathode.

A ternary CuO-Fe2 O3 -mesocarbon microbeads (MCMB) conversion anode was characterized and combined with a high-voltage Li1.35 Ni0.48 Fe0.1 Mn1.72 O4 spinel cathode in a lithium-ion battery of relevant performance in terms of cycling stability and rate capability. The CuO-Fe2 O3 -MCMB composite was prepared by using high-energy milling, a low-cost pathway that leads to a crystalline structure and homogeneous submicrometrical morphology as revealed by XRD and electron microscopy. The anode reversibly exchanges lithium ions through the conversion reactions of CuO and Fe2 O3 and by insertion into the MCMB carbon. Electrochemical tests, including impedance spectroscopy, revealed a conductive electrode/electrolyte interface that enabled the anode to achieve a reversible capacity value higher than 500 mAh g-1 when cycled at a current of 120 mA g-1 . The remarkable stability of the CuO-Fe2 O3 -MCMB electrode and the suitable characteristics in terms of delivered capacity and voltage-profile retention allowed its use in an efficient full lithium-ion cell with a high-voltage Li1.35 Ni0.48 Fe0.1 Mn1.72 O4 cathode. The cell had a working voltage of 3.6 V and delivered a capacity of 110 mAh gcathode-1 with a Coulombic efficiency above 99 % after 100 cycles at 148 mA gcathode-1 . This relevant performances, rarely achieved by lithium-ion systems that use the conversion reaction, are the result of an excellent cell balance in terms of negative-to-positive ratio, favored by the anode composition and electrochemical features.

High Power Lithium-ion Battery based on Spinel Cathode and Hard Carbon Anode

Power performance of lithium-ion batteries (LIBs) is generally controlled by the Li+ diffusion within crystalline framework of electrode materials, and thus nano-sized electrode materials with shortened diffusion length have been widely used to build high power LIBs. However, the undesired effects from nano-sized electrode materials, such as low tap density, low thermal stability and increased interface also discount the overall performance of LIBs. Accordingly, it is desired to develop high power LIBs with micro-sized electrode materials. Herein, we demonstrate that hard carbon displays fast Li-storage kinetics which is not controlled by Li+ diffusion in the crystalline framework. Furthermore, it is found that micro-sized spinel LiNi0.5Mn1.5O4 and LiMn2O4 have high rate performance, owing to their three-dimensional channels for Li+ diffusion. Finally, the micro-sized spinel LiNi0.5Mn1.5O4 (or Li1.1Mn2O4) and micro-sized hard carbon are used as cathode and anode, respectively, to fabricate the full cells that exhibit supercapacitor-like high power performance. The achieved results point a way to develop high power LIBs besides nano-sizing electrode materials.

A nano-LiNbO3 coating layer and diffusion-induced surface control towards high-performance 5 V spinel cathodes for rechargeable batteries

The surface of a spinel LiNi0.5Mn1.5O4 cathode was modified with a nano-LiNbO3 coating layer by employing a Nb citrate-coated Ni0.25Mn0.75(OH)2 precursor and subsequent single calcination with LiOH at 900 °C.

Power characteristics of spinel cathodes correlated with elastic softness and phase transformation for high-power lithium-ion batteries

We present the phase transformation kinetics associated with mechanical deformations and electrochemical properties of LiNi0.5Mn1.5O4 (LNMO) and LiNi0.5Mn1.5−xTixO4 (LNMTO) that elucidate the correlation between power characteristics, mechanical deformations, and phase transformations.

Preliminary study of dysprosium doped LiMn2O4 spinel cathode materials

In current research work, we are presenting dysprosium (Dy) doped spinel cathode materials LiMn2-xDyxO4 (x=0.0, 0.01, 0.02, 0.03) and it’s applications as cathode materials in lithium ion rechargeable batteries (LIRB) using a simple and sober sol-gel process. New materials were characterized using x-ray diffractometer and scanning electron microscope (SEM) which informed about the spinel phase purity and small grain size (∼1µm) compared to pristine LiMn2O4. The elementary electrochemical characterizations revealed that reversible and fast diffusion of Li+ ions have improved reversibility and initial specific capacity 124.18 and 124.68 mAhg-1 for Dy01 and Dy02 respectively which 103% of 120 mAhg-1 specific capacity LiMn2O4 at C/10 rate. The AC impedance spectra showed that the reduction in overall impedance via Dy doping in LiMn2O4. The galvenostatic charge-discharge study revealed the improved rate performance of doped LMO-Dy02 cathode.

Kinetic Study of High Voltage Spinel Cathode Material in a Wide Temperature Range for Lithium Ion Battery

This study represents the electrochemical performance and lithium transportation behaviors of spinel LiNi0.5Mn1.5O4 cathode operated in a wide range of temperatures from −20 to 60°C. The correlative lithium diffusion coefficients are derived via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques, respectively. Based on the modeling of EIS, the lithium diffusivity of LiNi0.5Mn1.5O4 is estimated in the range of 10−11 around 25°C. The specific capacity of LiNi0.5Mn1.5O4 cathode is highly associated with the change of Li-ion mobility, which reveals a distinctive trend with applied temperatures. A strong correlation is also found between the apparent activation energy and lithium diffusivity. The change of activation energy is a key factor in dominating the kinetic reaction of Li/LiNi0.5Mn1.5O4 cells. Furthermore, the voltage polarization recorded from CV profile also perfectly follows the lithium transportation scenario. This study elaborates a profound discussion for temperature effects on electrochemical properties of LiNi0.5Mn1.5O4 cathode material.

Effects of excess Li on the structure and electrochemical performance of Li1+zMnTiO4+δ cathode for Li-ion batteries

Spinel-based LiMn2O4 is the most attractive cathode for Li-ion battery due to high voltage, low cost, and non-toxicity. The cycle life of the spinel cathodes could be improved by replacing Mn4+ with Ti4+ leading to the formation of new spinel cathode, LiMnTiO4. However, its application is restricted due to the associated loss in the specific capacity. In this work, spinel-layered Li1+zMnTiO4+δ (z=0, 0.5, and 1.0; δ is the value to reflect the composite character of the material) cathodes were fabricated to achieve long cycle life, without compromising on the specific capacity. Cathodes with excess Li (z=0.5 and 1.0) formed a spinel-layered composite structure with notation (1-a)LiMn2-xTixO4.aLi2MnyTi1-yO3 [y=0.5–((1/a−1)(1−x))]. These cathodes exhibited an enhanced specific capacity of ∼218mAhg−1 (20% higher), with a capacity retention of 94% after 60 cycles. The structural and electrochemical properties of these cathodes were investigated using X-ray diffraction, galvanostatic cycling, cyclic voltammetry, and the galvanostatic intermittent titration technique to understand the mechanisms underlying the enhanced capacity and cycle stability. The effect of the Li-rich layered phase on the electrochemical performance of the Li1+zMnTiO4+δ cathodes was also investigated.

High-rate and long-life performance of a truncated spinel cathode material with off-stoichiometric composition at elevated temperature

A truncated octahedral structure spinel cathode material with a nominal composition of Li1.08Al0.08Mn1.85Co0.05O3.9F0.1 (LAMCOF) and an Al-rich surface layer is successfully prepared by a sol-gel route combined with a temperature-controlled heat-treatment process. Concentration gradient of Mn4+ ions is found to decrease through the surface to the interior of the as-prepared sample. As the consequence, the LAMCOF sample delivers high rate capability and excellent cycling stability at elevated temperature, showing an initial discharge capacity of 111.1mAhg−1 and capacity retention of 70.5% over 850 cycles at 1C rate under 55°C. Even at 5C rate under 55°C, it also displays a high capacity of 102.5mAhg−1 with capacity retention of 80.0% over 850 cycles. These results reveal the importance of an off-stoichiometric strategy and a temperature-controlled heat-treatment process for the preparation of LiMn2O4-based spinel cathode material with unique crystal orientation and Mn4+-rich surface layer, which both decrease the Mn dissolution and provide interfacial stability while preserving fast Li+ diffusion, resulting in improvement of cycle performance and rate capability of the as-prepared material. This proposed synthesis method does not need a supplementary coating process and is likely suitable to prepare other high performance cathode materials.

An investigation into the temperature phase transitions of synthesized materials with Al- and Mg-doped lithium manganese oxide spinels by in situ powder X-ray diffraction

Three spinel materials were prepared and characterized by in situ powder X-ray diffraction (PXRD) techniques to track their phase changes that occurred in the typical batch synthesis process from a sol–gel mixture to the final crystalline spinel oxide. The materials were also characterized by thermal gravimetric analysis, whereby the materials decomposition mechanisms that were observed as the precursor, was gradually heated to the final oxide. The results showed that all the materials achieved their total weight loss at about 400 °C. The in situ PXRD analysis showed the progression of the phase transitions where certain of the materials changed from a crystalline precursor to an amorphous intermediate phase and finally to the spinel cathode oxide (Li1.03Mg0.2Mn1.77O4). For other materials, the precursor would start as an amorphous phase and upon heating, convert into an impure intermediate phase (Mn2O3) before forming the final spinel oxide (Li1.03Mn1.97O4). On the other hand, the LiAl0.4Mn1.6O4 would start with an amorphous precursor, with no intermediate phases and immediately formed the final spinel oxide phase. The in situ PXRD study also showed the increases in the materials respective lattice parameters of the crystalline unit cells upon heating and the significant increases in their crystallite sizes when heated above 600 °C.

Amorphous Lithium Lanthanum Titanate for Solid-State Microbatteries

Lithium lanthanum titanate (LLTO) is a promising solid state electrolyte for solid state batteries due to its demonstrated high bulk ionic conductivity. However, crystalline LLTO has a relatively low grain boundary conductivity, limiting the overall material conductivity. In this work, we investigate amorphous LLTO (a-LLTO) thin films grown by pulsed laser deposition (PLD). By controlling the background pressure and temperature we are able to optimize the ionic conductivity to 3 × 10−4 S/cm and electronic conductivity to 5 × 10−11 S/cm. XRD, TEM, and STEM/EELS analysis confirm that the films are amorphous and indicate that oxygen background gas is necessary during the PLD process to decrease the oxygen vacancy concentration, decreasing the electrical conductivity. Amorphous LLTO is deposited onto high voltage LiNi0.5Mn1.5O4 (LNMO) spinel cathode thin films and cycled up to 4.8 V vs. Li showing excellent capacity retention. These results demonstrate that a-LLTO has the potential to be integrated into high voltage thin film batteries.

Preparation of Water-Resistant Surface Coated High-Voltage LiNi0.5Mn1.5O4 Cathode and Its Cathode Performance to Apply a Water-Based Hybrid Polymer Binder to Li-Ion Batteries

Water-resistant LiNi0.5Mn1.5O2 spinel cathode was prepared by surface coating with carbon, Al2O3 and Nb2O5 to use a water-based hybrid polymer (TRD202A, JSR, Japan) as a binder and to form the cathode film on an Al current collector. The surface composition and degree of the surface coverage of carbon, Al2O3 and Nb2O5 were characterized with field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The coated LiNi0.5Mn1.5O2 particles not only exhibited water-resistant property but also showed no decrease in discharge capacity and only a small degradation of discharge rate performance. In addition, the coated LiNi0.5Mn1.5O2 particles, that were exposed to water-based binder solution for one week, exhibited the same charge/discharge cycle performance as observed for the cathode of the pristine LiNi0.5Mn1.5O4 particles, suggesting that the coated particles are promising as cathode materials with a water-resistant property and therefore water can be used as solvent for preparing the cathode slurry solution in the place of e.g., carcinogenic N-methyl-2-pyrrolidone which is used actually.

Review—Manganese Dissolution from Spinel Cathode: Few Unanswered Questions

The choice of cathode material critically influences the performance, cost and energy density in a Li ion battery. LiMn2O4 (LMO) cathode is an attractive cathode material because of its high rate capability, low cost, safety and non-toxicity. However, low cycle life or capacity fading with cycling is a big hurdle in the practical application of LMO cathodes. The dominant cause of the capacity fading, Mn dissolution from LMO, is still a challenge to overcome. In this review, we attempt to emphasize the loopholes in the understanding related to the Mn dissolution phenomenon in LMO cathodes in the presence of both aqueous and non-aqueous electrolytes. The underlying mechanism behind the dissolution process is often explained with the help of ionic charge disproportionation argument. Nevertheless, there are experimental and theoretical evidence in the literature to counter the simplistic view of dissolution due to charge disproportionation. Moreover, the correlation between the metal dissolution and the capacity fading is not causally established yet in the literature which hinders the formulation for a systematic strategy to prevent the capacity loss. In the current article we discuss all the relevant investigations related to the understanding of the cause, effect and prevention strategies of Mn-dissolution. We attempt to point out the gaps and contradictions in the literature and motivate further targeted studies in this seminally important material for better Li-ion batteries having higher rate capability and capacity retention.