Stability and Rate Capability of Al Substituted Lithium-Rich High-Manganese Content Oxide Materials for Li-Ion Batteries

The effect of synthesis method and aluminum doping on layered lithium-manganese rich, mixed metal oxides is presented. Coprecipitation and sol-gel synthesized lithium-manganese rich composite materials revealed differences in capacity and cycle life, which appears from X-ray photoelectron spectra to be strongly related to the particles' surface reactivity. Small amounts of aluminum doping to the sol-gel material were shown to improve the rate capability and cyclability, in addition to decreasing voltage fade, as shown by differential capacity plots. The electrochemistry of an aluminum doped material was revealed to be highly dependent on the degree of aluminum doping -with the behavior of 1% doped material giving a maximum capacity of 201 mAh g −1 at 150 mAg −1 and a capacity retention of 88% after 200 cycles. The increasing energy consumption of modern societies has created a considerable demand for better approaches to not only the production and management of energy, but also its storage. Due to their high energy density and good specific energies lithium-ion batteries are attractive candidates for use in many applications such as portable devices, though there is considerable impetus for further improvement.One potentially attractive family of cathode materials are layered lithium-manganese rich, mixed metal oxides (LMR-MMO materials), of the form xLi 2 MnO 3 :(1-x)LiMO 2 (where 0 < x < 1, and M represents transition metals such as cobalt, manganese and/or nickel). Their high capacities (at low cycling rates in excess of 220 mAh g −1 at room temperature and 300 mAh g −1 at 60 • C) have generated considerable interest.1-6 However, there are still significant challenges to overcome -chiefly the material exhibits power loss due to voltage fade on cycling. 1,7,8 Furthermore, whilst properties such as capacity and cyclability are self-evidently of considerable importance, many applications require rapid access to stored energy and fast recharge times. Consequently, developing materials capable of operating at high rates is potentially quite significant.From previous studies it is clear that the electrochemical and physical properties vary depending on the material's constituent elements, stoichiometry and method of synthesis. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Given the importance of both the particle bulk and the surface to the behavior of these materials, 17,18 understanding in what way the synthetic route affects these properties is of considerable importance -particularly if careful choice and optimisation of synthetic route may mitigate voltage fade.Another possible approach to decreasing voltage fade and improving rate capability would be to dope the lithium-manganese rich material. While investigations into using chromium 19,20 and ruthenium 21 have been carried out, one potentially particularly attractive dopant is comparatively inexpensive aluminum. A computational study 22 has suggested that a small degree of aluminum doping should have a stabilizing effect on the structure, resulti...

Section: Resultssupporting

confidence: 80%

Characterization of Aluminum Doped Lithium-Manganese Rich Composites for Higher Rate Lithium-Ion Cathodes

Iftekhar

Drewett

Armstrong

et al. 2014

“…37 In a detailed theoretical study, Dianat et al studied the effect of Al doping on Li-Mn-Ni-O based cathode materials.…”

mentioning

confidence: 99%

Unraveling the Effects of Al Doping on the Electrochemical Properties of LiNi_0.5Co_0.2Mn_0.3O₂Using First Principles

Dixit

Markovsky

Aurbach

et al. 2017

130

108

One of the prevailing approaches to tune properties of materials is lattice doping with metal cations. Aluminum is a common choice, and numerous studies have demonstrated the ability of Al 3+ doping to stabilize different positive electrode materials, such as Li [Ni-Co-Mn] In recent decades, rechargeable batteries have demonstrated tremendous promise as alternate energy storage devices. In particular, Li-ion batteries (LIB) have revolutionized electronic devices, ranging from portable electronics to electric vehicles (EVs), due to their excellent power and energy density.1 The bottleneck of LIB in terms of capacity and performance is often considered to be the nature of the positive electrodes (cathodes).1-6 Among the cathode materials for LIB, layered transition metal (TM) oxides (LiTMO 2, TM = Ni, Co, Mn) are very promising candidates, and in particular LiCoO 2 . However, in spite of the commercialization and wide use of LiCoO 2 in portable LIB, it suffers from several drawbacks. Key disadvantages include high cost and safety concerns associated with cobalt.2-6 Other limitations of LiCoO 2 include low practical capacity (140 mAhg −1 ) and oxygen loss on charge. 7-10 Consequently, in a quest to move beyond LiCoO 2 , a new class of mixed transition metal oxides were designed, wherein Ni and Mn were introduced into the material (i.e. Li[Ni x Co y Mn z ]O 2 or simply NCM).11,12 The Ni-rich variants of these materials have emerged as the most promising low-cost and high capacity alternatives to the already mature LiCoO 2 . 10,13,14,11 These Nirich materials show improved performance; however, the capacities and stabilities are still too low for practical commercialization for EVs. 12Key hurdles in the commercialization of these materials for EV applications are associated with oxygen release at high voltages and cation migration, which leads to structural transformations. 15,16 Recently, it has been demonstrated that oxygen loss and cation migration are concurrent events. 16,17 To address these challenges, lattice doping of cations 18 has been adopted to improve the performance of these materials, and various cations were explored.18-24 A particularly promising dopant for these materials is Al, although its effect is still not fully understood. Early theoretical studies proposed that Al substitution in LiCoO 2 25 and NCMs 26 could increase the intercalation potential, and these predictions were verified experimentally. 27 Various studies reported beneficial effects of Al doping on LiCoO 2 and LiNiO 2 and NCMs. ), and found that Al doping reduces the reversible capacity, but significantly improves the thermal stability of the electrode in the de-intercalated state.36 Al doping in Li-rich-Mn-rich NCMs has also improved the thermal stabilities of these materials. 37 In a detailed theoretical study, Dianat et al. studied the effect of Al doping on Li-Mn-Ni-O based cathode materials.38 They reported that Al doping stabilizes the partially intercalated states, but increases the Li-diffusion barriers. Park et al. studie...

“…8,9 Referring to the reports by the Thackeray group, OLO material properties such as particle size, morphology control, compositional control by cationic substitution, and surface modification of parent OLO materials have been investigated to improve electrochemical properties. [10][11][12][13][14][15][16] Among the various researches published, investigations of surface modification mostly aim to decrease the initial irreversible capacity at initial cycles and suppress the side reaction between the cathode and electrolyte. Most materials for surface modification can be categorized into three groups: inorganic oxides, carbonbased materials, and polymer-based materials.…”

mentioning

confidence: 99%

Surface Modification of Over-Lithiated Layered Oxides with PEDOT:PSS Conducting Polymer in Lithium-Ion Batteries

Lee

Choi

2015

Over-lithiated layered oxide (OLO) materials were coated with a PEDOT:PSS conducting polymer via a simple wet-coating method. The prepared samples were observed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The electrochemical properties of the samples were determined by galvanostatic testing and electrochemical impedance spectroscopy (EIS). PEDOT:PSS coated cathode materials showed better rate capability and cyclability between 2.0 V and 4.6 V. X-ray photoelectron spectroscopy (XPS) data imply that the improved electrochemical performance of coated OLO is due to the suppression of the formation and growth of the solid electrolyte interface. 1-7 Among the many candidates, over-lithiated layered oxide (OLO), reported by the Thackeray group in 2005, exhibits a higher capacity (>200 mAh/g) and can reduce the use of expensive cobalt. Therefore, OLO is receiving attention as a cathode material for lithium-ion batteries (LIBs). 8,9 However, OLO experiences an inevitable oxygen loss and, subsequently, an irreversible capacity during the initial charge and discharge process. Additionally, the layered structure of OLO transforms into the spinel phase on cycling. The Li 2 MnO 3 phase in OLO materials exhibits a relatively low electronic conductivity owing to the insulating characteristics of the Li 2 MnO 3 component. 8,9 Referring to the reports by the Thackeray group, OLO material properties such as particle size, morphology control, compositional control by cationic substitution, and surface modification of parent OLO materials have been investigated to improve electrochemical properties. [10][11][12][13][14][15][16] Among the various researches published, investigations of surface modification mostly aim to decrease the initial irreversible capacity at initial cycles and suppress the side reaction between the cathode and electrolyte. Most materials for surface modification can be categorized into three groups: inorganic oxides, carbonbased materials, and polymer-based materials. The inorganic materials, which include AlF 3 , AlPO 4 , CoPO 4 , TiO 2 , V 2 O 5 , Al 2 O 3 , MnO 2 , ZnO, ZrO, MgO, Sm 2 O 3 , Li-Mn-PO 4 , and Li-Ni-PO 4 , are known to decrease the irreversible capacity and improve the electrochemical performances of OLO materials owing to the enforcement of stability on the surface in the high-voltage region. 17-31The carbon materials, including graphene-based materials, are employed to improve the electronic conductivity of OLO cathode materials.19,32-34 Also, surface modification by conducting polymers, such as polypyrrole, has been recently reported to provide improved electronic conductivity as well as a thin protective layer on OLO cathode materials. 35 Among various conducting polymers, thin film Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT: PSS) is known to exhibit superior electronic conductivity.36 Also, * Electrochemical Society Active Member. z E-mail: wonchangchoi@kist.r...