In Situ Investigation of Phase Transitions of Li[sub 1+y]Mn[sub 2]O[sub 4] Spinel during Li-Ion Extraction and Insertion

Mat

2005

Ionics

Abstract. The demand for high power density and low cost material for lithium-ion battery is very high. Commercially available material, such as LiCoO2, has limited capacity and high cost; this has caused the exploration of alternative materials. In this paper, Mn doped into Li[NixC%_• 2 host structure was prepared by a mixed hydroxide technique. XRD results show that the synthesized powder has a higher degree of crystallinity with the separation between the (108) and (110) peaks being more obvious for Mn doped powder. The morphology of synthesized powder, determined by Field Effect Scanning Electron Microscope (FE-SEM), shows that both samples having multi-angle particle shapes. Energy Dispersive X-ray (EDAX) analysis shows that all the expected elements were present in the synthesized materials. Cyclic voltammogram (CV) of the investigated samples show that the onset of the Jahn-Teller effect was shifted to the higher voltage when the Li[Ni 0 ~Co02]02 was doped with Mn, and has improved the cycle performance.

Section: Resultssupporting

confidence: 91%

Physical and electrochemical properties of Li[NixCo1−x]O2 doped with manganese

Mat

2005

Ionics

“…In literature this has been ascribed to a phase transition comparable with that between LiMn 2 O 4 and Li 0.5 Mn 2 O 4 . 8 However, the observed phase transition is less pronounced as described by Sun et al 9 This can be related to aluminum doping. The ionic radius of Al 3+ (57 pm) is between that of Mn 3+ (70 pm) and Mn 4+ (52 pm).…”

Section: Resultsmentioning

confidence: 86%

Origin of the Synergetic Effects of LiFe_0.3Mn_0.7PO₄– Spinel Blends via Dynamic In Situ X-ray Diffraction Measurements

Klein

Axmann

Wohlfahrt‐Mehrens

2016

J. Electrochem. Soc.

The origin of the synergetic effects of LFMP/LMO blend electrodes via dynamic in situ XRD analysis during cycling is explained. Blend electrodes are prepared by adding LiFe 0.3 Mn 0.7 PO 4 (LFMP) and LiMn 1.9 Al 0.1 O 4 spinel (LMO) in order to obtain a composite which utilizes the high capacity of LFMP and the rate capability of the spinel. Positive synergetic effects are observed for the electrochemical performance at high rates (3C), even exceeding theoretical calculations. A combined in situ X-ray diffraction (XRD) -electrochemistry cell is developed and tested during galvanostatic cycling. Its functionality is demonstrated by reproducing ex situ measurements from literature. A calibration curve of the spinel phase has been established in order to correlate the lattice parameter a to its depth of discharge (DoD). By concentrating only on the spinel component structural changes in blend electrodes during pulse power discharge at the manganese redox plateau can be investigated. During relaxation (I = 0), after a pulse has been applied, a shift in the XRD pattern can be observed indicating the partial re-charge of the spinel component by the LFMP. Lithium-Ion Batteries have become a widespread technology for use in energy-consuming mobile and stationary applications. In order to fulfill increasing demands on the electrochemical performance of the batteries, new cathode materials are investigated and well known materials are further optimized. 1,2Olivine LFMP is a promising cathode material because of its high capacity and high energy density. [3][4][5] In addition, manganese and iron are inexpensive and environmentally benign elements.1,6 LFMP exhibits promising capacity retention at higher C-rates, however, a detailed view of the galvanostatic curves reveals a dramatic potential drop at the manganese redox plateau, which decreases the energy-and power density at higher rates. 7 Optimizing the electrode by blending LFMP with a material supplying faster kinetics in the 4 V region may be beneficial to overcome this issue.Recently we demonstrated that some characteristics of LFMP electrodes can be custom-tailored with the addition of spinel, in addition to positive synergetic effects observed in the electrode properties. 7 Different blend ratios have been studied in detail. While tap density and capacity show a linear relationship, depending on the ratio, remarkable synergetic effects of LFMP/LMO blend electrodes can be observed in terms of potential stability, pulse power behavior, power density at high states of charge and manganese dissolution, improving the electrochemical performance at higher C-rates.In this work, we provide insight on the origin of the observed synergetic effects of LFMP/spinel blend electrodes with a defined mixing ratio using a developed in situ XRD/electrochemistry measurement cell. ExperimentalPreparation.-The olivine LiFe 0.3 Mn 0.7 PO 4 (LFMP) provided by Johnson Matthey Battery Materials GmbH and a 1.5 wt% Al-doped spinel LiMn 1.9 Al 0.1 O 4 (LMO, pre-commercial material) were mixed ...

Electrochem. Solid-State Lett.

“…Although the two cubic phases formed at (1 Ϫ x) Ϸ 0.3-0.5 were clearly evident from the distinct and well separated reflections in the case of Li 1Ϫx Mn 2 O 4 , such a clear separation of reflections was not seen in the case of Li 1Ϫx Mn 2Ϫ2y Li y Ni y O 4 (0.05 р y р 0.1) samples; instead, the latter exhibited only broad peaks at (1 Ϫ x) Ϸ 0.3-0.5 due to very close lattice parameter values between the two cubic phases. 15 For example, the Li 1Ϫx Mn 1.9 Li 0.05 Ni 0.05 O 4 sample exhibits broad reflections at (1 Ϫ x) ϭ 0.31 ͑two-phase region͒ while the reflections are sharp enough to show the separation between the K␣ 1 and K␣ 2 peaks for other 1 Ϫ x values ͑single phase region͒ as seen in Fig. 5.…”

Section: Resultsmentioning

confidence: 93%

High Rate, Superior Capacity Retention LiMn[sub 2−2y]Li[sub y]Ni[sub y]O[sub 4] Spinel Cathodes for Lithium-Ion Batteries

Shin

Manthiram

2003

LiMn 2Ϫ2y Li y Ni y O 4 (0.05 р y р 0.1) cathodes synthesized by solid-state reactions at 800°C exhibit superior capacity retention and rate capability both at room temperature and 60°C compared to the LiMn 2 O 4 cathodes. For example, the y ϭ 0.05, 0.075, and 0.1 samples exhibit little capacity fades of, respectively, 3.2, 0.9, and 0.5% at room temperature and 7.4, 2.6, and 2.4% at 60°C in 50 cycles with initial capacities of around 90-115 mAh/g compared to around 40-50% fade for LiMn 2 O 4 . The y ϭ 0.075 and 0.1 samples retain 98% of their capacity on going from C/10 to 4C rate with excellent cycling performance at 4C rate as well. The superior performances of these cathodes are attributed to the smaller lattice parameter differences between the two cubic phases formed during the discharge/charge process. The low cost and environmentally benign nature of these cathodes coupled with the high rate capability may make them attractive for electric vehicles despite slightly lower capacity values.Lithium-ion batteries have become attractive power sources for portable electronic devices such as cellular phones and laptop computers. However, the high cost and toxicity associated with the currently used LiCoO 2 cathodes pose difficulties in employing them for electric vehicles ͑EVs͒. Development of inexpensive and environmentally benign cathode hosts is needed to successfully adopt the lithium-ion technology for EVs. Manganese oxides have become appealing in this regard, but the LiMn 2 O 4 spinel that has been investigated extensively over the years exhibits severe capacity fade particularly at elevated temperatures. Several capacity fading mechanisms such as Jahn-Teller distortion, 1,2 manganese dissolution into electrolyte, 3-5 formation of two cubic phases, 6 and loss of crystallinity during cycling 7,8 have been suggested to be the source of capacity fade.Substitution of other cations for manganese as well as modification of the preparation methods have been found to show improvement in the cyclability of LiMn 2 O 4 cathodes. 7-12 We showed recently that the cationic substitutions suppress the development of microstrain, which could originate from the differences in the lattice parameters between the two cubic phases formed in the 4 V region. 12 Utilizing this understanding, we present here the development of LiMn 2Ϫ2y Li y Ni y O 4 (0.05 р y р 0.1) cathodes that exhibit superior cyclability with high rate capability at both ambient and elevated temperatures, which are attractive for EV applications. Additionally, we present a correlation of the capacity fade to the lattice parameter differences between the two cubic phases. ExperimentalLiMn 2Ϫ2y Li y Ni y O 4 (0 р y р 0.1) samples were synthesized by firing required amounts of Li 2 CO 3 , Mn 2 O 3 , and NiO at 800°C for 48 h in air. Chemical extraction of lithium was carried out by stirring the LiMn 2Ϫ2y Li y Ni y O 4 powder with an acetonitrile solution of the oxidizing agent NO 2 BF 4 at room temperature for 2 days under argon atmosphere using a Schlenk line fol...