Synthesis of High-Voltage (4.5 V) Cycling Doped LiCoO<sub>2</sub> for Use in Lithium Rechargeable Cells

Zou, Meijing; Yoshio, Masaki; Gopukumar, S.; Yamaki, Jun‐ichi

doi:10.1021/cm0347032

Cited by 125 publications

(73 citation statements)

References 13 publications

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“…Although the conventional layered cathode such as LiCoO 2 , LiNiO 2 , and LiNi 1/3 Co 1/3 Mn 1/3 O 2 have a theoretical capacity of more than 250 mAh g −1 , they cannot retain their layered structure after deep charging/discharging, owing to the excessive participation of oxygen redox. [4][5][6][7] To obtain high capacity cathode with good cycles, numerous researchers have emphasized the importance of developing wileyonlinelibrary.com © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ruthenium ions have little possibility of hopping to lithium layer as observed in the previous work, [ 13,14 ] providing a stable environment to study. Li 2 RuO 3 powders were prepared by a simple solid-state reaction involving the sintering of a uniform mixture of RuO 2 Although its theoretical capacity, estimated through the redox reaction of Ru 4+ /Ru 5+ , was 164 mAh g −1 , it still delivers a specifi c capacity of more than 220 mAh g −1 after 30 cycles under deep charge-discharge, showing a better stability.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Stability for Li‐Rich Layered Oxide Li₂RuO₃ Cathode

Shao

Yan

et al. 2016

Adv Funct Materials

133

123

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wileyonlinelibrary.comcathode materials with well-ordered structures where most of doping metal atoms exist in the transition-metal sublattice. However, the conventional layered oxide cathode after modifi cation can only deliver a practical capacity of less than 200 mAh g −1 .In recent years, lithium-rich layered oxides based on Li 2 MO 3 (M = Mn, Ru etc.) with layered structure are considered as promising cathodes for Li-ion batteries due to their higher capacity of more than 220 mAh g −1 and higher stability at high voltage as compared with the conventional LiMO 2 layered oxides, provoking worldwide attentions. [8][9][10][11][12][13][14] The common feature accounting for the high capacities of these lithium-rich layered oxides is the two redox processes involving both of cation and anion. [ 10,13,15,16 ] Despite the same process of partly charge compensation by oxygen during deep charging/discharging process, the lithiumrich layered oxides can deliver much higher reversible capacity than that of conventional cathode materials. To the best of our knowledge, such difference on the structural stability between the conventional and lithium-rich layered oxides has attracted limited attention. It is of high importance that there must be some unknown mechanism leading to the stability difference since the geometric and electronic structure between these two kinds of layered materials are similar, except for the superlattice structure. In present work, we elucidate why lithium-rich layered oxides Li 2 RuO 3 exhibit high capacities without undergoing a structural collapse for a certain number of cycles by tracking the electronic and geometric structural changes induced in Li 2 RuO 3 during charging/discharging. Backed up with the density functional theory (DFT) calculations and a series of in situ experiments, we unravel that the presence of the lithium atoms in the transition metal layer could make the lithium-rich structure fl exible, facilitating the formation of O 2 2− -like species, which favors the structural integrity and providing high capacity. Results and DiscussionWe chose Li 2 RuO 3 as the model lithium-rich compound because it contains a single metal, making it convenient to track the electronic and geometric structural changes during charging/discharging process without interference. In addition,

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Section: Introductionmentioning

confidence: 99%

Understanding the Stability for Li‐Rich Layered Oxide Li₂RuO₃ Cathode

Shao

Yan

et al. 2016

Adv Funct Materials

133

123

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“…These attempts have met varying degrees of success. 15,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] 15,[20][21][22][23]26,[28][29][30] Most studies attribute the improvements in LCO cycling performance to Mg either providing structural stability 15,21,26,27 or improving the conductivity of the material. 20,23,29,30 Recently, Shim et al reported a retention of 85% capacity after 500 cycles and 60% after 700 cycles in 2900 mAh prismatic full cells (LCO/graphite) cycling up to 4.4 V (4.48 V vs Li/Li + ) utilizing a combination of ionic conductor coating and Mg doping.…”

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confidence: 99%

Synthesis of Mg and Mn Doped LiCoO₂and Effects on High Voltage Cycling

Liu

Shunmugasundaram

et al. 2017

J. Electrochem. Soc.

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LiCo 1-2x Mg x Mn x O 2 (0 ≤ x ≤ 0.05) materials were prepared from Co 1-2x Mg x Mn x (OH) 2 (0 ≤ x ≤ 0.05) co-precipitated precursor materials by mixing precursor materials with stoichiometric amounts of Li 2 CO 3 and heating to 900 • C for 10 h. All precursor and lithiated materials were characterized by Scanning Electron Microscopy, X-ray Diffraction (XRD), Inductively Coupled PlasmaOptical Emissions Spectroscopy and electrochemical testing. In situ XRD was performed on LiCo 1-2x Mg x Mn x O 2 (x = 0, 0.02, 0.05) electrodes while cycling to study the effects of substitution on phase transitions and unit cell variations. Increasing Mg/Mn substitution in the material was found to slightly increase the 1 st charge capacity, decrease the 1 st discharge capacity and increase the 1 st cycle irreversible capacity (3.6 V-4.7 V). Cells with even 1% Mg/Mn doping were shown to have markedly improved cycling performance, and results suggest that the improvements stem from suppressing the cell impedance growth, not from the suppression of the O3-O6-O1 phase transitions. Lithium ion (Li-ion) batteries are used to power cell phones, laptops, other portable electronics, electric vehicles and grid storage. With an ever-increasing demand for energy, battery manufacturers and researchers constantly look for ways to increase the energy density while maintaining a long lifetime. LiCoO 2 (LCO) positive electrode materials, proposed by Mizushima et al. in 1980, 1 have been utilized since the commercialization of Li-ion battery technology by Sony in 1991. 2 Significant improvements have been made since then, but commercially available batteries never push LCO electrodes past 4.48 V (vs Li/Li + ), corresponding to the deintercalation/intercalation of ∼0.7 Li (per LCO) or a capacity of ∼190 mAh/g (out of a theoretical capacity of ∼274 mAh/g). In order to unlock more capacity and increase the energy density, the LCO electrodes have to cycle to voltages above 4.5 V (vs Li/Li + ). However, pushing cells with LCO electrodes to an even higher voltage result in a dramatic decrease in long term cycling performance. [3][4][5][6][7][8][9] There are multiple causes for this drop in performance, including structural instability of highly delithiated LCO,[6][7][8]10,11 electrolyte oxidation 5-7,9,10,12,13 and Co dissolution. 3,5,7,8,14,15 To further understand the structural instability that arises from high voltage cycling, X-ray diffraction (XRD) has been instrumental in studying the unit cell lattice parameter changes and phase formations. 10,11,16,17 Theoretical work has also confirmed the majority of these occurrences and helped shed light in understanding phase formation at low lithium content. 18,19 As Li deintercalates from LCO, the material undergoes a series of phase changes. The first is an insulatormetal transition, resulting in a 2-phase region. 10,16 As the material continues to deintercalate, LCO will undergo an order-disorder transition around 0.5 Li.16,18 Both of these transitions occur reversibly and are not detrimental to cycli...

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“…[19][20][21] In addition, it is expected that the influence of these compositions on ASS-LIBs is different from that of the conventional LIBs employing liquid electrolytes. Hence, based on this assumption, we considered it worthy to investigate the effect of lithium stoichiometry on the electrochemical performance of Li 1+x CoO 2 in sulfide solid electrolyte systems.…”

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confidence: 99%

Electrochemical Properties of Li_1+xCoO₂Synthesized for All-Solid-State Lithium Ion Batteries with Li₂S-P₂S₅Glass-Ceramics Electrolyte

Kim

Park

et al. 2015

J. Electrochem. Soc.

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The over-stoichiometric Li 1+x CoO 2 (x = 0.1, 0.2, and 0.3) cathode materials were synthesized from an aqueous solution of lithium nitrate (LiNO 3 ) as an excess lithium precursor and their effects on the electrochemical properties of all-solid-state lithium batteries employing Li 2 S-P 2 S 5 glass-ceramics solid electrolytes are investigated. A combination of X-ray diffraction, Fourier transform infrared spectroscopy, and inductively coupled plasma atomic emission spectroscopy reveals that the excess lithium forms a residual Li 2 CO 3 layer on the surface of as-prepared Li 1+x CoO 2 particles during the synthesis process. While regarded as an impurity phase in lithium battery systems using liquid electrolytes due to its detrimental effects on electrochemical performance, the Li 2 CO 3 formed on the surface of the over-stoichiometric Li 1+x CoO 2 powders is identified in all-solid-state lithium battery systems using sulfide solid electrolytes to act as an effective coating material to suppress the interfacial side reactions despite its low ionic and electronic conductivity. All-solid-state lithium ion batteries (ASS-LIBs) including inorganic solid electrolytes are consistently at the center of attention in the discussion on safety issues arising from the flammability of liquid electrolytes in conventional LIBs. ASS-LIB technology has come a long way in the last few decades through the development of oxide and sulfide solid electrolytes with practical levels of high ionic conductivities comparable to organic liquid electrolytes.1-4 Therefore, the rate determining step is now no longer Li + ion migration in the solid electrolyte and overall cell resistance is determined mainly at the interface between the cathode active material and solid electrolyte. However, ASS-LIBs employing oxide and sulfide solid electrolytes have some crucial interfacial problems resulting in low reversible capacity and capacity fade for practical applications, due to limited contact area and undesirable interfacial side reactions between the cathode active material and the oxide/sulfide solid electrolyte. 5,6 Many studies are in progress to understand and resolve the interfacial side reaction problem responsible for this capacity loss in order to develop ASS-LIBs with high energy density and long cycle life required for electric vehicles. Several researchers have suggested that the origin of the interfacial degradation is mutual diffusion of chemical species between solid electrolyte and cathode, 5,7 or the formation of a space-charge layer. 8,9 When garnet-structured Li 7 La 3 Zr 2 O 12 (LLZ) is contacted with LiCoO 2 , mutual diffusion of Co and La, Zr occurs at the interface during a thermal treatment to improve adhesion between the cathode material and the oxide solid electrolyte.10 Problems regarding this mutual diffusion of Co and S have been also reported in ASS-LIBs with Li 2 S-P 2 S 5 solid electrolytes, especially during initial charging process. At present, the fundamental mechanism is not clear, but interfacial control via sur...

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Synthesis of High-Voltage (4.5 V) Cycling Doped LiCoO₂ for Use in Lithium Rechargeable Cells

Abstract: High-voltage cycling doped LiCoO2 has been synthesized using the solid-state technique and it is observed that LiMn0.05C00.95O2 delivered a capacity of ∼160 mA·h/g after 50 cycles in the voltage range 3.5−4.5V.

Cited by 125 publications

References 13 publications

Understanding the Stability for Li‐Rich Layered Oxide Li₂RuO₃ Cathode

Understanding the Stability for Li‐Rich Layered Oxide Li₂RuO₃ Cathode

Synthesis of Mg and Mn Doped LiCoO₂and Effects on High Voltage Cycling

Electrochemical Properties of Li_1+xCoO₂Synthesized for All-Solid-State Lithium Ion Batteries with Li₂S-P₂S₅Glass-Ceramics Electrolyte

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Synthesis of High-Voltage (4.5 V) Cycling Doped LiCoO2 for Use in Lithium Rechargeable Cells

Abstract: High-voltage cycling doped LiCoO2 has been synthesized using the solid-state technique and it is observed that LiMn0.05C00.95O2 delivered a capacity of ∼160 mA·h/g after 50 cycles in the voltage range 3.5−4.5V.

Cited by 125 publications

References 13 publications

Understanding the Stability for Li‐Rich Layered Oxide Li2RuO3 Cathode

Understanding the Stability for Li‐Rich Layered Oxide Li2RuO3 Cathode

Synthesis of Mg and Mn Doped LiCoO2and Effects on High Voltage Cycling

Electrochemical Properties of Li1+xCoO2Synthesized for All-Solid-State Lithium Ion Batteries with Li2S-P2S5Glass-Ceramics Electrolyte

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Synthesis of High-Voltage (4.5 V) Cycling Doped LiCoO₂ for Use in Lithium Rechargeable Cells

Understanding the Stability for Li‐Rich Layered Oxide Li₂RuO₃ Cathode

Understanding the Stability for Li‐Rich Layered Oxide Li₂RuO₃ Cathode

Synthesis of Mg and Mn Doped LiCoO₂and Effects on High Voltage Cycling

Electrochemical Properties of Li_1+xCoO₂Synthesized for All-Solid-State Lithium Ion Batteries with Li₂S-P₂S₅Glass-Ceramics Electrolyte