Cation and anion Co-doping synergy to improve structural stability of Li- and Mn-rich layered cathode materials for lithium-ion batteries

Chen, Guorong; An, Juan; Meng, Yiming; Yuan, Changzhou; Matthews, Bryan; Dou, Fei; Shi, Liyi; Zhou, Yongfeng; Song, Pingan; Wu, Gang; Zhang, Dengsong

doi:10.1016/j.nanoen.2018.12.049

Cited by 173 publications

(98 citation statements)

References 39 publications

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“…Clearly, the crystal structure of the pristine sample (Figure c) has partially undergone transformation from a layered to rock‐salt structure (NiO phase). This is caused by Ni 2+ migration from the transition metal layer into the lithium layer during the repeated charge steps to high voltage (above 4.6 V), which is the origin of the voltage fading in LRNMs 11a,29. However, in the microscopy images of the 3 at% Fe‐doped material after cycling (Figure d) hardly any regions with rock‐salt structure can be identified, while the layered structure is well preserved.…”

Section: Resultsmentioning

confidence: 99%

Elucidating the Effect of Iron Doping on the Electrochemical Performance of Cobalt‐Free Lithium‐Rich Layered Cathode Materials

Kim

Kuenzel

et al. 2019

Advanced Energy Materials

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Lithium-rich materials provide the highest specific energies (up to 900 Wh kg −1) among all lithium-ion positive electrode materials. [1] Potentially meeting the high requirements for automotive applications, they receive much attention for use in "next-generation" Li-ion batteries (LIBs). Their large specific capacity originates from the structural peculiarity of lithium-rich layered materials, which can be seen as mixtures of two phases, LiMO 2 (M = Ni, Mn, and Co, rhombohedral R-3m structure) and Li 2 MnO 3 (monoclinic C2/m structure). This latter component provides additional lithium located inside the transition metal layer. [2] However, to access this additional capacity, the Li 2 MnO 3 component must be "activated" by charging to relatively high cutoff voltages (i.e., 4.6-4.8 V). [1a,3] During such activation, Li + ions are extracted from the structure while oxygen anion redox activity occurs possibly through a few different processes. However, transition metal migration into the formed Li vacancies correspondingly occurs, finally resulting in the phase transformation from layered to spinel-like and eventually, rock-salt structure. [4] This is widely regarded as the origin of the two main challenges of lithiumrich materials, that is, voltage and capacity degradation, leading to relatively poor cycle-life. To solve these issues, many strategies have been developed over the past years, which are, for example, modifications of the binder [5] or the electrolyte, [6] and surface treatments [4,7] and lattice doping [8] of the lithium-rich materials. Lattice doping is one of the most suitable methods to address the voltage fading as reported in a few earlier works. Nayak et al. [8b] could maintain higher specific capacity as well as discharge voltage upon cycling, by doping the structure with aluminum (on the account of manganese). This is due to the stabilized surface of the active material and suppressed transformation from layered to spinel-like phase. Chromium has also been adopted as a possible dopant and confirmed to be incorporated into the crystal lattice. It enabled higher average voltage, which was ascribed to a decreased amount of spinel domains generated upon cycling. [9] Moreover, other elements, such as Ti, [10] Mg, [11] and Cu [12] were investigated leading to similar improvements. Besides doping into the transitional metal layer, also lithium site The eco-friendly and low-cost Co-free Li 1.2 Mn 0.585 Ni 0.185 Fe 0.03 O 2 is investigated as a positive material for Li-ion batteries. The electrochemical performance of the 3 at% Fe-doped material exhibits an optimal performance with a capacity and voltage retention of 70 and 95%, respectively, after 200 cycles at 1C. The effect of iron doping on the electrochemical properties of lithium-rich layered materials is investigated by means of in situ X-ray diffraction spectroscopy and galvanostatic intermittent titration technique during the first charge-discharge cycle while high-resolution transmission electron microscopy is used to follow the structural ...

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Section: Resultsmentioning

confidence: 99%

Elucidating the Effect of Iron Doping on the Electrochemical Performance of Cobalt‐Free Lithium‐Rich Layered Cathode Materials

Kim

Kuenzel

et al. 2019

Advanced Energy Materials

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“…[9] This process, commonly referred to as cation mixing, gradually increases during cycling, leading to a transformation of the layered oxide into spinel-like, disordered TM layers and, eventually, into the rock-salt structure. [6,10,11] At the same time, the high upper cut-off voltage is outside of the electrochemical stability window of conventional, organic carbonate-based electrolytes, which additionally leads to unwanted side reactions and gas evolution. [12] Moreover, such electrolytes are highly flammable and volatile, bearing safety risks of LIB technology.…”

Section: Introductionmentioning

confidence: 99%

Reducing Capacity and Voltage Decay of Co‐Free Li_1.2Ni_0.2Mn_0.6O₂ as Positive Electrode Material for Lithium Batteries Employing an Ionic Liquid‐Based Electrolyte

Kim

Diemant

et al. 2020

Advanced Energy Materials

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Lithium‐rich layered oxides (LRLOs) exhibit specific capacities above 250 mAh g−1, i.e., higher than any of the commercially employed lithium‐ion‐positive electrode materials. Such high capacities result in high specific energies, meeting the tough requirements for electric vehicle applications. However, LRLOs generally suffer from severe capacity and voltage fading, originating from undesired structural transformations during cycling. Herein, the eco‐friendly, cobalt‐free Li1.2Ni0.2Mn0.6O2 (LRNM), offering a specific energy above 800 Wh kg−1 at 0.1 C, is investigated in combination with a lithium metal anode and a room temperature ionic liquid‐based electrolyte, i.e., lithium bis(trifluoromethanesulfonyl)imide and N‐butyl‐N‐methylpyrrolidinium bis(fluorosulfonyl)imide. As evidenced by electrochemical performance and high‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, and online differential electrochemical mass spectrometry characterization, this electrolyte is capable of suppressing the structural transformation of the positive electrode material, resulting in enhanced cycling stability compared to conventional carbonate‐based electrolytes. Practically, the capacity and voltage fading are significantly limited to only 19% and 3% (i.e., lower than 0.2 mV per cycle), respectively, after 500 cycles. Finally, the beneficial effect of the ionic liquid‐based electrolyte is validated in lithium‐ion cells employing LRNM and Li4Ti5O12. These cells achieve a promising capacity retention of 80% after 500 cycles at 1 C.

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“…[10][11][12][13][14][15][16] Most recently, the development of novel layered materials attracts great interest in various elds. [17][18][19][20][21] There exist many techniques to prepare LDHs, the most common being co-precipitation, urea hydrolysis, ion exchange and hydrothermal synthesis. 2,[22][23][24] LDHs can be prepared with a variety of metal combinations that can be tailored to the desired applications and can have different structural, chemical and photoelectric properties dependent on the incorporated metals and preparation methods.…”

Section: Introductionmentioning

confidence: 99%

Comparison of transition metal (Fe, Co, Ni, Cu, and Zn) containing tri-metal layered double hydroxides (LDHs) prepared by urea hydrolysis

et al. 2019

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Cation and anion Co-doping synergy to improve structural stability of Li- and Mn-rich layered cathode materials for lithium-ion batteries

Cited by 173 publications

References 39 publications

Elucidating the Effect of Iron Doping on the Electrochemical Performance of Cobalt‐Free Lithium‐Rich Layered Cathode Materials

Elucidating the Effect of Iron Doping on the Electrochemical Performance of Cobalt‐Free Lithium‐Rich Layered Cathode Materials

Reducing Capacity and Voltage Decay of Co‐Free Li_1.2Ni_0.2Mn_0.6O₂ as Positive Electrode Material for Lithium Batteries Employing an Ionic Liquid‐Based Electrolyte

Comparison of transition metal (Fe, Co, Ni, Cu, and Zn) containing tri-metal layered double hydroxides (LDHs) prepared by urea hydrolysis

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Cation and anion Co-doping synergy to improve structural stability of Li- and Mn-rich layered cathode materials for lithium-ion batteries

Cited by 173 publications

References 39 publications

Elucidating the Effect of Iron Doping on the Electrochemical Performance of Cobalt‐Free Lithium‐Rich Layered Cathode Materials

Elucidating the Effect of Iron Doping on the Electrochemical Performance of Cobalt‐Free Lithium‐Rich Layered Cathode Materials

Reducing Capacity and Voltage Decay of Co‐Free Li1.2Ni0.2Mn0.6O2 as Positive Electrode Material for Lithium Batteries Employing an Ionic Liquid‐Based Electrolyte

Comparison of transition metal (Fe, Co, Ni, Cu, and Zn) containing tri-metal layered double hydroxides (LDHs) prepared by urea hydrolysis

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Reducing Capacity and Voltage Decay of Co‐Free Li_1.2Ni_0.2Mn_0.6O₂ as Positive Electrode Material for Lithium Batteries Employing an Ionic Liquid‐Based Electrolyte