Improvement of the Cycling Performance of LiNi0.6Co0.2Mn0.2O2 Cathode Active Materials by a Dual-Conductive Polymer Coating

Ju, Seo Hee; Kang, Ik Su; Lee, Yoon Sung; Shin, Won Kyung; Kim, Saheum; Shin, Kyomin; Kim, Dong-Won

doi:10.1021/am404965p

Cited by 179 publications

(118 citation statements)

References 47 publications

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“…The SAED pattern corresponding to the PP-coated layer (right side) exhibited a hollow ring pattern without bright spots, thus indicating that the coated layer consisted of disordered polymer materials. The image in the right inset shows some bright spots in the SAED pattern, which is typical of crystalline NCS cathode material [2,8]. These results thus provide conclusive evidence that the NCS particles are uniformly coated by the nano-sized polymer layer.…”

Section: Resultssupporting

confidence: 60%

“…Furthermore, the conductive polymer coating layer effectively suppresses the SEI film formation and HF attack by blocking the contact between the electrolyte and the cathode material. A simple coating methods has been reported by D.W. Kim and coworkers [8]. However, it is difficult to apply to the cathode material because of the high price of conductive polymers.…”

Section: Introductionmentioning

confidence: 99%

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Improvement of Electrochemical Properties and Thermal Stability of a Ni-rich Cathode Material by Polypropylene Coating

Yoo¹,

Son²

2016

Journal of Electrochemical Science and Technology

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The interface between the surface of a cathode material and the electrolyte gives rise to surface reactions such as solid electrolyte interface (SEI) and chemical side reactions. These reactions lead to increased surface resistance and charge transfer resistance. It is consequently necessary to improve the electrochemical characteristics by suppressing these reactions. In order to suppress unnecessary surface reactions, we coated cathode material using polypropylene (PP). The PP coating layer effectively reduced the SEI film that is generated after a 4.3 V initial charging process. By mitigating the formation of the SEI film, the PP-coated Li[(Ni 0.6 Co 0.1 Mn 0.3 ) 0.36 (Ni 0.80 Co 0.15 Al 0.05 ) 0.64 )]O 2 (NCS) electrode provided enhanced transport of Li + ions due to reduced SEI resistance (R SEI ) and charge transfer resistance (R ct ). The initial charge and discharge efficiency of the PP-coated NCS electrode was 96.2 % at a current density of 17 mA/g in a voltage range of 3.0 ~ 4.3 V, whereas the efficiency of the NCS electrode was only 94.7 %. The presence of the protective PP layer on the cathode improved the thermal stability by reducing the generated heat, and this was confirmed via DSC analysis by an increased exothermic peak.

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Section: Resultssupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Improvement of Electrochemical Properties and Thermal Stability of a Ni-rich Cathode Material by Polypropylene Coating

Yoo¹,

Son²

2016

Journal of Electrochemical Science and Technology

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“…The cells containing 0.5_E_VC_TTSPi or 0.5_EE_VC_TTSPi electrolyte experienced rapid capacity fade at both testing temperatures. Nelson et al 25 Ma et al 24 and others [43][44][45] have shown that the major reason for rapid capacity loss in NMC/graphite cells tested at 55…”

Section: Resultsmentioning

confidence: 98%

Dramatic Effects of Low Salt Concentrations on Li-Ion Cells Containing EC-Free Electrolytes

Xiong¹,

Hynes²,

Dahn³

2017

J. Electrochem. Soc.

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Different concentrations of LiPF 6 (0.3 M-2 M) in ethyl methyl carbonate (EMC) electrolyte and ethylene carbonate (EC)-based electrolyte were studied in LiNi 0.4 Mn 0.4 Co 0.2 O 2 (NMC442)/graphite pouch cells. Fresh cells containing 0.3 M LiPF 6 in EMC electrolyte showed extremely large charge transfer resistance while those with 0.3 M LiPF 6 in EC/EMC electrolyte did not. Impedance spectra taken on symmetric cells and ionic conductivity measurements suggest this difference is due to difficulty in dissociating and desolvating Li + ions from the EMC-based electrolyte to intercalate into both the electrodes. After elevated temperature storage experiments at 4.5 V, cells with 0.3 M LiPF 6 in EC/EMC showed a large increase in positive electrode charge transfer impedance, presumably caused by electrolyte oxidation. With salt concentrations greater than 1 M, charge transfer resistance was much smaller in EMC-based electrolytes and was stable during storage for both electrolyte types. Conductivity and cycle testing measurements suggest that 1.5 M LiPF 6 should be used in EC-free EMC-based electrolytes to optimize cell performance. Using high potential positive electrodes can increase the energy density of Li-ion cells. [1][2][3][4] Layered LiNi x Mn y Co z O 2 (x + y + z = 1) (NMC) electrodes have been extensively studied because they are cheaper materials than LiCoO 2 (LCO) and can operate at high working potentials.5-15 LiNi 0.4 Mn 0.4 Co 0.2 O 2 (NMC442) is a possible choice for high voltage application due to its high working potential, high specific capacity, moderate cost and excellent safety. [16][17][18][19] NMC442 has been shown to be structurally stable up to 4.7 V 16,17 and its specific capacity increases almost linearly as the upper cutoff voltage increases from 4.1 V to 4.7 V. At 4.7 V, NMC442 can deliver a reversible specific capacity of ∼207 mAh/g. NMC442 shows attractive safety features compared to other NMC grade materials as well. 19It is difficult to create NMC442/graphite cells that show long lifetime when operated continually to an upper cutoff potential above 4.4 V. Electrolyte additives such as pyridine boron fluoride (PBF), 20,21 triallyl phosphate (TAP) 22 and additive blends such as prop-1-ene-1,3-sultone (PES) + 1,3,2-dioxathiolane-2,2-dioxide (DTD) + tris-(trimethyl-silyl) phosphite (TTSPi) [23][24][25][26][27] in EC-based electrolyte have been used to improve charge-discharge cycle life and calendar life of cells operated to 4.4 V. Sulfone-based and fluorinated electrolyte systems have also shown to be of value in getting NMC442/graphite cells to operate beyond 4.4 V. 28,29 In spite of these improvements, further improvement is required. Recently, it was found that EC-free electrolyte using only ethyl methyl carbonate as the solvent can enhance high voltage operation and lifetime of NMC442/graphite pouch cells compared to EC-based electrolyte.30-32 However, only a salt concentration of 1 M LiPF 6 in this novel electrolyte was investigated.The concentration of LiPF 6 in EC-based electrolyte...

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“…To solve these defects, some conductive polymers and fast ionic conductor materials were widely used as surface coating layer on the cathode active materials. [24][25][26][27][28][29][30] materials is coated with various amount of LBO glass via a simple wet chemical process followed by heat-treatment. As expected, the LBO coated materials exhibit obvious improvement both in electrochemical performances and thermal stability under high voltage.…”

Section: Introductionmentioning

confidence: 99%

Multifunctional Li2O-2B2O3 coating for enhancing high voltage electrochemical performances and thermal stability of layered structured LiNi0.5Co0.2Mn0.3O2 cathode materials for lithium ion batteries

Wang

et al. 2015

Electrochimica Acta

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Improvement of the Cycling Performance of LiNi_0.6Co_0.2Mn_0.2O₂ Cathode Active Materials by a Dual-Conductive Polymer Coating

Cited by 179 publications

References 47 publications

Improvement of Electrochemical Properties and Thermal Stability of a Ni-rich Cathode Material by Polypropylene Coating

Improvement of Electrochemical Properties and Thermal Stability of a Ni-rich Cathode Material by Polypropylene Coating

Dramatic Effects of Low Salt Concentrations on Li-Ion Cells Containing EC-Free Electrolytes

Multifunctional Li2O-2B2O3 coating for enhancing high voltage electrochemical performances and thermal stability of layered structured LiNi0.5Co0.2Mn0.3O2 cathode materials for lithium ion batteries

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