Hydrophobic Ni-Rich Layered Oxides as Cathode Materials for Lithium-Ion Batteries

Doo, Sung Wook; Lee, Su-Yeon; Kim, Hanseul; Choi, Jeong‐Yoon; Lee, Kyu‐Tae

doi:10.1021/acsaem.9b00786

Cited by 55 publications

(64 citation statements)

References 55 publications

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“…To prove the previous arguments and firmly understand the role of PVDF on the rheology of cathode slurries, systemic studies should be performed with model systems consisting of solely target components. The present study aims to reveal the role of PVDF in microstructure and rheological properties of cathode slurries consisting of Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 (NCM) [ 29 , 30 ] as an active material, carbon black (CB) as a conductive agent, PVDF as a polymeric binder, and NMP as a solvent. Following the three cases of model suspensions were prepared to understand the role of PVDF in the rheology and microstructure of cathode slurries: CB/PVDF/NMP, NCM/PVDF/NMP, and NCM/CB/PVDF/NMP.…”

Section: Introductionmentioning

confidence: 99%

Role of PVDF in Rheology and Microstructure of NCM Cathode Slurries for Lithium-Ion Battery

et al. 2020

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A binder plays a critical role in dispersion of coating liquids and the quality of coating. Poly(vinylidene fluoride) (PVDF) is widely used as a binder in cathode slurries; however, its role as a binder is still under debate. In this paper, we study the role of PVDF on the rheology of cathode battery slurries consisting of Li(Ni1/3Mn1/3Co1/3)O2 (NCM), carbon black (CB) and N-methyl-2-pyrrolidone (NMP). Rheology and microstructure of cathode slurries are systemically investigated with three model suspensions: CB/PVDF/NMP, NCM/PVDF/NMP and NCM/CB/PVDF/NMP. To highlight the role of PVDF in cathode slurries, we prepare the same model suspensions by replacing PVDF with PVP, and we compare the role of PVDF to PVP in the suspension rheology. We find that PVDF adsorbs neither onto NCM nor CB surface, which can be attributed to its poor affinity to NCM and CB. Rheological measurements suggest that PVDF mainly increases matrix viscosity in the suspension without affecting the microstructure formed by CB and NCM particles. In contrast to PVDF, PVP stabilizes the structure of CB and NCM in the model suspensions, as it is adsorbed on the CB surface. This study will provide a useful insight to fundamentally understand the rheology of cathode slurries.

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Section: Introductionmentioning

confidence: 99%

Role of PVDF in Rheology and Microstructure of NCM Cathode Slurries for Lithium-Ion Battery

et al. 2020

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“…This way, one can achieve optimal and robust surface coverage, which gives mechanical support to particles against fracturing and ultimately improved the electrochemical performance (from 66.3 % to 88.7 % capacity retention after 100 cycles; 20 mA/g and 200 mA/g in the first five and the subsequently cycles, respectively). Another interesting approach was demonstrated by Doo et al, where the authors applied a 15 nm hydrophobic polydimethylsiloxane coating to NCM811 to prevent the formation of LiOH and Li 2 CO 3 on the particle surface. The coating increased the hydrophobicity of the NCM surface, as shown by contact angle measurements.…”

Section: Coatingsmentioning

confidence: 99%

Surface Modification Strategies for Improving the Cycling Performance of Ni‐Rich Cathode Materials

et al. 2020

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Ni‐rich layered lithium metal oxides are the cathode active materials of choice for high‐energy‐density Li‐ion batteries. While the high content of Ni is responsible for the excellent capacity, it is also the source of interfacial instability, limiting the material's lifetime due to a variety of correlated in‐ and extrinsic factors. Hence, reconciling the opposing trends of high Ni content and long‐term cycling stability by modifying the material's surface is one of the challenges in the field. Here, we review various studies on surface modification of Ni‐rich (≥ 80 %) layered cathode active materials in order to categorize current research efforts. Broadly, the three strategies of coating, surface doping and washing are discussed, each with their advantages and shortcomings. In conclusion, we highlight new directions of research that could bring Ni‐rich layered lithium metal oxide cathodes from the laboratory to the real world.

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“…After being exposed to ambient air for 1 month, the capacity retention of the LiMn 1.9 Al 0.1 O 4 coated LiNi 0.7 Co 0.15 Mn 0.15 O 2 sample is compared to the fresh one (Oh et al, 2016 1 O 2 after being exposed to a humidity chamber at 50% RH and 25°C, respectively. Adapted from [Doo et al, 2019] with permission from American Chemical Society. (F) Schematic illustration of the preparation process of OPAcoated NCM811 and (G) TEM images of OPA-coated NCM811; SEM images of (H) bare NCM811 and (I) OPA-coated NCM811 after 14-day air exposure; Cycling performance of (J) bare NCM811 and (K) OPA-coated NCM811 after different air exposure durations.…”

Section: Surface Coatingmentioning

confidence: 99%

“…Since moisture is one of the essential conditions for the formation of residual lithium compounds, thereby constructing a hydrophobic layer tightly coated on the cathode surface is highly expected to overcome this intractable issue (Doo et al, 2019;Gu et al, 2020). The modified hydrophobic surface effectively blocks the direct contact between moisture and the chemically unstable surface of Ni-rich cathode materials, further suppressing the formation of residual lithium compounds.…”

Section: Surface Coatingmentioning

confidence: 99%

“…Till now, various organic molecules are adopted as surface coating materials for modifying Ni-rich cathode materials. As shown in Figure 5A-E, hydrophobic polydimethylsiloxane (PDMS) coated NCM811, with a strong M−O−Si covalent bond, exhibited the enhanced air storage stability (Doo et al, 2019). Additionally, octadecyl phosphate (OPA) can be utilized to form a hydrophobic self-assembled monolayer on the surface of Ni-rich cathode Cycling performance of (D) pristine NCA and (E) CGCS after air exposure with a relative humidity of about 30% for different numbers of days between 3.0 and 4.3 V. Adapted from [Shi et al, 2017] with permission from American Chemical Society.…”

Section: Surface Coatingmentioning

confidence: 99%

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The Formation, Detriment and Solution of Residual Lithium Compounds on Ni-Rich Layered Oxides in Lithium-Ion Batteries

Chen

Wang

et al. 2020

Front. Energy Res.

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Ni-rich layered transition-metal oxides with high specific capacity and energy density are regarded as one of the most promising cathode materials for next generation lithium-ion batteries. However, the notorious surface impurities and high air sensitivity of Ni-rich layered oxides remain great challenges for its large-scale application. In this respect, surface impurities are mainly derived from excessive Li addition to reduce the Li/Ni mixing degree and to compensate for the Li volatilization during sintering. Owing to the high sensitivity to moisture and CO2 in ambient air, the Ni-rich layered oxides are prone to form residual lithium compounds (e.g. LiOH and Li2CO3) on the surface, subsequently engendering the detrimental subsurface phase transformation. Consequently, Ni-rich layered oxides often have inferior storage and processing performance. More seriously, the residual lithium compounds increase the cell polarization, as well as aggravate battery swelling during long-term cycling. This review focuses on the origin and evolution of residual lithium compounds. Moreover, the negative effects of residual lithium compounds on storage performance, processing performance and electrochemical performance are discussed in detail. Finally, the feasible solutions and future prospects on how to reduce or even eliminate residual lithium compounds are proposed.

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Hydrophobic Ni-Rich Layered Oxides as Cathode Materials for Lithium-Ion Batteries

Cited by 55 publications

References 55 publications

Role of PVDF in Rheology and Microstructure of NCM Cathode Slurries for Lithium-Ion Battery

Role of PVDF in Rheology and Microstructure of NCM Cathode Slurries for Lithium-Ion Battery

Surface Modification Strategies for Improving the Cycling Performance of Ni‐Rich Cathode Materials

The Formation, Detriment and Solution of Residual Lithium Compounds on Ni-Rich Layered Oxides in Lithium-Ion Batteries

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