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- Jin, Feng, et al.
(författare)
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Enhanced rate capability and high-voltage cycling stability of single-crystal nickel-rich cathode by surface anchoring dielectric BaTiO3
- 2022
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 619, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- The single-crystal Ni-rich Li(NixCoyMn1_x_y)O-2 cathode (NCM) demonstrates better cycle performance, enhanced tap density and improved mechanical structure stability, compared with polycrystalline NCM. However, limited Li+ transports, (003) plane slips and microcracks in large single particles hinder rate capability and cycle performance. To overcome these shortcomings, single-crystal NCM cathodes have been modified by nanosized tetragonal BaTiO3. Due to the dielectric properties, BaTiO(3 )particles induce electric field concentration at the BaTiO3-NCM-electrolyte interface. Thus, a large amount of lithium vacancies can be formed, providing sufficient sites for the hopping diffusion of lithium ions, thereby significantly enhancing the diffusion coefficient of Li+. Moreover, the redistribution of charges can inhibit the formation and accumulation of cathode-electrolyte-interface. Owing to the synergetic effect of BaTiO3, the BT-modified single-crystal NCM with the optimized loading shows a remarkable initial discharge capacity of 138.5 mAh g(_1) and maintains 53.8% of its initial discharge capacity after 100 cycles under 5C at 4.5 V cut-off voltage. Overall, the proposed dielectric cathode-electrolyte-interface strategy can enhance Li+ ion transport and stabilize the interface structure, leading to improved rate performance. Meanwhile, the diffusion-induced state of charge gradient can also be inhibited, resulting in high structure stability of single-crystal NCMs under high rate and cut-off voltage cycling. (C) 2022 Elsevier Inc. All rights reserved.
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| 2. |
- Xue, Xiaoyin, et al.
(författare)
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Enhanced Storage and Interface Structure Stability of NCM811 Cathodes for Lithium-Ion Batteries by Hydrophobic Fluoroalkylsilanes Modification
- 2022
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Ingår i: ENERGY TECHNOLOGY. - : Wiley-VCH Verlagsgesellschaft. - 2194-4288 .- 2194-4296. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- The nickel-rich ternary-layered oxide LiNixCoyMn(1-x-y)O2 (NCM) cathode exhibits high reversible capacity and low cost; however, severe capacity fade and aggravated air degradation prohibit its widespread commercialization. Herein, the hydrophobic fluoroalkylsilane-modified NCM811 cathode materials are reported. To better understand the effects of electrochemical properties of lithium-ion batteries, a variety of characterization techniques and electrochemical methods are utilized to study the surface chemistry at the cathode/electrolyte interphase. The hydrophobic fluoroalkylsilanes-grafted NCM811 cathode materials suppress the formation of residual lithium even after 30 days in humid air. The fluoroalkylsilanes layer can also provide chemical stabilization to the NCM811 cathode materials by anchoring transition metals (TM) and suppressing TM dissolution during long immersion times in electrolytes. Moreover, the degree of improvement depends on the structure of the fluoroalkylsilanes, such as the number of F groups and the length of carbon chains. As a result, FAS17-modified NCM811 cathode materials after 30-day humid air exposure (humidity 70%) exhibit the greatest overall capacity retention of 74.2% after 200 charge/discharge cycles.
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