In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2019-01, No. 2 ( 2019-05-01), p. 263-263
Abstract:
Layered lithium nickel oxide (LiNiO 2 ), with a specific charge-storage capacity of almost 250 mA h g -1 , an operating voltage of 3.8 V vs. Li + /Li, and a high packing density of above 3.4 g cm -3 , offers a very high energy density approaching the limits of layered oxide cathode materials for lithium-ion batteries. However, despite early interests in the community, practical application of LiNiO 2 was soon dismissed for a multitude of problems. This includes (i) poor thermal-abuse tolerance triggering battery thermal runaway at high states of charge, and (ii) severely restricted reversible capacity of 〈 200 mA h g -1 for desired cycle/calendar life owing to a high surface reactivity with conventional ethylene carbonate (EC)-based electrolytes and not fully reversible rhombohedral H2/H3 phase transition at 〉 4.2 V vs. Li + /Li. In spite of recent efforts on stabilizing ultrahigh-nickel layered oxides (Ni 〉 0.9) during battery operation through compositional tuning, the poor thermal stability and cyclability over a broad Li content range remain challenges of LiNiO 2 -based cathodes. Here we design nonaqueous electrolytes with exclusively aprotic acyclic carbonate solvents (such as ethyl methyl carbonate, EMC) tailored to an ultrahigh-nickel layered oxide cathode (LiNi 0.94 Co 0.06 O 2 ). Common lithium-conducting salts ( e.g ., lithium hexafluorophosphate, LiPF 6 ) and interphase-forming additives ( e.g ., vinylene carbonate, VC) are adopted in two model electrolyte systems. Assembled graphite|LiNi 0.94 Co 0.06 O 2 pouch-type full cells in the two EC-free electrolyte systems show excellent long-term cycling performance of ~ 80% capacity retention after 1,000 charge-discharge cycles at 25 o C (1C, 2.5 – 4.2 V), notably superior to the same cells in the baseline EC-containing electrolyte (1.0 M LiPF 6 /EC-EMC(3:7)+2%VC). Through time-of-flight secondary-ion mass spectrometry coupled with lithium isotopic labelling and in situ X-ray diffraction, we demonstrate suppressed unwanted electrode-electrolyte reactions and irreversible structural degradation of LiNi 0.94 Co 0.06 O 2 at highly delithiated states in the EC-free electrolytes during battery operation. In addition, through differential scanning calorimetry, we also show significantly inhibited self-heating of the ultrahigh-Ni layered oxide cathode at full charge in the EC-free electrolytes, outperforming charged LiNi 0.8 Co 0.15 Al 0.05 O 2 in the EC-containing electrolyte. In summary, we present a facile approach of nonaqueous EC-free electrolytes to address the long-standing challenges of LiNiO 2 -based cathode materials for safer and long-life high-energy-density lithium-ion batteries.
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2019-01/2/263
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2019
detail.hit.zdb_id:
2438749-6
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