In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2014-04, No. 2 ( 2014-06-10), p. 421-421
Abstract:
Introduction Lithium rich layered material has attracted much attention because of its high capacity, however, the low effciency in the 1st cycle and poor rate property is a big issue for its practical use. We adopted a (NH 4 ) 2 S 2 O 8 treatment on Li 1.2 Ni 0.16 Co 0.08 Mn 0.56 O 2 material, the prodcut showed a greatly increased 1 st cycle efficinecy of above 90% and a capacity as high as 200mAh. g -1 at 4C rate. Experiment Li 1.2 Ni 0.16 Co 0.08 Mn 0.56 O 2 was prepared by a rheological method. Stoichiometric amount of Li 2 CO 3 , Ni(CH 3 COO) 2 ·4H 2 O, Co(CH 3 COO) 2 ·4H 2 O, Mn(CH 3 COO) 2 ·4H 2 O and oxalic acid were mixed. And then a proper amount of water was added. After stirring the mixture at 80-90 ºC for 4 h, it was dried at 120 ºC for 10 h, followed by annealing at 850 ºC for 20 h. (NH 4 ) 2 S 2 O 8 solution with different concerntration was used to treat the above Li 1.2 Ni 0.16 Co 0.08 Mn 0.56 O 2 sample, the product was named as 20%-RL,30%-RL, 40%-RL, 50%-RL according the different concerntration of (NH 4 ) 2 S 2 O 8 solution. Cycling test was conducted to evaluate the cyclcing stability and rate property of the products. The samples were characterized in terms of XRD, SEM, XPS and Raman measurement. Result and discussion The 1 st charge/discharge curves are compared in Fig.1. The pristine Li 1.2 Ni 0.16 Co 0.08 Mn 0.56 O 2 shows an intial caapcity of 224.0 mAh g -1 but with a low efficiency of 79%. With the increasing of the (NH 4 ) 2 S 2 O 8 concerntration, the product shows an increased effciency and reachs 99% in the “40%-RL” sample. Additionally, the (NH 4 ) 2 S 2 O 8 treatment leads to an improvement in the cycling stability. In Fig.2, untreated Li 1.2 Ni 0.16 Co 0.08 Mn 0.56 O 2 maintains 88% capacity in the 100 th cycle, while the “40%-RL” sample shows capacity retention of 97% after 100 cyles. The (NH 4 ) 2 S 2 O 8 -treated samples also present greatly improved rate performance. In Fig.3, the increase of the current rate from 0.1C to 4C causes a capacity decrease from 255mAh.g -1 to 67mAh.g -1 for the pristine Li 1.2 Ni 0.16 Co 0.08 Mn 0.56 O 2 sample. For the (NH 4 ) 2 S 2 O 8 -treated samples, they all exhibit a much better rate property than the untreated phase. Especially for the “30%-RL” and “40%-RL” sample, they both present a capcity above 200mAh.g -1 at the 4C rate. XRD measurements prove that the (NH 4 ) 2 S 2 O 8 -treatment weakens the super lattice in the Lithium rich layered material. ICP and Raman analysis furtheres reveal that the Li content in Li 2 MnO 3 decreased after the (NH 4 ) 2 S 2 O 8 -treatment, which can be the main reason of the efficiency increase in the 1 st cycle.
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2014-04/2/421
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2014
detail.hit.zdb_id:
2438749-6
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