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Title: Thermal Stability and Reactivity of Cathode Materials for Li-Ion Batteries

Here, the thermal stability of electrochemically delithiated Li 0.1Ni 0.8Co 0.15Al 0.05O 2 (NCA), FePO 4 (FP), Mn 0.8Fe 0.2PO 4 (MFP), hydrothermally synthesized VOPO 4, LiVOPO 4, and electrochemically lithiated Li 2VOPO 4 is investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis, coupled with mass spectrometry (TGA-MS). The thermal stability of the delithiated materials is found to be in the order of NCA < VOPO 4 < MFP < FP. Unlike the layered oxides and MFP, VOPO 4 does not evolve O 2 on heating. Thus, VOPO 4 is less likely to cause a thermal run-away phenomenon in batteries at elevated temperature and so is inherently safer. The lithiated materials LiVOPO 4, Li 2VOPO 4, and LiNi 0.8Co 0.15Al 0.05O 2 are found to be stable in the presence of electrolyte, but sealed-capsule high-pressure experiments show a phase transformation of VOPO 4 → HVOPO 4 → H 2VOPO 4 when VOPO 4 reacts with electrolyte (1 M LiPF 6 in EC/DMC = 1:1) between 200 and 300 °C. Using first-principles calculations, we confirm that the charged VOPO 4 cathode is indeed predicted to be marginally less stable than FP but significantly more stable than NCA in the absencemore » of electrolyte. An analysis of the reaction equilibria between VOPO 4 and EC using a multicomponent phase diagram approach yields products and reaction enthalpies that are highly consistent with the experiment results.« less
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [1] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Binghamton Univ., Binghamton, NY (United States)
  2. Univ. of California, San Diego, La Jolla, CA (United States)
Publication Date:
Grant/Contract Number:
SC0012583; AC02-98CH10886
Type:
Published Article
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 8; Journal Issue: 11; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society (ACS)
Research Org:
Univ. of California, San Diego, La Jolla, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; cathode; electrolyte; Li-ion battery; oxides; phosphates; thermal stability
OSTI Identifier:
1241419
Alternate Identifier(s):
OSTI ID: 1436505