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Title: A New Strategy for High-Voltage Cathodes for K-Ion Batteries: Stoichiometric KVPO 4F

Abstract

The exploration of high-energy-density cathode materials is crucial to the practical use of K-ion batteries. Layered K-metal oxides have too high a voltage slope due to their large K +–K + interaction, resulting in low specific capacity and average voltage. In contrast, the 3D arrangement of K +, with polyanions separating them, reduces the strength of the effective K +-K + repulsion, which in turn increases specific capacity and voltage. Here, stoichiometric KVPO 4F for use as a high-energy-density K-ion cathode is developed. The KVPO 4F cathode delivers a reversible capacity of ≈105 mAh g -1 with an average voltage of ≈4.3 V (vs K/K +), resulting in a gravimetric energy density of ≈450 Wh kg -1. During electrochemical cycling, the K xVPO 4F cathode goes through various intermediate phases at x = 0.75, 0.625, and 0.5 upon K extraction and reinsertion, as determined by ex situ X-ray diffraction characterization and ab initio calculations. Moreover, our research explains the role of oxygen substitution in KVPO 4+xF 1-x: the oxygenation of KVPO 4F leads to an anion-disordered structure which prevents the formation of K +/vacancy orderings without electrochemical plateaus and hence to a smoother voltage profile.

Authors:
 [1];  [2];  [1];  [2];  [1];  [1];  [2];  [2];  [3]; ORCiD logo [4]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States)
  3. Sungkyunkwan Univ., Suwon (Korea)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1542315
Alternate Identifier(s):
OSTI ID: 1460888
Grant/Contract Number:  
AC02-05CH11231; AC02‐06CH11357; C02-05CH11231; AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Advanced Energy Materials
Additional Journal Information:
Journal Volume: 8; Journal Issue: 26; Journal ID: ISSN 1614-6832
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; 36 MATERIALS SCIENCE; cathodes; fluorophosphate; K‐ion batteries; polyanion

Citation Formats

Kim, Haegyeom, Seo, Dong-Hwa, Bianchini, Matteo, Clément, Raphaële J., Kim, Hyunchul, Kim, Jae Chul, Tian, Yaosen, Shi, Tan, Yoon, Won-Sub, and Ceder, Gerbrand. A New Strategy for High-Voltage Cathodes for K-Ion Batteries: Stoichiometric KVPO4F. United States: N. p., 2018. Web. doi:10.1002/aenm.201801591.
Kim, Haegyeom, Seo, Dong-Hwa, Bianchini, Matteo, Clément, Raphaële J., Kim, Hyunchul, Kim, Jae Chul, Tian, Yaosen, Shi, Tan, Yoon, Won-Sub, & Ceder, Gerbrand. A New Strategy for High-Voltage Cathodes for K-Ion Batteries: Stoichiometric KVPO4F. United States. doi:10.1002/aenm.201801591.
Kim, Haegyeom, Seo, Dong-Hwa, Bianchini, Matteo, Clément, Raphaële J., Kim, Hyunchul, Kim, Jae Chul, Tian, Yaosen, Shi, Tan, Yoon, Won-Sub, and Ceder, Gerbrand. Wed . "A New Strategy for High-Voltage Cathodes for K-Ion Batteries: Stoichiometric KVPO4F". United States. doi:10.1002/aenm.201801591. https://www.osti.gov/servlets/purl/1542315.
@article{osti_1542315,
title = {A New Strategy for High-Voltage Cathodes for K-Ion Batteries: Stoichiometric KVPO4F},
author = {Kim, Haegyeom and Seo, Dong-Hwa and Bianchini, Matteo and Clément, Raphaële J. and Kim, Hyunchul and Kim, Jae Chul and Tian, Yaosen and Shi, Tan and Yoon, Won-Sub and Ceder, Gerbrand},
abstractNote = {The exploration of high-energy-density cathode materials is crucial to the practical use of K-ion batteries. Layered K-metal oxides have too high a voltage slope due to their large K+–K+ interaction, resulting in low specific capacity and average voltage. In contrast, the 3D arrangement of K+, with polyanions separating them, reduces the strength of the effective K+-K+ repulsion, which in turn increases specific capacity and voltage. Here, stoichiometric KVPO4F for use as a high-energy-density K-ion cathode is developed. The KVPO4F cathode delivers a reversible capacity of ≈105 mAh g-1 with an average voltage of ≈4.3 V (vs K/K+), resulting in a gravimetric energy density of ≈450 Wh kg-1. During electrochemical cycling, the KxVPO4F cathode goes through various intermediate phases at x = 0.75, 0.625, and 0.5 upon K extraction and reinsertion, as determined by ex situ X-ray diffraction characterization and ab initio calculations. Moreover, our research explains the role of oxygen substitution in KVPO4+xF1-x: the oxygenation of KVPO4F leads to an anion-disordered structure which prevents the formation of K+/vacancy orderings without electrochemical plateaus and hence to a smoother voltage profile.},
doi = {10.1002/aenm.201801591},
journal = {Advanced Energy Materials},
issn = {1614-6832},
number = 26,
volume = 8,
place = {United States},
year = {2018},
month = {7}
}

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