Preparation and characterization of LiFePO
4
xLi
3
V
2
(PO
4
)
3
composites by
two-step solid-state reaction method for lithium-ion batteries
Wenhua Cheng
a,b
, Lei Wang
a,
⇑
, Zhipeng Sun
b,
⇑
, Zhaojun Wang
a,
⇑
, Qibing Zhang
a,b
, Dingding Lv
a,c
,
Wei Ren
a
, Liang Bian
a,d
, Jinbao Xu
a
, Aimin Chang
a
a
Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Xinjiang Key Laboratory of Electronic Information Materials and
Devices, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Ürümqi 830011, China
b
Key Laboratory of Energy Materials Chemistry (Xinjiang University), Ministry of Education, Institute of Applied Chemistry, School of Physics Science and Technology,
Xinjiang University, Ürümqi 830046, China
c
University of Chinese Academy of Sciences, Beijing 100049, China
d
Key Laboratory of Solid Waste Treatment and Resource Recycle, South West University of Science and Technology, Mianyang 621010, China
article info
Article history:
Received 15 November 2016
Received in revised form 9 March 2017
Accepted 2 April 2017
Available online 6 April 2017
Keywords:
Nanocomposites
Electrical properties
Energy storage and conversion
Lithium-ion batteries
abstract
LiFePO
4
xLi
3
V
2
(PO
4
)
3
(LFPxLVP, x = 0, 0.05, 0.1, 0.15, 0.2) composites were prepared by the two-step
solid-state method. The structure, morphology and electrochemical properties were characterized by
X-ray diffraction, scanning electron microscope, cyclic voltammetry, charge-discharge performance test
and electrochemical impedance spectroscopy. It was indicated that composites were presented rough
in surface of ball-like particles. Two phase of LFP and LVP combination improved electrochemical prop-
erties of LFP. The LFP0.1LVP has the highest discharge capacity of 154 mAh/g at 0.2 C. Compared with
LFP, the rate performance of the LFP0.1LVP increased 13% and 8% at 1 C and 10 C after five cycles. It pos-
sessed excellent cycle life of 99.8% after 100 cycles at 1 C especially. The all preparation process without
any solvent addition was easy operation, energy saving and environmentally friendly.
Ó 2017 Elsevier B.V. All rights reserved.
1. Introduction
Olivine structure LiFePO
4
(LFP) is one of the most potential
lithium ion battery cathodes for large scale energy storage and
power source in electric vehicles (EV) and hybrid electric vehicles
(HEV), because of its rich raw material sources, low cost, environ-
mental non-toxic, high theoretical specific capacity and high volt-
age platform [1,2]. However, the low electronic conductivity and
slow lithium ion diffusion rate constrain the electrochemical
performance, especially the high-rate performance [3,4].
Consequently, great efforts have been devoted to improve these
drawbacks, such as reducing particle size, carbon coating, and dop-
ing with supervalent cations [5,6]. More recently, making the com-
posites from both active components has attracted much attention.
It was demonstrated that the introduction of Li
3
V
2
(PO
4
)
3
(LVP) acts
to improve electronic conductivity and lithium ion diffusion rate of
LiFePO
4
(LFP) [7–9]. Zhong et al. [10] have been synthesized
uniform 9LiFePO
4
Li
3
V
2
(PO
4
)
3
/C (9LFPLVP/C) composite cathode
material by a sol-gel method. Compared with the LFP/C, its rate
capability and cycle performance are both remarkably improved.
Yang et al. [11] studied the synthesis of carbon coated LFPLVP
materials by the solution method, which exhibited a high dis-
charge capacity. Compared with these liquid phase synthesis pro-
cesses, two-step solid-state reaction method is simple in process,
low in cost and saving in time and environmentally friendly
[12,13].
Herein, the precursors of LFPxLVP composites were prepared
by room-temperature solid-state reaction method, and then high
heating solid-state reaction method was used to synthesize
LFPxLVP powder. All reaction process without any solvent addi-
tion was energy saving and environmentally friendly.
2. Experimental procedure
The LFPxLVP samples were prepared via CH
3
COOLi2H
2
O,
FeC
2
O
4
2H
2
O, NH
4
VO
3
and NH
4
H
2
PO
4
by two-step solid-state reac-
tion method. Primarily, stoichiometric ratios of CH
3
COOLi2H
2
O,
FeC
2
O
4
2H
2
O and NH
4
VO
3
were mixed in an agate mortar and
ground thoroughly for 15 min. Secondly, stoichiometric ratio of
NH
4
H
2
PO
4
was added and ground for another 30 min. Meanwhile,
the mixture suffered room-temperature solid-state reaction during
the mixing process. It was found that the solid powder first
http://dx.doi.org/10.1016/j.matlet.2017.04.008
0167-577X/Ó 2017 Elsevier B.V. All rights reserved.
⇑
Corresponding authors.
E-mail addresses: wangl@ms.xjb.ac.cn (L. Wang), zpsunxj@163.com (Z. Sun),
wzj@xju.edu.cn (Z. Wang).
Materials Letters 198 (2017) 172–175
Contents lists available at ScienceDirect
Materials Letters
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