Understanding and development of olivine LiCoPO₄cathode materials for lithium-ion batteries

Abstract

Understanding and development of olivine LiCoPO4cathode materials for lithium-ion batteries are systematically reviewed.

Dynamically visualizing battery reactions by operando Kelvin probe force microscopy

“…Figure 1c shows the CV curve during the KPFM measurements. Oxidation and reduction current peaks represent the charge and discharge reactions of the cathode active materials, respectively [18][19][20][21] . The shape of the peaks during the forward and backward sweeps was asymmetric.…”

“…Thus, we deduced that the state of the conductive network varied depending on the charge state of the active material. The initial incomplete formation of the conductive network arose from the low electronic conductivity of LCP particles 20 , and the state of the conductive network was improved by the increase in electronic conductivity due to the charge reactions (in which Li þ ions are extracted, and the oxidation state of Co ions is changed from Co 2þ to Co 3þ ). The collapse of the conductive network was induced by the re-lowering of the electronic conductivity of the LCP particles owing to the discharge reactions (Li þ ion insertion and reduction of Co ions).…”

“…LCP is known to exhibit two oxidation peaks and two reduction peaks in the CV curve arising from two distinct two-phase reactions 18,[20][21][22][23] . However, the CV curve of the ASS-LIB showed only a single peak during the forward sweep, whereas a peak and shoulder features were observed during the backward sweep, resulting in asymmetric peak shapes.…”

Nano‐Sized AlPO4 Coating Layer on Graphite Powder to Improve the Electrochemical Properties of High‐Voltage Graphite/LiNi0.5Mn1.5O4 Li‐Ion Cells

“…Nevertheless, along with the rapid development of electric vehicles, the energy densities (<200 Wh kg −1 ) of the state‐of‐the‐art LIBs based on LiCoO 2 /LiMn 2 O 4 /LiFePO 4 /LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathodes and graphite anode cannot meet the requirements of automotive power batteries . To further improve the energy density of LIBS, researchers have developed some high capacity and/or high‐voltage cathode materials such as spinel LiNi 0.5 Mn 1.5 O 4 (LNMO), olivine LiCoPO 4 , nick‐rich‐layered oxides such as LiNi 1‐ x − y Co x Al y O 2 /LiNi 1− x − y Co x Mn y O 2 ( x + y < 0.2), and layered—layered materials such as x Li 2 MnO 3 (1− x )LiMO 2 (M = Ni, Co, and Mn) . Among these cathode materials, LNMO has received a great deal of attention because of its high voltage (4.7 V vs Li/Li + ), high theoretical specific capacity (147 mAh g −1 ), rapid Li + ions diffusion channels, and low cost .…”

“…Nevertheless, along with the rapid development of electric vehicles, the energy densities (<200 Wh kg À1 ) of the state-of-the-art LIBs based on LiCoO 2 /LiMn 2 O 4 / LiFePO 4 /LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathodes and graphite anode cannot meet the requirements of automotive power batteries. [1,2] To further improve the energy density of LIBS, researchers have developed some high capacity and/or high-voltage cathode materials such as spinel LiNi 0.5 Mn 1.5 O 4 (LNMO), [3][4][5][6] olivine LiCoPO 4 , [7,8] [1,9,10] Among these cathode materials, LNMO has received a great deal of attention because of its high voltage (4.7 V vs Li/Li þ ), high theoretical specific capacity (147 mAh g À1 ), rapid Li þ ions diffusion channels, and low cost. [1,11] When LNMO cathodes are combined with traditional graphite anodes, the obtained lithium-ion batteries have an average working voltage of %4.6 V and energy density of %230 Wh Kg À1 .…”