One-Step Synthesis of LiCo1-1.5xYxPO4@C Cathode Material for High-Energy Lithium-ion Batteries

Abstract

Intrinsically low ion conductivity and unstable cathode electrolyte interface are two important factors affecting the performances of LiCoPO4 cathode material. Herein, a series of LiCo1-1.5xYxPO4@C (x = 0, 0.01, 0.02, 0.03) cathode material is synthesized by a one-step method. The influence of Y substitution amount is optimized and discussed. The structure and morphology of LiCo1-1.5xYxPO4@C cathode material does not lead to obvious changes with Y substitution. However, the Li/Co antisite defect is minimized and the ionic and electronic conductivities of LiCo1-1.5xYxPO4@C cathode material are enhanced by Y substitution. The LiCo0.97Y0.02PO4@C cathode delivers a discharge capacity of 148 mAh g−1 at 0.1 C and 96 mAh g−1 at 1 C, with a capacity retention of 75% after 80 cycles at 0.1 C. Its good electrochemical performances are attributed to the following factors. (1) The uniform 5 nm carbon layer stabilizes the interface and suppresses the side reactions with the electrolyte. (2) With Y substitution, the Li/Co antisite defect is decreased and the electronic and ionic conductivity are also improved. In conclusion, our work reveals the effects of aliovalent substitution and carbon coating in LiCo1-1.5xYxPO4@C electrodes to improve their electrochemical performances, and provides a method for the further development of high voltage cathode material for high-energy lithium-ion batteries.

Scalable Precursor-Assisted Synthesis of a High Voltage LiNiyCo1−yPO4 Cathode for Li-Ion Batteries

“…Generally, a LiNiPO4 cathode exhibits a flat plateau at approximately 5 V, corresponding to the Ni 3+ /Ni 2+ redox couple [58]. The LNCP cathode shows a discharge voltage plateau at about 4.8 V, which is slightly lower considering the expected Ni 3+ /Ni 2+ redox couple but is in good agreement with previous publications for the Co 3+ /Co 2+ redox couple in LiCoPO4 [11,13]. When an LNCP cathode is combined with an LTO anode, this full cell displays a discharge plateau at 3.12 V in the voltage profile during the galvanostatic cycling test (Figure 4d).…”

“…Nevertheless, the sluggish kinetics of the electronic and lithium-ion transport for these cathodes pose a major constraint to their development. Numerous modifications have been adapted to improve the Li extraction/insertion kinetics and electronic conductivity, including morphology control [11,12], metal ion doping [13], metal oxide coating [14][15][16], and carbon coating [17,18]. Manickam Minakshi et al have conducted several studies on olivine cathodes [19][20][21][22][23].…”

How Synthetic Quench Rate and Composition Affect the Performance of Lithium Nickel Manganese Oxide Cathode Materials

“…[1][2][3] As such, there is a need for reliable cobalt free cathodes, and layered lithium rich nickel manganese oxides (LLRNMO), specifically those within the compositional range of Li[Ni x Li (1/3-2x/3) Mn (2/3−x/3) ]O 2 (x <.50), have demonstrated high (>200 mAh g −1 ) specific capacities, and high functional voltage windows (2.0-4.8 V), making them a promising family of cobalt free cathode materials. [4][5][6][7] LLRNMO materials have a large body of literature dedicated to their structure, and electrochemical behaviors. 4,5,[8][9][10] The main drawbacks of these materials are their low rate capabilities, and poor capacity retention caused by structural instability wherein the materials experience oxygen losses, and the migration of transition metal ions over the course of cycling.…”

“…4,5,[8][9][10] The main drawbacks of these materials are their low rate capabilities, and poor capacity retention caused by structural instability wherein the materials experience oxygen losses, and the migration of transition metal ions over the course of cycling. [5][6][7][8][11][12][13] Several complex synthetic routes using scaffolds, dopants or surface modifications and coatings on LLRNMOs can help mitigate oxygen loss and thus serve to improve functionality. 6,[14][15][16][17][18][19][20][21] More recently it has been demonstrated that an O2-type oxygen structure can prevent undesirable irreversible transition metal ion migration, thereby greatly improving capacity retention.…”

“…As seen in Table I the number of investigations exploring the effects of nickel composition on the performance LLRNMO cathodes has decreased over time; with few studies exploring multiple nickel compositions or nickel compositions below x = 0.2. 4,5,7 Table I also shows that there are significant inconsistencies in synthetic routes employed across studies. Additionally, there are few studies that perform a detailed comparative assessment relating the effects of synthetic approach to performance of LLRNMO cathodes.…”