Constructing hierarchical heterojunction structure for K/Co co-substituted Na3V2(PO4)3 by integrating carbon quantum dots

Zeyi Tian; Yanjun Chen; Shiqi Sun; Honglang Liu; Chao Wang; Que Huang; Changcheng Liu; Yanzhong Wang; Li Guo

doi:10.1016/j.jcis.2021.12.195

Constructing hierarchical heterojunction structure for K/Co co-substituted Na₃V₂(PO₄)₃ by integrating carbon quantum dots

J Colloid Interface Sci. 2022 May:613:536-546. doi: 10.1016/j.jcis.2021.12.195. Epub 2022 Jan 5.

Authors

Zeyi Tian¹, Yanjun Chen², Shiqi Sun¹, Honglang Liu¹, Chao Wang³, Que Huang⁴, Changcheng Liu⁴, Yanzhong Wang¹, Li Guo⁵

Affiliations

¹ School of Materials Science and Engineering, North University of China, Taiyuan, China; Advanced Energy Materials and Systems Institute, North University of China, Taiyuan, China.
² School of Materials Science and Engineering, North University of China, Taiyuan, China; Advanced Energy Materials and Systems Institute, North University of China, Taiyuan, China. Electronic address: yjchen@nuc.edu.cn.
³ School of Materials Science and Engineering, North University of China, Taiyuan, China; Advanced Energy Materials and Systems Institute, North University of China, Taiyuan, China. Electronic address: wangchao_nuc@126.com.
⁴ Advanced Energy Materials and Systems Institute, North University of China, Taiyuan, China; School of Environment and Safety Engineering, North University of China, Taiyuan, China.
⁵ Advanced Energy Materials and Systems Institute, North University of China, Taiyuan, China. Electronic address: guoli@nuc.edu.cn.

PMID: 35063785
DOI: 10.1016/j.jcis.2021.12.195

Abstract

Na₃V₂(PO₄)₃ (NVP) has been widely adopted as cathode in sodium ion battery devices. Nevertheless, the weak intrinsic conductivity and serious structural collapse limit the further development. Herein, a simultaneous modified strategy of doping K/Co and integrating carbon quantum dots (CQD) is proposed. Substituting K⁺ is beneficial to afford amount of Na⁺ transport within the stabled and expanded lattice. The introduction of Co²⁺ generates beneficial hole carriers to improve conductivity. Furthermore, the bonding of conductive CQD guides to obtain nano-sized NVP grains, reducing the pathway for ionic migration to accelerate the diffusion capability. Importantly, a unique p-n type heterojunction construction is established in the interface between CQD (n-type) and NVP (p-type). This heterojunction structure enhances the mobility of electrons owing to the free pathways, in which the electrons transport in a relatively lower energy level without the scatter and collision of anions dopants. Ultimately, K_0.1Na_2.95V_1.95Co_0.05(PO₄)₃@CQD exhibits with the best energy output level. It's initial capacity under 5C is 109.8 mA h g^-1 and the retention is 87.6% after cycle 400 cycles. Even at 20 and 50C, its output is 93.5 and 82.6 mA h g^-1 for 1st and 66.6 and 52.1 mA h g^-1 for 1000th cycle, respectively. Finally, an asymmetric full cell test confirms its application practically.

Keywords: CQD; Heterojunction structure; K/Co co-substituted; Na(3)V(2)(PO(4))(3); Sodium ion batteries.