Safe, Low‐Cost, Fast‐Kinetics and Low‐Strain Inorganic‐Open‐Framework Anode for Potassium‐Ion Batteries

• Published in: Angewandte Chemie International Edition Vol. 58; no. 46; pp. 16474 - 16479
• Main Authors: Zhang, Ruding, Huang, Jiajia, Deng, Wenzhuo, Bao, Jingze, Pan, Yilong, Huang, Shuping, Sun, Chuan‐Fu
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 11.11.2019
• Edition: International ed. in English
• Subjects: Anodes; Batteries; Cell size; Conductors; Disintegration; electrochemistry; Electrode materials; fast kinetics; inorganic open-framework; Insertion; Kinetics; Lattice strain; Life span; low strain; Organic chemistry; Plateaus; Potassium; Potassium titanyl orthophosphate; potassium-ion batteries; Reaction kinetics; Rechargeable batteries; Solid solutions; Structural stability; low strain; fast kinetics; electrochemistry; inorganic open-framework; potassium-ion batteries
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201909202

A key challenge for potassium‐ion batteries is to explore low‐cost electrode materials that allow fast and reversible insertion of large‐ionic‐size K+. Here, we report an inorganic‐open‐framework anode (KTiOPO4), which achieves a reversible capacity of up to 102 mAh g−1 (307 mAh cm−3), flat voltage plateaus at a safe average potential of 0.82 V (vs. K/K+), a long lifespan of over 200 cycles, and K+‐transport kinetics ≈10 times faster than those of Na‐superionic conductors. Combined experimental analysis and first‐principles calculations reveal a charge storage mechanism involving biphasic and solid solution reactions and a cell volume change (9.5 %) even smaller than that for Li+‐insertion into graphite (≈10 %). KTiOPO4 exhibits quasi‐3D lattice expansion on K+ intercalation, enabling the disintegration of small lattice strain and thus high structural stability. The inorganic open‐frameworks may open a new avenue for exploring low‐cost, stable and fast‐kinetic battery chemistry. Inorganic‐open‐framework (IOF) KTiOPO4 allows reversible K+ intercalation into its large interstitial vacancies under a stepwise biphasic and solid solution reaction mechanism. Its fast K+‐transport kinetics (≈10 times higher than those of Na superionic conductors), low‐strain feature (a cell volume change even smaller than that of Li+ insertion in graphite), and high stability, highlight IOFs as a promising new anode category for K‐ion batteries.