Topotactic Transformation of Surface Structure Enabling Direct Regeneration of Spent Lithium-Ion Battery Cathodes

Abstract

Recycling spent lithium-ion batteries (LIBs) has become an urgent task to address the issues of resource shortage and potential environmental pollution. However, direct recycling of the spent LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathode is challenging because the strong electrostatic repulsion from a transition metal octahedron in the lithium layer provided by the rock salt/spinel phase that is formed on the surface of the cycled cathode severely disrupts Li + transport, which restrains lithium replenishment during regeneration, resulting in the regenerated cathode with inferior capacity and cycling performance. Here, we propose the topotactic transformation of the stable rock salt/spinel phase into Ni 0.5 Co 0.2 Mn 0.3 (OH) 2 and then back to the NCM523 cathode. As a result, a topotactic relithiation reaction with low migration barriers occurs with facile Li + transport in a channel (from one octahedral site to another, passing through a tetrahedral intermediate) with weakened electrostatic repulsion, which greatly improves lithium replenishment during regeneration. In addition, the proposed method can be extended to repair spent NCM523 black mass, spent LiNi 0.6 Co 0.2 Mn 0.2 O 2 , and spent LiCoO 2 cathodes, whose electrochemical performance after regeneration is comparable to that of the commercial pristine cathodes. This work demonstrates a fast topotactic relithiation process during regeneration by modifying Li + transport channels, providing a unique perspective on the regeneration of spent LIB cathodes.

Fundamentals, status and challenges of direct recycling technologies for lithium ion batteries

“…13c). 167 By adding NH 3 ·H 2 O during the hydrothermal process, the rock salt and spinel phases were topotactically transformed into Ni 0.5 Co 0.2 Mn 0.3 (OH) 2 , which provided a path with low migration energy for Li + .…”

“…Fig. 13 (a) Schematic of the repair process of spent NCM622 by pre-oxidation and Li supplement calcination, 160 Copyright 2021, American Chemical Society; (b) saturated vapor pressure of H 2 O under different temperatures associated with equipment changes during the hydrothermal repair process of NCM111, 166 Copyright 2022, Elsevier; (c) schematic of the failure and topotactic transformation regeneration process of NCM523, 167 Copyright 2023, American Chemical Society; (d) schematic of the molten salt assisted process of degraded NCM523, 170 Copyright 2022, American Chemical Society; (e) synthesis scheme of three kinds of ionic liquid for the repair of NCM111, 171 In addition to the above three mainstream direct recycling strategies, other methods such as redox mediation-assisted recycling and electrochemical relithiation, can be used for the repair and regeneration of layer ternary materials. [172][173][174] As the popularity of EVs grows exponentially, the requirements for technical indicators such as service life, endurance mileage and fast-charging performance are also rapidly increasing.…”

Cathode regeneration and upcycling of spent LIBs: toward sustainability

“…Before that happens, cathodes (with current collectors) need to be manually separated from other cell components (including anodes, separators, and battery cases), then rinsed with organic solvents to remove side products from parasitic reactions in the cathode electrolyte interphase (CEI) and electrolyte residual. 34,35 Then, active cathode materials can be peeled off from the current collectors via soaking in solvents under stirring and ultrasonication. In addition, in order to remove conductive carbon and polymer binders, the precipitated spent cathode powders are further annealed at high temperatures.…”

“…46,49 Beyond these reports, considering that the Li + transport can be impeded by the strong electrostatic repulsion from a TM octahedron in the Li layer provided by the inactive impurity phases (rock-salt/spinel), Zhou and coworkers proposed a novel topotactic solid-state sintering regeneration method for spent layered oxide materials. 34 Li-poor phases (rock-salt/spinel), formed on the surface of the cycled cathode materials, were firstly treated with ammonium hydroxide to get TM hydroxides (TM(OH) 2 ) ready for further lithium replenishment, and then back to NCM/LCO cathodes via a facile solid-state sintering process with the addition of LiOH. Solid-state sintering is applicable to various cathode materials with different structures (Table 1).…”

Complete Metal Recycling from Lithium-Ion Batteries Enabled by Hydrogen Evolution Catalyst Reconstruction

“…Lithium-ion batteries (LIBs) have been widely used in portable electronics, electric vehicles, and large-scale energy storage systems for smart grids, the global market of which is estimated to reach $95 billion by 2025. , Considering that the lifetimes of LIBs are around 3–10 years, about 11 million metric tons of spent LIB waste are expected to be generated by 2030 . Most current spent LIBs are disposed of in landfill, and only less than 6% of them are recycled worldwide. , In fact, these end-of-life LIBs can act as secondary resources of metals, considering the depletion of finite resources and continuously increasing prices of these raw materials. , Recycling LIBs could not only eliminate potential environmental pollution but also recover and reuse valuable metals. − Therefore, it is of great importance to recycle spent LIBs. − Unfortunately, existing recycling technologies of LIBs are still economically or environmentally unsustainable. ,, …”