Recycled LiMn2O4 from the spent lithium ion batteries as cathode material for sodium ion batteries: Electrochemical properties, structural evolution and electrode kinetics

Toward Circular Energy: Exploring Direct Regeneration for Lithium-Ion Battery Sustainability

Lithium-ion batteries (LIBs) are rapidly developing into attractive energy storage technologies. As LIBs gradually enter retirement, their sustainability is starting to come into focus. The utilization of recycled spent LIBs as raw materials for battery manufacturing is imperative for resource and environmental sustainability. The sustainability of spent LIBs depends on the recycling process, whereby the cycling of battery materials must be maximized while minimizing waste emissions and energy consumption. Although LIB recycling technologies (hydrometallurgy and pyrometallurgy) have been commercialized on a large scale, they have unavoidable limitations. They are incompatible with circular economy principles because they require toxic chemicals, emit hazardous substances, and consume large amounts of energy. The direct regeneration of degraded electrode materials from spent LIBs is a viable alternative to traditional recycling technologies and is a nondestructive repair technology. Furthermore, direct regeneration offers advantages such as maximization of the value of recycled electrode materials, use of sustainable, nontoxic reagents, high potential profitability, and significant application potential. Therefore, this review aims to investigate the state-of-the-art direct LIB regeneration technologies that can be extended to large-scale applications.

MnCO3 Cuboids from Spent LIBs: A New Age Displacement Anode to Build High-Performance Li-Ion Capacitors

The advantage of hybridizing battery and supercapacitor electrodes has succeeded recently in designing hybrid charge storage systems such as lithium-ion capacitors (LICs) with the benefits of higher energy than supercapacitors and more power density than batteries. However, sluggish Li-ion diffusion of battery anode is one of the main barriers and hampers the development of high-performance LICs. Herein, is introduced a new conversion/displacement type anode, MnCO₃ , via effectively recycling spent Li-ion batteries cathodes for LICs applications. The MnCO₃  cuboids are regenerated from the spent LiMn₂ O₄  cathodes by organic acid lixiviation process, and hydrothermal treatment displays excellent reversibility of 535  mAh g^-1  after 50  cycles with a Coulombic efficiency of >99%. Later, LIC is assembled with the regenerated MnCO₃  cubes in pre-lithiated form (Mn⁰  + Li₂ CO₃ ) as anode and commercial activated carbon (AC) as the cathode, delivering a maximum energy density of 169.4 Wh kg^-1  at 25 °C with ultra-long durability of 15,000 cycles. Even at various atmospheres like -5 and 50 °C, this LIC can offer a energy densities of 53.8 and 119.5 Wh kg^-1 , respectively. Remarkably, the constructed AC/Mn⁰  + Li₂ CO₃ -based LIC exhibits a good cycling performance for a continuous 1000 cycles with >91% retention invariably for all temperature conditions.

A Review on Regenerating Materials from Spent Lithium-Ion Batteries

Recycling spent lithium-ion batteries (LIBs) have attracted increasing attention for their great significance in environmental protection and cyclic resources utilization. Numerous studies focus on developing technologies for the treatment of spent LIBs. Among them, the regeneration of functional materials from spent LIBs has received great attention due to its short process route and high value-added product. This paper briefly summarizes the current status of spent LIBs recycling and details the existing processes and technologies for preparing various materials from spent LIBs. In addition, the benefits of material preparation from spent LIBs, compared with metals recovery only, are analyzed from both environmental and economic aspects. Lastly, the existing challenges and suggestions for the regeneration process are proposed.

Turning commercial MnO2 (≥85 wt%) into high-crystallized K+-doped LiMn2O4 cathode with superior structural stability by a low-temperature molten salt method

The obtainment of low-cost, easily prepared and high-powered LiMn₂O₄ is the key to achieve its wide application in various electronic devices. In this work, a mild and easily scaled molten salt method (KCl@LiCl) is utilized to convert commercial MnO₂ to the high-performance LiMn₂O₄. At the same reaction temperature, the molten salt method leads to the formation of K⁺-doped LiMn₂O₄ with higher crystallinity compared to the conventional solid state method, which contributes to the improved inner charge transfer. The Li₃PO₄ protective layer is coated on the surface of K⁺-doped LiMn₂O₄ to elevate the interfacial stability and the Li⁺ transfer on interface. Thus, the optimized electrode shows a higher specific discharge capacity (103/60 mAh g^-1 at 0.02/2 A g^-1) and a longer cyclic life (80 mAh g^-1 after 500 cycles at 0.5 A g^-1) compared to those of LiMn₂O₄ by solid state method (49/2 mAh g^-1 at 0.02/2 A g^-1 and 20 mAh g^-1 after 500 cycles at 0.5 A g^-1).

Spinel-Layered Intergrowth Composite Cathodes for Sodium-Ion Batteries

The vital challenge of a layered manganese oxide cathode for sodium-ion batteries is its severe capacity degradation and sluggish ion diffusion kinetics caused by irreversible phase transitions. In response to this problem, the spinel-layered manganese-based composite with an intergrowth structure is ingeniously designed by virtue of an interesting spinel-to-layered transformation in the delithiated LiMn₂O₄ under Na⁺ insertion. This unique spinel-layered intergrowth structure is strongly confirmed by combining multiple structure analysis techniques. The layered component can provide more reversible capacity, while the spinel component is crucial for the stabilized crystal structure and accelerated ion diffusion kinetics. As an appealing cathode for sodium-ion batteries, the layered-spinel composite delivers a high reversible capacity of 180.9 mAh g^-1, excellent cycling stability, and superior rate capability with 55.7 mAh g^-1 at 12 C. Furthermore, the reaction mechanism upon Na⁺ extraction/insertion is revealed in detail by ex situ X-ray diffraction and X-ray photoelectron spectroscopy, indicating that Na⁺ ions can be accommodated by the layered structure at a low voltage and by the spinel at a high voltage. This study will provide a new idea for the rational design of an advanced cathode for sodium-ion batteries.

Efficient process for recovery of waste LiMn2O4 cathode material precipitation thermodynamic analysis and separation experiments

An efficient process is proposed for recovery of waste LiMn₂O₄ cathode material, which is one of the most commonly used cathode materials in LIBs. This report constitutes the precipitation thermodynamic analysis and separation experiments based on the water-leaching solutions during the processes of low-temperature calcination with (NH₄)₂SO₄ and water-leaching. Precipitation thermodynamic analysis is undertaken to investigate the effects of initial concentration of the target solution, [N]_T1, excess precipitant, and addition of (NH₄)₂SO₄ on the manganese precipitation in the Mn²⁺-Li⁺-SO₄^2--NH₃-NH₄⁺-CO₃^2--H₂O system. Moreover, the effects of initial concentration of the target solution, [N]_T2, and excess precipitant on the lithium precipitation in the Li⁺-SO₄^2--NH₃-NH₄⁺-CO₃^2--H₂O system are investigated. All these factors clearly influence the manganese and lithium precipitation, particularly the [N]_T and the presence of excess precipitant in the system. The precipitation experimental results demonstrate that the optimal conditions are: a precipitation temperature of 35 °C; an excess coefficient of the precipitant of 2.4; the use of NHC-3 to precipitate the ML-3 solution; a maximum precipitation percentage of manganese of 99.96%; and an absence of Li₂CO₃ precipitation. The double-sulfate salts (Li(NH₄)SO₄ & (NH₄)₂SO₄) evaporated and crystallised from the Li⁺/NH₄⁺ solution are mixed with the waste LiMn₂O₄ cathode material for calcination and water leaching, for which the efficiencies of Li and Mn are 100% and 96.89%, respectively. The double-sulfate salts are calcined at 550 °C for 45 min to obtain the Li₂SO₄ product. Finally, the complete recovery and separation of Mn and Li in the waste LiMn₂O₄ cathode material are achieved.