Alternate Synthesis Method for High‐Performance Manganese Rich Cation Disordered Rocksalt Cathodes

Abstract

Cation‐disordered rocksalt (DRX) cathodes have recently emerged as a promising class of cobalt‐free, high‐capacity cathodes for lithium‐ion batteries. To facilitate their commercialization, the development of scalable synthesis techniques providing control over composition and morphology is critical. To this end, a sol‐gel synthesis route to prepare Mn‐rich DRX cathodes with high capacities is presented here. Several compositions with varied Mn content and nominal F doping are successfully prepared using this technique. In‐situ X‐ray diffraction measurements demonstrate that DRX formation proceeds at moderate temperature (800 °C) through the sol‐gel route, which enables intimate mixing among reactive intermediate phases that form at lower temperatures. All synthesized compositions possess cation short‐range order, as evidenced by neutron pair distribution function and electron diffraction analysis. These DRX materials demonstrate promising electrochemical performance with reversible capacities up to 275 mAh g. Compared to the baseline oxide (Li1.2Mn0.4Ti0.4O2), the Mn‐rich compositions exhibit improved cycling stability, with some showing an increase in capacity upon cycling. Overall, this study demonstrates the feasibility of preparing high‐capacity DRX cathodes through a sol‐gel based synthesis route, which may be further optimized to provide better control over the product morphology compared to traditional synthesis methods.

Ultrahigh‐Capacity Rocksalt Cathodes Enabled by Cycling‐Activated Structural Changes

“…Table S1, Supporting Information, summarizes previously reported DRX compositions and their cycling behavior. Similar changes in voltage profiles and capacity evolution were observed on DRX materials with either higher Mn or F content, [15,34,40,14,68,69] although the detailed structural analysis was not reported in these studies. This includes studies carried out on Li 1.2 Mn 0.6 Ti 0.2 O 1.8 F 0.2 , [40] Li 1.2 Mn 0.7 Ti 0.1 O 2 , [68] Li 1.2 Mn 0.7 Nb 0.1 O 1.8 F 0.2 , [34] Li 1.2 Mn 0.7 Ti 0.1 O 1.7 F 0.3 , [69] Li 1.1 Mn 0.8 Ti 0.1 O 1.9 F 0.1 (M80, this study), and Li 1.05 Mn 0.9 Nb 0.05 O 2 .…”

“…Similar changes in voltage profiles and capacity evolution were observed on DRX materials with either higher Mn or F content, [15,34,40,14,68,69] although the detailed structural analysis was not reported in these studies. This includes studies carried out on Li 1.2 Mn 0.6 Ti 0.2 O 1.8 F 0.2 , [40] Li 1.2 Mn 0.7 Ti 0.1 O 2 , [68] Li 1.2 Mn 0.7 Nb 0.1 O 1.8 F 0.2 , [34] Li 1.2 Mn 0.7 Ti 0.1 O 1.7 F 0.3 , [69] Li 1.1 Mn 0.8 Ti 0.1 O 1.9 F 0.1 (M80, this study), and Li 1.05 Mn 0.9 Nb 0.05 O 2 . [14] Based on the above observations, we estimated an Mn content threshold of about 0.6, above which the structural transformations occur.…”

Enhancing the Electrode Gravimetric Capacity of Li1.2Mn0.4Ti0.4O2 Cathode Using Interfacial Carbon Deposition and Carbon Nanotube-Mediated Electrical Percolation

“…Li 1.2 Mn 0.4 Ti 0.4 O 2 DRX powder was synthesized using a sol−gel-based approach, as detailed in a previous publication. 12 To produce a batch of 1.5 g of product, stoichiometric amounts of anhydrous LiNO 3 (Stream Chemicals, 99%) and Mn(CH 3 COO) 2 •4H 2 O (Sigma-Aldrich, ≥99%) were dissolved in ethanol sequentially, and then titanium isopropoxide (Alfa Aesar, 95%) was added dropwise to this solution. 0.25 g of glacial acetic acid (Alfa Aesar, 99.7+%) and 0.15 g amount of water were added to this solution.…”

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes Enabled by a Graphite Conductive Additive

“…The present study reports how three different conductive carbon additives (Super C65, synthetic graphite KS-6, and ketjenblack EC600JD) impact the structure and performance of Li 1.2 Mn 0.5 Ti 0.3 O 1.9 F 0.1 (LMTOF01) DRX cathodes. The electrochemical performance of LMTOF01/carbon/binder composite cathodes with varying carbon contents (10,15, and 20 wt %, denoted as 80:10:10, 75:15:10, and 70:20:10 cathode compositions, respectively) for each carbon type are reported. To complement the electrochemical investigations, a suite of in situ and ex situ characterization methods was employed to probe the differences in the cathodes' structure and performance.…”

“…Lithium-excess disordered rocksalt (DRX) oxides and oxyfluorides have recently emerged as a promising class of next-generation Li-ion cathodes containing earth-abundant elements including Mn and Ti. − DRX cathodes exhibit high reversible capacities (up to 300 mAh g –1 ) by utilizing a combination of transition-metal and oxygen redox processes. − Recent research on DRX cathodes has focused on understanding the synthesis, structure–property relationships, and redox mechanisms in these materials. − However, DRX cathodes are still in their infancy, and several challenges need to be overcome before they can compete with market-dominant chemistries such as LiCoO 2 (LCO) and LiNi x Mn y Co 1– x – y O 2 (NMC). One such challenge is to reduce the carbon content in composite DRX cathodes without compromising the active material’s reversible capacity or cycling stability.…”