How Synthetic Quench Rate and Composition Affect the Performance of Lithium Nickel Manganese Oxide Cathode Materials

Abstract

A survey of layered lithium-rich nickel manganese oxides cathodes, (formula Li[NixLi(1/3–2x/3)Mn(2/3−x/3)]O2), was conducted. We varied the nickel content from 0.1 to x = 0.25, and the post-calcination quench rate was controlled by employing three different methods: direct metal contact, water immersion, and liquid nitrogen immersion. Both composition and quench methodology impacted materials properties and electrochemical function. We observed that there is a synthetic limit for LLRNMO cathodes that occurs in the range of 0.17 > x > 0.10 below which quenching proved to be critically important in determining phase content and electrochemical behavior. Galvanostatic testing revealed the specific discharge capacities of the LLRNMO cathodes increased over the course of cycling, while the XRD characterization after cycling revealed reduced transition metal ordering. We found that the layered lithium-rich nickel manganese oxide materials made with water quenching performed the best with initial C/20 capacities increasing from around 200 mAh g−1 to over 250 mAh g−1 after 28 cycles while retaining C/2 capacities in excess of 200 mAh g−1.

Native lattice strain induced structural earthquake in sodium layered oxide cathodes

“…Quenching-induced strain generation has been well known in steel manufacturing 44 . It has been also often used for the fabrication of battery cathode materials to control grain size, oxygen vacancies, and etc 45 , 46 . During quenching, a highly inhomogeneous temperature field is generated, which can result in heterogeneous thermal stresses, thus leading to residual stresses being introduced at the end of the quenching process.…”

The Importance of Structural Uniformity and Chemical Homogeneity in Cobalt‐Free Lithium Excess Nickel Manganese Oxide Cathodes

“…These results are consistent with our previous investigation's findings that more rapidly quenched samples demonstrated increased capacity and capacity growth. [ 1 ]…”

“…understudied, part of cathode synthesis, and previous results indicate that lithium excess cathode materials are particularly sensitive to cooling rate. [1] In this investigation, we explore the impacts of cooling rate on the chemical and structural homogeneity of the resultant lithium excess cathodes. [1,3,4] Several contemporary cathodes, such as Li[Ni x Mn (1/2−x/2) Co (1/2−x/2) ]O 2 (NMC) where 0.33 ≤ x ≤ 0.8 and Li[Ni x Co y Al z ]O 2 where x + y + z = 1 (NCA), are derivates of the lithium cobalt oxide cathode first described by John B. Goodenough.…”

“…[1] In this investigation, we explore the impacts of cooling rate on the chemical and structural homogeneity of the resultant lithium excess cathodes. [1,3,4] Several contemporary cathodes, such as Li[Ni x Mn (1/2−x/2) Co (1/2−x/2) ]O 2 (NMC) where 0.33 ≤ x ≤ 0.8 and Li[Ni x Co y Al z ]O 2 where x + y + z = 1 (NCA), are derivates of the lithium cobalt oxide cathode first described by John B. Goodenough. [5,6] These oxides have a R-3m layered structure where there are alternating layers of lithium and transition metals with a layer of oxygen between.…”

“…[3,4,12,15,16,18,19,21,22,[38][39][40][41][42][43][44] The literature frequently reports that the differences in the structure are, in great part, the result of differing synthetic routes, and/or variance in the utilized synthetic steps and conditions. [1,4,15,22,41,42] The ambiguity concerning whether these materials consist of nanocomposites of Li 2 MnO 3 and LiNi .5 Mn 0.5 O 2 , or aare instead a single-phase/solid solution material, has made it difficult to accurately attribute the various shortcomings these materials exhibit to any root causes. Despite this, previous investigations have revealed several methods for postproduction processing that can mitigate or eliminate some of the challenges of low-rate capabilities, capacity and voltage fade, and structural instability.…”