Low‐Temperature Synthesis of LiNiO2 : Reaction Mechanism, Stability, and Electrochemical Properties

Abstract

A thorough study was made concerning the formation of LiNiO2 by a low‐temperature ion‐exchange reaction under hydrothermal conditions. LiNiO2 with a low degree of cationic mixing and good electrochemical performance was prepared either from pure β‐NiOOH, γ‐NiOOH, or a mixture of both where the γ phase was the majority. The synthesized product false(LT‐LiNiO2false) presents electrochemical properties similar to LiNiO2 prepared by conventional powder synthesis false(HT‐LiNiO2false) in spite of the difference in Brunauer, Emmett, and Teller (BET) surfaces, around 20 m2/g for LT‐LiNiO2 and 0.7 m2/g for HT‐LiNiO2 . The thermal and moisture stabilities of LT‐LiNiO2 were studied and turned out to be much lower than those of HT‐LiNiO2 . This moisture instability was found (i) to be intrinsic to LiNiO2 , since ground HT‐LiNiO2 samples presented a similar behavior, (ii) to be enhanced by decreasing the LiNiO2 particle size, and (iii) to be much larger than that of LiCoO2 . In view of electrochemical applications, cobalt‐substituted products should be used in order to ensure the stability against both reduction‐delithiation and hydrolysis.

Layered lithium transition metal oxide cathodes towards high energy lithium-ion batteries

“…One can expect an effective capacity of about 200 mAh g À1 when assembling this material for LIBs. The unit cell parameters of LiNiO 2 are very close to the corresponding values of a cubic unit cell, suggesting that the displacement of Ni and Li ions takes place without a dimensional mismatch compared with that for LiCoO 2 53,55. This results in the wellknown difficulty in preparing ordered phases without contamination of Ni cations in the Li layers.…”

There and Back Again—The Journey of LiNiO2 as a Cathode Active Material

“…Excess water was proposed to lead to severe extraction of Li from the layered structure, while ethanol was suggested to be a promising (but more costly) alternative . It should also be noted that LNO is structurally related to NiOOH polymorphs, so that washing using water may result in Li/H exchange, as recently suggested for NCM materials . In general, the above considerations about water apply also to the moisture sensitivity of the compound, thus handling in a dry atmosphere is crucial.…”

Hin und zurück – die Entwicklung von LiNiO2 als Kathodenaktivmaterial

“…Da vermutet wurde, dass überschüssiges Wasser zu einer starken Li‐Extraktion aus der Schichtstruktur führen könnte, wurde Ethanol als vielversprechende (jedoch kostspieligere) Alternative vorgeschlagen . Es sollte beachtet werden, dass LNO strukturell mit NiOOH‐Polymorphen verwandt ist, sodass das Waschen mit Wasser zu einem Li/H‐Austausch führen könnte, wie kürzlich für NCM‐Materialien vermutet wurde . Generell gelten die obigen Überlegungen auch für die Feuchtigkeitsempfindlichkeit der Verbindung, weshalb Handhabung in trockener Atmosphäre besonders wichtig ist.…”