Oxidation Reaction of Polyether-Based Material and Its Suppression in Lithium Rechargeable Battery Using 4 V Class Cathode, LiNi_1/3Mn_1/3Co_1/3O₂

Abstract

The all solid-state lithium battery with polyether-based solid polymer electrolyte (SPE) is regarded as one of next-generation lithium batteries, and has potential for sufficient safety because of the flammable-electrolyte-free system. It has been believed that polyether-based SPE is oxidized at the polymer/electrode interface with 4 V class cathodes. Therefore, it has been used for electric devices such as organic transistor, and lithium battery under 3 V. We estimated decomposition reaction of polyether used as SPE of all solid-state lithium battery. We first identified the decomposed parts of polyether-based SPE and the conservation of most main chain framework, considering the results of SPE analysis after long cycle operations. The oxidation reaction was found to occur slightly at the ether bond in the main chain with the branched side chain. Moreover, we resolved the issue by introducing a self-sacrificing buffer layer at the interface. The introduction of sodium carboxymethyl cellulose (CMC) to the 4 V class cathode surface led to the suppression of SPE decomposition at the interface as a result of the preformation of a buffer layer from CMC, which was confirmed by the irreversible exothermic reaction during the first charge, using electrochemical calorimetry. The attained 1500 cycle operation is 1 order of magnitude longer than those of previously reported polymer systems, and compatible with those of reported commercial liquid systems. The above results indicate to proceed to an intensive research toward the realization of 4 V class "safe" lithium polymer batteries without flammable liquid electrolyte.

Intermolecular Chemistry in Solid Polymer Electrolytes for High‐Energy‐Density Lithium Batteries

“…The former is especially important for the application of high HOMO polymer coupled with high‐voltage cathode materials. To ensure the stability of polymer, lithium salts (such as LiPF 6 , LiBOB, Li[(CF 3 SO 2 )( n ‐C 4 F 9 SO 2 )N] (LiTNFSI)) and binder (namely carboxymethylcellulose) have been employed to build a stable interface. The anions of lithium salts can access to the cathode materials through electromigration during cycling.…”

“…Furthermore, T. Kobayashi et al has observed the oxidation reaction of the polyether‐based electrolyte (P(EO/MEEGE) by FTIR and gel permeation chromatography (GPC). They proposed the oxidation reaction occurring slightly at the ether bond in the main chain with the branched side chain . Therefore, the key factor is ether oxygen group rather than lithium salt anion limiting the electrochemical stability of electrolyte.…”

Interface Issues and Challenges in All‐Solid‐State Batteries: Lithium, Sodium, and Beyond

“…[ 67 ] Therefore, improving high‐voltage stability is important for advanced polymer‐based solid‐state batteries. Grafting of functional groups, [ 68 ] blending with different polymers, [ 69 ] inorganic/organic composite electrolyte, [ 70 ] etc., can significantly broaden the window voltage. In addition, with the selected lithium salts, in situ polymerization of novel PVCA‐based SPEs has also exhibited a high stable voltage of 4.5 V. [ 71 ] A recent study indicated that coating ion‐conductive but electron‐insulating interlayer on the cathodes, such as the LATP coated LiCoO 2 , [ 72 ] LATP coated LiNi 0.6 Co 0.2 Mn 0.2 O 2 , [ 73 ] or high‐voltage PMA layer coated LiCoO 2 , can remarkably enhance the cell performance (Figure 6c).…”

High‐Performance Sodium‐Ion Batteries and Sodium‐Ion Pseudocapacitors Based on MoS2/Graphene Composites

“…These features point to the great potential of sodium-ion batteries for renewable energy and smart grids. [3,4] To date, various cathode materials, including layered transition metal oxides, [5][6][7][8] organic polymers, [3,9,10] and polyanion fluorophosphates, [11][12][13][14][15] have been reported to reversibly accommodate Na ions. Anode research is mainly focused on carbonaceous material, [16][17][18] alloyable metals, [19] alloyable metal oxides/sulfides [20][21][22][23] and non-metal elements.…”