Improved Structural Reversibility and Cycling Stability of Li2MnSiO4 Cathode Material by the Pillar Effect of [TiOx] Polyanions. Issue 15 (18th April 2018)

• Record Type: Journal Article
• Authors: Wu, Xia; Zhao, Shi‐Xi; Wei, Lei; Zhao, En‐Lai; Li, Jing‐Wei; Nan, Ce‐Wen
• Is Part Of: ChemistrySelect. Volume 3:Issue 15(2018)
• Page Start: 4047
• Page End: 4057
• Publication Date: 2018-04-18
• Subjects: Li2MnSiO4 -- [TiO4] Tetrahedrons -- [TiO6] Octahedrons -- Pillaring Effect -- Structure Reversibility; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201800036
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: Li2 MnSiO4 cathode material suffers from structural distortion caused by irreversible transition of [MnO4 ] tetrahedron to [MnO6 ] octahedron and layer exfoliation upon full delithiation, thus resulting in rapid capacity decay during cycling. In this study, Ti was introduced into the Mn site in Li2 MnSiO4 as pillars to prevent the structural collapse. The results showed that [TiO4 ] tetrahedrons and [TiO6 ] octahedrons coexisted in Mn sites, and the proportion of [TiO6 ] octahedrons increased with increasing Ti. [TiO x ] pillared Li2 MnSiO4 samples presented greatly improved cycling stability, especially [TiO6 ] enriched Li2 Mn0.85 Ti0.15 SiO4, which achieved the highest initial Coulumbic efficiency (86%) and the best capacity retention at C/20 rate. Moreover, Li2 Mn0.85 Ti0.15 SiO4 exhibited excellent rate performance and retained 93% of initial discharge capacity after 50 th cycles at C/2 rate. Ex‐situ XPS revealed [TiO x ] pillars, especially [TiO6 ] pillars facilitated the reversible transition of [MnO x ] during cycling. Ex‐situ XRD demonstrated better structure reversibility of [TiO6 ] enriched sample. The enhanced structural reversibility and cycling stability are ascribed to the pillaring effect of [TiO x ], especially large [TiO6 ] octahedrons in structure, which ensure the reversible oxidation/reduction of Mn and alleviate the layer exfoliation during cycling. Abstract : The pillaring effect: Ti IV ions are introduced into Mn sites of Li2 MnSiO4 and form [TiO4 ] tetrahedrons and [TiO6 ] octahedrons. Stable [TiO x ] polyhedrons as a pillaring network effectively suppress irreversible transition from Mn II to Mn IV . [TiO6 ] enriched Li2 Mn0.85 Ti0.15 SiO4 exhibits a high initial Columbic efficiency (86%) and excellent cycling stability, retaining ∼93% of the initial discharge capacity after 50 th cycles.