Polyanionic (Phosphates, Silicates, Sulfates) Frameworks as Electrode Materials for Rechargeable Li (or Na) Batteries

Abstract

From Oxides to Ionically Conducting Polyanionic Frameworks as Positive Electrodes in Li Batteries 6553 2. The Early Days: The NASICON and Anti-NASICON Structures Used as Model Frameworks 6554 2.1. Structural Considerations 6554 2.2. The Inductive Effect: Tuning the M n+ /M (n−1)+ Redox Couple in the NASICON Structure by Changing the Chemical Nature of the XO 4 n− Groups 6555 2.3. Relative Positions of Various M n+ /M (n−1)+ Redox Couples (M = Fe, Ti, V, Nb) in NASICON-type Phosphates 6555 2.3.1. Position of the Ti 4+ /Ti 3+ Couple versus Li + /Li or Na + /Na 6555 2.3.2. Position of the Fe 3+ /Fe 2+ Couple versus Li + /Li or Na + /Na 6556 2.3.3. Position of the V n+ /V (n−1)+ Couples versus Li + /Li or Na + /Na 6556 2.4. Complex Redox Phenomena in Anti-NASI-CON Compositions Li x M 2 (PO 4 ) 3 (0 < x < 5 ; M = Fe, V) 6556 2.4.1. Li + Insertion into Monoclinic Fe 2 (SO 4 ) 3 , Li 3 Fe 2 (PO 4 ) 3 , and Li 3 Fe 2 (AsO 4 ) 3 6557 2.4.2. Li + Insertion/Extraction into Monoclinic Li 3 V 2 (PO 4 ) 3 6557 3. LiMPO 4 Compositions Based on the Olivine Structure: Fifteen Years of Great Achievements 6558 3.1. The Early Days: From an Academic Curiosity to First Industrial Realizations 6558 3.2. A Myriad of Synthesis Routes Developed for Optimal Electrochemical Response of LiMPO 4 Powders, Industrial Process Ability, and Cost Reduction 6559 3.2.1. Solid-State Syntheses 6559 3.2.2. Solution-Based Syntheses 6560 3.2.3. Carbon Coating and Purity Control of LiFePO 4 6562 3.3. The Highly Insulating LiMnPO 4 6562 3.4. Substitutions of Mn and/or Co for Fe in LiFePO 4 6563 3.5. Intrinsic Physicochemical Properties of LiFe-PO 4 and Mechanism of Li + Extraction 6565 3.5.1. Crystal Structure, Defects, e − Transport, Li + Diffusion 6565 3.5.2. Reactivity with Moisture and/or Air 6566 3.5.3. Mechanism 6567 4. Alternative Polyanionic Structures and Compositions: Hydrated Phosphates, Diphosphates, Alluaudites, Silicates, and Borates 6569 4.1. Fe 3+ /Fe 2+ Couple in Amorphous or Crystalline Iron Phosphates: FePO 4 •nH 2 O 6569 4.

Phosphate Framework Electrode Materials for Sodium Ion Batteries

“…Phosphate framework materials have attracted increasing attention due to their excellent electrochemical performance and versatile structure,29 and are considered as promising Na‐storage electrodes due to the following considerations: (i) phosphate frameworks have high structural stability due to the very stable P‐O frameworks, thus ensuring long‐term cycling and safety of SIBs; the thermal properties of phosphate materials are linked directly to the stability of the phosphate‐metal bonds, which greatly reduce the likelihood of oxygen liberation from the structure; (ii) the 3D framework possesses many roomy interstices, thus leading to lower volumetric expansion and less phase transition during Na ion insertion/extraction, which benefits the structural stability; (iii) phosphate or other substituent groups exhibit inductive effect on the redox couple, thus to give rise to higher redox potential values vs Na/Na + . However, the big size and intrinsic isolating nature of the PO 4 3– groups lead to a moderate capacity and low electron conductivity.…”

NaFe3(HPO3)2((H,F)PO2OH)6: A Potential Cathode Material and a Novel Ferrimagnet

“…Due to the similarity in the operation of lithium and sodium ion batteries, sodium equivalents of the lithium based electrode materials, such as hard carbon, phosphates, pyrophosphates and oxides, have been described. [8][9][10] Layered oxides, AMO 2 , where A = Li, Na and M is one or more transition metals, exhibit very different behavior depending on the alkali ion. For example, electrochemically inactive LiFeO 2 and LiCrO 2 behave well in their sodium forms, NaFeO 2 and NaCrO 2 , due to the accessibility of the Fe 4+ and Cr 4+ states when A = Na.…”

Electrospun P2-type Na2/3(Fe1/2Mn1/2)O2 Hierarchical Nanofibers as Cathode Material for Sodium-Ion Batteries

“…7,8 Layered sodium metal oxides are classified as O3-and P2-types, based on the location of the Na-ion at octahedral and prismatic sites, respectively, and there are sub-groups of new phases such as the new O3 and P`3-phases. 9 The P2-type layered oxides such as Na 0.6 MnO 2 and Na 0.7 CoO 2 show improved initial capacity when compared to those of the O3-type NaMO 2 (M = Co, Cr, V, Ni 0.5 Mn 0.5 , etc.…”