Melt Synthesis of Lithium Manganese Iron Phosphate: Part I. Composition, Physical Properties, Structural Analysis, and Charge/Discharge Cycling

Abstract

Melt synthesis is a fast and simple process to make dense LiMnyFe1-yPO4 (LMFP with 0 ≤ y ≤ 1) from all-dry, low-cost precursors with zero waste. This study characterizes melt LMFP materials with 0-100% Mn after particle size reduction by planetary milling and carbon coating with glucose. The melt LMFP samples show higher electrical conductivity at similar pellet density than LFP (0% Mn) and LMFP (79% Mn) reference samples made by traditional methods. The melt LMFP samples exhibit higher crystallinity than the reference samples and show no crystalline impurities. Their unit cell volume and crystallographic density scale with Mn content; the percentage of Fe and/or Mn in Li positions is below 1.5%, which is comparable to reference samples. Crystallite sizes of at least 100 to 175 nm are observed for melt LMFP, which is larger than the fine ~50 nm crystallites of reference LMFP. Melt LFP shows specific discharge capacity and cycling stability comparable to reference LFP, but the melt LMFP samples with 25-100% Mn shows worse performance than reference LMFP (79% Mn). Part two of this study will quantify the solid-state lithium diffusion coefficient in melt LMFP materials and correlate it to their electrochemical performance.

Reversible Self-discharge of LFP/Graphite and NMC811/Graphite Cells Originating from Redox Shuttle Generation

“…13 An additional 4.2 V hold after formation does not have a strong influence on the initial capacities (see Fig. 3b-1), since LFP has no capacity beyond 3.65 V. 16,17 CTRL cells show high reversible losses even at T S = 40 °C (see Fig. 3a-1).…”

LiMn0.8Fe0.2PO4/C Nanoparticles via Polystyrene Template Carburizing Enhance the Rate Capability and Capacity Reversibility of Cathode Materials

“…Moreover, the production cost of LMFP is relatively low, making it more competitive in the market. 27,28 LiFe x Mn 1−x PO 4 and LiMnPO 4 are two common cathode materials for lithium-ion batteries, and they exhibit significant differences in chemical composition and structure, leading to distinct electrochemical performance and application characteristics. 29 First, in terms of chemical composition, LiFe x Mn 1−x PO 4 contains iron, while LiMnPO 4 primarily consists of manganese.…”

“…In terms of environmental friendliness, LMFP is relatively eco-friendly as it does not contain harmful heavy metal elements like nickel and cobalt, reducing its negative impact on the environment. Moreover, the production cost of LMFP is relatively low, making it more competitive in the market. , …”

Correlating Mn Dissolution and Capacity Fade in LiMn0.8Fe0.2PO4/Graphite Cells During Cycling and Storage at Elevated Temperature

“…Additionally, LFP particles need to be very small to account for low Li diffusivity, further limiting the volumetric energy density. 3 Additionally, LFP has a low crystallographic density, 3.5 g/cc, 4 compared to NMC, 4.8 g/cc, 5 further lowering the energy density. A proposed alternative to LFP is LiMn x Fe 1−x PO 4 (LMFP).…”

“…Unfortunately, the electrochemical performance of LMFP is inferior to other positive electrode materials, due to poor Li diffusion caused by lattice distortion from Jahn-Teller active Mn 3+ , [8][9][10] in addition to rapid capacity fade compared to LFP. 4 It has been shown that the dominant failure mechanism for Li-ion batteries containing LFP is Li inventory loss due to parasitic reactions damaging the solid-electrolyte interface (SEI) at the negative electrode, where Li is consumed to repair the damage. [11][12][13] Additionally, it has been shown that Mn deposition on the negative electrode can amplify SEI degradation, [14][15][16] which would then increase Li inventory loss in LMFP full cells.…”