ИСТИНА

Phosphate cathode materials are a major alternative to oxide compounds as lithium-ion battery (LIB) cathodes, primarily due to the success story of lithium iron phosphate LiFePO4, often referred to as LFP. The main difference between phosphate materials and oxide ones is the presence of phosphate (PO4) or pyrophosphate (P2O7) groups, which form a reliable structural framework and “bind” oxygen anions. Due to these factors, phosphate-based materials demonstrate stable cycling over thousands of charge-discharge cycles, the ability to quickly charge or discharge, as well as increased thermal stability, i.e. safety of use. Currently, LFP has become the basis of an entire direction both in research activities and in the field of LIB industry - actively developing and extremely promising. However, the issue of increasing the specific energy density of batteries with the transition from oxide materials to LFP arises very acutely, and today there are three main ways to solve it: 1) increasing energy density by replacing part or all of Fe with Mn, with an increase in the average cell voltage from 3.4 V vs. Li/Li+ for LFP to 4.1 V vs. Li/Li+ for LiMnPO4 (LMP), 2) improving the density of deposition of active layers and increasing the proportion of active material in the total mass of the battery and 3) transition to solid electrolyte and metal lithium (or so-called “anodeless” systems ) at the anode. The report discusses the results of the main ways to achieve these goals. In particular, the use of the solvothermal method for the synthesis of Li(Fe,Mn)PO4 phosphates in combination with spray drying makes it possible to obtain powders of cathode materials with a fairly high tap density, and the use of water-based binders and single-walled carbon nanotubes improves the electrochemical properties of materials even with a high mass fraction of phosphate in the electrode composite and a load of more than 3 mAh/cm2. In addition, the report discusses the fundamental difference between LFP and LMP in terms of synthesis and their electrochemical properties. Particularly, to optimize experimental conditions for the synthesis and post-processing of mixed Li(Fe,Mn)PO4 phosphates, we systematically investigated the solvothermal synthesis of LiFePO4 (LFP) and LiMnPO4 (LMP) using water or 1:1 mixtures of water with ethylene glycol, diethylene glycol, or propylene glycol as solvents. LMP consistently formed smaller particles than LFP under identical synthesis conditions. Furthermore, LMP particle size showed significantly less dependence on the solvent composition compared to LFP. Despite this, the co-solvent choice affected the electrochemical properties of LMP, with diethylene glycol yielding the best performance. Using this co-solvent, we synthesized well-crystallized LiFe0.5Mn0.5PO4 (LFMP) nanoparticles exhibiting a fairly high capacity, although with a low initial tap density. Subsequent spray drying increased the LFMP tap density by 70% (from 0.7 to 1.2 g cm- 3). Electrodes prepared with water-based binder (carboxymethyl cellulose + styrene-butadiene rubber) and containing 95 wt% active material demonstrated excellent electrochemical performance, delivering a reversible capacity of 150 mAh/g with 89% retention after 300 cycles at a 1C current density.