Electrochemical Performance of Sol-Gel Synthesized LiFePO[sub 4] in Lithium Batteries

Abstract

LiFePO 4 , Li 0.98 Mg 0.01 FePO 4 , and Li 0.96 Ti 0.01 FePO 4 were synthesized via a sol-gel method, using a variety of processing conditions. For comparison, LiFePO 4 was also synthesized from iron acetate by a solid state method. The electrochemical performance of these materials in lithium cells was evaluated and correlated to mean primary particle size and residual carbon structure in the LiFePO 4 samples, as determined by Raman microprobe spectroscopy. For materials with mean agglomerate sizes below 20 µm, an association between structure and crystallinity of the residual carbon and improved utilization was observed. Addition of small amounts of organic compounds or polymers during processing results in carbon coatings with higher graphitization ratios and better electronic properties on the LiFePO 4 samples and improves cell performance in some cases, even though total carbon contents remain very low (<2%). In contrast, no performance enhancement was seen for samples doped with Mg or Ti. These results suggest that it should be possible to design high power LiFePO 4 electrodes without unduly compromising energy density by optimizing the carbon coating on the particles.

Optimization of carbon coatings on LiFePO4

“…LiFePO 4 was synthesized by a sol-gel procedure described in our previous publications [9,11]. Pyromellitic acid (PA) and ferrocene were dissolved in acetone or ethanol and added to the sample after initial firing at 500°C under flowing N 2 .…”

All‐Solid‐State Lithium‐Ion Microbatteries: A Review of Various Three‐Dimensional Concepts

“…It has also shown to be effective as thin fi lm electrode, which can be deposited by pulsed laser deposition [ 61 , 62 ] and sputter deposition. [63][64][65] Sol-gel techniques have been applied to form LiFePO 4 powders, [66][67][68][69] but this method can possibly be extended to thin fi lm deposition.…”

Enhanced Electrochemical Properties of LiFePO&lt;sub&gt;4&lt;/sub&gt; as Positive Electrode of Li-Ion Batteries for HEV Application

“…The high-temperature performance is also a critical issue because batteries may be operated at elevated temperatures (around 60˚C). The early drawback of highly resistive LiFePO 4 has been resolved by painting the particle surface with carbon [3][4][5][6].…”