Alkali-iron-cobalt phosphates and related electrode active materials

#This invention relates to electrode active materials, electrodes, and batteries. In particular, this invention relates to active materials comprising lithium or other alkali metals, iron, cobalt, and other transition metals, and phosphates or similar moieties.

#A wide variety of electrochemical cells, or “batteries,” is known in the art. In general, batteries are devices that convert chemical energy into electrical energy, by means of an electrochemical oxidation-reduction reaction. Batteries are used in a wide variety of applications, particularly as a power source for devices that cannot practicably be powered by centralized power generation sources (e.g., by commercial power plants using utility transmission lines).

#Batteries can be generally described as comprising three components: an anode that contains a material that is oxidized (yields electrons) during discharge of the battery (i.e., while it is providing power); a cathode that contains a material that is reduced (accepts electrons) during discharge of the battery; and an electrolyte that provides for transfer of ions between the cathode and anode. During discharge, the anode is the negative pole of the battery, and the cathode is the positive pole. Batteries can be more specifically characterized by the specific materials that make up each of these three components. Selection of these components can yield batteries having specific voltage and discharge characteristics that can be optimized for particular applications.

#An electrode active material of formula Li1.025Co0.85Fe0.05Al0.025Mg0.05PO4(LiCo0.85Fe0.05Al0.025Mg0.05Li0.025PO4) is made as follows. The following sources of Li, Co, Fe, Al, Mg, and phosphate are provided containing the respective elements in a molar ratio of 1.025:0.85:0.05:0.025:0.05:1. 1 0.05125 moles Li2CO3 (mol. wt. 73.88 g/mol) 3.8 g 0.02833 moles Co3 O4 (240.8 g/mol) 6.82 g 0.0025 moles Fe2 O3 (159.7 g/mol) 0.4 g 0.0025 moles Al (OH)3 (78 g/mol) 0.195 g 0.005 moles Mg(OH)2 (58 g/mol) 0.29 g 0.1 moles (NH4)2HPO4 (132 g/mol) 13.2 g 0.2 moles elemental carbon (12 g/mol) (>100% excess) 2.4 g

#The above starting materials are combined and ball milled to mix the particles. Thereafter, the particle mixture is pelletized. The pelletized mixture is heated for 4-20 hours at 750° C. in an oven in an argon atmosphere. The sample is removed from the oven and cooled. An x-ray diffraction pattern shows that the material has an olivine type crystal structure. An electrode is made with 80% of the active material, 10% of Super P conductive carbon, and 10% poly vinylidene difluoride. A cell with that electrode as cathode and a carbon intercalation anode is constructed with an electrolyte comprising 1 M LiPF6 dissolved in a 2:1:1 by weight mixture of γ-butyrolactone:ethylene carbonate:dimethyl carbonate.

#An electrode active material of the formula Li0.025Co0.8Fe0.1Al0.025Mg0.05PO4(LiCo0.8Fe0.1Al0.025Mg0.05Li0.025PO4) is made as follows. The following sources of Li, Co, Fe, Al, Mg, and phosphate are provided containing the respective elements in a molar ratio of 1.025:0.8:0.1:0.025:0.05:1. 2 0.05125 moles Li2CO3 (mol. wt. 73.88 g/mol) 3.8 g 0.02667 moles Co3 O4 (240.8 g/mol) 6.42 g 0.005 moles Fe2 O3 (159.7 g/mol) 0.8 g 0.0025 moles Al (OH)3 (78 g/mol) 0.195 g 0.005 moles Mg(OH)2 (58 g/mol) 0.29 g 0.1 moles (NH4)2HPO4 (132 g/mol) 13.2 g 0.2 moles elemental carbon (12 g/mol) (>100% excess) 2.4 g