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Materials Data on Li3PO4 by Materials Project

Li3PO4 is Enargite structured and crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four O2- atoms to form LiO4 tetrahedra that share corners with four equivalent PO4 tetrahedra and corners with eight equivalent LiO4 tetrahedra. There are a spread of Li–O bond distances ranging from 1.98–2.05 Å. In the second Li1+ site, Li1+ is bonded to four O2- atoms to form LiO4 tetrahedra that share corners with four equivalent PO4 tetrahedra and corners with eight LiO4 tetrahedra. There are a spread of Li–O bond distances ranging from 1.95–2.00 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with twelve LiO4 tetrahedra. All P–O bond lengths are 1.56 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to three Li1+ and one P5+ atom to form distorted corner-sharing OLi3P tetrahedra. In the second O2- site, O2- is bonded to three Li1+ and one P5+ atom to form distorted corner-sharing OLi3P tetrahedra. In the third O2- site, O2- is bonded to three Li1+ and one P5+ atom to form corner-sharing OLi3P tetrahedra.

36 MATERIALS SCIENCE↗

Materials Data on Li3PO4 by Materials Project

Li3PO4 is beta beryllia-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four O2- atoms to form LiO4 tetrahedra that share corners with four equivalent PO4 tetrahedra, corners with six LiO4 tetrahedra, and an edgeedge with one LiO4 tetrahedra. There are a spread of Li–O bond distances ranging from 1.95–2.03 Å. In the second Li1+ site, Li1+ is bonded to four O2- atoms to form LiO4 tetrahedra that share corners with four equivalent LiO4 tetrahedra, corners with four equivalent PO4 tetrahedra, and edges with two equivalent LiO4 tetrahedra. There are a spread of Li–O bond distances ranging from 1.96–2.05 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with twelve LiO4 tetrahedra. All P–O bond lengths are 1.56 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to three Li1+ and one P5+ atom to form corner-sharing OLi3P tetrahedra. In the second O2- site, O2- is bonded to three Li1+ and one P5+ atom to form a mixture of distorted edge and corner-sharing OLi3P tetrahedra. In the third O2- site, O2- is bonded to three Li1+ and one P5+ atom to form a mixture of distorted edge and corner-sharing OLi3P trigonal pyramids.

36 MATERIALS SCIENCE↗

Solid-State High-Temperature Power Cells

All-solid-state electrochemical power cells have been fabricated and tested in a continuing effort to develop batteries for instruments for use in environments as hot as 500 C. Batteries of this type are needed for exploration of Venus, and could be used on Earth for such applications as measuring physical and chemical conditions in geothermal and oil wells, processing furnaces, and combustion engines. In the state-of-the-art predecessors of the present solid-state power cells, fully packaged molten eutectic salts are used as electrolytes. The molten-salt-based cells can be susceptible to significant amounts of self-discharge and corrosion when used for extended times at elevated temperatures. In contrast, all-solid-state cells such as the present ones are expected to be capable of operating for many days at temperatures up to 500 C, without significant self-discharge. The solid-state cell described here includes a cathode made of FeS2, an electrolyte consisting of a crystalline solid solution of equimolar amounts of Li3PO4 and Li4SiO4, and an anode made of an alloy of Li and Si (see figure). The starting material for making the solid electrolyte is a stoichiometric mixture of Li3PO4, SiO2, and Li3CO2. This mixture is ball-milled, then calcined for two hours at a temperature of 1,100 C, then placed in a die atop the cathode material. Next, the layers in the die are squeezed together at a pressure between 60 and 120 MPa for one hour at a temperature of 600 C to form a unitary structure comprising the solid electrolyte and cathode bonded together. Finally, the lithium-alloy anode is pressure-bonded to the solid electrolyte layer, using an intermediate layer of pure lithium. In one test of a cell of this type, a discharge rate of about 1 mA per gram of cathode material was sustained for 72 hours at a temperature of about 460 C. This is about three times the discharge rate required to support some of the longer duration Venus-exploration mission scenarios.

Whitacre, Jay↗

NiF2/NaF:CaF2/Ca Solid-State High-Temperature Battery Cells

Experiments and theoretical study have demonstrated the promise of all-solid-state, high-temperature electrochemical battery cells based on NiF2 as the active cathode material, CaF2 doped with NaF as the electrolyte material, and Ca as the active anode material. These and other all-solid-state cells have been investigated in a continuing effort to develop batteries for instruments that must operate in environments much hotter than can be withstood by ordinary commercially available batteries. Batteries of this type are needed for exploration of Venus (where the mean surface temperature is about 450 C), and could be used on Earth for such applications as measuring physical and chemical conditions in geothermal wells and oil wells. All-solid-state high-temperature power cells are sought as alternatives to other high-temperature power cells based, variously, on molten anodes and cathodes or molten eutectic salt electrolytes. Among the all-solid-state predecessors of the present NiF2/NaF:CaF2/Ca cells are those described in "Solid-State High-Temperature Power Cells" (NPO-44396), NASA Tech Briefs, Vol. 32, No. 5 (May 2008), page 40. In those cells, the active cathode material is FeS2, the electrolyte material is a crystalline solid solution of equimolar amounts of Li3PO4 and LiSiO4, and the active anode material is Li contained within an alloy that remains solid in the intended high operational temperature range.

West, William↗

Lithium metal negative electrode and method of manufacturing the same

A negative electrode for an electrochemical cell of a secondary lithium metal battery is manufactured by a method in which a precursor solution is applied to a major surface of a lithium metal substrate to form a precursor coating thereon. The precursor solution includes an organophosphate, a nonpolar organic solvent, and a lithium-containing inorganic ionic compound dissolved therein. At least a portion of the nonpolar organic solvent is removed from the precursor coating to form a protective interfacial layer on the major surface of the lithium metal substrate. The protective interfacial layer exhibits a composite structure including a carbon-based matrix component and a lithium-containing dispersed component. The lithium-containing dispersed component is embedded in the carbon-based matrix component and includes a plurality of lithium-containing inorganic ionic compounds, e.g., lithium phosphate (Li3PO4) and lithium nitrate (LiNO3).

Xiao, Xingcheng↗

In Situ Conversion of Artificial Proton‐Rich Shell to Inorganic Maskant Toward Stable Single‐Crystal Ni‐Rich Cathode

Single-crystal high-nickel oxide with an integral structure can prevent intergranular cracks and the associated detrimental reactions. Yet, its low surface-to-volume ratio makes surficial degradation a more critical factor in electrochemical performance. Herein, artificial proton-rich (ammonium bicarbonate) shell is successfully introduced on the nickel-rich LiNi 0.92 Co 0.06 Mn 0.02 O 2 single crystals for in situ electrochemically conversing into inorganic maskant to enhance stability of cathode. The process is that the surficial enriched proton, once released from the ammonium bicarbonate shell (proton reservoir) during 1st charge, is immediately captured by LiPF 6 , in situ electrochemically conversing to LiF and Li 3 PO 4 sub-nano particle dense maskant (sub-nano F-&P-maskant). The in situ formed compact nano F-&P-maskant significantly resists the cathode against electrolyte attack and improves the surface stability of particles during long-term cycling. Consequently, this surface modification enables 95% capacity retention after 100 cycles at a high voltage of 4.5 V in the half cell and 83% capacity retention after 800 cycles in the full cell. In conclusion, this work demonstrates a strategy for reconstructing the protective layer using the rational design of surficial enriched proton shells for advanced lithium batteries.

25 ENERGY STORAGE↗