| Lithium borohydride | |
|---|---|
| IUPAC name |
Lithium tetrahydridoborate(1–)
|
| Other names | Lithium hydroborate, Lithium tetrahydroborate Borate(1-), tetrahydro-, lithium |
| Identifiers | |
| CAS number | 16949-15-8  |
| PubChem | 4148881 |
| RTECS number | ED2725000 |
| Properties | |
| Molecular formula | LiBH4 |
| Molar mass | 21.784 g/mol |
| Appearance | White solid |
| Density | 0.666 g/cm3[1] |
| Melting point |
275 °C[1] |
| Boiling point |
380 °C (decomp) |
| Solubility in water | reacts |
| Solubility in ether | 2.5 g/100 mL |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
-8.759 kJ/g |
| Specific heat capacity, C | 3.792 J/g K |
| (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
|
| Infobox references | |
Lithium borohydride (LiBH4) is a tetrahydroborate and known in organic synthesis as a reducing agent for esters.
Contents |
Preparation
Lithium borohydride may be prepared by the metathesis reaction between the more commonly available sodium borohydride, and lithium bromide:[citation needed]
- NaBH4 + LiBr → NaBr + LiBH4
Reactions
Lithium borohydride reacts largely like sodium borohydride, in that it is a hydride-donating reducing agent in organic synthesis.
Energy storage
It is also renowned as one of the highest energy density chemical energy carriers. When reacting with atmospheric oxygen it liberates 65 MJ/kg heat. Since it has a density of 0.67 g/cm3, oxidation of liquid lithium borohydride gives 43 MJ/L. In comparison, gasoline gives 44 MJ/kg (or 35 MJ/L), while liquid hydrogen gives 120 MJ/kg (or 8.0 MJ/L).[nb 1] The high specific energy density of lithium borohydride has made it an attractive candidate to propose for automobile and rocket fuel, but despite the research and advocacy it has not been used widely. As with all chemical-hydride-based energy carriers, lithium borohydride is very complex to recycle (i.e. recharge) and therefore suffers from a low energy conversion efficiency. While batteries such as lithium ion carry an energy density of up to 0.72 MJ/kg and 2.0 MJ/L, their DC to DC conversion efficiency can be as high as 90%. In view of the complexity of recycling mechanisms for metal hydrides,[2] such high energy conversion efficiencies are beyond practical reach.
| Substance | Specific energy MJ/kg | Density g/cm3 | Energy density MJ/L |
|---|---|---|---|
| LiBH4 | 65.2 | 0.666 | 43.4 |
| Regular Gasoline | 44 | 0.72 | 34.8 |
| Liquid Hydrogen | 120 | 0.0708 | 8 |
| lithium ion battery | 0.72 | 2.8 | 2 |
See also
Notes
- ^ The greater ratio of energy density to specific energy for hydrogen is because of the very low mass density (0.071 g/cm3).
References
- ^ a b Sigma-Aldrich Product Detail Page
- ^ US Patent 4002726 (1977) lithium borohydride recycling from lithium borate via a methyl borate intermediate
External links
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