Lithium hydroxide monohydrate (LiOH·H2O, CAS 1310-66-3, molecular weight 41.96) is a white crystalline powder with a density of 1.46 g/cm³, melting point 462 °C, decomposition at 924 °C, and water solubility of 109 g/L at 20 °C [S2].
Two industrial routes dominate: a lithium-carbonate-causticisation route that has shipped for decades, and a direct-lithium-from-brine route that pairs nanofiltration or selective adsorption with homogeneous electrodialysis to lift brine concentration before conversion, with 20,000 t/y salt-lake LiOH plants now in operation [S3].
Two commercial process routes compared
The causticisation route reacts refined Li2CO3 with slaked lime (Ca(OH)2) at 100–200 °C in stirred reactors: Li2CO3 + Ca(OH)2 → 2 LiOH + CaCO3↓. The CaCO3 precipitate is filtered off; the LiOH mother liquor is evaporated and crystallised as the monohydrate (LiOH·H2O, MW 41.96, density 1.46 g/cm³) [S2]. This route is feed-agnostic — any high-purity Li2CO3 source, including spodumene acid-roast leachate, will work — but it is locked to a stoichiometric CO2/CO3 chemistry that effectively forfeits one mole of reagent-grade alkali per mole of LiOH made.
The direct route treats Li-rich salt-lake brine: adsorption or nanofiltration first lifts Li⁺ concentration, and a homogeneous-membrane electrodialysis (ED) stack then concentrates the eluate to the LiOH-precursor specification without intermediate carbonate precipitation. Hangzhou Lanran commissioned an additional ED unit for a 20,000 t/year LiOH project at the Lago Co Salt Lake in Xizang, China, in 2026, and reports that the ED unit is now operating steadily as part of the overall production process [S3].
Material spec, packaging and handling baseline
Commercial LiOH·H2O ships as a white, free-flowing crystalline powder, density 1.46 g/cm³, melting point 462 °C and 109 g/L water solubility at 20 °C; it is freely soluble in water, only sparingly soluble in alcohol, strongly alkaline and classed as strongly corrosive rather than flammable [S2]. The material absorbs CO2 from air and degrades to Li2CO3, so sealed packaging and humidity-controlled storage are mandatory; laboratory-grade packs are sold at 25 g and 500 g SKU sizes against listing reference prices of roughly ¥585 (S1 instrument-portal listing, 2026-06-01), with bulk industrial drums typically 25 kg or 1 t supersacks.
Strong-corrosive labelling under GHS H314 (skin corrosion) and the dust-control burden of a hygroscopic, CO2-scavenging powder push most battery-grade LiOH producers toward sealed, glove-box or nitrogen-pad transfer at the crystalliser outlet.
Battery-grade purity targets and downstream use
End-use is dominated by nickel-rich NCM cathode synthesis, where LiOH·H2O is preferred over Li2CO3 because the higher solubility (109 g/L at 20 °C [S2]) and lower calcination CO2 burden produce denser, lower-carbonation cathodes. Specifications for battery-grade LiOH·H2O typically target Li ≥ 56.5 wt%, Na ≤ 50 ppm, Ca ≤ 50 ppm, Mg ≤ 5 ppm, SO4 ≤ 100 ppm, Fe ≤ 5 ppm, Cl⁻ ≤ 20 ppm and Cu ≤ 5 ppm; the producer's QC envelope is bracketed by ICP-OES for cations and ion chromatography for anions.
Other industrial applications of lithium hydroxide include metallurgy, petroleum, glass, and ceramics.
Salt-lake brine route: where electrodialysis fits
In modern salt-lake lithium extraction trains, electrodialysis sits between upstream Li-selective adsorption (or nanofiltration) and the downstream LiOH conversion step, doing the brine concentration lift that old solar-evaporation ponds used to do. Lanran's homogeneous-membrane ED is qualified for that slot and is now running on the 20,000 t/y LiOH line at Lago Co, with the additional stack commissioned in 2026 [S3].
The advantages claimed versus solar evaporation are the same as in any other brine-mining project: a smaller land footprint, no dependence on high-irradiance weather windows, and a faster ramp from feed-brine flow to on-spec LiOH. The trade-off is membrane replacement cost, divalent-cation scaling risk, and the energy budget of the ED stack itself, which scales with the Li⁺ concentration lift required.
Selection criteria: which route fits which feed
Pick the causticisation route when the feed is already a refined Li2CO3 stream (spodumene, lepidolite, or imported technical-grade Li2CO3) and the project tolerates a stoichiometric CaCO3 by-product and a CO2-absorbing solid-handling train. Pick the direct-from-brine ED route when the feed is a low-grade salt-lake brine with a high Mg/Li ratio and the project needs a fast, weather-independent concentration step before the LiOH conversion reactor [S3].
For a process engineer, the gate is simpler: if you already have a Li2CO3 line, causticisation is the lowest-risk, lowest-Capex add-on; if you are greenfield on a salt-lake asset and the evaporation pond is the bottleneck, an ED unit sized to the brine flow is the higher-CapEx but faster-ROI move.
Quality, testing and standards
Producer QC typically couples XRF or ICP-OES for major cations with ion chromatography for sulphate, chloride and carbonate. The Chinese national standard referenced in the Sogou Baike entry for the LiOH·H2O monograph is project plan 20110653-T-610 under the Standardization Administration of China, which governs the Chinese national test method framework for the product [S2].
For battery-grade shipment, lot-release certificates normally include a 30-day-on-shelf CO2-pickup test (a LiOH cake is titrated for Li2CO3 formation) plus a particle-size laser-diffusion report with D50 typically in the 50–200 µm range, depending on crystalliser tuning.
Failure modes and operating constraints
The recurring process upsets are well known: carbonation from air ingress (Li2CO3 build-up raises the impurity budget and ruins the cathode calcining step), divalent-cation carryover (Ca²⁺ and Mg²⁺ pass through the ED stack and poison downstream LiOH product if the selective-adsorption step is out of spec), and membrane fouling in the ED train when total dissolved solids climb above the membrane's design ceiling. [S1]
On the equipment side, pressure transmitters on the ED hydraulic loop and flow meters on the brine feed are the primary control elements; industrial valves on the lime-slurry and CaCO3-sludge lines see the most severe abrasive service, which is why pinch-valve or ceramic-lined ball valves are common on the underflow. Process engineers sizing these skids should treat the crystalliser-circulation loop as the controlling pressure drop and start the multifunction process calibrator verification schedule at every shutdown.
Signals to watch next
Two trackable signals will move the spec sheet: the next ED-unit commissioning announcement for a >30,000 t/y salt-lake LiOH plant (the 20,000 t/y Lago Co line is the current benchmark [S3]), and any tightening of Chinese GB or cathode-maker impurity limits on Na, Ca and sulphate in battery-grade LiOH·H2O, which would push producers toward more selective brine-upstream steps rather than downstream polishing. For broader materials context, the graphite electrode smart manufacturing map covers the parallel anode-side capacity build-out that any new LiOH line is implicitly serving.