China’s Tianqi Lithium has given the green light to a $300 million expansion of its lithium hydroxide processing plant still under construction at Kwinana.

The new investment will increase Tianqi’s outlay in WA to more than $860 million, making the group one of the State’s biggest mining-related investors outside of iron ore.

Construction of Kwinana’s $400 million first stage began in October last year. The expansion will double the plant’s production of battery-grade lithium hydroxide to 48,000 tonnes a year and increase its permanent workforce by 55 to 170.

“This is great news for West Australians and I thank Tianqi Lithium for its investment in our State,” WA Premier Mark McGowan said in a statement.

Tianqi’s board ticked off on the additional investment just days after a visit by founding chairman Jiang Weiping and chief executive Vivian Wu to Kwinana, where the plant’s first stage is tracking towards completion late next year.

The group’s Australian general manager Phil Thick said the visit had been important in assuring the Tianqi board about the quality and progress of the construction work.

Camera Icon Tianqi Lithium chief executive Vivian Wu visited WA earlier this month to check on progress at the Kwinana plant. Credit: Sharon Smith

“That was not insignificant in terms of their confidence levels in us being able to do the stage two work straight away,” he said.

“Australian standards are as good as anything in the world.”

The plant will tap high-grade spodumene from Tianqi’s 51 per cent-owned mine at Greenbushes, south of Perth, where the group and its US partner are spending $300 million to also double production.

The investments are part of a development boom aimed at capturing demand for lithium from the electrical vehicle and power storage industries.

Mr Thick said since Tianqi launched a feasibility study into the Kwinana expansion in May, “they are even more confident the case is robust and the market is continuing to strengthen”.

Approvals for the new work are already in place with completion set for the end of 2019.

Mr Thick said orders for long lead items and the bigger pieces of equipment had already been placed and construction contracts were being finalised.

The majority, between 80 per cent and 85 per cent, of the materials and work for the development have been sourced locally.

This includes tanks and pipeworks fabricated locally using Australian steel.

News of the expansion coincides with the launch of several community initiatives by Tianqi, including a $5 million partnership with the WA Museum.