Synthesis and optimisation mechanism of functionalised adsorption materials for lithium-ion extraction: a review

•Synthesis scheme and improvement strategy of lithium adsorbents are reviewed.•Selective adsorption mechanism and properties of lithium adsorbents are analysed.•The advantages and disadvantages of various lithium adsorbents are discussed.•The processing and application of powdered adsorbent materials are summarised.•Future development direction of adsorbent materials for Li+ extraction is proposed.