A series of non-van der Waals 2D quaternary thiophosphates with nominal composition, Li 2 MP 2 S 6 (M = V, Mn, Fe, Co, Ni, and Zn), has been successfully synthesized through solid-state metathesis reactions by a building block approach as well as starting with a stoichiometric combination of elements. Li 4−nx M x n+ P 2 S 6 (M = V, Fe, Ni, Co, and Zn; x = 0.5−1, n = 2 or 3) crystallize in the P3̅ 1m space group, while Li 2 MnP 2 S 6 crystallizes in R3̅ . All the compounds form a 2D layered structure through edge sharing MS 6 octahedra and P 2 S 6 units with Li atoms occupying the interlayer spaces. X-ray diffraction and thermogravimetric analyses reveal spontaneous water intercalation tendencies of these materials, leading to two distinct hydrated phases (HY-I and HY-II) when they are exposed to air for shorter and extended times, respectively. Thermodiffractograms demonstrate the reversibility of phase transformation upon deintercalation of water molecules from the interlayer regions. The crystal structure of hydrated phase I from single-crystal and synchrotron powder X-ray diffraction indicates formation of a monolayer of water with interlayer expansion. Additionally, Li 4−nx M x n+ P 2 S 6 (M = V, Mn, Fe, and Ni) also display huge affinity toward NH 3 intercalation in the interlayer space when subjected to a liquid or gaseous ammonia environment. The magnetic measurements on Li 2 MP 2 S 6 (M = Mn and Ni) show the paramagnetic nature of the compounds down to 2 K. AC impedance spectroscopy on Li 2.56 Zn 0.72 P 2 S 6 shows a room-temperature ionic conductivity of 2.69 × 10 −3 mS/cm, which is four order higher in magnitude than Li 4 P 2 S 6 , while hydrated Li 2.56 Zn 0.72 P 2 S 6 display 7-fold higher ionic conductivity (1.85 × 10 −2 mS/cm) than its anhydrous counterpart. The study also reports electrochemical Li (de)intercalation in Li 2 FeP 2 S 6 in a Li-ion battery with a liquid electrolyte for the first time.