The present invention relates to compounds and their nonlinear optical (NLO) crystals of A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4), their producing method and uses thereof. The series of compounds have a chemical formula of A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4), which are namely K.sub.3B.sub.11P.sub.2O.sub.23, Rb.sub.3B.sub.11P.sub.2O.sub.23, Cs.sub.3B.sub.11P.sub.2O.sub.23 and (NH.sub.4).sub.3B.sub.11P.sub.2O.sub.23. The series of NLO crystals having the chemical formula of A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4), belong to rhombohedral crystal system, and have a space group of R3, crystal cell parameters of a=b=10.016(5)-12.591(5) , c=12.105(6)-14.905(6) , Z=3. A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4) compounds were prepared by a solid-state reaction method or a hydrothermal method, and A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4) NLO crystals were prepared by a high-temperature solid-state reaction method, a hydrothermal method, or a solution method. T They meet the requirements for the frequency conversion of UV wavelength lasers and could be used to prepare nonlinear optical devices.

A high-compaction lithium iron phosphate positive electrode material, a preparation method thereof, a positive electrode and a battery including the same. The high-compaction lithium iron phosphate positive electrode material comprises lithium iron phosphate of formula LiFe.sub.1-x-yV.sub.xTi.sub.y(BO.sub.3).sub.z(PO.sub.4).sub.1-z, and carbon coated on a surface of the lithium iron phosphate, wherein, 0.001x0.01, 0.001y0.01, and 0.05z0.2. The high-compaction lithium iron phosphate positive electrode material has a high compacted density, a high specific capacity, and excellent rate performance and cycle performance, and is useful for preparing batteries having a high compacted density, a high capacity, good rate performance and cycle performance, which are suitable for high-end pure electric vehicles having a long driving mileage.

A solid electrolyte contains an internal component and an external component coated on a surface of the internal component. The internal component is represented by a formula Li.sub.1+xM.sub.xZr.sub.2x(PO.sub.4).sub.3, M is one or more elements selected from a group consisting of Al, La, Cr, Ga, Y, and In, and 0.05x0.4. The external component contains a plastic deformable material and has a conductivity of about 10.sup.7 S/cm to about 10.sup.5S/cm. A method of preparing the solid electrolyte and a lithium ion battery including the solid electrolyte are also provided.

The present invention relates to compounds and their nonlinear optical (NLO) crystals of A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4), their producing method and uses thereof. The series of compounds have a chemical formula of A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4), which are namely K.sub.3B.sub.11P.sub.2O.sub.23, Rb.sub.3B.sub.11P.sub.2O.sub.23, Cs.sub.3B.sub.11P.sub.2O.sub.23 and (NH.sub.4).sub.3B.sub.11P.sub.2O.sub.23. The series of NLO crystals having the chemical formula of A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4), belong to rhombohedral crystal system, and have a space group of R3, crystal cell parameters of a=b=10.016(5)-12.591(5) , c=12.105(6)-14.905(6) , Z=3. A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4) compounds were prepared by a solid-state reaction method or a hydrothermal method, and A.sub.3B.sub.11P.sub.2O.sub.23 (A=K, Rb, Cs, NH.sub.4) NLO crystals were prepared by a high-temperature solid-state reaction method, a hydrothermal method, or a solution method. T They meet the requirements for the frequency conversion of UV wavelength lasers and could be used to prepare nonlinear optical devices.