The invention relates to a composite
solid electrolyte membrane, a preparation method thereof, and a
solid battery. The composite
solid electrolyte membrane includes a multilayer
electrolyte layer composited in the thickness direction, the electrolyte layer contains an inorganic solid electrolyte and a
polymer electrolyte, and in the direction from the positive
electrode side to the negative
electrode side of the composite solid electrolyte membrane, in each electrolyte layer, The content gradient of the inorganic solid electrolyte decreases, and the content gradient of the
polymer electrolyte increases. The composite solid electrolyte membrane provided by the present invention has a high content of inorganic solid electrolyte on the positive
electrode side, can withstand higher voltages, improves
lithium ion conductance, and has a high content of
polymer electrolyte on the negative electrode side, which can better inhibit
lithium dendrites and alleviate The
volume expansion of the negative electrode and the differentiated design of the electrolyte membrane make full use of the characteristics of the positive and negative electrodes. While ensuring high
ionic conductivity, it achieves
high pressure resistance and suppresses the
volume expansion of
lithium dendrites and negative electrodes.