Electrode and electrolyte materials for batteries
Disclosed are open-framework solids that possess superior ion-transport properties pertinent to the electrochemical performance of next-generation electrode materials for battery devices. Disclosed compounds including compositions and architectures relevant to electrical energy storage device applications have been developed through integrated solid-state and soft (solution) chemistry studies. The solids can adopt a general formula of A x M y (XO 4 ) z , where A=mono- or divalent electropositive cations (e.g., Li + ), M—trivalent transition metal cations (e.g., Fe 3+ , Mn 3+ ), and X═Si, P, As, or V. Also disclosed are oxo analogs of these materials having the general formulae A a M b O c (PO 4 ) d (a≧b), and more specifically, A n M n O 3x (PO 4 ) n-2x , where A=mono- or divalent electropositive cations (e.g., Li + ), M is either Fe or Mn, and x is between 0 and n/2.
1. A method for forming an electrode or electrolyte material comprising:
carrying out an ion exchange process on a starting material, the starting material having the formula:
Cs 7 Fe 7 O 2 (PO 4 ) 8
the ion exchange process exchanging the Cs cation component of the starting material with a smaller cation A* to form a product electrode or electrolyte material having the formula:
A*Fe 7 O 2 (PO 4 ) 8
wherein the ratio of A* to Fe in the product is greater than one.
2. The method according to claim 1 , wherein the smaller cation A* is lithium.
3. The method according to claim 1 , wherein the ion exchange process is carried out under hydrothermal conditions at a temperature of between about 150° C. and about 200° C.
4. The method according to claim 3 , wherein the ion exchange process is carried out in a solution of LiNO 3 or n-BuLi.
5. The method according to claim 1 , wherein the starting material is formed according to the following reaction scheme:
7SrO+7Fe 2 O 3 +4P 4 O 10 +(CsCl/Csl flux) →2Cs 7 Fe7O 2 (PO 4 ) 8 +side products.