NOVELTY - A rechargeable lithium ion and hydrogen ion electrochemical cell comprises: a first electrode (102) configured to store energy by interacting with lithium cations; a second electrode (104) configured to store energy by interacting with hydrogen cations; and an aqueous electrolyte (108) configured to separate the first electrode from the second electrode and to provide both the lithium cations and the hydrogen cations.    USE - As rechargeable lithium ion and hydrogen ion electrochemical cell useful in a battery system (claimed); and in electric/hybrid vehicles, large-scale power storage, handheld processing devices, communication devices, gaming devices, electric motors, and backup power supplies.    ADVANTAGE - The energy storage cell is designed such that the aqueous electrolyte does not break down or otherwise release hydrogen or oxygen across a desired stable voltage range. The careful selection of the electrodes allows for the energy storage cell to operate entirely within the stable range of the aqueous electrolyte. This results in a stable and safe energy cell with lower cost and more attractive energy storage properties. The batteries comprising the cell are significantly safer than those that are currently available; and the cell uses new families of materials that are considerably lighter weight and lower cost than those that are currently used. Thus, the battery cells offer safe operation with high specific capacity that can be sustained over numerous recharge cycles.    DETAILED DESCRIPTION - A rechargeable lithium ion and hydrogen ion electrochemical cell comprises: a first electrode (102) configured to store energy by interacting with lithium cations; a second electrode (104) configured to store energy by interacting with hydrogen cations; and an aqueous electrolyte (108) configured to separate the first electrode from the second electrode and to provide both the lithium cations and the hydrogen cations. The aqueous electrolyte has a stability limit and the first and second electrodes have reaction potentials that are within the stability limit of the aqueous electrolyte. INDEPENDENT CLAIMS are included for the following:    (1) a battery system comprising: several hybrid energy storage cells, where each cell includes a positive electrode configured to store energy by interacting with lithium cations; a negative electrode configured to store energy by interacting with non-lithium cations; and an aqueous electrolyte configured to separate the positive electrode from the negative electrode and to provide both the lithium cations and the non-lithium cations; and    (2) manufacturing a hybrid energy storage cell, involving: providing a structure that includes an aqueous electrolyte that provides both lithium cations and hydrogen cations; providing a first electrode that includes a first material designed to store energy by interacting with the lithium cations; and providing a second electrode that includes a second material to store energy by interacting with hydrogen cations and that is electrically separated from the first electrode by the aqueous electrolyte.    DESCRIPTION OF DRAWING(S) - The figure shows a view of the basic components of the rechargeable energy storage cell.    Positive electrode (102)    Negative electrode (104)    Charger (106)    Electrolyte (108)