The present invention generally relates to using water-based binders for high voltage cathode materials, such as LMNO (spinel LiNi0.5Mn1.5O4), in Li-ion batteries. An example of a water compatible polymer binder according to some embodiments of the present invention is a combination of CMC (carboxymethylcellulose) and a second water compatible polymer that produce coatings of adequate thickness and loading (mAh/cm2). A method of forming a cathode for a Li-ion battery may include: preparing an aqueous solution of CMC; mixing together LMNO and carbon black; combining the LMNO and carbon black mixture with the CMC solution, an aqueous polyacrylic solution and distilled water, and mixing to form a slurry; coating a conductive substrate with the slurry; and drying the coated substrate, forming a cathode layer on the substrate. Furthermore, this invention describes a cathode for Li-ion batteries and tools for carrying out the above method.