TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Components: The battery has retained capacity of 90% over 50 cycles relative to the 6th cycle at discharge of C/3. The battery further comprises supplemental lithium. Preferred Components: The electrode: has an irreversible capacity loss of 25-15%; retains at least 80% of capacity up to 50 charge/discharge cycles; has a discharge specific capacity of at least 2000 mAh/g; and is contacting a current collector (108) with a loading on one side of the current collector of 1.4-4 mg/cm2.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The method further comprises: etching the intermediate with acid to remove the metal oxide to form the porous crystalline elemental silicon; milling the porous silicon with carbon nanofibers to form a silicon-carbon nanofibers composite material; and coating the porous silicon with a carbon coating to form porous silicon based material. The etching step is accompanied by heating. The heating step is: performed by a gradual temperature ramp with a ramp of 0.5-20 degrees C/minute to reach the target temperature; and paused at a step for 15 minutes to 1.5 hours. Preferred Components: The material further comprises a carbon coating on the porous silicon. The porous silicon has a surface area of 10-200 m2/g. The material has an average pore size of 15-200 nm. The material has the X-ray diffraction spectrum with a broad monotonically decreasing amorphous scattering of 2 theta of 10-25 degrees . The porous silicon based material further comprises: a carbon coating on the porous crystalline element silicon; and carbon nanofibers blended with the porous crystalline elemental silicon. The porous silicon is substantially free of carbon. The acid is hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, and/or nitric acid. The reducing metal comprises lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, aluminum, nickel, and/or zirconium. The reducing metal powder is ball milled with the silicon dioxide for 1-10 hours at 100-500 revolutions per minute.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The binder comprises a polyimide binder. EXAMPLE - No suitable example given.