Messi Biology states that magnesium oxide (MgO) in lithium batteries has been upgraded from a “supporting role” to a “multi-functional interface engineer,” spanning the three major areas of electrode manufacturing, electrolyte modification, and interface stabilization. With its dual advantages of “high chemical stability + controllable interface,” magnesium oxide has completed the transition from an “additive” to a “key functional layer” in the field of lithium batteries, becoming an indispensable core material for high-energy-density, high-safety, and wide-temperature-range battery systems.
1. “Process Catalyst” for Positive Electrode Material Preparation
- Co-precipitation pH Modifier: During the synthesis of Ni-Co-Mn ternary precursors, adding nano-magnesium oxide as an alkaline pH buffer can stabilize the system in the optimal precipitation window, obtaining hydroxide precursors with uniform particle size and high tap density, thereby improving the specific capacity and cycle life of the positive electrode.
- Magnesium Doping Modification: Introducing Mg²⁺ into the lithium iron manganese phosphate lattice through solid-state reactions to form magnesium-doped lithium iron manganese phosphate. The measured discharge capacity can reach 240 mAh/g, and the dissolution of Fe/Mn at high voltage is significantly suppressed.
2. “Acid Scavenger” for Electrolytes
- HF Scavenger: Adding 0.5–2wt% nano-MgO to a conventional LiPF₆ electrolyte can reduce its free HF content to <20ppm, weakening the corrosion of HF on the positive electrode and current collector. Capacity retention is increased by 8–12% after 500 cycles.
- Low-Temperature Flowability Promoter: The latest research from the Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, shows that nano-magnesium hydroxide (D50=15nm) modified in situ with Tween80 can form a magnesium-rich inorganic CEI film on the surface of ternary positive electrodes. Through the “alkyl chain rocking” mechanism, it maintains a capacity of over 80 mAh/g even at –15°C, achieving stable cycling in a wide temperature range (–15°C to 60°C).
3. “Safe Skeleton” for Solid-State Electrolytes and Separators
- High-Ion-Conductivity Solid-State Electrolyte: After compounding high-purity MgO (99.99%) with Li₆.₄La₃Zr₁.₄Ta₀.₆O₁₂(LLZTO), an ionic conductivity of 1.2 mS/cm can be obtained at room temperature, and the lithium dendrite suppression effect is significant. It has been used in semi-solid-state power battery prototypes.
- Separator Ceramic Coating: An MgO nano-coating with a thickness of <1µm can reduce the thermal shrinkage rate of PE separators from 60% at 120°C to less than 5%, and increase the needle penetration pass rate by 40%, meeting the safety requirements of 300Wh/kg high-energy batteries.
4. “Volume Buffer Pad” for High-Capacity Negative Electrodes
- Tin-Based Composite Anode: Introducing 5wt% micron-sized MgO as an inactive skeleton in the Sn-Co-C negative electrode can buffer the 260% volume expansion during the Sn alloying process, and still maintain >85% initial capacity after 200 cycles.
5. Industrialization Pace
- Demand Side: By 2025, China’s solid-state battery demand for high-purity MgO has reached 20,000 tons, and is expected to exceed 100,000 tons in 2030, with an annual compound growth rate of 20%.
- Cost Side: Battery-grade magnesium oxide produced by chemical synthesis methods has higher content and lower cost than traditional processes, and has become the specified specification for leading companies such as CATL and BYD.