Tin silicon anode active material
Improved anodes and cells are provided, which enable fast charging rates with enhanced safety due to much reduced probability of metallization of lithium on the anode, preventing dendrite growth and related risks of fire or explosion. Anodes and/or electrolytes have buffering zones for partly reducing and gradually introducing lithium ions into the anode for lithiation, to prevent lithium ion accumulation at the anode electrolyte interface and consequent metallization and dendrite growth. Various anode active materials and combinations, modifications through nanoparticles and a range of coatings which implement the improved anodes are provided.
1. An anode, comprising anode active material particles which comprise 5-80% tin, wherein the anode active material particles further comprise nanoparticles attached thereto, wherein the nanoparticles are at least one order of magnitude smaller than the anode active material particles.
2. The anode of claim 1 , wherein the anode active material particles further comprise at least one of germanium, silicon, boron, alloys and mixtures thereof.
3. The anode of claim 1 , wherein the anode active material particles are 100-500 nm in diameter and have nanoparticles attached thereto which are 10-50 nm in diameter.
4. The anode of claim 1 , wherein the nanoparticles are embedded in the anode active material particles.
5. The anode of claim 1 , wherein the nanoparticles are made of boron carbide and/or tungsten carbide.
6. The anode of claim 5 , wherein the nanoparticles are B 4 C nanoparticles, which are attached at between 2-25 weight % of the anode active material particles.
7. The anode of claim 1 , wherein the anode active material particles further comprise a 1-10 nm thick surface layer of any of: an amorphous carbon, graphene and graphite.
8. The anode of claim 1 , wherein the anode active material particles further comprise a 1-10 nm thick surface layer of a transition metal.
9. The anode of claim 1 , wherein the anode active material particles further comprise a 1-10 nm thick surface layer of a lithium polymer.
10. The anode of claim 9 , wherein the surface layer comprises a buffering zone configured to receive lithium ions from an interface of the anode active material particles with an electrolyte, partially reduce the received lithium ions, and enable the partially reduced lithium ions to move into an inner zone of the anode active material particles for lithiation therein.
11. The anode of claim 1 , wherein the anode active material particles further comprise a coating by a polymer which is conductive and/or lithiated.
12. The anode of claim 11 , wherein the anode active material particles are 20-500 nm in diameter and the coating is 2-200 nm thick.
13. A lithium ion cell comprising the anode of claim 1 .