Negative electrode for non-aqueous electrolyte secondary battery
Gas evolution during the high-temperature storage of a non-aqueous electrolyte secondary battery is suppressed to improve the high-temperature storage characteristics of the non-aqueous electrolyte secondary battery. A negative electrode for a non-aqueous electrolyte secondary battery contains silicon-containing particles and graphite particles. A covering layer is disposed on each of the graphite particles. The covering layer contains a first covering material and a second covering material, the first covering material containing particles that can be made to swell with a non-aqueous electrolytic solution, the second covering material containing a water-soluble polymer material. The first covering material is disposed on a surface of each of the graphite particles. The mass ratio of the second covering material to the first covering material is higher than 1.
1. A negative electrode for a non-aqueous electrolyte secondary battery, the negative electrode comprising silicon-containing particles and graphite particles,
wherein a covering layer is disposed on each of the graphite particles,
the covering layer contains a first covering material and a second covering material, the first covering material containing particles that can be made to swell with a non-aqueous electrolytic solution, the second covering material containing a water-soluble polymer material,
the first covering material is disposed on a surface of each of the graphite particles,
a mass ratio of the second covering material to the first covering material in a negative electrode mixture is higher than 1,
wherein coverage of the graphite particles with the first covering material ranges from 10% to 50%, and
wherein the second covering material is disposed on a surface of the first covering material.
2. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein a mass of the first covering material ranges from 0.1% to 5% of a mass of each of the graphite particles.
3. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the covering layer has an average thickness in the range of 10 to 800 nm.
4. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the first covering material contains a styrene-butadiene rubber, and the second covering material contains carboxymethyl cellulose.
5. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein a mass ratio of the silicon-containing particles to the graphite particles ranges from 1:99 to 20:80.
6. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein a mass of the second covering material ranges from 1% to 5% of a mass of each of the graphite particles.
7. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein that the covering layer has a thickness in the range of 10 to 400 nm.