A. preface

Since the launch of lithium ion battery by Sony in 1991, lithium ion battery has been valued for its high specific energy density and long service life, and developed rapidly. The United States, South Korea and Taiwan are also focusing on lithium-ion batteries. In recent years, lithium secondary battery develops rapidly, trying to replace cadmium nickel and nickel hydrogen battery, among which polymer (polymer material) is used as electrode and electrolyte material.

2. Electrode material for a battery

2.1 anode materials

1) lithium anode materials: mainly LiCoO2, LiNiO2 and LiMnO2

2) polymer cathode materials: mainly heterocyclic polymers such as polyrabbit (Ppy), polythiophene (PTh) and their derivatives

2. Negative material

(1) carbon materials: natural graphite, coke and carbon fiber, etc

(2) negative electrode materials based on tin oxide: mixed oxides containing divalent tin can be prepared by heating the mixture of SnO, SiO2 and a small amount of Al2O3, B2O3 and P2O3 at 1000℃ or slightly higher temperature for 12h under the atmosphere of argon.

3. The electrolyte

In the last 20 years, polymer materials with high ionic conductivity have attracted much attention. In 1973, Wright et al. first discovered that polyoxyethylene (PEO) has ionic conductivity in coordination with alkali metal salts. In 1978, Armand proposed PEO/ alkali metal salt complex as the ionic conductor of new rechargeable batteries with alkali metal electrodes, which made polymer solid electrolyte become a hot topic in polymer research field in the past 20 years. High polymer solid electrolyte is characterized by high ionic conductivity, wide potential, easy film forming, soft, light, elastic, transparent and other advantages, which cannot be realized by inorganic glass solid electrolyte containing ionic conductivity.

3.1 polymer/salt complex electrolytes

Polymer solid electrolyte (SPE) with PEO and lithium coordination

3.2 copolymer/salt complex electrolyte

(1) random copolymer

There are two main structures: one is oxyethylene - oxyethylene methylene, the other is oxyethylene - oxyepropylene (eo-po) random copolymer

(2) comb copolymer

Structure: the polyether chain with molecular weight is grafted on the main chain of a high polymer (low Tg).

(3) block copolymers

Structure: oxymethylene bonded polystyrene - polyoxyethylene - polystyrene triblock polymer

(4) polymer with network structure

There are two main production methods: one is to connect the branch chain of polyether on the inorganic polymer to form a two-phase structure, namely the inorganic support phase and the organic conductive phase; Another method is to polymerize and cross-link unsaturated polyethers (macromolecular monomers) to generate networked polymer electrolytes.

3.3 polymer/inorganic blends. The polymer - ceramic composite electrolyte was prepared by adding inorganic particles into the polymer electrolyte.

3.4 emulsion particle/salt complex electrolyte. A series of two - phase polymer solid electrolytes are prepared from latex particles with different properties.

1) styrene butadiene rubber (SBR) and cyanogen butadiene rubber (NBR) latex particles.

2) composite latex particles with core-shell structure were synthesized with rubber and non-polar polybutadiene (PB) as the core and polar and glass polyvinyl pyrrolidone (PVP) as the shell.

3.5 polymer gel/salt complex electrolyte. Gelatinous CPE is an electrolyte.

Four. The difference between polymer lithium ion batteries and liquid lithium ion batteries. The fundamental difference between polymer lithium ion batteries and liquid lithium ion batteries is that they use different electrolytes. Polymer lithium battery electrolyte from the appearance of solid, known as the polymer solid electrolyte. The e electrolyte is a kind of polymer material which is in solid state, but can dissolve and support electrolyte like liquid, and can conduct ion migration.

Five. Eight advantages of polymer lithium ion batteries.

1. Good safety performance. Polymer e lithium batteries in the structure of the aluminum plastic flexible packaging, different from the metal shell of the liquid battery, once the safety hazard occurs, the liquid battery is easy to explode, and the polymer battery at most will only gas drum.

2. Small thickness, can be made thinner. Ordinary liquid lithium battery adopts the method of customizing the shell first and then plugging the materials of positive and negative poles. There is a technical bottleneck in the thickness below 3.6mm, while there is no such problem in the polymer battery core. The thickness can be below 1mm, which is in line with the current direction of mobile phone demand.

3. Light weight. The e weight of polymer batteries is 40% lighter than steel - based lithium batteries of the same capacity and 20% lighter than aluminum - based batteries.

4. Large capacity. Polymer e battery than the same size of steel shell battery capacity 10 ~ 15%, 5 ~ 10% higher than aluminum shell battery, become the first choice of color screen mobile phone and MMS mobile phone, now on the market the new color screen and MMS mobile phone is also mostly used polymer battery.

5. Low internal resistance. The internal resistance of the polymer batteries is less than liquid batteries, the current domestic internal resistance of the polymer batteries can even do below 35 m Ω, greatly reduced the battery power consumption, extend the standby time of mobile phone, can reach with international level. This kind of polymer lithium battery, which supports large discharge current, is an ideal choice for remote control model and has become the most promising product to replace nickel metal hydride battery.

6. Shape can be customized. Polymer e batteries can be based on customer demand to increase or reduce the thickness of the battery, the development of new battery models, cheap, mold cycle is short, some can even be customized according to the shape of the phone, to make full use of the battery shell space, improve the battery capacity.

7. Good discharge performance. Polymer batteries use colloidal electrolytes, compared with liquid electrolytes, colloidal electrolytes have stable discharge characteristics and higher discharge platform.

8. Simple design of protection board. Due to the use of polymer materials, the battery does not fire, do not explode, the battery itself has enough safety, so the polymer battery protection circuit design can consider to omit PTC and fuse, so as to save the battery cost.