A. preface

 

Sony company since 1991 since the development of lithium ion battery listed, lithium-ion batteries for its high specific energy density and long service life and be taken seriously, is developing rapidly. The United States, South Korea and Taiwan, among others, are also focusing on lithium-ion batteries. Developing rapidly in recent years, lithium secondary battery, trying to replace nickel cadmium and nickel-metal hydride batteries, which USES the polymer (polymer materials) for the electrodes and the electrolyte materials research and development is striking.

 

2. The electrode material of a battery

 

2.1 the anode material

 

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

 

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

 

2. Negative material

 

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

(2) based on tin oxide anode materials: use of SnO, SiO2 and small amounts of Al2O3, B2O3 and P2O3 mixture under argon atmosphere heats up to 1000 ℃ or higher heating temperature for 12 h, can be obtained with a mixture of divalent tin oxide.

 

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 the ionic conductivity of the coordination of polyoxyethylene (PEO) and alkali metal salt. In 1978, those proposed PEO/alkali metal salt complexes with alkali metal ion conductors of a new type of rechargeable battery electrode, the proposal makes polymer solid electrolyte polymer research hot topic very conspicuous in 20 years. The characteristics of polymer solid electrolyte are high ionic conductivity, wide potential, easy film forming, soft, light, elastic, transparent and other advantages, which cannot be achieved by inorganic glass solid electrolyte containing ionic conductivity.

 

3.1 polymer/salt complex electrolytes

Polymer solid electrolyte (SPE) with PEO and lithium

 

3.2 copolymer/salt complex electrolyte

(1) random copolyethers

There are two main structures: one is ethylene oxygen-methylene oxygenate structure, the other is ethylene oxygen-propylene oxygenate (eo-po) random copolymer

(2) the comb copolymer

Structure: molecular weight polyether chain grafted on the main chain of polymer (lower Tg),

(3) block copolymer

Structure: polystyrene-polyoxyethylene-polystyrene triblock polymer bonded by methylene oxide

(4) polymer network structure

 

There are two main production methods: one is the inorganic polymer connected polyether branch chain, forming a two-phase structure, namely inorganic support phase and organic conductive phase; Another r method is to generate network structure polymer electrolyte through polymerization and cross-linking of unsaturated polyether (macromolecular monomer).

 

3.3 polymer/inorganic blends. Macromolecular ceramic composite electrolyte was prepared by incorporation of inorganic particles into macromolecular electrolyte.

 

3.4 / salt composite latex particles electrolytes. There are two methods for preparing a series of polymer solid electrolytes with two-phase structure from latex particles with different properties.

1) SBR and NBR latex particles.

2) compound latex particles with core-shell structure were synthesized with rubber polybutadiene (PB) as the core and glassy polyvinylpyrrolidone (PVP) as the shell.

 

3.5 polymer gel/salt composite electrolyte. Gelatinous CPE is the electrolyte.

Four. 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 polymer solid electrolyte. This electrolyte is a kind of polymer material that is in a solid state, but can dissolve the supporting electrolyte as a liquid and can cause ion migration.

 

5. The eight advantages of polymer lithium ion battery.
 

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

2.Small thickness, can be made thinner. Ordinary liquid lithium battery adopts the method of first customizing the shell, and then plug the positive and negative electrode material, the thickness is below 3.6mm, there is a technical bottleneck, the polymer cell does not exist this problem, the thickness can be less than 1mm, in line with the current mobile phone demand direction.

3.Light weight. Polymer batteries are 40 percent lighter than lithium batteries with the same capacity and 20 percent lighter than aluminum batteries.

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

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 the ideal choice for remote control model and becomes the most promising alternative to nimh battery.

6. The shape can be customized. Polymer battery can be according to customer demand to increase or reduce the thickness of the cell, the development of new cell model, cheap, mold opening cycle is short, some can even be tailored according to the shape of the mobile phone, in order to make full use of the battery shell space, improve the battery capacity.

7. Discharge characteristics. Polymer battery USES colloidal electrolyte, compared with liquid electrolyte, colloidal electrolyte has stable discharge characteristics and higher discharge platform.

8. Simple protection plate design. Due to the use of polymer materials, the cell does not fire, does not explode, the cell itself has enough safety, so the polymer battery protection circuit design can consider omiting PTC and fuse, thus saving the cost of the battery.